层合板干涉螺接分层损伤及其临界干涉量

复合材料层合板的干涉配合连接具有优越的性能,是飞机复合材料结构连接的发展趋势。然而,层合板在干涉连接过程中易出现分层损伤。针对以上问题,采用理论建模与有限元模拟方法研究了碳纤维增强树脂基复合材料(CFRP)层合板干涉螺接过程中的分层损伤及其临界干涉量。首先,对CFRP层合板的干涉螺接工艺过程和分层损伤进行力学行为分析;然后,基于虚功原理,建立了各层界面的分层损伤临界轴向力计算模型,结合插钉力与干涉量间的关系,建立临界干涉量的预测模型,求得分层损伤的临界干涉量;最后,采用ABAQUS有限元软件对CFRP层合板干涉螺接过程进行数值模拟,应用内聚力单元建立层合板层间界面,模拟了CFRP层合板在不同干涉量时的分层损伤机理,并通过扫描电子显微镜(SEM)实验观测了细观分层损伤。研究结果显示:干涉量是影响CFRP层合板分层损伤的主要工艺参数;层合板中越靠下边的层间界面,其不产生分层损伤的临界轴向力和临界干涉量越小,即越容易产生分层损伤。

Delamination damage and critical interference percentage for interference fit bolt joint of laminates

The interference fit joint of composite laminates boasts high performance, which is the development trend of composite structures in aircraft. However, delamination damage is easy to occur during the interference fit process. So the delamination damage and critical interference percentage are investigated during the interference fit process of carbon fiber reinforced plastics (CFRP) laminates by theoretical modeling and finite element method. Firstly, the mechanical behavior of interference fit bolt joint process and delamination damage are analyzed. Secondly, the critical thrust force without delamination damage of each interlaminar interface is modeled based on the virtual work principle, and then the critical interference percentage is predicted depending on the relation of inserting force and interference value. Finally, the interference fit bolt joint process of CFRP laminates is simulated by ABAQUS platform, and cohesive elements are applied in the interlaminar interface to simulating delamination damage mechanism of various interference percentages. In addition, microscopic delamination damage is evaluated by scanning electron microscope (SEM) in experiments. It is observed that the interference percentage is the principal parameter inducing delamination damage of CFRP laminates. The critical thrust force and critical interference percentage without delamination damage of CFRP laminates decrease with the interlaminar interface moving downward, which indicates that the closer to the bottom of CFRP laminates, the easier to be delamination.