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Advanced Structural Light-Weight Architectures for Electric Vehicles

Final Report Summary - E-LIGHT (Advanced Structural Light-Weight Architectures for Electric Vehicles)

Executive Summary:
The e-light project has run for three years, focusing on developing an innovative lightweight architecture for urban EV. The work has been revolved around three main areas: requirements to be complied, materials and manufacturing, and the performance of the designs in terms of structure, vibrations and safety.

The main findings of the project have been:
1. Developing a methodology to short the requirments from the Original Equipment Manufacturer (OEM) to be translated into engineering language and to define the properties to be achieved by the materials and the designs.
2. A deep analysis of most appropriate materials, and their most efficient manufacturing processes to be used by the automotive industry. This work led the consortium to define the decision matrices and to present a methodology that will support automotive industry with a powerful tool in the design of EV.
3. An innovative design, composite intensive (Carbon Fibre Reinforced Polymers) that actually achieves 50% weight reductions when compared to the starting point of the project, which was an actual EV earlier developed by Pininfarina in metallic spaceframe.
The knowledge generated by the project, has been summarised and presented in the form of three public guidelines to support SME in the automotive supply chain to increase their competitiveness and understand the lightweight design that will drive newly introduced EV.

Three different guidelines have been completed:
1. General design guidelines/requirements: The project results, and main findings, in terms of the most suitable materials and their use in the developed architectures, the modules to be used in the EV, and the manufacturing techniques have been summarised and presented in this document. The document also provides designers with general recommendations with regards to the further study of body in white solutions for urban EV. This document will support industry designers in altomotive industry to achieve lightweight EV architectures minimizing costs and manufacturing times, and maximising production.
2. General Safety requirements: The document provides a summary of current safety and testing procedures that should be applied to EV without changes, European and USA standards have been analysed and a detailed list of new requirements for electric motors, power electronics and battery packs safety has been produced, with special attention paid to crash behaviour.
3. Testing procedures recommendations: This document summarised the assessment to be performed in the early stages of the design phase, since an accurate assessment of vehicle requirements is key to the definition of targets for new vehicle concepts. To achieve this objective a combination of industrial experience, detailed objective testing, specialised computed aided engineering and dynamic analysis tools are needed. The proper way to combine these skills is presented in this document to support evaluating new EV concepts.

Project Context and Objectives:
The project targets urban electric vehicles. Their specific peculiarities in several areas make necessary to study new solutions specifically designed for them. Therefore, e-light aimed at exploring all the aspects and requirements needed for designing optimal electric vehicle architectures. This approach proposes a methodology that will support designers to achieve lightweight design. Advanced metallic materials, reinforced composites, joining and manufacturing technologies, as well as modularity, ergonomics and safety are the main topics considered within this project.

This project is using the Pininfarina NIDO electric vehicle as the starting point to decrease the weight of the body in white by analysing new materials and technologies. Electric vehicles have a different cost-benefit ratio when compared to internal combustion vehicles. By using the NIDO, and decreasing substantially the weight of its architecture, while maintaining the safety, modularity and ergonomics, the partners will develop a design methodology for electric vehicles. e-Light has monitored and analysing the safety regulations for electric vehicles that are being reviewed. This methodology, together with the testing requirements for components, materials and joining technologies, was used as the core for the design guidelines.

The specific e-light technological and measurable objectives to improve the NIDO concept are:
- Architecture development with a maximum vehicle weight of 600 kg (without batteries), a maximum body in white weight of 200 kg, (although this target was decreased to 150 kg. after month 18) and an electric motor in the range from 25 to 35 kW.
- Ergonomics of developed EV architecture: on board space 4 passengers.
- Suitable and feasible joining technologies and manufacturing processes for the multi-material EV architectures developed.
- Equivalent performance to an IC vehicle architecture (improved compared to quadricycle and as close as possible to class A) regarding crash, fatigue and NVH.

e-Light has used the knowledge and experience obtained achieving those targets to produce design guidelines and testing procedures. Those will allow companies working in the automotive supply chain to increase their knowledge, and will be oriented to SMEs. This will increase their competitiveness by providing those companies with a technological added value.

e-Light is a small focussed collaborative project funded by the EC under the FP7. There are 7 partners in the project (CIDAUT, USFD, Tecnalia, Ricardo, EAST-4D, Pininfarina and PVF) from 5 different countries, and it has a budget of 2,938,649 €.

