Abstract：Carbon fiber reinforced polymer (CFRP) thin-walled tubes are widely used as lightweight energy-absorbing components in aerospace and transportation structures because of their high specific strength, high specific stiffness, and excellent crashworthiness. In practical engineering applications, CFRP tubes often require mechanical fastening, which inevitably introduces holes into the structure. These holes interrupt fiber continuity and cause severe stress concentration, which may significantly alter the crushing behavior, failure mechanisms, and energy absorption efficiency of the structure under axial compression. However, the combined effects of open-hole defects, ply angle, and stacking sequence on the crashworthiness of CFRP square tubes are still not fully understood, especially for complex layup configurations inspired by biological helicoidal structures.
In this study, we investigate the quasi-static axial crushing behavior of perforated CFRP square tubes through a systematic numerical approach. A progressive damage finite element model is developed based on continuum damage mechanics. The model accounts for intralaminar damage initiation and evolution in fiber and matrix under tension and compression, as well as stiffness degradation associated with damage growth. Contact interactions between adjacent plies and between the tube and loading plates are also considered to realistically capture the crushing process. The numerical model is validated by comparing the predicted load–displacement response, failure modes, and energy absorption with available experimental results, showing good agreement and acceptable error in total absorbed energy.
Based on the validated model, a comprehensive parametric study is conducted to examine the influence of ply angle and stacking sequence on the crashworthiness of perforated CFRP square tubes. Three categories of layup designs are considered: single-angle layups, gradient symmetric layups, and bio-inspired helicoidal layups with different angular variation patterns. Key crashworthiness indicators, including peak crushing force, total energy absorption, specific energy absorption, mean crushing force, and crushing force efficiency, are evaluated. The results show that introducing an appropriate amount of 30° plies significantly improves both energy absorption capacity and crushing stability. Single-angle 45° layups tend to promote global buckling and unstable failure, while gradient and helicoidal designs can effectively suppress catastrophic fracture by promoting progressive damage.
Furthermore, the study reveals that inner plies play a dominant role in load bearing and energy dissipation during axial crushing. Structures with smaller angular differences between adjacent inner plies exhibit more stable damage evolution and higher energy absorption efficiency. In bio-inspired helicoidal configurations, concentrating larger angular gradients in the outer plies while maintaining smoother angular transitions in the inner plies leads to superior crashworthiness performance.
The findings of this work provide clear design guidelines for optimizing the stacking sequence of perforated CFRP tubes. The proposed strategies are expected to be valuable for the crashworthy design of lightweight composite structures in aerospace, automotive, and other energy-absorbing engineering applications.
2026, Vol. 47 
