Final Report Summary - SMARTPRO (Lightweight, flexible and smart protective clothing for law enforcement personnel)
Executive Summary:
SMARTPRO aimed to develop optimized protective textiles and apply innovative surface treatments to improve their performance on an areal density basis. Thus, fewer fabric layers would be required, resulting in increased flexibility and reduced weight of the armour. Main parameters considered also include protection of vulnerable body parts other than the torso, physiological comfort and ergonomic design. Additionally, the development and integration of smart systems was envisaged to increase users’ awareness.
According to the above objectives, a plain weave Kevlar® fabric was selected as the basic protective textile and alternative surface treatments were applied on it. The treatments explored include: (a) application of shear thickening fluids (STF), (b) application of dilatant powder, (c) coating with ceramic material by thermal spraying, (d) application of nanofibres and SiC particles, (e) coating with crosslinkable, side-functionalized aromatic polymer and (f) coating with graphene. Resulting treated Kevlar® fabrics were combined also with untreated layers in various assemblies aiming to develop a panel exhibiting both ballistic (Level IIIA) and stab (Level 1) resistance while weighing up to 5.72 kg/m2 (according to the end-users’ requirements defined through dedicated workshop and questionnaire survey). While several lightweight panels passed either the ballistic or the stabbing test, combining both protective properties proved challenging, due to the different impact mechanism. At the end, two panel assemblies passed both tests, one weighing 5.76 kg/m2 (very close to the target), and the other 6.00 kg/m2.
In parallel, scale-type composite structures were developed to be used as impact protection systems, required in the case of riot police. The structures consisted of Kevlar-reinforced epoxy composite, patterned in hexagonal scales. The scales structure allows for flexibility of the overall structure, while the selected material exhibits high impact strength.
In the frame of the project, a modular carrier for riot police and special units’ officers was designed, with the end-users being actively involved in the process. Prototype body armours were manufactured accordingly. In parallel, prototype armours for male and female patrol officers were manufactured having the same design as currently used by Mossos d’ Esquadra (end user participating in the consortium). In this case the outer fabric of the carrier was treated with a photocatalytic polymer endowing self-cleaning and de-polluting properties, while a 3D knitted fabric was used as liner to improve thermal comfort.
The following smart systems were developed: (a) textile-based heart rate sensor, (b) miniaturized ZnO nanowire gas sensor and (c) textile antenna. The heart rate sensor was integrated on an undergarment, while the gas sensor and textile antenna were appropriately integrated on a body armour prototype.
LCA and preliminary cost analysis indicate that the newly developed armours are competitive in terms of cost to existing solutions, while having reduced environmental impact.
Project Context and Objectives:
Until recently, the research on body armours for law enforcement personnel concentrated on their ballistic properties. In this context, several new fibres have been developed including Kevlar®, Dyneema®, Gold Flex®, Spectra®, Twaron® and Zylon®. These high-performance yarns are characterized by low density, high strength and high energy absorption. However, to meet the protection requirements for typical ballistic threats, 20-50 layers of fabric are required. This results in bulky and stiff armours that limit the wearers’ mobility and agility and are impractical for use on joints, arms, legs, etc. It is worth noting that the problem of reduced mobility is also very important for custodial and correctional officers who perform their duties in confined areas, such as cells and hallways, where the ability to move and fight off an attacker is very critical. Therefore, despite the progress achieved in terms of materials’ development, the demand for improved flexibility and performance-to-weight ratio of body armours remains high.
Moreover, body armour materials have traditionally been designed to protect the wearer against ballistic threats and, thus, they provide only a limited level of protection against knives and sharp blades. This is because the impact force of these objects stays concentrated to a relatively small area, allowing them to puncture even the bullet-resistant fabrics. In fact, the response of a material to stabbing has a completely different mechanism compared to its response to ballistic impact. Besides the basically dissimilar structure and size of the objects to be stopped, their kinetic impact energy is fundamentally different. While a bullet with a mass of a few grams impacts the target at a very high velocity, the typical terminal velocity of a knife attack is relatively low with a mass of up to several hundred grams. Although stab resistance was not traditionally the main concern when developing personal body armours, recent studies reveal that stabbing has become a main cause of police officers’ injuries. Accordingly, there is an obvious need to develop body armours combining ballistic and stab resistance, at the minimum weight and maximum flexibility.
Another issue that has not received much attention is the increased physiological strain which is imposed by protective armours due to the added load, increased clothing insulation and vapour resistance. In many cases, law enforcement officers avoid wearing their armour because of the acute discomfort induced by its impermeable components. Although loose weave undershirts are commonly used to provide a modest improvement in airflow and sweat evaporation, more effective solutions to ensure physiological comfort are required.
Even more, although the main scope of body armour is to provide protection against stab and ballistic threats, unseen hazards, like toxic chemicals, are more challenging to mitigate. For example, typical dangerous chemicals found in clandestine drug laboratories include carbon monoxide, benzene and hydrochloric acid. While commercial chemical detection devices are too cumbersome and expensive to use on a regular basis, innovative solutions need to be sought to allow the incorporation of chemical sensors on textiles.
Additional smart functions may further increase the efficiency of the body armour, eventually leading to reduced casualties. In this context, development and integration of heart rate sensors and wearable positioning systems (GPS) may increase users’ awareness.
Emphasis also needs to be given on the design of the body armour, as well as on the functionalities of the outer fabric. More specifically, the design should allow adaptation of the protection level to the risk level encountered in distinct situations. Therefore, modularity of the body armour is a key demand. In parallel, the design should consider the ergonomic requirements of the end users. Concerning the outer fabric of the body armour, its surface functionalization to provide self-cleaning and de-polluting properties may reduce maintenance requirements, which is particularly important considering the limited number of body armours usually available to law enforcement personnel.
Finally, innovative solutions are needed for the protection of vulnerable body parts other than the torso. Existing protective gear for law enforcement authorities is usually limited to the body armours, including, in some cases, similar systems adjusted around the neck and the groin to protect these vulnerable body parts. Solutions that improve the ballistic and stab resistance of textiles on an areal density basis could be adopted for such systems in order to increase their flexibility and allow the wearer to move more freely.
Based on the above, the distinct scientific and technical objectives which were set at the SMARTPRO proposal preparation stage are summarized as follows, along with the approaches proposed to address them:
- Development of flexible and lightweight ballistic and/or stab resistant textile panels -> (a) optimization of composition and structure of protective textiles, (b) application of alternative surface treatments to increase the ballistic and/or stab protection provided by textiles on an areal density basis (shear thickening fluids, dilatant powders, ceramic coatings, silicon carbide particles, crosslinkable side-functionalized aromatic polymers), (c) assembly of protective textile layers in order to maximize the level of protection while keeping the weight and cost of the panel as low as possible, (d) development of fish-scale type composites as impact protection materials.
- Reduced maintenance requirements -> Functionalization of the outer fabric of the body armour to induce self-cleaning and de-polluting properties.
- Increased awareness -> Development and integration of smart solutions, including wearable antenna, heart rate sensor and miniaturized gas sensor.
- Comfort and user acceptance -> (a) Use of 3D fabric for reduced thermal stress, (b) Optimized design considering modularity and ergonomic requirements of the end-users.
- Realization and evaluation of prototypes -> Manufacture of prototype body armours including protective gear for body parts other than the torso and their evaluation by end-users.
Project Results:
The main scientific and technological results of SMARTPRO are herein presented in four sections. Under the section “Protective Materials and Panels” the work conducted to develop lightweight protective panels, which are inserted in the body armour to ensure stab and ballistic resistance, is overviewed. The section “Armour Carriers” describes the design and manufacture of the vests carriers. Next section, “Smart Systems”, summarizes the development of heart rate sensors, gas sensors and textile antennas and their integration on a body armour prototype. Finally, the section “Life Cycle and Cost Analysis” focuses on the assessment of the environmental impact and cost associated with the new body armours’ development.
Protective materials and panels
The protective panel is the assembly of textile layers which is placed in the body armour carrier and provides the protective properties (ballistic/ stab resistance). The number of fabric layers and the weight of the protective panel is directly related to the level of protection provided. For example, the average weight to area ratio of a panel providing only ballistic protection of Level IIIA according to the NIJ Standard remains about 6 kg/m2.
A key objective of SMARTPRO was to develop lightweight protective panels providing both ballistic and stab protection. More specifically, in accordance to the end-users’ requirements defined early in the project, the target was to develop a panel weighing up to 5.72 kg/m2 and ensuring Level IIIA ballistic resistance and Level 1 stab resistance, according to NIJ standards 0101.04 and 0115.00 respectively.
To reach this objective, the consortium followed a bottom-up approach, starting with the selection of basic fabrics, their surface treatment to increase their protective efficiency and the assembly of alternatively treated fabrics in panels, as described below.
Selection of protective textiles
The first step towards the selection and manufacture of the basic protective textiles was the definition of fibres types to be used. Recent innovations in materials and manufacturing technologies have led to the discovery of advanced manmade fibres (such as aramid, ultra-high molecular weight polyethylene and others) that provide body armour with extraordinarily improved ballistic protection levels at a significantly reduced weight. Following a literature and market survey, the most attractive options in terms of yarns to be used for the basic protective textiles were defined. Among those, it was finally decided to use Kevlar® yarns, considering that some of the proposed surface treatments, e.g. the thermal spraying of ceramic powders, require high thermal stability of the substrate, which is ensured in the case of Kevlar®, or are expected to apply better on aramid fabrics (e.g. the crosslinkable, side-functionalized aromatic polymers are expected to adhere better on Kevlar® due to their similar chemical structure).
The next step was to define the fabric geometry (i.e. type of weave, fibres per yarn, weave density, etc.). This can be a challenging task when aiming at both ballistic and stab resistance, since design parameters for optimizing ballistic defense and stab defense often work against each other. In fact, textiles designed for ballistic protection require sufficient yarn mobility within the weave to avoid premature failures and will not perform well for stab protection. Textiles designed for stab resistance require dense weaves to prevent yarns from being pushed aside from the tip of sharp-pointed objects such as knives, needles, awls and ice picks. Dense weaves that prevent punctures can lead to premature or punch-through failures in ballistic impacts. Usually, ballistic fabrics are densely woven square plain weave or basket weave. It has been observed that loosely woven fabrics and fabrics with unbalanced weaves result in inferior ballistic performance. The packing density of the weave, indexed by the “cover factor” has an important role in defining the ballistic performance. It is determined by the width and pitch of the warp and weft yarns and gives an indication of the percentage of gross area covered by the fabric. In general, fabrics with cover factors between 0.6 and 0.95 are more effective when used in ballistic applications. When cover factors are higher than 0.95 the yarns are typically damaged during the weaving process and when cover factors fall below 0.6 the fabric may be too loose to be protective.
In the frame of SMARTPRO, a series of woven Kevlar® fabrics with varying weights and structures (plain weave, basket weave, warp-rib and a combination of diagonal and reverse face warp rib weave) were manufactured and characterized in terms of mechanical properties and cover factors. According to the characterization results, a plain weave Kevlar® fabric weighing 200 g/m2 and having a cover factor in the suitable range for ballistic applications was selected as basic protective textile.
Surface treatments to increase the protective efficiency
Alternative surface treatments were proposed, developed and applied on the aforementioned basic protective fabric. The aim was to enhance the performance of the fabric, which would allow using fewer layers and, thus, developing a lighter panel. The treatments proposed and studied in SMARTPRO were:
• Application of shear thickening fluids (STFs)
• Application of dilatant polymers
• Application of ceramic coatings
• Application of carbide and graphene-coated carbide particles
• Application of crosslinkable, side-functionalized aromatic polymers
• Application of graphene coatings
More details on each of the above treatments follow.
Application of shear thickening fluids
Shear thickening fluids (STFs) exhibit a yield stress fluid and deformable behaviour under ordinary conditions. However, once a strong impact is applied, they turn solid-like as their viscosity suddenly diverges, showing a non-Newtonian flow behaviour. Hence, according to studies reported in the literature, STFs can be used as aid materials to improve the performance of regular body armours, allowing the wearer flexibility for a normal range of movement, yet turning rigid and resisting penetration under impact.
Accordingly, the work conducted in SMARTPRO aimed to: (1) develop STFs with optimized composition and characterize them in terms of their rheological behaviour and (2) apply the optimized STFs in protective panels, to increase the protection level on an areal density basis.
Different types of particles were considered for the preparation of STFs, including sterically stabilized PMMA model hard sphere particles, raspberry-like particles, fumed silica nanoparticles and non-fumed silica microparticles. Based on the rheological characterization of the fluids composed thereof, it was decided to focus on STFs based on non-fumed silica microparticles, since they exhibit effective shear thickening effect, while having an original viscosity (under no shear) that allows their handling.
