Energy-absorbing mechanisms and crashworthiness design of CFRP multi-cell structures

This study aims to investigate crashworthiness and energy-absorbing capacity of CFRP mull-cell structures under the quasi-static axial loading. In the present study, CFRP single-cell and mull-cell tubes are manufactured, and the same overall dimensions and mass for all specimens are guaranteed through allocating different thickness of each side. The crushing process and energy-absorbing capacity of all specimens are experimentally investigated under the quasi-static axial crushing load. According to the experimental results, it is known that the single-cell tube develops unstable local buckling mode, and the mull-cell tubes with two configurations crush progressively. Total energy absorption of the mull-cell tubes are almost 69% higher than that of the single-cell tube. Subsequently, numerical simulations are further conducted to provide additional insights into the underlying energy-absorbing mechanisms of the mull-cell tubes. The numerical results indicate that intralaminar energy is the primary energy-absorbing mechanism for all configurations, and the energy absorbed by each part in the mull-cell tubes are much higher than the corresponding part in the single-cell tube. Based on the validated numerical models, the influences of wall thickness and cells number (n) on crashworthiness characteristics of mull-cell tubes are further investigated by performing a comparative analysis. It is found that the energy-absorbing capacity is slightly increased with raising cells number, and energy-absorbing capacity gradually increases with increasing layer number of inner cross beam. Finally, the CFRP mull-cell tube with n = 3 is further optimized, and as a result SEA is improved by 4.68% from the initial design. This study is expected to provide guideline for crashworthiness design of CFRP multi-cell structures.