The technical objectives of the project has been broken down in the following technical objectives:
1. Identification of architectural requirements for EV architectures to be developed, focusing on lightweight for different battery and electric motor configurations (front or rear stand alone, wheel in hub). The main themes to be studied in order to achieve lightweight are modularity, ergonomics and safety requirements.
Modularity of new electric propulsion systems allows innovative architectures. Those architectures present several advantages, when compared to conventional vehicles, especially increasing the accessibility and the on-board space. Other advantages those architectures present are improved aerodynamic efficiency, as well as improved safety by means of having the possibility of placing those modules and components in the most efficient way without IC vehicle’s thermal, mechanical and geometrical limitations. One relevant issue regarding future EV architectures is the effect that battery volume and mass will have deciding the optimal EV architecture design.
Electric powertrains allow having very compact elements and components connected to each other by electric plugs and refrigerating conduits. The successful integration of such elements into the EV architecture designed in the E-Light project will have several important advantages over ergonomics and modularity. Those advantages will be studied and optimized to achieve lightweight. Finally, the mechanical, thermal and geometrical limitations due to electric powertrains are less than those due to ICE. The total amount of components, and the range of temperatures those components will have under service conditions, are less than those from ICE, which will also be taken into account.

2. Identification of optimal multi-materials solution to become part of the EV architectures to be developed. In EV the cost-benefit ratio for materials in order to achieve lightweight is very different from conventional vehicles, due to the higher cost of the battery pack while in IC vehicles a small increase in engine power is enough to cover extra weight. In order to demonstrate the industrial feasibility of those materials, the most suitable and feasible joining techniques and manufacturing processes will be studied. Technical and industrial feasibility for multi-material EV architecture is needed to ensure the impact of E-Light project results, as well as their industrial implementation by the European automotive industry.
The effect of the vehicle mass when accelerating and stopping in town and city conditions is another area where the mass of the electric vehicle will have considerable influence on vehicle performance.
If the vehicle brakes this energy is converted into heat. In light vehicles the losses associated with continually creating and then losing kinetic energy are much less. Apart from the importance of minimising vehicle weight, it is also important to try to minimise the moment of inertia of rotating components, as these store rotational kinetic energy. In conclusion, mass reduction in Electric Vehicles is an imperative necessity so light materials not yet considered for mass production shall be taken into account. An exhaustive technical and economical feasibility analysis for new materials considering the lower volumes of the electric vehicles in the short and medium term as well as a Life Cycle Analysis must be realized for the alternative materials. It will be the first step in the aim of reducing the weight.

3. Optimal geometries and designs for designing EV architectures will be analysed, taking into account previously studied architectural requirements and materials. The performance of those architectures from structural, safety, noise and vibration points of view will be studied.
In order to guarantee the performance of designed EV architectures, structural, crash and energy absorption, and noise and vibration simulations will be run over the models for those EV architectures developed in E-Light project. Those simulations will save time and costs associated with prototyping and testing these EV architectures, and allow validating the identification of EV architecture requirements and the materials and joining techniques needed to manufacture them.

4. Definition of design methodology and testing procedures to develop general design guidelines and testing procedures, to guide automotive designers towards more sustainable, lightweight, modular concepts from the very beginning of the design process. The results from E-Light project will be summarized in two documents, “General Design Guideline for EV architectures” and “Testing procedures and recommendations for EV architecture design”. Those documents and the cost-benefit analysis, together with the technical feasibility study, will be the basis for future EV architecture design processes.

Project Results:
The initial activities of e-Light were centred on exploring and developing new Electric Vehicle (EV) architectures from a structural point of view. Those took into account the lack of restraints such vehicles presents when compared to conventional vehicles equipped internal combustion engines. The influences that those architectures have on the Ergonomic, Modular and Safety aspects were covered by e-Light. Those results, together with an analysis of most suitable advanced metallic and reinforced composite materials and their joining technologies were used in defining the overall architecture to be analysed in the finite element simulations that will start on the second half of the project. At the end of the project, the information on materials, simulation and designs will be summarised in Design Guidelines and Testing Procedure Recommendation documents for the automotive industry.

