碳纤维复合材料铆接接头力学性能与失效机制研究

STUDY ON MECHANICAL PERFORMANCE AND FAILURE MECHANISM OF CARBON FIBER COMPOSITE RIVETED JOINTS

铆接工艺是飞机装配中常用的连接方式,但复合材料接头的复杂损伤和变形会导致其在服役阶段出现复杂的拉伸失效模式。为深入研究单搭接复合材料铆接接头的变形特征、力学性能与失效行为,应用三维Hashin损伤判据判断复合材料损伤起始,采用指数型刚度退化方式,建立了一种复合材料渐近损伤预测模型,对不同铆接工艺参数的铆接件进行了铆接成型和准静态拉伸仿真模拟,并将相应的模拟结果与实验结果进行了对比。结果表明,铆钉杆在铆接力作用下径向膨胀不均匀,成形损伤主要发生在铆钉镦头附近的孔壁,以纤维断裂和基体压溃为主,孔直径为4.82 mm接头的钉杆膨胀比4.9 mm的接头更均匀,接头具有更好的极限承载强度。数值模型预测的位移-载荷曲线可以准确地捕捉实际力学性能的趋势和特征,所预测的极限强度水平与试验相当。同时,承载平面上的纤维断裂和基体压溃的微观形貌在数值模型中得到很好的体现,验证了损伤预测模型的正确性。

The riveting process is a frequently utilized technique for joining components in aircraft assembly,but the complex damage and deformation of riveted joints may lead to intricate and unpredictable failure modes during the service phase.In order to thoroughly examine the deformation characteristics,mechanical properties and failure behavior of single-lap composite riveted joints,the three-dimensional Hashin failure criteria and exponential stiffness degradation method was used to establish an asymptotic damage prediction model for composite materials.Riveting forming and quasi-static tensile simulation were performed on riveted parts with different riveting process parameters,and the corresponding simulation results were compared with experimental results.The results indicate that the radial expansion of the rivet shank is non-uniform when subjected to pressure riveting force.Furthermore,the forming damage primarily transpires in the hole wall near the driven head,wherein the fiber crushing and interfacial shear cracks dominate.The uniformity of the hole expansion in the joint with a 4.82 mm diameter is superior to that of a 4.9 mm diameter,resulting in better ultimate bearing strength.Moreover,the numerical model's displacement-load curve aptly reflects the trend and features of the actual mechanical properties.The predicted ultimate strength level is also comparable to the test results.Notably,the numerical model effectively captures the damage forms and range of fibers and matrix in the micro-morphology on the bearing plane,confirming the validity of the damage prediction model.