三维六向编织复合材料单剪搭接连接结构在拉伸载荷下的力学性能

通过试验测试与数值模拟相结合的方法对三维六向编织复合材料的螺栓连接性能进行了研究。首先,通过拉伸试验对不同侧向约束螺接方式连接件的连接强度进行了测试。测试结果表明:单搭连接结构的二次弯曲现象明显,连接强度与侧向约束有一定的关系,使用垫片可有效提高连接强度,螺栓拧紧力矩增加对连接强度影响不大;连接结构的破坏模式包括挤压破坏和拉伸破坏,在孔径较小时其主导破坏模式是挤压破坏。随后,基于测试中发现的破坏模式,建立了基于点应力准则的分析模型,并使用升温法实现螺栓拧紧力矩的施加。通过数值结果与试验结果的比较验证了分析模型的可靠性。最后,利用得到验证的分析模型,分析了单搭连接的二次弯曲现象,获得了侧向约束面积、螺栓拧紧力矩及连接平板厚度对单搭单螺栓连接结构力学性能的影响规律。分析结果表明:当侧向约束应力增加时,连接强度表现为先增加后降低的规律。

Mechanical properties of 3D six-directional braided composites single-lap bolted joints under tensile load

The properties of 3D six-directional braided composite bolted joint structure were investigated by the test and numerical simulation. First, the joint strength of bolted joint structure with different lateral restraint was tested by tensile test. The test results show that the second bend phenomenon of the single-lap joint structure is obvious, there is a certain relationship between joint strength and lateral restraint. The joint strength can be effectively improved by using the gasket. The increase of tightening torque of bolted has little effect on joint strength. The failure modes of joint structure include bearing failure and tensile failure. The dominant failure mode is bearing failure when the aperture is small. Then based on the failure mode which was found in test, the analytical model was established basing on the point stress criteria, and the tightening torque was applied to the bolted joints by using temperature rising method. The reliability analysis model can be verified by comparing the numerical results with the test results. Finally, the verified analytical model was used to analyze the second bend phenomenon of single-lap bolted joint structures. The effects of lateral restraint area, tightening torque of bolted joints and the plate thickness on mechanical properties of single-lap bolted joint structures were obtained. The results indicate the joint strength first increases and then decreases with the increase of lateral restraint stress.