The first activity, carried out during e-Light, was addressing lightweight design by exploring the differences regarding conventional ICE architectures. In particular, the requirements for future EV set the basis of the whole work and defined the Design Drivers and the Design Matrix. The design drivers defined by Pininfarina as vehicle manufacturer, together with the results of reinforced composite and metallic materials study, and the analysis done on safety and functional modules allowed the partners to define the design matrix. The definition and development of these was a team activity, different partners’ involvement, as well as the relationship with regard to the material and manufacturing processes analysis can be summarized in the following scheme:

During the kick-off meeting, it was agreed to develop the Design Drivers from a business case currently ongoing at the Pininfarina premises; the advantage of working on a real car is to use the information and data necessary to perform the further analysis in the future work packages based on an industrial case. These Design Drivers, described in deliverable 2.1 were enhanced to include driver performance expectations.
Taking them as basis, a preliminary Design Matrix was created. This Matrix is an instrument that cross-references different solutions against a list of key factors; each factor has been characterized by a score (weight). The solutions were ranked through the weighted scores. In this way, the best solution could be identified and selected for the next steps. A general diagram of such tool is shown in the following image.
The process adopted to assign values to each design matrix follows a Trade-Off process. Some of the scores have already been evaluated for Pininfarina’s internal business case; the others were, and will be, defined during the e-Light project. This fact means that the Design Matrix is a living document, evolving through the execution of the work packages, and it will be updated and diffused regularly. Finally, it allowed the most appropriate configurations to be easily chosen to be defined in later stages of e-Light.
Parallel to the definition of the Design Drivers, a detailed analysis of the state of the art was made covering the following technologies:
- Battery pack
- Electric Motor
- Powertrain
- Materials & Technology

The results from this study were used as starting points for further considerations in the definition of the Design Matrix, in addition to the engineering consideration made to identify the best solution for EV architecture to be pursued and optimized.
The business case considered is not derived from an ICE vehicle, but it has been conceived directly as an EV. It is an A-segment city car, which is fully electric, has 2 + 1 places, 2 doors, a modular rear end for van version (and eventually pick-up version) with high safety standards.
This modularity / flexibility and production technology permit the development of a product family with diverse uses and optimized investment & costs to ensure the competitiveness of the product. Mass production is foreseen for small series (500-1000 vehicles/year), due to the niche in which Pininfarina targets its business case.
Of course other possibilities were investigated, but the most innovative of them are still at the prototype stage, so they could present a heavy industrial risk. At the end of the second year, and through careful simulation studies carried out on the third year of the project, e-Light came out with an innovative design, including a door ring in composite materials. The prototyping of such design is out of the scope of e-Light, nevertheless, USFD, Pininfarina and Cidaut agreed on following the e-Light results on Evolution (http://evolutionproject.eu) to achieve prototyping of e-Light results and implementation of those in an EV.
The traditional concept of Body in White is revised, being decomposed into an Underbody and a Space frame; this breakdown allows for the specialization of conventional systems, redefining their functions and missions. This solution is highly flexible, allowing the creation of different shapes and types of vehicles for substitution or addition to a limited number of structural elements and skin panels. The multi-material architecture approach puts the overall vehicle’s functionalities first, and then splits them into sub-modules and parts, selecting the optimal material on a part-by-part basis based on overall vehicle performances. Savings in weight as well as increases in efficiency contribute directly to the size of the batteries which are both heavy and expensive.
The Space Frame consists of a skeleton structure, made of extruded and curved profiles which are mutually joined, carrying the external skins which have an aesthetical function; it is dimensioned for a specific structural target, which is defined by the ergonomics of the vehicle. Currently the Space Frame is made in Aluminium with as many extruded parts as possible, as shown below:
General structural performances, crash behaviour, handling and mechanical support will be demanded of the Under-body, where the modularity will be guided by the maximization of functions for each component and the possibility to set up several vehicles with a single platform, changing the geometric characteristics (pitch, track width, height).
There are several possible solutions for the underbody The current plan is to make it in Al, like the Space Frame, but there are several possibilities to be explored during the e-Light project, based on lightweight materials.

The structural part of the body can be divided into two parts, as shown in the following image:
1. Floor module (front underbody)
2. Roof module (upperbody)

For each part an analysis of structural functions was performed, decomposing the system in subsystems. Results are summarized on the two next tables, one for the Underbody, the other for the Upperbody.

As it is explained on the section dealing with WP4 work, this initial approach was later improved by developing the Door-ring approach, developing a highly composite intensive central body with two aluminium sections, one on the front and another on the rear parts of the architecture.
Regarding the results from the different materials to become part of urban EVs, the main results achieved by e-Light can be summarised as follows:

