Crashworthiness analysis and design of composite tapered tubes under multiple load cases

Carbon fibre reinforced plastics (CFRP) are characterized by lightweight, high specific strength and stiffness, superior energy-absorbing capacity, and excellent design flexibility. Thus, use of CFRP thin-walled structure as crashworthy application can improve fuel economics and crashworthiness characteristics compared with their metal counterparts. In this study, we reported crushing behavior of several CFRP tapered tubes with various cross-sectional profiles and tapered angles under multiple load cases through numerical simulations. The influences of cross-sectional profiles, tapered angle and loading angle on crashworthiness of all configurations were explored by comparing their failure modes, load-displacement curves, crashworthiness indicators and energy-absorbing mechanisms. It was found that a positive correlation between total energy-absorbing capacity and the edge number of cross section profile was demonstrated, and the tapered tubes with circular profile showed the best total energy-absorbing capacity under both axial and oblique loadings. Besides, it was indicated that the energy-absorbing capacity of the tubes reduced in different degrees with increasing impact angle, and raising tapered angle of the tube was capable to mitigate this reduction degree. Further, the complex proportional assessment method (COPRAS) was adopted to effectively pick up the optimal configuration from all configurations concerned. It was found that H-6, which is the CFRP tapered tube with hexagonal profiles and tapered angle of 6°, was the best configuration, indicating its superiority in crashworthiness characteristics under multiple load cases. Finally, the CFRP tapered tube H-6 was further optimized by using a discrete optimization method to improve its crashworthiness characteristics, and the results showed that the SEAα was improved by 4.35% from the initial design. This study demonstrated that the proposed two-step process (firstly select the best optimal configuration based on COPRAS; then perform the discrete optimization) was fairly effective to obtain an optimal configuration for crashworthiness design of CFRP tapered tubes under multiple load cases.