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Improving the crashworthiness of composite transportation structures

Periodic Reporting for period 1 - ICONIC (Improving the crashworthiness of composite transportation structures)

Reporting period: 2016-10-01 to 2018-09-30

The central aim of ICONIC is to develop a critical mass of research and engineering leaders with a world-leading capability in the design of lightweight aeronautical, automotive and rail transportation composite structures with superior crashworthiness. These challenges are being addressed by bringing together 15 early stage researchers (ESRs), recruited from an international talent pool, in an innovative, integrated, multiscale and multidisciplinary research and skills development programme that goes beyond the state of the art. The ICONIC research programme, takes a multiscale approach, ranging from material development and characterisation at the nano- and microscales; high fidelity numerical modelling of composite damage at the micro and mesoscales; through to the structural design and optimisation of representative structures (macrosale) with superior energy-absorption and crashworthiness. The influence of processing parameters on structural performance, ageing, sustainability and life-cycle costs are also addressed within this network.
Over the past 24 months the 15 Early Stage Researchers (ESRs) were recruited at different times so that some variability in the level of progress made by the individual ESRs is expected.

ESR1 is focussing on improving hydraulic test machine based methods for testing fibre-reinforced plastics at intermediate strains (from 1 to 200/s). ESR2 is working in close partnership with ESR1 where his specific project concerns the materials characterisation of composites at high strain rates (greater than 200/s) and involves the use of a Split Hopkinson Pressure Bar (SHPB) as opposed to a hydraulic test machine.

ESR3 is working on the development of 3D woven architectures for the design of crush tubes, and other energy absorbing structures, used in the automotive industry. ESR4 is investigating the process-structure-property relationship of nano-enhanced low-cost thermoplastic composites as a possible route to developing cost-effective lightweight automotive structural components which will exhibit a high level of energy absorption. ESR5 has been working towards the identification of optimum processing parameters to improve the impact resistance of self-reinforced polypropylene (PP).

ESR6 is focussing on micro/meso multiscale computational modelling of the crushing of woven composites and is collaborating with ESR 1 and ESR2 as he further develops the model to account for strain-rate effects. ESR7’s work complements that of ESR6 where he is also developing micro/mesoscale computational tools for modelling the energy absorbing/crush behaviour of composites. ESR8 is exploring efficient modelling strategies to enable the modelling of large-scale (mesoscale) structures using a ‘stacked shell’ modelling approach which will include strain rate effects.

ESR9 is pursuing research at Bombardier Aerospace with the ultimate objective of developing the computational strategy to simulate the effects of a burst duct event on a composite nacelle structure.
ESR10 and ESR11 are exploring structural joints, and their potential energy-absorbing capacity. ESR12 is studying a novel form of composite material known as Tape-Based Discontinuous Composites (TBDC). This material has huge potential for the automotive industry and preliminary research suggests that this material also exhibits simpler behaviour in crash. ESR13 and ESR14’s research concerns different aspects of the design and structural testing of large-scale automotive composite structures.

The work of ESR15 complements that of ESR8 who are both pursuing computationally efficient means of modelling complex structural phenomena associated with composite damage and crushing. ESR15 has developed a local-global approach whereby a highly efficient “Carrera Unified Formulation” is used for 3D local detailand a commercial FEA package used for the global modelling.
The previous section demonstrates the substantial innovative developments that have been achieved to date through the contributions of each ESR. Each research programme aims to progress beyond the state-of-the-art and the following provides a brief summary of how this will be achieved.

ESR1 will deliver a new test procedure for the reliable and accurate material characterisation of orthotropic fibre reinforced composites at intermediate strain rates. ESR2, whose work is closely related to that of ESR1, will further develop the use of a SHPB and drop tower testing apparatus for the high strain rate composite material characterisation in tension, compression and shear. Together these research outcomes will provide a comprehensive suite of reliable test methods for the testing of composite materials at different strain rates.

The work of ESR3 should lead to a deeper understanding of the influence of weave parameters on the energy absorption capacity of different architectures. Ultimately, this research will yield an optimised 3D woven fibre architectures tailored for superior energy absorption whilst also fulfilling other structural requirements. ESR4’s research will provide a deeper understanding of the influence of processing parameters on the dispersion of graphene-based nanoparticles in a thermoplastic elastomer and nylon 6 blends and their subsequent performance as structural/semi-structural components and their associated energy absorbing capacity in a crash scenario.

The research in self-reinforced plastics, by ESR5, will lead to the state-of-the-art in impact resistant, energy absorbing self-reinforced composites. Moreover, new hybridised composite material systems which will combine thin-ply glass fibre composites with thin sheets of self-reinforced plastics, has the potential of creating a new lightweight structural material which could be commercially exploited.

ESR6, ESR7, ESR 8 and ESR 15 will work together to establish the state-of-the-art in the modelling of woven and non-crimp fabric (NCF) composites undergoing damage and crushing. This will enable the design of optimal energy absorbing composite structures and will be of particular utility to ESR9.

The work of ESR10 will lead to a new approach in the design of energy-absorbing composite bolted joints. Similarly, ESR11’s work is expected to result in the development of a new type of joint, based on interlocking features and exhibiting high energy absorption capacity. At the conclusion of ESR12’s research programme, it is envisaged that a new thermoplastic-based thin-ply TBDC, optimised for the automotive industry, will be offered for further development to interested manufacturers.

The main aim of ESR13 is to design a new highly energy-absorbing composite crash box to replace the current metallic ones on high-end composite road vehicles manufactured by Fiat. ESR14’s research will lead to the development of efficient test programmes in the development of automotive composite structures.

One overarching societal benefit that this highly multidisciplinary programme will deliver is a projected reduction in operational environmental impact arising from the increased use of lightweight composite materials in transportation structures. Various global efforts, undertaken over the past few decades, to reduce poverty, has enabled a larger sector of the global community to become more mobile, with the consequence of a predicted significant increase in demand for transportation vehicles.
3D woven textile preform architectures
Different steps in material model development
Digital Element Method applied to the 3D through-thickness orthogonal interlock
Multiscale computational approach
Mechanical behaviour of satin weave carbon/epoxy laminate in compression at different strain rates
ESR9a_Compact tension test simulation
FE model of pin bearing test (meshed parts and model assembly)
Process flow diagram for preparation of nanocomposite samples and test specimens
SEM images of nylon 6 nanocomposites
Predicted UC geometry of 3D woven composite
Modulus and Ultimate Tensile Strength of the consolidated laminates with compaction temperature
Fastener-less joint mould-in manufacturing method
Steps to create an RVE of a 3D woven textile