Reinforced composite materials:
A Trade-off of materials model was developed applicable to the development of urban electric vehicles. Technical requirements, preferred design concepts and manufacturing processes were taken into account, all of them direct results of the work performed in analysing the requirements of EVs.
The weights applied to each selection criteria depended on the type of company, state of the art, component, and market context. For this reason, in each case they have different values. Similarly, sometimes it was necessary to modify the resolution or scale scores to differentiate more clearly the different options.
The application of decision matrices to select materials for the process of developing (Electrical Automotive Market) can reduce the arbitrariness, provide traceability in decision-making and facilitate the participation of more people and points of view. This gives more confidence in the decision.
Since the methodology developed is a first version, its use will make it possible to identify areas for improvement to be implemented in later versions, and in different type of vehicles. This methodology will become one section of the design guidelines to be produced at the end of e-Light.
During the project, it was considered that for the first selection of optimum materials it was not necessary to work with quantified technical criteria (e.g. mechanical or thermal properties). After that, it will be necessary to have more detailed information on the materials, to choose the most suitable concepts for the architecture. And his information, together with the feedback resulting from the simulation analysis of the architecture performance, will provide the necessary information to fully define and perform the cost-benefit and the life cycle analysis.
The main objective of the composite material study was not to develop a database of such materials, but to advance in identifying the product development methodologies to reduce the risk of taking wrong decisions during the early stages of work, endangering the technical feasibility and competitiveness of the final product.

Finally the Trade-off was identified and prioritized; two main families of materials were chosen according the defined criteria:
- Technical thermoplastic materials for injection and GMT processes. To ensure critical technical requirements of materials (Mechanical behaviour, joining capability and ageing or durability)
- Thermoset materials for liquid moulding processes (RTM-Var, Casting and RTM). To ensure economical feasibility for short runs
In both cases pre-finished sheet (GMT and SMC) was the best scored regarding the preferential design concepts. Depending on that concept (Sandwich structure or Hybrid structure) the process to be prioritized is low or high pressure.

Metallic materials:
The main result achieved, in this study of advanced metallic materials, was to establish a short list of materials susceptible to be used in the BIW of the e-project vehicle.
It was concluded that the aluminium has a great potential to be used in almost all the processes considered:
- The extrusion of 2xxx, 6xxx and 7xxx series is suitable to be applied in the BIW structure in competence with the high strength steels. In the e-light project 6005 A T6 will be considered for the extruded components.
- The rolling of 6xxx series is suitable to be used in body panels going in competence with some plastic materials. In the e-light project 6111 T4 will be considered for panels.
- The aluminium processed by high die pressure casting has the limitation of the high cost of the tooling that makes it application for low series unaffordable.
- The moulding of 3xx series is also suitable for some structural parts of the body in white. In the e-light project AlSi7Mg will be considered.
The magnesium alloys were rejected to be applied for structural components, although some other uses were found in internal structures and components’ covers.
The MMCs were estimated as not suitable for their application in the e-light project, due to their lack of application in structural components and the high cost of the rest of possible applications.
The analysis of the high strength steels shown their great potential to be applied in the BIW structure, but in competence with extruded aluminium. It is important to notice that in the case of a hybrid solution steel-aluminium the galvanic corrosion should be studied in the joints of both materials.
This short list of materials will be used in the life cycle and in the cost-benefit analysis as well as in defining the simulation model, New EV design dynamics to select the most suitable materials attending to sustainability, cost and mechanical behaviour criteria.

Joining techniques and manufacturing processes:
The values of the matrices used in this analysis were extracted directly or indirectly from the descriptive of materials, processes and joining technologies. The process selection was mainly based on the underlying design concept and the degree of integration. A list of process discriminators helps to make the trade-off between performance and assembly cost:
- Size & Access Limitations
- Joint Quality & Tolerance
- Investment & Operational Costs
- Equipment, Tooling & Labor Requirements
- Process Performance (Production Rate & Lead Time)
The assembly architecture and integration of parts during concept design of the product were determined. While considering all the assembly cost drivers, it has to be decided whether the product will have an integral or modular design. Both concepts need to meet design requirements, which in turn will affect performance and producibility.
A major strategy to reduce cost in composite fabrication was the integration of parts. While trying to keep the part performance (strength & stiffness) constant, various degrees of integration were evaluated in terms of their costs. In general, the higher the part count, the more labor intensive is the assembly. A further cost driver were the joining methods used to assemble composites. For example, co-cure, which also can be described as "soft" assembly because most of the components are still flexible and possess more degrees of freedom than their rigidly assembled counterparts. Co-cure are can reduce delays and costs due to over constraints and tolerance build-up. However, higher integration can create increased manufacturing risks since the potential scrapping of a part becomes progressively more expensive.
Minimizing assembly costs was identified as a design function and this must include proper consideration and identification of all cost drivers:
- Production Volume
- Process Cycle Time (Non-recurring & recurring)
- Number of Components
- Fastening Method
- Accessibility
- Shimming & Surface Preparation
- Dimensional Tolerance
- Labor & Equipment Rates
- Productivity & Utilization
- Quality & Rework Rate
The number of parts in an assembly has a significant impact to the total assembly cost. Generally, the goal is to generate a design with the minimum number of parts, while achieving the necessary functionality at the same time. Less parts results in reduced assembly operations and less assembly material (fasteners, adhesives). Less assembly material also contributes to weight savings. However a more integrated structure tends to create a more complex design, which makes access more difficult. Lack of accessibility can also limit the use of automatic fastener installation technology. A more complex design requires also complicated and expensive tooling.