Two approaches were explored for their application in protective panels. The first involved impregnation of the protective fabric with the fluids by padding. Following this approach an improvement of stab resistance was observed; however, none of the panels including STF-treated layers satisfied the requirements set in the project. According to the second approach, the STFs were used to soak 3D knitted Kevlar® fabric (developed and industrially produced in SMARTPRO), which was subsequently confined in plastic bags. The bags containing the STF-soaked fabric could be used as inserts between Kevlar® fabrics in the protective panel. However, due to the high weight of the STF-containing bags, this approach was not further tested.
Application of dilatant polymers
Application of dilatant polymers on the protective fabric was explored through two alternative routes: (1) coating with dilatant powders obtained from a dilatant foam and (2) coating with a dilatant dispersion obtained from a dilatant gum. The dilatant foam is a STF encapsulated into a foam, while the dilatant gum is a polymer exhibiting high elasticity and specific rheological properties, i.e. almost immediate hardening upon impact.
• Coating with a dilatant foam powder: A dilatant powder was obtained from a dilatant foam using milling equipment. The powder was then applied onto the fabric, pre-impregnated with a binder, by electrostatic deposition. The binder aimed to improve the adhesion of the powder to the textile surface. After spraying with electrostatic powder spray gun, a reticulation process of the resin was applied. However, following this approach it was not possible to achieve homogenous dispersion and adherence of the powder on the textile.
• Coating with a dilatant compound: A dispersion of dilatant compound was prepared and applied on protective fabrics by different techniques (padding and coating) and process conditions. The resulting coated fabrics were subjected to impact testing following a modification of EN 13277-7:2009 standard. Although these tests showed higher impact reduction (referring to the impact force received by the reverse textile surface, in respect with the initial impact force applied to the front surface) for the coated fabrics compared to untreated ones, it was not possible to obtain a lightweight stab and ballistic resistant panel using such coated layers.
Application of ceramic coatings
Different thermal spray techniques were implemented as surface treatments on aramid-based protective textiles to enhance their protective properties by applying thin ceramic oxide and metallic layers. Thermal spray techniques are easy to apply and relatively low-cost, offering the flexibility of depositing layers of a wide range of materials (even very high melting point ones) on a variety of substrates with complex geometries on large surfaces. It is worth noting that this work is highly innovative as very few research teams are working on textiles protective properties improvement using thermal spraying.
In the frame of SMARTPRO the potential use of Atmospheric Plasma Spraying (APS) and Liquid Plasma Spraying (LPS) in terms of layers deposition on textile surfaces was investigated and thermal spray parameters (plasma power, spraying distance, feed rate etc.) were optimized for each material applied. Critical aspects that influenced the design of experiments methodology were the very low surface roughness of the selected textiles and the substrate temperature raise during deposition, since thermal spray is a high temperature technique.
Due to the fact that LPS requires suspensions as feedstock materials, stability and homogeneous dispersion of different ceramic oxides (Al2O3, TiO2, SiO2) and binary mixtures (60-80 wt % Al2O3 - 20-40 wt % TiO2, 60-80 wt % Al2O3 - 20-40 wt % TiO2) was optimized. However, the LPS technique proved unsuitable for successful layers deposition due to the necessity of small spraying distance and consequent textile temperature raise.
The APS technique was used for the deposition of a metallic bond coat layer prior to ceramic oxide layers to promote adhesion of the coating on the textile. The ceramic oxide (alumina) layer that followed was deposited again using the same thermal spray technique. Optimization of the critical APS deposition parameters was also performed for the oxide layer. Ιτwas shown that after deposition the fabric used as substrate remains unaffected, exhibits uniform deposition of both layers and fabric texture is followed by the coatings system. Optimization of thermal spray deposition parameters was performed for each deposited layer on the textile substrate. Different optimized set of parameters were selected with the aim to maintain the coating adhesion and simultaneously minimize the weight gain of the textile.
The treated textiles obtained through the thermal spray deposition of ceramic materials were, in fact, successfully used in combination with untreated and alternatively treated fabrics, for the development of lightweight (ca. 5.7 kg/m2) ballistic resistant protective panels. In the frame of SMARTPRO it was not possible to obtain a panel containing ceramic-coated fabrics and exhibiting both protective properties with that weight, even though further trials and assembly combinations could lead to such result.
Application of carbide and graphene-coated carbide particles
The popularity of silicon carbide (SiC) for use in lightweight armour systems is increasing rapidly, mainly due to the significant improvement in cost/performance ratio of SiC seen in recent years relatively to established materials like alumina. Moreover, despite the fact that SiC has a high/similar density (3.21 g/cm3) compared to other ceramics like B4C and Al2O3, it offers better resistance for impact pressures above 20 GPa (typical value for large ammunitions and impact at high velocities) .
For the application of the SiC particles the simple technology of pad-dry-curing was investigated here, in order to allow easy scale-up of the process at industrial scale. Pad-dry-curing also allows the deposition of a thin coating layer, leading to low weight increase compared to other technologies, such as spray coating. Since padding requires the immersion of the textile support into a solution, a specific particle/polymer dispersion had to be prepared. Aliphatic polyurethane (PU) resins were selected as the most suitable carriers for the particles. A challenge in ceramic coating application is the homogeneity of the ceramic oxide in the polymer dispersion. Ultrasonic (US) treatment was used to avoid agglomeration of solids in the liquids and induce fragmentation phenomena which reduce the particle size, ensuring that a large superficial area is available to interact with impact energy, maximising ballistic and stab resistance effects.
According to previous results, SiC dispersion (SiC: 10%wt./v; SILCOSPERSE: 10%wt./wt. SiC; US treatment @20 kHz for 20 minutes) was mixed (ratio 1:1) with a commercial PU resin, SANCURE 898. Since energy absorption is one of the most significant parameters in ballistic/antistab performances, the application of ceramic particles onto Kevlar® substrates was paired with the deposition of a thin nanofibrous layer before impregnation, considering that nanofibers significantly increase energy absorbing capability during impact.
In the frame of SMARTPRO, SiC-coated Kevlar® fabrics were successfully used in combination with untreated layers for the assembly of protective panels exhibiting both ballistic and stab resistance while weighing 5.76 kg/m2. It is worth noting that, while a process for the production of graphene-coated SiC particles was successfully established, the graphene coating did not appear to further enhance the protective properties and was not further explored in the project.
Application of crosslinkable, side-functionalized aromatic polymer
This work involved the synthesis of aromatic polyethers bearing side cross-linkable double bonds with optimized molecular weights, their coating onto selected Kevlar® fabrics and subsequent cross-linking. In specific, the target was the development of uniform high polymer loading Kevlar® fabrics followed by a thermal cross-linking procedure in order to further improve the strength and energy absorbing capability of the polymer-coated Kevlar® fabrics.
First, the newly synthesized copolymers were optimized in terms of molecular weight to obtain polymers with excellent film forming properties. Pilot scale monomer and polymer synthesis (up to 300g) was also accomplished to meet the needs of the project.
Regarding the coating of Kevlar® fabrics, in order to accomplish high polymer loadings and uniform coating, different methods (such as immersion into the polymeric solution and pad-dry cure) were applied. Although pad-dry-cure resulted in uniform coating, the polymer loading obtained was low. On the other hand, immersion of the Kevlar® fabrics into polymer solution with high concentration resulted in very high polymer loading, but low quality of the coating. Thus, an optimization of the conditions (polymer concentration, the number of times the Kevlar® fabric is dipped into the polymeric solution, etc) was conducted to produce uniform, high polymer loading on Kevlar® fabrics with improved mechanical properties. Indeed, we succeeded to produce Kevlar® fabrics with satisfactory polymer loading (12-15 wt%) and uniform coating using a homemade set up.
The thermal cross-linking process was selected among others (e.g. chemical cross-linking) as an easy way of creating an intermolecular polymer network with improved mechanical properties. The presence of propenyl groups enables thermal cross-linking without the need of any cross-linking agent. Optimization of the thermal cross-linking conditions in terms of temperature, time and air conditions took place. Thus, the Kevlar® fabrics were thermally treated under inert atmosphere at 260oC for 30 min up to 1h to be efficiently cross-linked.
Lightweight panels prepared using the optimized thermally cross-linked Kevlar® fabrics with high polymer loading passed successfully both stab and ballistic resistance tests.
Application of graphene coating
Multilayer graphene is an exceptional anisotropic material due to its layered structure composed of two-dimensional carbon. Having a breaking strength of 42 N m−1, where a hypothetical steel film of the same thickness would have a breaking strength of 0.4 N m−1, graphene is more than 100 times stronger than steel . Accordingly, it could be used to enhance the performance of Kevlar® fabrics.
Within the project, a combination of graphene and polyurethane (PU) was investigated, considering its ability to melt and reseal around the path of the projectile as it impacts the surface and passes through the bulk . Graphene nanoplatelets having a thickness of 10-30 nm, plane dimensions 20 to 50 μm, carbon content over 97 % and bulk density between 0.02 and 0.1 g/cm3 were used. A coating process was used to apply the nano-dispersion.
Thus, graphene (50 wt %) was added to a PU dispersion and then dried and fixed at 60°C for 1 h. The amount of graphene/PU resin deposited on the fabric is around 20-25 g/m2, while the presence of graphene was confirmed by SEM. Crock-meter tests (10 cycles) confirmed that the abrasion resistance is improved since there is no detachment of the coating even if the system is more rigid as confirmed by Bending Rigidity test (BFAST= 1300 µNm).
Assembly of the protective panel
Following the application of alternative surface treatments as described above, resulting textiles had to be selected, combined and assembled in protective panels which would provide Level IIIA ballistic resistance and Level 1 stab resistance, while weighing 5.72 kg/m2 or less (target set in the project). The assembly of the protective panel is itself a challenging task, as various parameters have to be defined, including: the type and number of fabric(s) layers, the assembly sequence (i.e. which fabrics are on the strike face and which are close to the body) and the sewing pattern. A key consideration when aiming at both ballistic and stab resistance is to combine rigid layers (which are generally effective in inhibiting penetration by sharp blades, i.e. stab protection) with more flexible ones which contribute to energy dissipation and, therefore, enhance the ballistic resistance of the panel. Accordingly, most of the panels developed in the project consisted of treated and untreated layers, the latter constituting the more flexible section of the armour.
Testing of the protective panel
Ballistic tests - Ballistic tests were performed according to NIJ 0104.4 on 40 x 40 cm panels. Since the target was to reach Level IIIA ballistic protection, the tests were performed with a 9-mm caliber FMJ (124 g) at a velocity over 435 m/s. According to the standard, a panel passes the test if both following conditions apply: (a) the panel is not perforated and (b) the back-face-signature (trauma) is lower than 40 mm.
Stabbing tests - Stab resistance was assessed according to NIJ 0115.0 under the conditions for protection Level 1. Accordingly, each panel was first hit with a knife at an energy of 24 J. Provided that the penetration of the knife was less than 7 mm, the panel was hit again at an over strike energy of 36 J. At this second strike, the penetration of the knife should be lower than 20 mm.
Results
Among the many different types of panels tested, several passed either the ballistic or the stabbing test but failed the other, while only two panels successfully passed both tests. One of them consisted of untreated Kevlar layers and layers treated with nanofibers, SiC particles and PU and weighed 5.76 kg/m2, while the other consisted of untreated Kevlar layers and layers treated with crosslinked polymer and weighed 6.00 kg/m2.
Scale composite for impact protection
Aiming to develop components for impact protection of extremities, we focused on the use of composite materials in the form of scales. Scales geometry allows flexibility, even when using rigid materials. Accordingly, an investigation on the protective scales geometries was first performed to evaluate the level of protected area and the flexibility that can be given to the protective ensemble. Three configurations were evaluated, namely patterns of triangular, square and hexagonal segments/scales. Scale composite prototypes were produced by 3D printing, aiming to reproduce the CAD designs and define the optimum scales structure. Based on the evaluation of the prototypes, the hexagonal structure was selected, since it provides the optimum balance between flexibility and protected area. A system comprising of two layers of scales structures was used so that one layer covers the unprotected areas of the other (edges of the scales). Furthermore, assessments were performed to define the optimum scales size.
Next, different composite materials were manufactured using Kevlar®, carbon and hybrid fabrics as reinforcement, to select the optimum material for the scales. Composites containing 4 to 10 fabric layers were manufactured by epoxy resin infusion and compared in terms of cost, nominal weight, thickness and penetration force.
Having selected the optimum material and geometry, samples of scales composites were manufactured using Kevlar® fabrics as reinforcement and epoxy resin as the matrix. The hexagonal pattern was created in the specimens through milling or water jet cutting (depending of the specimen type). Finally, the scale composites were glued on a Kevlar® textile support through contact glue with pressure and activation with temperature.
