分层对复合材料机械连接结构承载能力的影响

针对含孔边分层复合材料沉头螺栓连接结构，通过挤压试验及有限元仿真，研究了孔边分层对复合材料连接结构力学性能的影响。通过连接孔的挤压试验，得到了不同类型试验件的承载能力与破坏模式。有限元仿真中，基于ABAQUS有限元分析软件建立了复合材料机械连接的三维有限元模型，进行复合材料渐进失效损伤模拟，并采用内聚力单元来模拟预制分层。有限元计算得到载荷-位移曲线和变形模式与试验吻合较好，从而验证了有限元模型的有效性。在此基础上，分析了含孔边分层的复合材料机械连接结构的破坏机制，并研究了分层位置、分层面积大小和分层形状对该结构承载能力的影响。研究表明：复合材料的破坏始于沉头孔中的直孔区域，且当预制分层位于直孔区域时，结构的承载能力最低；分层形状为圆形和正方形时，会严重影响结构的承载能力，分层形状为椭圆形时，对承载能力影响较低。无论分层形状如何变化，分层总是从受挤压的一侧开始，以半圆弧的形状向受挤压方向进行扩展。

Bearing capacity of composite mechanical joint with hole delamination

The mechanical properties of the composite mechanical joint with hole delamination were studied by compressive test and numerical simulation. The loading capacity and failure mode of different test specimens were obtained by the compression test. In finite element simulation, the three-dimensional finite element model of composite mechanical joint was established based on ABAQUS software and the cohesive element was adopted to simulate the delamination. A good agreement was reached between the experiment and finite element method and the validity of the numerical method was verified. The failure mode, damage initiation and damage propagation of the composite structure were analyzed by the numerical model. A series of parametric studies were also performed to study the effects of the hole delamination position, the size of the delamination and the shape of the delamination on the compressive property of the composite mechanical joint. The results show that the load carrying capacity of the structure is the strongest when the delamination is located in the straight hole region and the bearing capacity of the composite structure with ellipse delamination is much bigger than the structure with square and circular shape delamination. In addition, no matter how the delamination shape changes, the delamination expands in the direction of compression as a semicircular shape.