Overall architecture designs analysed during the project:
The vehicle configuration will be used to define the simulation model (CAD and CAE) that will be simulated in the dynamic, structural and safety analysis to demonstrate the performance of the lightweight design. Within architecture designs analysis, the following results were achieved:
Definition of the electric motor size targets: capable of achieving an acceleration from 0 to 50kph in 7 seconds while achieving a recuperation from 20 to 60kph better that its ICE equivalent in second gear. The maximum speed was set in 120kph, and the slope climbing capacity the vehicle should be able of going up a 20% slope with a constant speed of 40kph. Those targets implied that the motor power needed is 30kW.
Definition of the battery size targets: In order to be able to cover a minimum distance accepted by the users, while having the smallest influence on the overall vehicle weight, several calculations were done using a mathematical model to define a battery size of 23kWh. The target for the range is 120km as a minimum and 150km recommended. The performance of such battery was compared using the European, American and Japanese driving cycles.
For the design of the vehicle architecture other issues were considered. The weight distribution, braking capacity and dynamic behaviour were studied for an urban electric vehicle, defining a weight distribution of 55% weight in the front axle when the vehicle is unloaded; a maximum braking distance of 13.5m when the vehicle speed is 60kph and a maximum braking distance of 37.5m when the vehicle speed is 100kph. Also other general characteristics were defined, attending at the dynamic behaviour of the vehicle, such are a good stability, a centre of gravity height, a maximum lateral acceleration higher than 0.7g and a under steer behaviour.
All vehicle configurations defined previously on the project were studied. The results previous analysis were compared through dynamic and weight analysis. The different characteristics of motor location, stand-alone, in wheels, and in the rear axle were compared in terms of modularity, ergonomics, safety, costs and weight to conclude that the most suitable configuration of the future urban electric vehicles is a 4 seat lay-out with a rear wheel drive axle, and that the vehicle will have a central battery.
Finally, the current situation regarding the Electro-Magnetic Compatibility of electric vehicles was studied. This is a very complicated issue that will require a full analysis, but that is out of the scope of e-Light. Nevertheless, a general analysis of feasibility was performed concluding that the proposed configuration is feasible from the point of view of EMC/EMI.

The initial activities of e-Light were centred on exploring and developing new Electric Vehicle (EV) architectures from a structural point of view. Those took into account the lack of restraints such vehicles presents when compared to conventional vehicles equipped internal combustion engines. The influences that those architectures have on the Ergonomic, Modular and Safety aspects were covered by e-Light. Those results, together with an analysis of most suitable advanced metallic and reinforced composite materials and their joining technologies were used in defining the overall architecture to be analysed in the finite element simulations that started on the second half of the project. At the end of the project, the information on materials, simulation and designs have been summarised in Design Guidelines and Testing Procedure Recommendation documents for the automotive industry.

The first activities, carried out during e-Light second term, were focused on finalising the EV architecture design. The Life Cycle Assessment (LCA) and the Const-benefit Analysis that were delayed on the first part of the project were carried out once the final design was completed and the materials and manufacturing techniques were defined.

The performance of the design in terms of Structure, Safety and NVH were determined and with the information coming from those analyses the EV design was modified to improve the lightweight as well as to include a composite intensive configuration. The modifications on the layout of the EV architecture and the inclusion of composites made reports on LCA and Cost-benefit analysis being delayed until the final EV design was completed. Finally, the guidelines for the EV Design, EV Safety and its Testing were completed and the knowledge generated in e-Light was included in them.

Second term started by analysing the structural and fatigue performances of the chosen EV architecture. In parallel the crash behaviour was also carried out.