Armours’ carriers
In SMARTPRO, body armour carriers were developed for patrol officers, as well as for riot police and special units’ officers, considering the tasks performed by each group and the respective users’ requirements. It is worth noting that end users were actively involved in the design of the body armours since very early in the project by providing guidelines to the manufacturers and by evaluating early prototypes developed as design demonstrators.
Patrol officers’ body armours’ carriers
The carrier of patrol officers' body armours has the same design as those currently used by patrol officers of Mossos d’ Esquadra (participating in the consortium), since it totally satisfies the end users, who had no requests for further adjustments. The key of the design is that the armour looks more like a normal vest, with two flap pieces closing on the front. However, the protective panel covers the entire area of the torso as it is placed in a single-piece pocket underneath the flap pieces. Protection is also ensured on the back and the sides. The prototype was kindly manufactured by FECSA, after receiving required materials by consortium partners.
A 3D knitted polyester fabric manufactured in the project was used as a liner to facilitate air circulation and enhance comfort properties. The fabric of the carrier was Taffeta Polyamide cordura that had been surface treated with photocatalytic polymer to achieve self-cleaning and de-polluting properties.
More specifically, within SMARTPRO, a photocatalytic finishing was set-up and applied on the outer fabric of the carrier to reduce maintenance requirements and, as side effect, to decompose chemical/biological harmful substances. The photocatalyst most frequently used is, undoubtedly, titanium dioxide, produced in large amounts and low cost compared to other semiconductors. However, according to National Institute for Occupational Safety and Health (NIOSH) study (Publication No. 2011–160, April 2011) fine particle (diameter < 100 nm) poses some safety concerns. In 2006, the International Agency for Research on Cancer (IARC) reviewed TiO2 and concluded that there was sufficient evidence of carcinogenicity in experimental animals and inadequate evidence of carcinogenicity in humans (Group 2B), “possibly carcinogenic to humans” [IARC 2010]. To overcome this limitation within SMARTPRO a photocatalytic polymer was used to replace toxic nanomaterials. Sulphonated Polyetherether Ketone (SPEEK) was synthetized at large scale and applied onto textile surface to generate stable radicals through the inhibition of proton transfer mechanism via hydrogen abstraction from a suitable donor. The hydrogen donor identified within the project was polyvinyl alcohol (PVA), since it is water soluble and commercially available. A SPEEK/PVA formulate was optimised (solid content 5.25%wt./v; composition: 95% wt. PVA, 5%wt. SPEEK + 5%wt. PVA, crosslinker, glutharaldehyde) and applied by spraying onto the selected outer fabric of the carrier. The presence of photocatalytic compound onto cordura fabric was monitored and degradation tests carried out on a model dyestuff proved that the photocatalyst degrades organics.
Special units and riot police officers’ body armours
A modular body armour carrier was designed and developed for riot police and special units’ officers. It is a full 360 degrees’ modular armour carrier vest, capable of holding front and rear soft armour inserts and hard plates. It can adopt on secondary neck protection, throat and shoulder soft armour brassard protective panels. The system has drop down and integrated front groin and rear Coccyx protection, making this a versatile combat armour carrier system. Each part of the attachments has an opening to insert the protective soft panels. The front vest cumber-band armored panel folds over the rear one. The protective plates can be inserted in the vest pockets by openings on the left or the right of the vest. On the rear, the vest carries two rescue grab handles for casualty evacuation.
Smart systems
Smart systems were developed and integrated in the body armours, to alert end-users in specific hazardous situations and increase their awareness. These include: heart rate sensors, nanotechnology-based gas sensors and textile antennas, as described in the following sections.
Heart rate sensor
The function of the heart rate sensor is to detect major injuries of the wearer by measuring valuable health parameters. The main work of this development is focused on textile electrodes that are integrated into the garment of the body armour wearer. These textile electrodes have to provide good (continuous) skin contact, low surface resistance and textile yet (machine) washable characteristics.
The development of a heart rate t-shirt for health monitoring is sectioned in three stages:
• Yarn-based conductive electrodes and positioning
• Connection of the heart rate measurement
• Heart rate sensor hardware and connection to body armour
Textile electrodes: Electrical conductive yarns are commercially available (by Statex Shieldex®, Imbut Elitex®, Amann Silver-tech®, Madeira HC®) especially for smart wearables or smart textiles though textile technologies for manufacturing are widely spread. Common fabrics for electrode application are knitted, woven, non-woven or embroidered fabrics (double-lock stitching). These structures have a two-dimensional structure and a rather rough surface. A technology providing three-dimensional electrode structures is moss-embroidery. Moss embroidery is created by a one-thread embroidery system where the needle goes through the carrier material and pulls the yarn out from under the needle, plate side up. Then, a loop is created by a rotary motion of the needle on the upper side of the carrier material. Repeating this pattern frequently produces a moss-like surface. The material used for electrical conductivity is Statex SHIELDEX® 110/34 dtex 2-ply HC, which is a silver-plated polyamide-based twined yarn. This material shows very good processability due to small yarn diameter compared to needle hook size. Electrodes in elliptical shape were manufactured and ECG measurements were conducted using an ECG mannequin. The moss-embroidered electrodes were compared to conventional adhesive electrodes and an ECG-shirt with knitted textile electrodes. The moss-embroidered electrodes showed high sensor agreement and performed better than knitted electrodes, which are already in use for commercially available products.
Two prototype shirts were manufactured by moss embroidery of Statex SHIELDEX® 110/34 dtex 2-ply HC in elliptical shape. Measurements on the ECG mannequin showed very good results regarding signal accuracy; though first tests conducted on a subject showed following issues that had to be further developed:
• positioning of electrodes
• continuous high conductivity of textile electrodes
• minimized stress and length of signal transmission
Therefore, tests were conducted using a shirt prototype with eight different electrode positions aligned throughout the shirt width and below and above the breast muscles. The shirt design was developed for female and male wearer’s though testing was conducted with a male subject. Different combinations of the electrodes on the chest area were tested and the results were evaluated regarding average QRS peak and lowest disturbance by movement. The optimum positions of the electrodes were defined accordingly, regarding highest voltage as well as minimized influence while moving. Those results lead to the used electrode configuration according to the first lead of Nehb. Additionally, a third electrode was positioned on the right hip as a ground electrode. For testing purposes, an adhesive electrode was chosen as ground electrode for possible positioning.
Due to female chest shape the vertical distance between left and right electrode was increased by about 5cm. For the end-user evaluation, a male t-shirt in large size and a female t-shirt in medium size had to be produced. The measurements were taken according to EU size standards subtracting minimum of 5 centimeters to obtain skin fit shirts. This also ensures continuous contact of the electrodes and the skin and therefore continuous heart rate measurement. Furthermore, testing was conducted with water and electrode gel to provide lowest skin surface resistivity. The electrodes were embroidered with a wave-like grid pattern to ensure overlapping between yarns and homogenous distribution. To reduce elongation within the textile electrode and therefore influencing signals a non-stretchable polyester substrate was chosen (Stiffy® 1950 by Gunold GmbH, Stockstadt, Germany). This material shows high flexibility and in the meantime the electrode area on the t-shirt textile cannot be stretched.
Connection of textile electrodes: Previous electrode prototypes were connected by press fasteners. These connectors are also used for commercially available adhesive electrodes. The influences from press fasteners on the transmitted signal are insignificant. The press fasteners were implemented in the center of the electrodes. Afterwards polyurethane (PU) film was applied by applying heat (ironing). The PU film showed following effects within testing: (a) reduced influence on HR signals after external contact (touch) on the outer electrode surface and (b) better water content management due to waterproof sealing of the electrode back side.
The connection between heart rate electrodes and ECG hardware device is based on cables and press fastener connection. A direct connection from heart rate shirt and body armour provides following advantages compared to a Bluetooth® wireless connection: (a) Secure and non-interfering data transmission, (b) External power supply can be used, (c) No additional integration of device/PCB onto heart rate shirt. Three connector pins are then combined to an audio jack (3-pin) that can be used with the ECG hardware device.
Heart rate sensor hardware: After intensive research, the hardware of choice was found in “SparkFun Single Lead Heart Rate Monitor-AD8232” (by Sparkfun Electronics, Niwot, USA) which can be easily integrated in the Arduino programming libraries. The audio jack cable can be easily connected into the socket and a red LED shows heart rate signals by different intense blinking. The signal reading (as low voltage current) is registered by the ECG module and processed within the Arduino® hardware (Arduino® Lilypad) and software. The ECG information is processed by QRS peak counting within the software. After a minimum setup time (e.g. 10 seconds) the heart rate (in beats per minute) is sent to the Arduino® Lilypad.
Textile antenna
Especially for on-body use, planar antennas with a ground plane such as patch antennas are the most suitable topologies since these reduce the radiation in the direction of the body. The three main components of each patch antenna are Radiator, Ground plane (both conductive) and Substrate (non-conductive). The radiator as well as the ground plane must have a high conductivity and a low surface-resistance. These layers are produced using conductive textiles. The substrate has to be a non-conductive material with low permittivity (εr ≈ 1) and low loss (tan δ ≈ 0). This can be achieved by using a non-compressible textile such as fleece, a non-woven fabric or felt. The size of the antenna corresponds directly to the frequency used: A lower frequency results in a bigger antenna.
A first prototype for GPS antennas was developed and manufactured as follows: (a) The antenna design is printed on a double-sided adhesive sheet, (b+c) The adhesive sheet is glued to the conductive textile using an iron, (d) Shows the material necessary for the cutting of radiator: The conductive textile is cut along a ruler using a scalpel, (e) Finished radiator with conductive sheet on backside, (f) Prepared layers of non-woven substrate: these two layers are glued together using the same method of double-sided conductive sheets, (g) Assembly of antenna parts and (h+i) Finished prototype.
After suitable antenna topologies, frequencies, materials, designs and textile production technologies were identified, evaluation of the HF characteristics of the textile antennas was initiated and the influence of the antenna performance under bending conditions was evaluated. It can be concluded that the antenna performance is negatively affected by the combination of bending and human skin contact. However, the determined decrease is so small, that it will not negatively affect the performance of the textile antenna within the body armour.
Antenna performance was evaluated in a field test. Therefore, the antenna has been integrated into a jacket comparing the developed textile GPS antennas to conventional GPS antennas and receivers. A Ceramic Patch Antenna „Neo 6M“ by u-blox AG, Germany and a GPS-mouse „HOLUX GR-213“ by „HOLUX Technology,.Inc“, Taiwan were used for comparison.
The results of the field tests show that the average accuracy of the textile antenna was higher compared to the tested conventional antennas, due to lower positioning errors (in meters). The human body influences the antenna but it is not relevant for the antenna performance. The GPS-mouse used for the testing is comparable to other GPS sensors integrated in other devices, e.g. smartphones. Irrespective of the size of commercially available GPS sensors, the textile antenna showed the highest accuracy in the field test in terms of positioning compared to established systems such as a ceramic patch antenna or a GPS-mouse.
Within the project conductive fabrics were produced by SOLIANI. The material type “Volta-VO.NICU” shows the lowest resistivity (8.2 mOhm/sq) being lower than the “Statex Kassel” material which was used for the first antenna prototype. Both materials show almost the same thickness but differ in weight per square meter. The “Volta-VO.NICU” was selected for the production of further antenna prototypes, e.g. GPS and GSM communication. The architecture and connection of the systems is as follows: the GPS module is receiving GPS raw data and in the meantime the GSM module is checking network status and connection. The GPS raw data is then sent to a remote server where it is interpreted as latitude and longitude GPS data. Both GPS and GSM antenna were finalized with electro conductive fabrics “Volta-VO.NICU” by SOLIANI. The final connection of the GPS localisation hardware is provided by µFL cable connectors. The GSM/GPS module is combining GPS receiver and GSM sender. The GPS data is then provided to Arduino® Lilypad #1 which is also detecting the heart rate.
Gas sensor
Motivation: Gas sensors are devices that can convert the concentration of an analyte gas in an electronic signal and are an important component of devices commonly known as “electric noses”. The current Task was devoted to the development of wearable miniature gas sensors able to rapidly detect and monitor toxic gasses for the efficient use of both law-enforcement personnel and civilians. The main objective wa to fabricate sensors that: (i) operate reliably in the detection of toxic chemicals within an acceptable reaction time, (ii) are able to detect agent concentrations at levels which are lower than those which pose health risks, (iii) are not affected by other factors in the environment such as humidity, (iv) operate at short reaction and recovery times, and (v) can be fabricated so as to be portable and wearable.
