Numerical investigation of energy absorbers in composite materials for automotive applications

Nowadays, there is increasing interest in lightweight automotive structures capable of absorbing large quantities of energy in case of a crash phenomenon. These requirements are satisfied by composite devices, provided they are properly designed. The aim of the present paper is the investigation of the crashworthy behaviour of composite material tubes with woven laminae subjected to dynamic axial compression. The research was done by combining experimental and numerical analysis; without any experimental feedback, in fact, engineers might not accurately design an innovative structure. After the numerical characterisation of the used CFRP (carbon fibre-reinforced polymer) material, different simulations with the non-linear explicit dynamic code LS-DYNA have been done in order to understand how the structure absorbs energy by varying its geometrical and material parameters. In particular, circular and square tubes have been investigated with different resistant section, wall thickness, fibres orientation and staking sequence. The numerical analysis has been carried out taking into account different composite material models present in the LS-DYNA library, where each of them implements a different damage criterion. The choice of model to be used was made only after performing crash tests on the same tubes using a drop tower, appropriately instrumented in order to measure the main impact characteristics. The comparison between numerical and experimental results gave satisfactory outcomes, providing the basis for the design methodology of impact attenuators that are geometrically more complex