复合材料层合板自由边缘冲击失效机制

Failure mechanisms of composite laminate subjected to edge-on impact

低速冲击复合材料层合板结构的自由边缘会严重威胁其安全性。本文对T700/YPH307复合材料层合板进行了边缘冲击试验与数值仿真研究。试验中通过目视检测、超声C扫描、电子显微观测及X-ray计算机断层扫描(CT)技术检测了层合板边缘冲击后的损伤状态,揭示了不同边缘冲击能量下,材料内部损伤的三维空间分布形貌。基于Mohr失效面理论,建立了一种考虑各向异性材料断裂面角度的连续介质损伤力学模型,同时结合内聚力模型综合表征了层合板边缘受低速冲击时层内纤维基体损伤与层间分层的起始、扩展和耦合细节。数值预测结果与试验值吻合较好,表明边缘冲击失效机制主要包括两种典型特征,即极限冲击力时形成冲头下方局部碎片楔及稳定波动阶段因楔入作用造成的外侧子层弯曲断裂。此外,边缘冲击能量越高,层合板内部损伤越严重,而铺层顺序对边缘冲击响应与损伤形貌影响相对有限。

Low velocity impact on the structural free edge would threaten the safety of laminated composite structures.In this paper,experimental and numerical investigations were conducted to study the edge-on impact behaviors of T700/YPH307 composite laminates.Visual inspection,ultrasonic C-scanning,electron microscopy and X-ray computed tomography(CT)technique were performed to detect the post-impact damage status of composite laminates subjected to edge-on impact,which could further reveal 3D spatial distribution of internal damage.Based on the Mohr's theory of fracture plane,a continuum damage mechanics model,considering fracture plane angle within anisotropic materials,was established.And with combination of cohesive zone model,the initiation,propagation and interaction of complicated edge-on impact damage modes,i.e.intra-laminar fiber and matrix failure and inter-laminar delamination,could be characterized in detail.There is a good agreement between numerical and experimental results.It is suggested that failure mechanisms induced by edge-on impact mainly include two distinct characteristics,namely the generation of localized debris wedge beneath the impactor corresponding to peak value of impact force,and the bending fracture of outer plies due to the wedge effect at the stage of stable fluctuations in impact force.Furthermore,it is found that the internal damage would be more serious with the impact energy increasing,while stacking sequence has a relatively small influence on the edge-on impact responses and damage morphology.