Why resistive sensors: Several types of gas sensing mechanisms have been proposed and explored. The main categories include: electrochemical, catalytic bead, photoionization, infrared point, infrared imaging, semiconducting materials (resistive), ultrasonic and holographic. Resistive sensors stand out as a promising type for the fabrication of miniaturized devices and due to the simple sensing mechanism. Metal oxide semiconductors (MOS) are used as the sensing material. Nanostructured MOS sensors detect gases based on a chemical reaction that takes place on the material’s surface, when the gas comes in direct contact with the MOS. The target gas interacts with the surface of the MOS film (generally through surface adsorbed oxygen ions), which results in a change in charge carrier concentration of the material. This serves to alter the conductivity (or resistivity,) of the material. An n-type semiconductor is one where the majority charge carriers are electrons, and upon interaction with a reducing gas an increase in conductivity occurs. Conversely, an oxidising gas serves to deplete the sensing layer of charge carrying electrons, resulting in a decrease in conductivity. This change is used to signify the presence of the gas and may be used to calculate the gas concentration.
ZnO nanowire-based gas sensors: The work performed in SMARTPRO pursued rational synthetic routes for the controlled growth of nanowire-based arrays, which would demonstrate high performance in specific gas sensing and in particular carbon monoxide (CO). CO is a colorless and odorless gas, hence undetectable to humans. It is considered as one of the leading cause of poisoning worldwide, especially in many industrial countries. The maximum time weighted average exposure is 35 ppm over an 8 h period. Owing to the ubiquitous presence of CO, such sensors have a dazzling variety of applications, not just for law enforcement authorities, also in home safety, in measuring atmospheric concentrations, in the exhaust of cars, and for process monitoring in industrial plants.
The synthesis and characterization of the ZnO nanowire (NW) arrays and a work station for gas sensing were realized during the first period of the project. ZnO NW arrays were grown using hydrothermal synthesis. Over that period, we accomplished the development of a synthetic route for the controlled and reliable growth of ZnO nanowire arrays with high aspect ratio and surface area, good crystallinity and negligible defect density, and appropriate adhesion and orientation normal to the substrate. The method is fully controllable and shows very high degree of reproducibility. In parallel, the development of a home-made set-up took place for the detailed characterization of the ZnO-based nanomaterials grown as efficient media for gas sensors.
Optimization of sensor parameters was based on a feedback mechanism in relation to the materials synthesis process in order to achieve the best morphology. Four main parameters are used to characterize the performance of a gas sensor:
- the sensor sensitivity (for reducing gas),
- the response time defined as the time required to achieve a 90% change in the resistance upon the supply of the gas,
- the recovery time defined as the time required to achieve a 90% change in the resistance upon removal of the gas, and
- the working temperature.
More than 100 experiments were conducted in order to optimize both the gas sensing materials and the experimental set up to obtain the optimum conditions for the gas sensors under development. Several parameters related to the material development have been examined:
• The type of the substrate (soda lime glass, silicon, quartz, and the conductive glass/FTO) were used in order to explore the role of conducting and insulating substrates on the gas sensor performance.
• The influence of the seed layer thickness deposited on the soda lime glass exerted on the gas sensing efficiency of ZnO NW arrays was investigated.
• The influence of the (i) operation temperature, (ii) gas concentration, (iii) doping with Al atoms, and (iv) decoration with noble atoms, on the gas sensing efficiency of ZnO NW arrays has also been explored.
The results obtained demonstrate that the developed materials exhibit far better sensing performance for the CO gas detection, in comparison to literature data, as regards both the operation temperature and the sensitivity parameter.
Integration of smart systems on the body armours
The developed systems – heart rate sensor, textile antennas and gas sensor – had to be integrated into the body armour meeting user-requirements such as: flexibility to minimize user movement hindrance, size and weight of the systems to provide maximum wearing comfort as well as water proofness for duties in heavy rain. The prototype used for the integration was the female version of patrol armour, manufactured by FECSA.
Waterproof encapsulation - In order to assure a total functionality even with adverse meteorological conditions like raining, water protection of the smart systems was carried out. It is important to remind that the wires are not affected by water, as they are already recovered with a polymer. The parts that can be affected in presence of water are the connections and the electronic components (e.g. the gas sensor, the antennas or the battery). All the components with its encapsulation are extractable with Velcro in the case of washing the armour vest. The rain protection of the electronic components is based on the encapsulation with polymeric film (translucent PVC film). The film was welded with an ultrasonic welding machine so that each component has its waterproof bag. When needed, an opening using Velcro was made. Besides, a welding trial to join the Velcro with the polymeric film has been done to avoid sewing it, since the little holes produced by a stitch can generate a weak point.
Waterproof validation - A test was done to verify the correct performance of the smart systems when it is raining. In order to assess this, the Bundesmann test was performed for an encapsulated electronic system, following the standard EN 29865. It is important to keep in mind that this is an approximation to the reality of the smart systems in the armour vest. Rain (drops of water) will never directly contact with the PCBs and the battery encapsulated on the vest, as they are placed behind the fabric of the armour and are not visible.
Textile antennas - After encapsulation, the textile antenna was integrated on the highest position within the body armour. This position was chosen in accordance to the user-requirements by security and law enforcement experts as it provides least hindrance by any carried accessories such as gun straps. Hence, it improves the antenna performance. Positioning tests conducted showed best performance for the textile GPS antenna on the highest position. The placement for the GSM antenna also requires a high position within the body armour, similar to GPS antenna. Due to limited space within the carrier a different position was chosen for the GSM. The textile antennas and the PCBs are integrated within the carrier for the anti-ballistic panel. Therefore, it is placed behind the panel to maintain higher safety in case of damage. Except the GPS antennas, all hardware components were integrated in the waist area of the vest. This provides a good accessibility to the battery while wearing the armour whilst ergonomics is not hampered. The battery itself is integrated in the Velcro pouch on the front side for easy access in case of removing or charging. The encapsulated antennas are integrated with Velcro straps to the inner side of the carrier (spacer fabric). The Velcro straps were integrated using sewing which cannot be seen on the inner side of the body armour. Three straps are used for the integration of each antenna.
Connection of all systems - In the latest stage, a single Arduino® Lilypad is able to substitute single Lilypads for ECG and GPS/GSM modules.
Gas sensor - The integration of the gas sensor provided by FORTH is based on the following steps:
(a) Miniaturization of the gas sensor and wire reorganization: Achieving the minimum possible volume is a decisive point in order to achieve a comfort for the user. The polymeric white part was replaced by small wires and a bigger wire was welded to connect the LED. Furthermore, connectors were added to achieve a more practical use of the entire system.
(b) Design concept housing and 3D printed prototype: In order to protect and locate the sensor, housing was designed using CAD software. It consists of two parts joined with screws that can be separated if needed. The housing was fabricated using 3D printing technology (Fused Deposition Modeling, FDM) and painted in black to make it less visible.
(c) Integration on the body armour: Finally, the integration of the sensor on the body armour was performed using high resistance Velcro that allows the system to be easily extracted if needed and an elastic band that covers a part of the sensor encapsulation and assures a consistent location.
Life Cycle Analysis and Life Cycle Cost
Life Cycle Analysis – To demonstrate the sustainability of the body armours developed in SMARTPRO the environmental impact related with their production was computed using a Life Cycle Assessment (LCA) approach. LCA is an analytic method to address the environmental aspects and potential environmental impacts throughout a product life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal (i.e. cradle-to-grave). The methodology is defined and regulated by the ISO 14040 and 14044 standards, while the broad provisions stated there have been further specified in the ILCD Handbook Guidelines which were taken as a reference for the development of this analysis. The functional unit chosen for the analysis was 1 body armour (size M).
In detail, a cradle-to-use phase approach was considered; thus, the analysis encompasses all cycle phases starting from the production of raw materials, spinning, fabric production, dyeing and finishing processes and chemicals used for the functionalization of the fabrics, the assembly of the protective panels and the final armour (including accessories) and specific impacts were computed according to ILCD 2011 method. The environmental performances of the two ballistic and antistab panels developed in SMARTPRO were compared to those of a commercially available armour from SIAMIDIS portfolio, featuring the same protective performances. Both armours developed in SMARTPRO have lower environmental impact than the reference one (total ecopoint compared to the reference armour is lower by 13 % and 5.3 % for the armour containing Kevlar®+nanocomposite structure and that containing Kevlar®+crosslinked polymer, respectively). The reduced environmental impact is due to the lower amount of Kevlar® fabric used in the new panels, as the production of such high-performance yarns appears to be the factor contributing the most to body armours’ environmental footprint.
Cost estimation - Technical performances of the functional textile exhibiting both ballistic and stab resistance properties have been paired with an economic study aiming to define the final price of body armour and its main components (in particular the protective panel). A preliminary analysis related with the production costs of the functional textile was assessed. Accordingly, the costs for the production of SMARTPRO protective panel have been estimated and compared with the costs for the production of conventional products featuring same technical performances (Ballistic: LEVEL IIIA; Antistab: LEVEL I).
The outcomes related with the economic evaluation of the efficient SMARTPRO solutions show that the most promising solutions seems to the the combination of Kevlar® and Nanocomposite since it allows to reduce up tp 10% the production costs compared to alternative solutions available in Siamidis portfolio featuring the same technical performances.
Potential Impact:
The global body armours market is expected to reach 4,8 billion Euros by 2024 (value in 2015 was 3,35 billion) according to Grand View Research Inc. Technological advances are the key instruments in accelerating the market growth, as innovative concepts, such as “liquid body armour” and “dragon skin” are gaining momentum. In addition to this, the demand for modular body armours is on a rise, due to their features offering enhanced protection. Prominent manufacturers of personal protective armours are increasingly investing in R&D activities for the development of advanced fibres, fabrics and other materials to improve the effectiveness of the body armour. It is worth noting that body armours exhibiting ballistic protection of Level IIIA accounted for 21.8 % of the overall market share, in terms of revenue, in 2015.
Law enforcement officers increasingly need to carry more, utilize more technology and operate in extreme environments. Advances in materials and technologies are thus required to alleviate the increased weight and related fatigue arising from these new demands.
The most significant potential requirements of future officers are listed below:
1) Weight reduction: A recent study by Defence Research and Development Canada indicates that increased weight and heat retention may reduce users’ performance by up to 25 %.
2) Thermal management for comfort: Thermal management covers both insulation in cold conditions and cooling in hot conditions, even if the latter is more critical. Heat stress is a serious concern because it can affect the health and safety of the individual as well as operational performance.
3) Biological and chemical protection: With growing concerns over the possibility of terrorist attacks using biological and chemical threats, protection is of increasing importance. Chemical threats refer to nerve and blister agents, while biological threats include bacteria (e.g. Anthrax), rickettsia (e.g. Typhus), toxins (e.g. Botulinum Toxin) and viruses. There are two parallel and complimentary research streams in this area: sensors and protective clothing. Sensors are important for early detection of contaminants, while light, comfortable and protective wear is essential for survival.
4) Modularity and flexibility: Armour should defeat high level threats, while maintaining the lowest possible weight and provide the wearer with unrestricted movement. Extremity armour is not a new concept. However, it is important to protect vulnerable areas with a minimal increase in weight and without adversely affecting the ability to perform operational tasks.
5) Power/data/conductive applications: The officers of the future will be carrying increasing amounts of high-tech equipment. Along with the need for new power systems and storage, novel ways to transfer data are needed. Examples of applications include antennas that are integrated and/or embedded within clothing or other pieces of equipment, flexible displays, equipment that is powered either through wired or wireless systems, novel interconnects for equipment and power harvesting and energy storage for technology life extension. In some cases, integrating these applications into intelligent textiles may be desirable.
It is important to note that SMARTPRO has addressed the above challenges by focusing on the development of lightweight, comfortable and modular body armours incorporating nanotechnology-based sensors for the detection of hazardous gasses, heart rate sensors and textile antennas.
It should be noted that using the technologies and materials developed in SMARTPRO military body armours as well as body armours for civilian use may be manufactured. Interestingly, the civilian demand for personal body armours accounted for 7.4% of the total market share (in terms of revenue) in 2015 and is anticipated to reach 7.7 % in 2024, as the significant rise in the crime rates and incidents of mass shooting is driving the demand for armour vests among civilians. It can also be anticipated that SMARTPRO results will create economic benefits for the EU through dual use applications. In fact, the materials developed for law enforcement could be transferred to the general public, through incorporation in protective gear for extreme sports or motorcyclists.
Last but not least, considering that the technological advancements of SMARTPRO are paired by a reduction of the environmental impact of body armours, the results of the project could bring significant environmental benefits and decrease the environmental footprint of the body armours’ sector.
List of Websites:
www.smartpro-project.eu
or contact s.pavlidou@ebetam.gr (Silvia Pavlidou, MIRTEC S.A.)