In order to ensure the crashworthiness of the e-Light design, several impact calculations were made including the most common situations included in the directives and regulations. So the first step was to analyse all the crash legislation and normative, this information and the main tests to be performed are summarized in Deliverable 4.2. This analysis was made taken into account three main groups of tests: the ones included in the European legislation, the ones included in the North American legislation and the one included in the Consumer Information Programs. After that, the selection of the most representative and critical frontal, lateral, low speed and rear impact were selected to be simulated on the e-light vehicle in order to optimize the designed BIW.
It is important to notice that, after a deep analysis, the pedestrian tests have not been considered. The main reason is that the results of this kind of tests depend mainly in the hood, the windscreen and the front bumper, and none of these components are included in the BIW (actually, they are out of the scope of the project), so no change from the original model from Pininfarina was to be made.

Once the crash tests were decided, several simple calculations were made to validate the concept. A simplified model was built in order to know if the carbon fibre was suitable to the body in white manufacturing. The calculations made on the simplified model were useful to achieve the following conclusions:
• The thickness analysis has demonstrated that a side protection bar is needed to fulfil the lateral impact requirements.
• The CFRP body in white is suitable for lateral crash.
• The section assessment made over the simplified model has allowed the selection of the most suitable ones.
Once that the concept was validated, a methodology was establish to optimize the BIW, minimising the weight and ensuring the fulfilment of all the crash requirements. The methodology can be summarized in next figure.
It is important to indicate that along the crash optimization several design iterations were made taken into account the results from the optimization process carried on during task 4.1: Structural Integrity, and also the results obtained from the analysis of the joint between aluminium and CFRP (this analysis is explained in detail in Deliverable 5.2).
The starting point for Work Package 4 was the aluminium design of Pininfarina Nido. In order to fix crash behaviour targets, the aluminium model was simulated in all the crash configurations considered: lateral, frontal, reparability and rear. After that, a black metal approach for CFRP was analysed. The black metal approach consists in changing the material properties maintaining the same geometry. As expected, the result of the black metal approach was very poor. But the analysis of the results was very useful to decide that a hybrid solution was needed with CFRP for the central part of the vehicle, and aluminium for the frontal and rear components absorbing the impacting energy.
Some hybrid structures were calculated considering frontal and lateral impact. Once the lateral requirements were covered, special attention was paid to frontal impact. Due to the difficulty of fully defining the frontal requirements, some simplifications were done in the simulation model. The most important one is that the BIW has been considered as a rigid body, and that all the efforts were focused in the optimization of the frontal aluminium structure.
After fulfilling the frontal requirements, a full model was calculated to make sure that the simplification was not too optimistic. The next step was simulating a low energy crash, because it is not allowed that in a low speed crash some structural components got broken. Again the rigid body simplification was used and the thickness of different frontal aluminium components was optimized to avoid the breakage of any CFRP part.
Once the low energy requirements were fulfilled, the rear crash behaviour optimization started, and after nine new iterations all the targets were achieved.
The criterion for the vehicle optimization was to improve the behaviour of the initial design made in aluminium. Also special emphasis was made on ensuring the battery’s safety. In the most critical tests: frontal, side and rear impacts a special analysis was made in order to ensure that no deformation of the battery casing would happen. The batteries are protected by structural beams and there is a safety space between the battery casing and the beams. In the worst case scenario, the displacement of the beams was 9mm, less than half of the safety gap (20 mm).
At the same time, and as shown in Figure 1, the structural and vibrations analysis was carries out. Although originally was planned as a single task, the design of the e-Light architecture required several loops in order to achieve its potential for weight reduction, as well as to include the peculiarities of the composite materials and the manufacturing methods.

A concept for a lightweight body structure for electric vehicle has been developed, using a combination of design skills, CAE optimisation and CAE validation tools. The e-light structure was based on an existing aluminium spaceframe structure (as explained the Pininfarina “Nido”), primarily selected to provide basic layout, package and hardpoint data.

A brainstorming process was used to generate a number of potential concepts and possibilities for the CFRP structure. An evaluation process was then used to select a design concept for further CAE validation and development. Initial development of the e-light structure was based on the requirements to achieve complete vehicle crash performance. This is reported in Deliverable 4.2 “Report on the energy absorption capabilities and crash performance of electric vehicles”.

Further development of the structure was then undertaken with respect to structural stiffness, durability and Noise, Vibration and Harshness (NVH). An advanced and complex multi-domain parametric CAE optimisation approach was applied to assist in developing the CFRP structure. The optimisation considered a large number of input variables such as structural member cross section size, CFRP thickness and CFRP fibre orientation angle. In some cases, the large number of design variables resulted in optimisation convergence issues and a simpler, two-step approach was required.

The final, optimised CFRP e-light solution achieved a 50% mass reduction when compared to the baseline “Nido” design. The stiffness, NVH and durability targets were all achieved.

