复合材料螺接力学行为精细化有限元分析方法

针对航空用纤维增强树脂基复合材料螺栓连接的力学行为研究难题,采用有限元软件二次开发的方法,提出了涵盖层合板高效建模、扭矩与预紧力关系、钉孔配合间隙与滑移过渡段、渐进损伤判断与性能退化等方面的精细化有限元分析模型。提出了基于应变等效原理的紧固件预紧力-扭矩试验测试方法,降低了紧固件预紧力-扭矩转换精度对数值模拟精度的影响。提出了基于修改螺栓头与层合板接触平面摩擦因数的方法以实现对含钉孔配合间隙的复合材料螺接接头的力-位移响应在滑移过渡段的较好模拟。复合材料单搭接螺接接头单剪试验和有限元预测的力-位移曲线对比结果显示极限载荷最大预测误差为17.2%,证明了所提方法能有效地预测复合材料单钉/多钉螺接结构的力学性能演变规律,且所提方法提高了预测结果与试验结果的匹配度,提升了有限元分析的效率,为航空先进复合材料连接结构的力学行为分析奠定了建模技术基础。

Refined Finite Element Analysis Method for Mechanical Behavior of Composite Bolted Joints

For problem of mechanical behavior study of bolted connections of fiber reinforced resin matrix composites for aviation, a refined finite element analysis method was proposed by finite element software further-development method, which concludes the high-efficiency modelling of laminates, the relationship between torque and preload, the fit clearance and slip transition section of pin hole, progressive damage judgment and performance degradation. Based on the principle of strain equivalence, the test method of preload-torque relationship of the fastener was proposed, which reduces the influence of fastener preload-torque conversion accuracy on numerical simulation accuracy. A method based on modifying the friction coefficient of the contact plane between the bolt head and the laminate was proposed to well simulate the sliding transition section on the load-displacement response for composite bolted joint considering bolt-hole clearance. The results of the load-displacement curves from experiments and finite element prediction of the single-lap composite bolted joints subjected to single-shear loading show that the maximum prediction error is 14.5%, which validates that the proposed method can effectively predict the evolution rule of mechanical behavior of composite single-bolt &multiple-bolt joints. The proposed method improves the matching degree between the prediction results and the experimental results,and it improves the finite element analysis efficiency, which lays a technical foundation of modelling for the mechanical behavior analysis of the advanced composite connection structures for aviation.