SMARTPRO aimed to develop optimized protective textiles and apply innovative surface treatments to improve their performance on an areal density basis. Thus, fewer fabric layers would be required, resulting in increased flexibility and reduced weight of the armour. Main parameters considered also include protection of vulnerable body parts other than the torso, physiological comfort and ergonomic design. Additionally, the development and integration of smart systems was envisaged to increase users’ awareness.
According to the above objectives, a plain weave Kevlar® fabric was selected as the basic protective textile and alternative surface treatments were applied on it. The treatments explored include: (a) application of shear thickening fluids (STF), (b) application of dilatant powder, (c) coating with ceramic material by thermal spraying, (d) application of nanofibres and SiC particles, (e) coating with crosslinkable, side-functionalized aromatic polymer and (f) coating with graphene. Resulting treated Kevlar® fabrics were combined also with untreated layers in various assemblies aiming to develop a panel exhibiting both ballistic (Level IIIA) and stab (Level 1) resistance while weighing up to 5.72 kg/m2 (according to the end-users’ requirements defined through dedicated workshop and questionnaire survey). While several lightweight panels passed either the ballistic or the stabbing test, combining both protective properties proved challenging, due to the different impact mechanism. At the end, two panel assemblies passed both tests, one weighing 5.76 kg/m2 (very close to the target), and the other 6.00 kg/m2.
In parallel, scale-type composite structures were developed to be used as impact protection systems, required in the case of riot police. The structures consisted of Kevlar-reinforced epoxy composite, patterned in hexagonal scales. The scales structure allows for flexibility of the overall structure, while the selected material exhibits high impact strength.
In the frame of the project, a modular carrier for riot police and special units’ officers was designed, with the end-users being actively involved in the process. Prototype body armours were manufactured accordingly. In parallel, prototype armours for male and female patrol officers were manufactured having the same design as currently used by Mossos d’ Esquadra (end user participating in the consortium). In this case the outer fabric of the carrier was treated with a photocatalytic polymer endowing self-cleaning and de-polluting properties, while a 3D knitted fabric was used as liner to improve thermal comfort.
The following smart systems were developed: (a) textile-based heart rate sensor, (b) miniaturized ZnO nanowire gas sensor and (c) textile antenna. The heart rate sensor was integrated on an undergarment, while the gas sensor and textile antenna were appropriately integrated on a body armour prototype.
LCA and preliminary cost analysis indicate that the newly developed armours are competitive in terms of cost to existing solutions, while having reduced environmental impact.
Project Context and Objectives:
Until recently, the research on body armours for law enforcement personnel concentrated on their ballistic properties. In this context, several new fibres have been developed including Kevlar®, Dyneema®, Gold Flex®, Spectra®, Twaron® and Zylon®. These high-performance yarns are characterized by low density, high strength and high energy absorption. However, to meet the protection requirements for typical ballistic threats, 20-50 layers of fabric are required. This results in bulky and stiff armours that limit the wearers’ mobility and agility and are impractical for use on joints, arms, legs, etc. It is worth noting that the problem of reduced mobility is also very important for custodial and correctional officers who perform their duties in confined areas, such as cells and hallways, where the ability to move and fight off an attacker is very critical. Therefore, despite the progress achieved in terms of materials’ development, the demand for improved flexibility and performance-to-weight ratio of body armours remains high.
Moreover, body armour materials have traditionally been designed to protect the wearer against ballistic threats and, thus, they provide only a limited level of protection against knives and sharp blades. This is because the impact force of these objects stays concentrated to a relatively small area, allowing them to puncture even the bullet-resistant fabrics. In fact, the response of a material to stabbing has a completely different mechanism compared to its response to ballistic impact. Besides the basically dissimilar structure and size of the objects to be stopped, their kinetic impact energy is fundamentally different. While a bullet with a mass of a few grams impacts the target at a very high velocity, the typical terminal velocity of a knife attack is relatively low with a mass of up to several hundred grams. Although stab resistance was not traditionally the main concern when developing personal body armours, recent studies reveal that stabbing has become a main cause of police officers’ injuries. Accordingly, there is an obvious need to develop body armours combining ballistic and stab resistance, at the minimum weight and maximum flexibility.
Another issue that has not received much attention is the increased physiological strain which is imposed by protective armours due to the added load, increased clothing insulation and vapour resistance. In many cases, law enforcement officers avoid wearing their armour because of the acute discomfort induced by its impermeable components. Although loose weave undershirts are commonly used to provide a modest improvement in airflow and sweat evaporation, more effective solutions to ensure physiological comfort are required.
Even more, although the main scope of body armour is to provide protection against stab and ballistic threats, unseen hazards, like toxic chemicals, are more challenging to mitigate. For example, typical dangerous chemicals found in clandestine drug laboratories include carbon monoxide, benzene and hydrochloric acid. While commercial chemical detection devices are too cumbersome and expensive to use on a regular basis, innovative solutions need to be sought to allow the incorporation of chemical sensors on textiles.
Additional smart functions may further increase the efficiency of the body armour, eventually leading to reduced casualties. In this context, development and integration of heart rate sensors and wearable positioning systems (GPS) may increase users’ awareness.
Emphasis also needs to be given on the design of the body armour, as well as on the functionalities of the outer fabric. More specifically, the design should allow adaptation of the protection level to the risk level encountered in distinct situations. Therefore, modularity of the body armour is a key demand. In parallel, the design should consider the ergonomic requirements of the end users. Concerning the outer fabric of the body armour, its surface functionalization to provide self-cleaning and de-polluting properties may reduce maintenance requirements, which is particularly important considering the limited number of body armours usually available to law enforcement personnel.
Finally, innovative solutions are needed for the protection of vulnerable body parts other than the torso. Existing protective gear for law enforcement authorities is usually limited to the body armours, including, in some cases, similar systems adjusted around the neck and the groin to protect these vulnerable body parts. Solutions that improve the ballistic and stab resistance of textiles on an areal density basis could be adopted for such systems in order to increase their flexibility and allow the wearer to move more freely.
Based on the above, the distinct scientific and technical objectives which were set at the SMARTPRO proposal preparation stage are summarized as follows, along with the approaches proposed to address them:
- Development of flexible and lightweight ballistic and/or stab resistant textile panels -> (a) optimization of composition and structure of protective textiles, (b) application of alternative surface treatments to increase the ballistic and/or stab protection provided by textiles on an areal density basis (shear thickening fluids, dilatant powders, ceramic coatings, silicon carbide particles, crosslinkable side-functionalized aromatic polymers), (c) assembly of protective textile layers in order to maximize the level of protection while keeping the weight and cost of the panel as low as possible, (d) development of fish-scale type composites as impact protection materials.
- Reduced maintenance requirements -> Functionalization of the outer fabric of the body armour to induce self-cleaning and de-polluting properties.
- Increased awareness -> Development and integration of smart solutions, including wearable antenna, heart rate sensor and miniaturized gas sensor.
- Comfort and user acceptance -> (a) Use of 3D fabric for reduced thermal stress, (b) Optimized design considering modularity and ergonomic requirements of the end-users.
- Realization and evaluation of prototypes -> Manufacture of prototype body armours including protective gear for body parts other than the torso and their evaluation by end-users.
Project Results:
The main scientific and technological results of SMARTPRO are herein presented in four sections. Under the section “Protective Materials and Panels” the work conducted to develop lightweight protective panels, which are inserted in the body armour to ensure stab and ballistic resistance, is overviewed. The section “Armour Carriers” describes the design and manufacture of the vests carriers. Next section, “Smart Systems”, summarizes the development of heart rate sensors, gas sensors and textile antennas and their integration on a body armour prototype. Finally, the section “Life Cycle and Cost Analysis” focuses on the assessment of the environmental impact and cost associated with the new body armours’ development.
Protective materials and panels
The protective panel is the assembly of textile layers which is placed in the body armour carrier and provides the protective properties (ballistic/ stab resistance). The number of fabric layers and the weight of the protective panel is directly related to the level of protection provided. For example, the average weight to area ratio of a panel providing only ballistic protection of Level IIIA according to the NIJ Standard remains about 6 kg/m2.
A key objective of SMARTPRO was to develop lightweight protective panels providing both ballistic and stab protection. More specifically, in accordance to the end-users’ requirements defined early in the project, the target was to develop a panel weighing up to 5.72 kg/m2 and ensuring Level IIIA ballistic resistance and Level 1 stab resistance, according to NIJ standards 0101.04 and 0115.00 respectively.
To reach this objective, the consortium followed a bottom-up approach, starting with the selection of basic fabrics, their surface treatment to increase their protective efficiency and the assembly of alternatively treated fabrics in panels, as described below.
Selection of protective textiles
The first step towards the selection and manufacture of the basic protective textiles was the definition of fibres types to be used. Recent innovations in materials and manufacturing technologies have led to the discovery of advanced manmade fibres (such as aramid, ultra-high molecular weight polyethylene and others) that provide body armour with extraordinarily improved ballistic protection levels at a significantly reduced weight. Following a literature and market survey, the most attractive options in terms of yarns to be used for the basic protective textiles were defined. Among those, it was finally decided to use Kevlar® yarns, considering that some of the proposed surface treatments, e.g. the thermal spraying of ceramic powders, require high thermal stability of the substrate, which is ensured in the case of Kevlar®, or are expected to apply better on aramid fabrics (e.g. the crosslinkable, side-functionalized aromatic polymers are expected to adhere better on Kevlar® due to their similar chemical structure).
The next step was to define the fabric geometry (i.e. type of weave, fibres per yarn, weave density, etc.). This can be a challenging task when aiming at both ballistic and stab resistance, since design parameters for optimizing ballistic defense and stab defense often work against each other. In fact, textiles designed for ballistic protection require sufficient yarn mobility within the weave to avoid premature failures and will not perform well for stab protection. Textiles designed for stab resistance require dense weaves to prevent yarns from being pushed aside from the tip of sharp-pointed objects such as knives, needles, awls and ice picks. Dense weaves that prevent punctures can lead to premature or punch-through failures in ballistic impacts. Usually, ballistic fabrics are densely woven square plain weave or basket weave. It has been observed that loosely woven fabrics and fabrics with unbalanced weaves result in inferior ballistic performance. The packing density of the weave, indexed by the “cover factor” has an important role in defining the ballistic performance. It is determined by the width and pitch of the warp and weft yarns and gives an indication of the percentage of gross area covered by the fabric. In general, fabrics with cover factors between 0.6 and 0.95 are more effective when used in ballistic applications. When cover factors are higher than 0.95 the yarns are typically damaged during the weaving process and when cover factors fall below 0.6 the fabric may be too loose to be protective.
In the frame of SMARTPRO, a series of woven Kevlar® fabrics with varying weights and structures (plain weave, basket weave, warp-rib and a combination of diagonal and reverse face warp rib weave) were manufactured and characterized in terms of mechanical properties and cover factors. According to the characterization results, a plain weave Kevlar® fabric weighing 200 g/m2 and having a cover factor in the suitable range for ballistic applications was selected as basic protective textile.
Surface treatments to increase the protective efficiency
Alternative surface treatments were proposed, developed and applied on the aforementioned basic protective fabric. The aim was to enhance the performance of the fabric, which would allow using fewer layers and, thus, developing a lighter panel. The treatments proposed and studied in SMARTPRO were:
• Application of shear thickening fluids (STFs)
• Application of dilatant polymers
• Application of ceramic coatings
• Application of carbide and graphene-coated carbide particles
• Application of crosslinkable, side-functionalized aromatic polymers
• Application of graphene coatings
More details on each of the above treatments follow.
Application of shear thickening fluids
Shear thickening fluids (STFs) exhibit a yield stress fluid and deformable behaviour under ordinary conditions. However, once a strong impact is applied, they turn solid-like as their viscosity suddenly diverges, showing a non-Newtonian flow behaviour. Hence, according to studies reported in the literature, STFs can be used as aid materials to improve the performance of regular body armours, allowing the wearer flexibility for a normal range of movement, yet turning rigid and resisting penetration under impact.
Accordingly, the work conducted in SMARTPRO aimed to: (1) develop STFs with optimized composition and characterize them in terms of their rheological behaviour and (2) apply the optimized STFs in protective panels, to increase the protection level on an areal density basis.
Different types of particles were considered for the preparation of STFs, including sterically stabilized PMMA model hard sphere particles, raspberry-like particles, fumed silica nanoparticles and non-fumed silica microparticles. Based on the rheological characterization of the fluids composed thereof, it was decided to focus on STFs based on non-fumed silica microparticles, since they exhibit effective shear thickening effect, while having an original viscosity (under no shear) that allows their handling.
