Energy absorption of metal, composite and metal/composite hybrid structures under oblique crushing loading

Abstract

Metal/composite hybrid structures, which combine low-density composites with low-cost metallic materials, exhibit considerable potential to provide cost-effective energy-absorbing devices for automotive applications. This study aimed to explore crashworthiness characteristics of aluminum/carbon fiber reinforced plastic (CFRP) hybrid tubes, experimentally and numerically, subjected to three different loading angles by comparing with the aluminum alone and CFRP alone tubes, in which the deformation patterns and several key indicators related to the crashworthiness of these structures were assessed. The experiments revealed that the CFRP tube has the highest SEA under the axial (37.82 J/g) and 15° loading (30.03 J/g) angles of all the configurations concerned; while the hybrid tube showed the greatest energy absorption. It was found that the energy absorption capacity of all specimens reduced in different extent with increasing loading angle. Specifically, with the loading angle up to 15°, SEA of the hybrid tube decreased by 10.0% from that with the axial loading; whereas SEA of the CFRP tube decreased by 20.6% from that of the axial loading. It means that the hybrid tube was more capable to mitigate the effects of oblique load on energy absorption capacity in comparison with the net CFRP tube. To better understand the crashing mechanism, numerical models were created and validated by the experimental data. A parametric study was further performed to investigate the effects of loading angle, thickness of aluminum layer, stacking sequence and thickness of CFRP layers on crashworthiness of these structures. It was found that the number of CFRP layers is more important to energy absorption of the hybrid tube. For the pure CFRP tube, there is significant difference between the axial and oblique loading conditions, making it disadvantageous to be a proper crashworthy structure. Whereas for the hybrid tube, the effect of loading angle on energy absorption capacity is considerably mitigated; and consequently, the hybrid configuration offers a higher energy absorption capacity for meeting the crashworthiness requirements accommodating complex impacting angles.