薄层复合材料螺栓连接结构渐进失效机制试验研究

分别采用单搭接结构和双搭接结构研究了薄层复合材料层压板螺栓连接接头准静态拉伸加载渐进挤压损伤失效的过程。通过中断测试的方法利用X射线Micro-CT和扫描电镜（SEM）观察了拉伸加载过程中薄层层压板连接区域在特殊加载位置的损伤形式和变形特征。结果显示薄层层压板渐进失效过程主要损伤形式和传统厚度复合材料层压板相比基本一致，主要包括纤维断裂、基体开裂、纤维扭折和纤维/基体脱胶。然而，在传统厚度层压板复合材料中常见的失效方式即在挤压失效平面区域和拉伸失效平面区域广泛存在的分层损伤并未出现，这主要是薄层复合材料对初始损伤裂纹有效抑制的结果。由于损伤抑制作用，薄层层压板可在加载过程中承受更高的挤压载荷，具有更大的损伤容限。

Experimental study on progressive failure mechanism of thin-laminate bolted joints

To understand the damage evolution and failure mechanism, the bolted joints of thin-ply laminated composites with single- and double-lap structures under quasi-static loading were studied experimentally. The specimens were observed using X-ray Microscopic Computerized Tomography (Micro-CT) scanning and Scanning Electron Microscope (SEM) imaging at special stages of the whole loading process to evaluate damage progression and deformation characteristics. The results show that the major failure modes of thin-ply laminates were found to be similar to those of conventional thick-ply laminates, including fiber breakage, matrix cracking, fiber kinking and fiber-matrix debonding. However, the major difference is that the common failure mode that has been reported in conventional thick-ply laminates, namely extensive delamination initiated from the bearing failure plane and tensile failure plane, was not seen in these thin-ply laminates due to the crack suppression ability of thin-ply prepreg. This ability allows the laminate to sustain additional bearing load and have higher damage tolerance.