Two approaches were explored for their application in protective panels. The first involved impregnation of the protective fabric with the fluids by padding. Following this approach an improvement of stab resistance was observed; however, none of the panels including STF-treated layers satisfied the requirements set in the project. According to the second approach, the STFs were used to soak 3D knitted Kevlar® fabric (developed and industrially produced in SMARTPRO), which was subsequently confined in plastic bags. The bags containing the STF-soaked fabric could be used as inserts between Kevlar® fabrics in the protective panel. However, due to the high weight of the STF-containing bags, this approach was not further tested.
Application of dilatant polymers
Application of dilatant polymers on the protective fabric was explored through two alternative routes: (1) coating with dilatant powders obtained from a dilatant foam and (2) coating with a dilatant dispersion obtained from a dilatant gum. The dilatant foam is a STF encapsulated into a foam, while the dilatant gum is a polymer exhibiting high elasticity and specific rheological properties, i.e. almost immediate hardening upon impact.
• Coating with a dilatant foam powder: A dilatant powder was obtained from a dilatant foam using milling equipment. The powder was then applied onto the fabric, pre-impregnated with a binder, by electrostatic deposition. The binder aimed to improve the adhesion of the powder to the textile surface. After spraying with electrostatic powder spray gun, a reticulation process of the resin was applied. However, following this approach it was not possible to achieve homogenous dispersion and adherence of the powder on the textile.
• Coating with a dilatant compound: A dispersion of dilatant compound was prepared and applied on protective fabrics by different techniques (padding and coating) and process conditions. The resulting coated fabrics were subjected to impact testing following a modification of EN 13277-7:2009 standard. Although these tests showed higher impact reduction (referring to the impact force received by the reverse textile surface, in respect with the initial impact force applied to the front surface) for the coated fabrics compared to untreated ones, it was not possible to obtain a lightweight stab and ballistic resistant panel using such coated layers.
Application of ceramic coatings
Different thermal spray techniques were implemented as surface treatments on aramid-based protective textiles to enhance their protective properties by applying thin ceramic oxide and metallic layers. Thermal spray techniques are easy to apply and relatively low-cost, offering the flexibility of depositing layers of a wide range of materials (even very high melting point ones) on a variety of substrates with complex geometries on large surfaces. It is worth noting that this work is highly innovative as very few research teams are working on textiles protective properties improvement using thermal spraying.
In the frame of SMARTPRO the potential use of Atmospheric Plasma Spraying (APS) and Liquid Plasma Spraying (LPS) in terms of layers deposition on textile surfaces was investigated and thermal spray parameters (plasma power, spraying distance, feed rate etc.) were optimized for each material applied. Critical aspects that influenced the design of experiments methodology were the very low surface roughness of the selected textiles and the substrate temperature raise during deposition, since thermal spray is a high temperature technique.
Due to the fact that LPS requires suspensions as feedstock materials, stability and homogeneous dispersion of different ceramic oxides (Al2O3, TiO2, SiO2) and binary mixtures (60-80 wt % Al2O3 - 20-40 wt % TiO2, 60-80 wt % Al2O3 - 20-40 wt % TiO2) was optimized. However, the LPS technique proved unsuitable for successful layers deposition due to the necessity of small spraying distance and consequent textile temperature raise.
The APS technique was used for the deposition of a metallic bond coat layer prior to ceramic oxide layers to promote adhesion of the coating on the textile. The ceramic oxide (alumina) layer that followed was deposited again using the same thermal spray technique. Optimization of the critical APS deposition parameters was also performed for the oxide layer. Ιτwas shown that after deposition the fabric used as substrate remains unaffected, exhibits uniform deposition of both layers and fabric texture is followed by the coatings system. Optimization of thermal spray deposition parameters was performed for each deposited layer on the textile substrate. Different optimized set of parameters were selected with the aim to maintain the coating adhesion and simultaneously minimize the weight gain of the textile.
The treated textiles obtained through the thermal spray deposition of ceramic materials were, in fact, successfully used in combination with untreated and alternatively treated fabrics, for the development of lightweight (ca. 5.7 kg/m2) ballistic resistant protective panels. In the frame of SMARTPRO it was not possible to obtain a panel containing ceramic-coated fabrics and exhibiting both protective properties with that weight, even though further trials and assembly combinations could lead to such result.
Application of carbide and graphene-coated carbide particles
The popularity of silicon carbide (SiC) for use in lightweight armour systems is increasing rapidly, mainly due to the significant improvement in cost/performance ratio of SiC seen in recent years relatively to established materials like alumina. Moreover, despite the fact that SiC has a high/similar density (3.21 g/cm3) compared to other ceramics like B4C and Al2O3, it offers better resistance for impact pressures above 20 GPa (typical value for large ammunitions and impact at high velocities) .
For the application of the SiC particles the simple technology of pad-dry-curing was investigated here, in order to allow easy scale-up of the process at industrial scale. Pad-dry-curing also allows the deposition of a thin coating layer, leading to low weight increase compared to other technologies, such as spray coating. Since padding requires the immersion of the textile support into a solution, a specific particle/polymer dispersion had to be prepared. Aliphatic polyurethane (PU) resins were selected as the most suitable carriers for the particles. A challenge in ceramic coating application is the homogeneity of the ceramic oxide in the polymer dispersion. Ultrasonic (US) treatment was used to avoid agglomeration of solids in the liquids and induce fragmentation phenomena which reduce the particle size, ensuring that a large superficial area is available to interact with impact energy, maximising ballistic and stab resistance effects.
According to previous results, SiC dispersion (SiC: 10%wt./v; SILCOSPERSE: 10%wt./wt. SiC; US treatment @20 kHz for 20 minutes) was mixed (ratio 1:1) with a commercial PU resin, SANCURE 898. Since energy absorption is one of the most significant parameters in ballistic/antistab performances, the application of ceramic particles onto Kevlar® substrates was paired with the deposition of a thin nanofibrous layer before impregnation, considering that nanofibers significantly increase energy absorbing capability during impact.
In the frame of SMARTPRO, SiC-coated Kevlar® fabrics were successfully used in combination with untreated layers for the assembly of protective panels exhibiting both ballistic and stab resistance while weighing 5.76 kg/m2. It is worth noting that, while a process for the production of graphene-coated SiC particles was successfully established, the graphene coating did not appear to further enhance the protective properties and was not further explored in the project.
Application of crosslinkable, side-functionalized aromatic polymer
This work involved the synthesis of aromatic polyethers bearing side cross-linkable double bonds with optimized molecular weights, their coating onto selected Kevlar® fabrics and subsequent cross-linking. In specific, the target was the development of uniform high polymer loading Kevlar® fabrics followed by a thermal cross-linking procedure in order to further improve the strength and energy absorbing capability of the polymer-coated Kevlar® fabrics.
First, the newly synthesized copolymers were optimized in terms of molecular weight to obtain polymers with excellent film forming properties. Pilot scale monomer and polymer synthesis (up to 300g) was also accomplished to meet the needs of the project.
Regarding the coating of Kevlar® fabrics, in order to accomplish high polymer loadings and uniform coating, different methods (such as immersion into the polymeric solution and pad-dry cure) were applied. Although pad-dry-cure resulted in uniform coating, the polymer loading obtained was low. On the other hand, immersion of the Kevlar® fabrics into polymer solution with high concentration resulted in very high polymer loading, but low quality of the coating. Thus, an optimization of the conditions (polymer concentration, the number of times the Kevlar® fabric is dipped into the polymeric solution, etc) was conducted to produce uniform, high polymer loading on Kevlar® fabrics with improved mechanical properties. Indeed, we succeeded to produce Kevlar® fabrics with satisfactory polymer loading (12-15 wt%) and uniform coating using a homemade set up.
The thermal cross-linking process was selected among others (e.g. chemical cross-linking) as an easy way of creating an intermolecular polymer network with improved mechanical properties. The presence of propenyl groups enables thermal cross-linking without the need of any cross-linking agent. Optimization of the thermal cross-linking conditions in terms of temperature, time and air conditions took place. Thus, the Kevlar® fabrics were thermally treated under inert atmosphere at 260oC for 30 min up to 1h to be efficiently cross-linked.
Lightweight panels prepared using the optimized thermally cross-linked Kevlar® fabrics with high polymer loading passed successfully both stab and ballistic resistance tests.
Application of graphene coating
Multilayer graphene is an exceptional anisotropic material due to its layered structure composed of two-dimensional carbon. Having a breaking strength of 42 N m−1, where a hypothetical steel film of the same thickness would have a breaking strength of 0.4 N m−1, graphene is more than 100 times stronger than steel . Accordingly, it could be used to enhance the performance of Kevlar® fabrics.
Within the project, a combination of graphene and polyurethane (PU) was investigated, considering its ability to melt and reseal around the path of the projectile as it impacts the surface and passes through the bulk . Graphene nanoplatelets having a thickness of 10-30 nm, plane dimensions 20 to 50 μm, carbon content over 97 % and bulk density between 0.02 and 0.1 g/cm3 were used. A coating process was used to apply the nano-dispersion.
Thus, graphene (50 wt %) was added to a PU dispersion and then dried and fixed at 60°C for 1 h. The amount of graphene/PU resin deposited on the fabric is around 20-25 g/m2, while the presence of graphene was confirmed by SEM. Crock-meter tests (10 cycles) confirmed that the abrasion resistance is improved since there is no detachment of the coating even if the system is more rigid as confirmed by Bending Rigidity test (BFAST= 1300 µNm).
Assembly of the protective panel
Following the application of alternative surface treatments as described above, resulting textiles had to be selected, combined and assembled in protective panels which would provide Level IIIA ballistic resistance and Level 1 stab resistance, while weighing 5.72 kg/m2 or less (target set in the project). The assembly of the protective panel is itself a challenging task, as various parameters have to be defined, including: the type and number of fabric(s) layers, the assembly sequence (i.e. which fabrics are on the strike face and which are close to the body) and the sewing pattern. A key consideration when aiming at both ballistic and stab resistance is to combine rigid layers (which are generally effective in inhibiting penetration by sharp blades, i.e. stab protection) with more flexible ones which contribute to energy dissipation and, therefore, enhance the ballistic resistance of the panel. Accordingly, most of the panels developed in the project consisted of treated and untreated layers, the latter constituting the more flexible section of the armour.
Testing of the protective panel
Ballistic tests - Ballistic tests were performed according to NIJ 0104.4 on 40 x 40 cm panels. Since the target was to reach Level IIIA ballistic protection, the tests were performed with a 9-mm caliber FMJ (124 g) at a velocity over 435 m/s. According to the standard, a panel passes the test if both following conditions apply: (a) the panel is not perforated and (b) the back-face-signature (trauma) is lower than 40 mm.
Stabbing tests - Stab resistance was assessed according to NIJ 0115.0 under the conditions for protection Level 1. Accordingly, each panel was first hit with a knife at an energy of 24 J. Provided that the penetration of the knife was less than 7 mm, the panel was hit again at an over strike energy of 36 J. At this second strike, the penetration of the knife should be lower than 20 mm.
Results
Among the many different types of panels tested, several passed either the ballistic or the stabbing test but failed the other, while only two panels successfully passed both tests. One of them consisted of untreated Kevlar layers and layers treated with nanofibers, SiC particles and PU and weighed 5.76 kg/m2, while the other consisted of untreated Kevlar layers and layers treated with crosslinked polymer and weighed 6.00 kg/m2.
Scale composite for impact protection
Aiming to develop components for impact protection of extremities, we focused on the use of composite materials in the form of scales. Scales geometry allows flexibility, even when using rigid materials. Accordingly, an investigation on the protective scales geometries was first performed to evaluate the level of protected area and the flexibility that can be given to the protective ensemble. Three configurations were evaluated, namely patterns of triangular, square and hexagonal segments/scales. Scale composite prototypes were produced by 3D printing, aiming to reproduce the CAD designs and define the optimum scales structure. Based on the evaluation of the prototypes, the hexagonal structure was selected, since it provides the optimum balance between flexibility and protected area. A system comprising of two layers of scales structures was used so that one layer covers the unprotected areas of the other (edges of the scales). Furthermore, assessments were performed to define the optimum scales size.
Next, different composite materials were manufactured using Kevlar®, carbon and hybrid fabrics as reinforcement, to select the optimum material for the scales. Composites containing 4 to 10 fabric layers were manufactured by epoxy resin infusion and compared in terms of cost, nominal weight, thickness and penetration force.
Having selected the optimum material and geometry, samples of scales composites were manufactured using Kevlar® fabrics as reinforcement and epoxy resin as the matrix. The hexagonal pattern was created in the specimens through milling or water jet cutting (depending of the specimen type). Finally, the scale composites were glued on a Kevlar® textile support through contact glue with pressure and activation with temperature.
