Study on multi-mode failure mechanisms and synergistic energy absorption effects of CFRP composite thin-walled tubes under oblique compression

In this paper, the mechanical behavior and energy absorption characteristics of carbon fiber reinforced polymer (CFRP) thin-walled tubes with different geometrical parameters (wall thickness and length) and their aluminum foam-filled tubes were investigated at four loading angles, namely, 0°, 15°, 30°, and 45°, through systematic experimental studies. Custom-angled molds were used for oblique loading tests. Structure-filler synergy was analyzed through damage morphology, load-displacement curves, and energy absorption indexes. The results show that the hollow tube under axial compression is dominated by progressive buckling, while the damage mode gradually evolves into local buckling, delamination, and lateral cracking with the increase of the angle during oblique loading, leading to a significant decrease in energy absorption efficiency. Aluminum foam filling can significantly enhance the energy absorption of CFRP thin-walled tubes under axial compression, and the enhancement is weakened in inclined angle loading compared with axial loading but still shows excellent energy absorption performance and stability. Geometric parameters significantly impact tube performance. Increased wall thickness enhances stiffness and energy absorption stability, but excessively thick tubes may exhibit unfavorable damage modes under large-angle compression. Tube length effects should be considered in conjunction with angle and wall thickness to optimize energy dissipation and stability.