Numerical Simulation and Comparison of GFRP and Green Composites for an Automotive Seat Backrest

In recent years, the automotive industry has been developing lightweight components in order to comply with stricter fuel consumption regulations. In fact, car mass reduction plays an important role to reduce fuel consumption and CO2 emissions. Materials such as Advanced High Strength Steels (AHSS), aluminium, magnesium, polymers and fibre-reinforced composites have the potential to reduce current vehicle mass by replacing traditional steel components, while ensuring safety requirements and structure reliability. Particularly, the composite materials are the most promising because of their high specific strength, although they have the drawback of having high cost and low recyclability. This thesis work aims to develop an LS-Dyna FEM model in order to carry out safety test simulations on an automotive seat and then assess the structural practicability of using a more sustainable material, the basalt reinforced-fibre polymer (BFRP), as a replacement of the original material, the glass reinforced-fibre polymer (GFRP). The starting point of this study was the mechanical characterisation of both traditional and green composites, in which a very similar mechanical behaviour was observed. Then, an optimisation of the LS-Dyna card material MAT-58 was performed to correlate the experimental and simulated results. Finally, static and energy absorption simulation tests were performed according to the ECE R17 regulation. For the energy absorption test, the maximum impactor’s deceleration was found to be 54.6 g (535.63 m/s²) for the glass fibre composite, whereas for the basalt composite it was 55.5 g (544.46 m/s²); also, no dangerous edge due to the impact has occurred. Furthermore, in the static test, the headform displacement was 53.4 mm in the GFRP design, whilst it was 53 mm in the BFRP design; in addition, no failure has occurred by the end of the simulation. Thus, the seat model was compliant with the safety requirements in all cases studied, and both composites presented a similar structural performance.