Armours’ carriers
In SMARTPRO, body armour carriers were developed for patrol officers, as well as for riot police and special units’ officers, considering the tasks performed by each group and the respective users’ requirements. It is worth noting that end users were actively involved in the design of the body armours since very early in the project by providing guidelines to the manufacturers and by evaluating early prototypes developed as design demonstrators.
Patrol officers’ body armours’ carriers
The carrier of patrol officers' body armours has the same design as those currently used by patrol officers of Mossos d’ Esquadra (participating in the consortium), since it totally satisfies the end users, who had no requests for further adjustments. The key of the design is that the armour looks more like a normal vest, with two flap pieces closing on the front. However, the protective panel covers the entire area of the torso as it is placed in a single-piece pocket underneath the flap pieces. Protection is also ensured on the back and the sides. The prototype was kindly manufactured by FECSA, after receiving required materials by consortium partners.
A 3D knitted polyester fabric manufactured in the project was used as a liner to facilitate air circulation and enhance comfort properties. The fabric of the carrier was Taffeta Polyamide cordura that had been surface treated with photocatalytic polymer to achieve self-cleaning and de-polluting properties.
More specifically, within SMARTPRO, a photocatalytic finishing was set-up and applied on the outer fabric of the carrier to reduce maintenance requirements and, as side effect, to decompose chemical/biological harmful substances. The photocatalyst most frequently used is, undoubtedly, titanium dioxide, produced in large amounts and low cost compared to other semiconductors. However, according to National Institute for Occupational Safety and Health (NIOSH) study (Publication No. 2011–160, April 2011) fine particle (diameter < 100 nm) poses some safety concerns. In 2006, the International Agency for Research on Cancer (IARC) reviewed TiO2 and concluded that there was sufficient evidence of carcinogenicity in experimental animals and inadequate evidence of carcinogenicity in humans (Group 2B), “possibly carcinogenic to humans” [IARC 2010]. To overcome this limitation within SMARTPRO a photocatalytic polymer was used to replace toxic nanomaterials. Sulphonated Polyetherether Ketone (SPEEK) was synthetized at large scale and applied onto textile surface to generate stable radicals through the inhibition of proton transfer mechanism via hydrogen abstraction from a suitable donor. The hydrogen donor identified within the project was polyvinyl alcohol (PVA), since it is water soluble and commercially available. A SPEEK/PVA formulate was optimised (solid content 5.25%wt./v; composition: 95% wt. PVA, 5%wt. SPEEK + 5%wt. PVA, crosslinker, glutharaldehyde) and applied by spraying onto the selected outer fabric of the carrier. The presence of photocatalytic compound onto cordura fabric was monitored and degradation tests carried out on a model dyestuff proved that the photocatalyst degrades organics.
Special units and riot police officers’ body armours
A modular body armour carrier was designed and developed for riot police and special units’ officers. It is a full 360 degrees’ modular armour carrier vest, capable of holding front and rear soft armour inserts and hard plates. It can adopt on secondary neck protection, throat and shoulder soft armour brassard protective panels. The system has drop down and integrated front groin and rear Coccyx protection, making this a versatile combat armour carrier system. Each part of the attachments has an opening to insert the protective soft panels. The front vest cumber-band armored panel folds over the rear one. The protective plates can be inserted in the vest pockets by openings on the left or the right of the vest. On the rear, the vest carries two rescue grab handles for casualty evacuation.
Smart systems
Smart systems were developed and integrated in the body armours, to alert end-users in specific hazardous situations and increase their awareness. These include: heart rate sensors, nanotechnology-based gas sensors and textile antennas, as described in the following sections.
Heart rate sensor
The function of the heart rate sensor is to detect major injuries of the wearer by measuring valuable health parameters. The main work of this development is focused on textile electrodes that are integrated into the garment of the body armour wearer. These textile electrodes have to provide good (continuous) skin contact, low surface resistance and textile yet (machine) washable characteristics.
The development of a heart rate t-shirt for health monitoring is sectioned in three stages:
• Yarn-based conductive electrodes and positioning
• Connection of the heart rate measurement
• Heart rate sensor hardware and connection to body armour
Textile electrodes: Electrical conductive yarns are commercially available (by Statex Shieldex®, Imbut Elitex®, Amann Silver-tech®, Madeira HC®) especially for smart wearables or smart textiles though textile technologies for manufacturing are widely spread. Common fabrics for electrode application are knitted, woven, non-woven or embroidered fabrics (double-lock stitching). These structures have a two-dimensional structure and a rather rough surface. A technology providing three-dimensional electrode structures is moss-embroidery. Moss embroidery is created by a one-thread embroidery system where the needle goes through the carrier material and pulls the yarn out from under the needle, plate side up. Then, a loop is created by a rotary motion of the needle on the upper side of the carrier material. Repeating this pattern frequently produces a moss-like surface. The material used for electrical conductivity is Statex SHIELDEX® 110/34 dtex 2-ply HC, which is a silver-plated polyamide-based twined yarn. This material shows very good processability due to small yarn diameter compared to needle hook size. Electrodes in elliptical shape were manufactured and ECG measurements were conducted using an ECG mannequin. The moss-embroidered electrodes were compared to conventional adhesive electrodes and an ECG-shirt with knitted textile electrodes. The moss-embroidered electrodes showed high sensor agreement and performed better than knitted electrodes, which are already in use for commercially available products.
Two prototype shirts were manufactured by moss embroidery of Statex SHIELDEX® 110/34 dtex 2-ply HC in elliptical shape. Measurements on the ECG mannequin showed very good results regarding signal accuracy; though first tests conducted on a subject showed following issues that had to be further developed:
• positioning of electrodes
• continuous high conductivity of textile electrodes
• minimized stress and length of signal transmission
Therefore, tests were conducted using a shirt prototype with eight different electrode positions aligned throughout the shirt width and below and above the breast muscles. The shirt design was developed for female and male wearer’s though testing was conducted with a male subject. Different combinations of the electrodes on the chest area were tested and the results were evaluated regarding average QRS peak and lowest disturbance by movement. The optimum positions of the electrodes were defined accordingly, regarding highest voltage as well as minimized influence while moving. Those results lead to the used electrode configuration according to the first lead of Nehb. Additionally, a third electrode was positioned on the right hip as a ground electrode. For testing purposes, an adhesive electrode was chosen as ground electrode for possible positioning.
Due to female chest shape the vertical distance between left and right electrode was increased by about 5cm. For the end-user evaluation, a male t-shirt in large size and a female t-shirt in medium size had to be produced. The measurements were taken according to EU size standards subtracting minimum of 5 centimeters to obtain skin fit shirts. This also ensures continuous contact of the electrodes and the skin and therefore continuous heart rate measurement. Furthermore, testing was conducted with water and electrode gel to provide lowest skin surface resistivity. The electrodes were embroidered with a wave-like grid pattern to ensure overlapping between yarns and homogenous distribution. To reduce elongation within the textile electrode and therefore influencing signals a non-stretchable polyester substrate was chosen (Stiffy® 1950 by Gunold GmbH, Stockstadt, Germany). This material shows high flexibility and in the meantime the electrode area on the t-shirt textile cannot be stretched.
Connection of textile electrodes: Previous electrode prototypes were connected by press fasteners. These connectors are also used for commercially available adhesive electrodes. The influences from press fasteners on the transmitted signal are insignificant. The press fasteners were implemented in the center of the electrodes. Afterwards polyurethane (PU) film was applied by applying heat (ironing). The PU film showed following effects within testing: (a) reduced influence on HR signals after external contact (touch) on the outer electrode surface and (b) better water content management due to waterproof sealing of the electrode back side.
The connection between heart rate electrodes and ECG hardware device is based on cables and press fastener connection. A direct connection from heart rate shirt and body armour provides following advantages compared to a Bluetooth® wireless connection: (a) Secure and non-interfering data transmission, (b) External power supply can be used, (c) No additional integration of device/PCB onto heart rate shirt. Three connector pins are then combined to an audio jack (3-pin) that can be used with the ECG hardware device.
Heart rate sensor hardware: After intensive research, the hardware of choice was found in “SparkFun Single Lead Heart Rate Monitor-AD8232” (by Sparkfun Electronics, Niwot, USA) which can be easily integrated in the Arduino programming libraries. The audio jack cable can be easily connected into the socket and a red LED shows heart rate signals by different intense blinking. The signal reading (as low voltage current) is registered by the ECG module and processed within the Arduino® hardware (Arduino® Lilypad) and software. The ECG information is processed by QRS peak counting within the software. After a minimum setup time (e.g. 10 seconds) the heart rate (in beats per minute) is sent to the Arduino® Lilypad.
Textile antenna
Especially for on-body use, planar antennas with a ground plane such as patch antennas are the most suitable topologies since these reduce the radiation in the direction of the body. The three main components of each patch antenna are Radiator, Ground plane (both conductive) and Substrate (non-conductive). The radiator as well as the ground plane must have a high conductivity and a low surface-resistance. These layers are produced using conductive textiles. The substrate has to be a non-conductive material with low permittivity (εr ≈ 1) and low loss (tan δ ≈ 0). This can be achieved by using a non-compressible textile such as fleece, a non-woven fabric or felt. The size of the antenna corresponds directly to the frequency used: A lower frequency results in a bigger antenna.
A first prototype for GPS antennas was developed and manufactured as follows: (a) The antenna design is printed on a double-sided adhesive sheet, (b+c) The adhesive sheet is glued to the conductive textile using an iron, (d) Shows the material necessary for the cutting of radiator: The conductive textile is cut along a ruler using a scalpel, (e) Finished radiator with conductive sheet on backside, (f) Prepared layers of non-woven substrate: these two layers are glued together using the same method of double-sided conductive sheets, (g) Assembly of antenna parts and (h+i) Finished prototype.
After suitable antenna topologies, frequencies, materials, designs and textile production technologies were identified, evaluation of the HF characteristics of the textile antennas was initiated and the influence of the antenna performance under bending conditions was evaluated. It can be concluded that the antenna performance is negatively affected by the combination of bending and human skin contact. However, the determined decrease is so small, that it will not negatively affect the performance of the textile antenna within the body armour.
Antenna performance was evaluated in a field test. Therefore, the antenna has been integrated into a jacket comparing the developed textile GPS antennas to conventional GPS antennas and receivers. A Ceramic Patch Antenna „Neo 6M“ by u-blox AG, Germany and a GPS-mouse „HOLUX GR-213“ by „HOLUX Technology,.Inc“, Taiwan were used for comparison.
The results of the field tests show that the average accuracy of the textile antenna was higher compared to the tested conventional antennas, due to lower positioning errors (in meters). The human body influences the antenna but it is not relevant for the antenna performance. The GPS-mouse used for the testing is comparable to other GPS sensors integrated in other devices, e.g. smartphones. Irrespective of the size of commercially available GPS sensors, the textile antenna showed the highest accuracy in the field test in terms of positioning compared to established systems such as a ceramic patch antenna or a GPS-mouse.
Within the project conductive fabrics were produced by SOLIANI. The material type “Volta-VO.NICU” shows the lowest resistivity (8.2 mOhm/sq) being lower than the “Statex Kassel” material which was used for the first antenna prototype. Both materials show almost the same thickness but differ in weight per square meter. The “Volta-VO.NICU” was selected for the production of further antenna prototypes, e.g. GPS and GSM communication. The architecture and connection of the systems is as follows: the GPS module is receiving GPS raw data and in the meantime the GSM module is checking network status and connection. The GPS raw data is then sent to a remote server where it is interpreted as latitude and longitude GPS data. Both GPS and GSM antenna were finalized with electro conductive fabrics “Volta-VO.NICU” by SOLIANI. The final connection of the GPS localisation hardware is provided by µFL cable connectors. The GSM/GPS module is combining GPS receiver and GSM sender. The GPS data is then provided to Arduino® Lilypad #1 which is also detecting the heart rate.
Gas sensor
Motivation: Gas sensors are devices that can convert the concentration of an analyte gas in an electronic signal and are an important component of devices commonly known as “electric noses”. The current Task was devoted to the development of wearable miniature gas sensors able to rapidly detect and monitor toxic gasses for the efficient use of both law-enforcement personnel and civilians. The main objective wa to fabricate sensors that: (i) operate reliably in the detection of toxic chemicals within an acceptable reaction time, (ii) are able to detect agent concentrations at levels which are lower than those which pose health risks, (iii) are not affected by other factors in the environment such as humidity, (iv) operate at short reaction and recovery times, and (v) can be fabricated so as to be portable and wearable.