Further development of the structure was then undertaken with respect to structural stiffness, durability and Noise, Vibration and Harshness (NVH). The approach for NVH analysis and the subsequent performance is detailed on Deliverable 4.3.

An advanced and complex multi-domain parametric CAE optimisation approach was applied to assist in developing the CFRP structure. The optimisation considered a large number of input variables such as structural member cross section size, CFRP thickness and CFRP fibre orientation angle. In some cases, the large number of design variables resulted in optimisation convergence issues and a simpler, two-step approach was required.

The final, optimised CFRP e-light solution achieved a 50% mass reduction when compared to the baseline “Nido” design. The NVH performance of e-Light was generally better than the reference Nido. Some assumptions in the analyses were made with respect to interior noise simulations and the lack of closures (doors). Also the specific NVH characteristics of electric machines were not considered within the analysis. Both assumptions are potential areas of consideration for further analysis.

After the analyses, the final design for the e-Light architecture was achieved. A concept for a lightweight body structure for electric vehicle composite intensive was developed using a combination of design skills, CAE optimisation and CAE validation tools.

Once the design was finalized, pending tasks from WP3 were able to be finished, the life cycle assessment and the cost-benefit analysis were carried out resulting in:

The aim of the cost-benefit analysis was to determine if a composite version of the E-light BIW structure could be cost competitive with a low cost aluminium intensive BIW. From the results it was seen that up to production volumes of 10,000 vehicles the aluminium intensive BIW is the most cost effective. Although the CFRP BIW structures do reduce in price, as the production quantity increases, due to the fact that the tooling needs to be replaced after 10,000 cycles this price will not reduce further. It was also seen that using a lower cost CFRP material it is possible to reduce the overall BIW cost by up to 50%.
The composite BIW achieved an important weight reduction but is more costly to produce and that as the production level goes up, from 1000 to 10,000, the cost of the aluminium intensive BIW is 71% of the original cost whereas the composite version is 96%. Due to a smaller reduction for the composite version there is actually an increase in the effective cost for the weight reduction as the production volume goes up.
The composite version is currently only at 89% of the original aluminium BIW weight. Earlier it was stated that a 36% reduction in the BIW should be possible. If we calculate the cost, assuming a 36% reduction, the composite version is actually cheaper to produce than the aluminium version. It can also be calculated that the two BIW designs break even at approximately 105kg or, effectively, at a 29% reduction.
The aim of the life cycle assessment was to determine whether aluminium or carbon fibre reinforced polymer had the greatest environmental impact when used to produce the body in white of a concept electric vehicle. The results showed quite clearly that in almost every impact category, the manufacturing stages of the CFRP BIW structures had a greater impact than that of the aluminium BIW. However, once the full life cycle is taken into consideration, the environmental impact of the aluminium BIW becomes greater than that of the CFRP structures. This suggests that the weight saving achieved by manufacturing the BIW using CFRP has the most significant effect, and essentially begins to counteract the substantial manufacturing impacts. Whilst the revised CFRP structure has a greater environmental impact than the original design, the improvements in structural performance are substantial – and the BIW remains lighter and maintains a lower environmental impact than the predominantly aluminium structure.

The sensitivity analysis further supports these conclusions, by showing that the assumptions made did not bias the results. However, it also provides a vital insight into how environmental impact could be reduced in all three BIW structures – i.e. by manufacturing in countries with a cleaner electricity mix, or by using a greater proportion of recycled aluminium.

It must be stated that whilst these results enable conclusions to be drawn concerning the BIW, the limited scope of the LCA does not represent the full electric vehicle. If a further study were to be conducted, focusing on optimizing the concept as a whole, then a more detailed LCA would have to be carried out, most likely including capital goods as well as the other vehicular components. Not only this, but the EcoInvent database was lacking several important component materials included in the BIW structures – most notably carbon fibre. Whilst these absent profiles were constructed using data from available literature, they would be more accurate and of greater consistency with the other profiles once they have been included in the database.

