变刚度碳纤维/环氧树脂复合材料薄壁圆管轴向压溃响应与破坏机制

通过控制缠绕线型改变轴管纤维角度，制备了一种轴向刚度渐变、压溃稳定的碳纤维增强树脂基复合材料(CFRP)变刚度薄壁圆管。对变刚度、±45°]_n以及90°]_n三类CFRP缠绕轴管进行轴向准静态压缩测试，结合数字图像相关技术(DIC)及有限元结果，对比三类结构压溃初始应变模式、损伤演化与应力状态结果，研究了变刚度结构的压溃响应与破坏机制。结果表明:不同纤维角度CFRP轴管因轴向刚度不同，压溃的初始破坏与损伤演化过程相异，三类结构产生不同的压溃响应与破坏模式。变刚度区连续变化的大角度纤维能有效地引发分层和“开花式”混合破坏，缓慢释放应变能，使变刚度CFRP轴管吸能效果明显优于其他两类结构。其峰值载荷为66.97 kN，压溃效率为50.8%，比吸能为10.1 kJ/kg，相对于±45°]_n结构比吸能提升156.35%，压溃效率提升518.76%，相对于90°]_n结构比吸能提升16.9%，压溃效率降低27.3%。 

Axial crushing response and failure mechanism of variable stiffness carbon fiber/epoxy resin composite thin-walled tube

The fiber angles of the winding tubes were changed by controlling the winding lines to realize the gradual change of the stiffness along the axial direction, and then the collapse-stable carbon fiber/epoxy resin composite thin-walled tubes with variable stiffness were fabricated. Finally, the axial quasi-static crushing tests were carried out for three types of winding tubes with variable stiffness, ±45°]_n and 90°]_n structures. Combined with digital image correlation (DSC) technology and finite element analysis results, the initial strain modes, damage evolution and stress states were compared to study the crushing response and failure mechanism of variable stiffness structures. The results show that the initial failure and damage evolution of the tubes with different fiber angles are different due to the various axial stiffness, so the different crushing response and failure modes are generated respectively, and the continuously changing circular fibers in the variable stiffness zone can effectively cause the delaminated and “flowering” mode mixed damage to release the strain energy slowly. Therefore, the energy absorption effect of the variable stiffness structure is obviously better than that of other two structures. Its peak load is 66.97 kN, crushing efficiency is 50.8%, and specific energy absorption is 10.1 kJ/kg. Compared with the ±45°]_n structure, the specific energy absorption increases by 156.35%, and the crushing efficiency increases by 518.76%. Compared with the 90°]_n structure, the specific energy absorption increases by 16.9%, and the crushing efficiency reduces by 27.3%.