Why resistive sensors: Several types of gas sensing mechanisms have been proposed and explored. The main categories include: electrochemical, catalytic bead, photoionization, infrared point, infrared imaging, semiconducting materials (resistive), ultrasonic and holographic. Resistive sensors stand out as a promising type for the fabrication of miniaturized devices and due to the simple sensing mechanism. Metal oxide semiconductors (MOS) are used as the sensing material. Nanostructured MOS sensors detect gases based on a chemical reaction that takes place on the material’s surface, when the gas comes in direct contact with the MOS. The target gas interacts with the surface of the MOS film (generally through surface adsorbed oxygen ions), which results in a change in charge carrier concentration of the material. This serves to alter the conductivity (or resistivity,) of the material. An n-type semiconductor is one where the majority charge carriers are electrons, and upon interaction with a reducing gas an increase in conductivity occurs. Conversely, an oxidising gas serves to deplete the sensing layer of charge carrying electrons, resulting in a decrease in conductivity. This change is used to signify the presence of the gas and may be used to calculate the gas concentration.
ZnO nanowire-based gas sensors: The work performed in SMARTPRO pursued rational synthetic routes for the controlled growth of nanowire-based arrays, which would demonstrate high performance in specific gas sensing and in particular carbon monoxide (CO). CO is a colorless and odorless gas, hence undetectable to humans. It is considered as one of the leading cause of poisoning worldwide, especially in many industrial countries. The maximum time weighted average exposure is 35 ppm over an 8 h period. Owing to the ubiquitous presence of CO, such sensors have a dazzling variety of applications, not just for law enforcement authorities, also in home safety, in measuring atmospheric concentrations, in the exhaust of cars, and for process monitoring in industrial plants.
The synthesis and characterization of the ZnO nanowire (NW) arrays and a work station for gas sensing were realized during the first period of the project. ZnO NW arrays were grown using hydrothermal synthesis. Over that period, we accomplished the development of a synthetic route for the controlled and reliable growth of ZnO nanowire arrays with high aspect ratio and surface area, good crystallinity and negligible defect density, and appropriate adhesion and orientation normal to the substrate. The method is fully controllable and shows very high degree of reproducibility. In parallel, the development of a home-made set-up took place for the detailed characterization of the ZnO-based nanomaterials grown as efficient media for gas sensors.
Optimization of sensor parameters was based on a feedback mechanism in relation to the materials synthesis process in order to achieve the best morphology. Four main parameters are used to characterize the performance of a gas sensor:
- the sensor sensitivity (for reducing gas),
- the response time defined as the time required to achieve a 90% change in the resistance upon the supply of the gas,
- the recovery time defined as the time required to achieve a 90% change in the resistance upon removal of the gas, and
- the working temperature.
More than 100 experiments were conducted in order to optimize both the gas sensing materials and the experimental set up to obtain the optimum conditions for the gas sensors under development. Several parameters related to the material development have been examined:
• The type of the substrate (soda lime glass, silicon, quartz, and the conductive glass/FTO) were used in order to explore the role of conducting and insulating substrates on the gas sensor performance.
• The influence of the seed layer thickness deposited on the soda lime glass exerted on the gas sensing efficiency of ZnO NW arrays was investigated.
• The influence of the (i) operation temperature, (ii) gas concentration, (iii) doping with Al atoms, and (iv) decoration with noble atoms, on the gas sensing efficiency of ZnO NW arrays has also been explored.
The results obtained demonstrate that the developed materials exhibit far better sensing performance for the CO gas detection, in comparison to literature data, as regards both the operation temperature and the sensitivity parameter.
Integration of smart systems on the body armours
The developed systems – heart rate sensor, textile antennas and gas sensor – had to be integrated into the body armour meeting user-requirements such as: flexibility to minimize user movement hindrance, size and weight of the systems to provide maximum wearing comfort as well as water proofness for duties in heavy rain. The prototype used for the integration was the female version of patrol armour, manufactured by FECSA.
Waterproof encapsulation - In order to assure a total functionality even with adverse meteorological conditions like raining, water protection of the smart systems was carried out. It is important to remind that the wires are not affected by water, as they are already recovered with a polymer. The parts that can be affected in presence of water are the connections and the electronic components (e.g. the gas sensor, the antennas or the battery). All the components with its encapsulation are extractable with Velcro in the case of washing the armour vest. The rain protection of the electronic components is based on the encapsulation with polymeric film (translucent PVC film). The film was welded with an ultrasonic welding machine so that each component has its waterproof bag. When needed, an opening using Velcro was made. Besides, a welding trial to join the Velcro with the polymeric film has been done to avoid sewing it, since the little holes produced by a stitch can generate a weak point.
Waterproof validation - A test was done to verify the correct performance of the smart systems when it is raining. In order to assess this, the Bundesmann test was performed for an encapsulated electronic system, following the standard EN 29865. It is important to keep in mind that this is an approximation to the reality of the smart systems in the armour vest. Rain (drops of water) will never directly contact with the PCBs and the battery encapsulated on the vest, as they are placed behind the fabric of the armour and are not visible.
Textile antennas - After encapsulation, the textile antenna was integrated on the highest position within the body armour. This position was chosen in accordance to the user-requirements by security and law enforcement experts as it provides least hindrance by any carried accessories such as gun straps. Hence, it improves the antenna performance. Positioning tests conducted showed best performance for the textile GPS antenna on the highest position. The placement for the GSM antenna also requires a high position within the body armour, similar to GPS antenna. Due to limited space within the carrier a different position was chosen for the GSM. The textile antennas and the PCBs are integrated within the carrier for the anti-ballistic panel. Therefore, it is placed behind the panel to maintain higher safety in case of damage. Except the GPS antennas, all hardware components were integrated in the waist area of the vest. This provides a good accessibility to the battery while wearing the armour whilst ergonomics is not hampered. The battery itself is integrated in the Velcro pouch on the front side for easy access in case of removing or charging. The encapsulated antennas are integrated with Velcro straps to the inner side of the carrier (spacer fabric). The Velcro straps were integrated using sewing which cannot be seen on the inner side of the body armour. Three straps are used for the integration of each antenna.
Connection of all systems - In the latest stage, a single Arduino® Lilypad is able to substitute single Lilypads for ECG and GPS/GSM modules.
Gas sensor - The integration of the gas sensor provided by FORTH is based on the following steps:
(a) Miniaturization of the gas sensor and wire reorganization: Achieving the minimum possible volume is a decisive point in order to achieve a comfort for the user. The polymeric white part was replaced by small wires and a bigger wire was welded to connect the LED. Furthermore, connectors were added to achieve a more practical use of the entire system.
(b) Design concept housing and 3D printed prototype: In order to protect and locate the sensor, housing was designed using CAD software. It consists of two parts joined with screws that can be separated if needed. The housing was fabricated using 3D printing technology (Fused Deposition Modeling, FDM) and painted in black to make it less visible.
(c) Integration on the body armour: Finally, the integration of the sensor on the body armour was performed using high resistance Velcro that allows the system to be easily extracted if needed and an elastic band that covers a part of the sensor encapsulation and assures a consistent location.
Life Cycle Analysis and Life Cycle Cost
Life Cycle Analysis – To demonstrate the sustainability of the body armours developed in SMARTPRO the environmental impact related with their production was computed using a Life Cycle Assessment (LCA) approach. LCA is an analytic method to address the environmental aspects and potential environmental impacts throughout a product life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal (i.e. cradle-to-grave). The methodology is defined and regulated by the ISO 14040 and 14044 standards, while the broad provisions stated there have been further specified in the ILCD Handbook Guidelines which were taken as a reference for the development of this analysis. The functional unit chosen for the analysis was 1 body armour (size M).
In detail, a cradle-to-use phase approach was considered; thus, the analysis encompasses all cycle phases starting from the production of raw materials, spinning, fabric production, dyeing and finishing processes and chemicals used for the functionalization of the fabrics, the assembly of the protective panels and the final armour (including accessories) and specific impacts were computed according to ILCD 2011 method. The environmental performances of the two ballistic and antistab panels developed in SMARTPRO were compared to those of a commercially available armour from SIAMIDIS portfolio, featuring the same protective performances. Both armours developed in SMARTPRO have lower environmental impact than the reference one (total ecopoint compared to the reference armour is lower by 13 % and 5.3 % for the armour containing Kevlar®+nanocomposite structure and that containing Kevlar®+crosslinked polymer, respectively). The reduced environmental impact is due to the lower amount of Kevlar® fabric used in the new panels, as the production of such high-performance yarns appears to be the factor contributing the most to body armours’ environmental footprint.
Cost estimation - Technical performances of the functional textile exhibiting both ballistic and stab resistance properties have been paired with an economic study aiming to define the final price of body armour and its main components (in particular the protective panel). A preliminary analysis related with the production costs of the functional textile was assessed. Accordingly, the costs for the production of SMARTPRO protective panel have been estimated and compared with the costs for the production of conventional products featuring same technical performances (Ballistic: LEVEL IIIA; Antistab: LEVEL I).
The outcomes related with the economic evaluation of the efficient SMARTPRO solutions show that the most promising solutions seems to the the combination of Kevlar® and Nanocomposite since it allows to reduce up tp 10% the production costs compared to alternative solutions available in Siamidis portfolio featuring the same technical performances.
Potential Impact:
The global body armours market is expected to reach 4,8 billion Euros by 2024 (value in 2015 was 3,35 billion) according to Grand View Research Inc. Technological advances are the key instruments in accelerating the market growth, as innovative concepts, such as “liquid body armour” and “dragon skin” are gaining momentum. In addition to this, the demand for modular body armours is on a rise, due to their features offering enhanced protection. Prominent manufacturers of personal protective armours are increasingly investing in R&D activities for the development of advanced fibres, fabrics and other materials to improve the effectiveness of the body armour. It is worth noting that body armours exhibiting ballistic protection of Level IIIA accounted for 21.8 % of the overall market share, in terms of revenue, in 2015.
Law enforcement officers increasingly need to carry more, utilize more technology and operate in extreme environments. Advances in materials and technologies are thus required to alleviate the increased weight and related fatigue arising from these new demands.
The most significant potential requirements of future officers are listed below:
1) Weight reduction: A recent study by Defence Research and Development Canada indicates that increased weight and heat retention may reduce users’ performance by up to 25 %.
2) Thermal management for comfort: Thermal management covers both insulation in cold conditions and cooling in hot conditions, even if the latter is more critical. Heat stress is a serious concern because it can affect the health and safety of the individual as well as operational performance.
3) Biological and chemical protection: With growing concerns over the possibility of terrorist attacks using biological and chemical threats, protection is of increasing importance. Chemical threats refer to nerve and blister agents, while biological threats include bacteria (e.g. Anthrax), rickettsia (e.g. Typhus), toxins (e.g. Botulinum Toxin) and viruses. There are two parallel and complimentary research streams in this area: sensors and protective clothing. Sensors are important for early detection of contaminants, while light, comfortable and protective wear is essential for survival.
4) Modularity and flexibility: Armour should defeat high level threats, while maintaining the lowest possible weight and provide the wearer with unrestricted movement. Extremity armour is not a new concept. However, it is important to protect vulnerable areas with a minimal increase in weight and without adversely affecting the ability to perform operational tasks.
5) Power/data/conductive applications: The officers of the future will be carrying increasing amounts of high-tech equipment. Along with the need for new power systems and storage, novel ways to transfer data are needed. Examples of applications include antennas that are integrated and/or embedded within clothing or other pieces of equipment, flexible displays, equipment that is powered either through wired or wireless systems, novel interconnects for equipment and power harvesting and energy storage for technology life extension. In some cases, integrating these applications into intelligent textiles may be desirable.
It is important to note that SMARTPRO has addressed the above challenges by focusing on the development of lightweight, comfortable and modular body armours incorporating nanotechnology-based sensors for the detection of hazardous gasses, heart rate sensors and textile antennas.
It should be noted that using the technologies and materials developed in SMARTPRO military body armours as well as body armours for civilian use may be manufactured. Interestingly, the civilian demand for personal body armours accounted for 7.4% of the total market share (in terms of revenue) in 2015 and is anticipated to reach 7.7 % in 2024, as the significant rise in the crime rates and incidents of mass shooting is driving the demand for armour vests among civilians. It can also be anticipated that SMARTPRO results will create economic benefits for the EU through dual use applications. In fact, the materials developed for law enforcement could be transferred to the general public, through incorporation in protective gear for extreme sports or motorcyclists.
Last but not least, considering that the technological advancements of SMARTPRO are paired by a reduction of the environmental impact of body armours, the results of the project could bring significant environmental benefits and decrease the environmental footprint of the body armours’ sector.
List of Websites:
www.smartpro-project.eu
or contact s.pavlidou@ebetam.gr (Silvia Pavlidou, MIRTEC S.A.)
