Residual crashworthiness of lotus stem-inspired composite tubes with transverse impact damage: Experimental and numerical study

Abstract

This study investigates the damage behaviour and residual crashworthiness of multi-cell composite tubes containing low-velocity impact damage, using a combined experimental and numerical approach. An efficient prediction framework for residual-performance is developed by employing an impact damage–mapping technique, which enables the accurate mapping of intralaminar and interlaminar damage as well as permanent deformation between different analysis models. To further elucidate the energy-absorption mechanisms during impact and subsequent axial crushing, energy absorption and dissipation calculations are integrated to a VUMAT subroutine. The finite element model demonstrates a high level of predictive accuracy when predicting both the transverse impact response and the post-impact compressive behaviour. Using this framework, the effects of transverse impacts on circumferential positions and height locations on the residual performance are systematically examined. The results show that transverse impact loading affects the energy-absorption characteristics of the composite tubes, with the multi-cell configuration exhibiting potential for reducing the effect of prior impact damage. The residual energy-absorption capacity of the circular tube decreased by approximately 61 %, whereas the multi-cell tubes suffer a more moderate reduction of approximately 23 %. During the impact phase, interlaminar damage dominates energy dissipation, whereas during axial crushing intralaminar failure represents the primary energy-absorbing mechanism. Although impact at circumferential locations results in different local responses, its effect on the global residual performance is limited. In contrast, impact at different height locations has a significant influence on both the remaining load-bearing capacity and the ensuing failure modes. The proposed framework provides a robust methodological basis for both the damage-tolerant assessment and the crashworthiness design of composite multi-cell thin-walled structures.

Keywords: Residual crashworthiness, Impact behaviour, Failure mechanisms, Finite element analysis