After finishing the design, and perform the LCA and cost-benefit analyses on the final e-Light architecture design, the knowledge generated, as well as th different steps recommended towards a lightweight design for urban EV were summarised in the project guidelines. Three different guidelines were completed:
4. General design guidelines/requirements: The project results, and main findings, in terms of the most suitable materials and their use in the developed architectures, the modules to be used in the EV, and the manufacturing techniques have been summarised and presented in this document. The document also provides designers with general recommendations with regards to the further study of body in white solutions for urban EV. This document will support industry designers in altomotive industry to achieve lightweight EV architectures minimizing costs and manufacturing times, and maximising production.
5. General Safety requirements: The document provides a summary of current safety and testing procedures that should be applied to EV without changes, European and USA standards have been analysed and a detailed list of new requirements for electric motors, power electronics and battery packs safety has been produced, with special attention paid to crash behaviour.
6. Testing procedures recommendations: This document summarised the assessment to be performed in the early stages of the design phase, since an accurate assessment of vehicle requirements is key to the definition of targets for new vehicle concepts. To achieve this objective a combination of industrial experience, detailed objective testing, specialised computed aided engineering and dynamic analysis tools are needed. The proper way to combine these skills is presented in this document to support evaluating new EV concepts.

The project reached its end on December 2013 although some delay in reporting was encountered. The Deliverables have been uploaded and the public reports are available through the project website.

Currently the project results are being used in several on-going FP7 projects in the field of Green Vehicle, EVoultion, UrbanEV, and Behicle are the most relevant ones. Cidaut, Pininfarina, Tecnalia and USFD are developing the e-Light designs to demonstrate feasibility of design by producing prototypes.
The door ring designed in e-Light will be prototyped by USFD, Pininfarina and Tecnalia in the Evolution project (http://evolutionproject.eu/).

Potential Impact:
The expected main scientific and technical result will be a comprehensive description of the knowledge and methodologies used in designing a lightweight architecture for urban EV. The project focuses on defining the design drivers, design matrix and the influence of safety and modularity. The metallic and reinforced composite materials, as well as the joining and manufacturing techniques will also influence the chosen model. The performance of the model and the feedback from the simulations to the life cycle and the cost-benefit analysis will determine the information and detailed the methodology.
These knowledge and methodologies will be summarised in three documents:
- General Design Guidelines for EV architectures.
- Safety aspects related to new EVs and their influence on vehicle architectures.
- Testing procedures and recommendations for EV architecture design involving the new materials and joining techniques.

The e-Light project aims to support the European automotive industry, especially it the SMEs in the supply chain by providing these companies with the knowledge and methodologies to design architectures for EVs. The project results, in the form of comprehensive guidelines and procedures will allow those companies to face the challenge of adapting their businesses to a new type of vehicle.
E-Light results will have a significant impact in enhancing the European automotive industry competiveness, allowing a closer and improved relationship between OEMs and large companies in this industry with the SMEs in their supply chain. By increasing their knowledge, e-light will facilitate European SMEs in the automotive market to consolidate their position while improving their adaptation towards the new requirement of electric mobility.
The e-Light results aim to support and boost the European automotive industry competitiveness, especially their SMEs, to continue being a pillar of the European economy, representing 3% of Europe’s gross domestic product, 7% of employment in the manufacturing sector and 8% of EU governments’ total revenue.
The results are illustrated by a new EV architecture design, performed over a current existing EV from Pininfarina. The design has achieved 50% weight reduction in a feasible way. The developed architecture is better from a structural and safety points of view, while it is economically feasible for the assumed vehicle production.
The project has focused on defining the design drivers, design matrix and the influence of safety and modularity. The metallic and reinforced composite materials, as well as the joining and manufacturing techniques will also influence the chosen model. The performance of the model and the feedback from the simulations to the life cycle and the cost-benefit analysis have determined the information and detailed the methodology.
In order to progress with the achieved designs, some of the partners (Tecnalia, Pininfarina, USFD and Cidaut) have decided to follow the findings and results from e-Light into real prototypes to be applied on EV. The FP7 on-going projects Behicle, Evolution, Urban-EV, and FreeMOBY will directly benefit from the knowledge generated in the project. And in the Evolution project USFD, Pininfarina and Cidaut will prototype the door ring designed in e-Light validating the results.

List of Websites:
Development of the Project website, if applicable

The e-Light website was established in February 2011. It aims to provide information on the main activities and results of the project, on project related events and announcements, i.e. workshop announcements, but also to provide news regarding EV and lightweight design to the public.

The target audience is the research, scientific and industrial public, although the general public is welcomed to read their contents. Its focus, for dissemination and exploitation purposed is the automotive industry supply chain. The website can be accessed through http://www.elight-project.eu/

The main page of e-Light website is shown in the following figure:

e-Light Website Main Page

Within public website, an private area was created in order to ensure project relevant data transfer between the different partners, especially those sensitive or of large size (such are CAD and CAE models)

Contact details:
Coordinator details: Dr. Esteban Cañibano, +34 983 548035, luipra@cidaut.es
Project contact: elight@cidaut.es