复合材料沉头螺栓连接强度分析与渐进损伤研究

发布时间：2019-02-20 18:07

【摘要】：复合材料凭借其比强度及比刚度高、抗疲劳及抗腐蚀性能好等优越性在航空器的设计制造方面得到了极大应用。随着飞机结构整体化设计的发展,构件和紧固件数量的大大减少,连接传递的载荷变得更大,因此连接成为更加关键的结构。复合材料连接中,因结构的形状和材料的间断极易引起高应力集中,加之铺层方式导致其各向异性,更增加了连接结构的复杂程度。沉头螺栓在具有良好的气动外形的同时可以减小孔边应力,还可抑制损伤向孔边扩展,在飞机连接中具有十分广泛的应用。本文对复合材料-钛合金沉头螺栓单剪搭接接头进行研究,分别建立单钉和双钉两种模型,采用改进的Tserpes失效准则,充分考虑了拉伸和挤压状态下的基体损伤、纤维断裂、基体-纤维剪切和分层等失效模式,并采用其改进的材料性能退化准则,在纤维损伤扩展至板宽或板端边缘为接头最终失效判据的基础上,增加孔边局部挤压损伤导致复合材料板最终失效的判据,同时,沉头螺栓剪切断裂也作为一种接头最终失效的判据被考虑在内,利用ANSYS的二次开发语言APDL将上述准则编程并嵌入到主程序中,实现参数化建模,并通过试验对比,验证了仿真模型的正确性;讨论了铺层方式、锪孔深度、拧紧力矩、板宽及端距等接头参数对连接强度及初始损伤的影响,并利用MATLAB软件对各参数与最终失效强度的关系进行优化处理,进一步选出接头的最优参数;对采用最优参数的接头进行渐进损伤过程的可视化分析,分别对比了单钉接头铺层角度为0°、45°、-45°和90°铺层从产生初始损伤,到损伤扩展最后导致接头最终失效的损伤扩展过程,对双钉接头不同角度铺层分析的同时,更加详尽地对沿复合材料板厚度方向不同位置铺层的损伤扩展情况进行对比分析。
[Abstract]:The composite material has been widely used in the design and manufacture of aircraft because of its advantages such as high specific strength and stiffness, good fatigue resistance and corrosion resistance. With the development of aircraft structure integrated design, the number of components and fasteners is greatly reduced, and the load transferred by the connection becomes larger, so the connection becomes a more critical structure. Due to the high stress concentration caused by the shape and discontinuity of the structure and the anisotropy caused by the layering mode, the complex degree of the connection structure is increased. The countersunk head bolt has good aerodynamic shape and can reduce the stress of the hole edge and restrain the damage spreading to the edge of the hole. It is widely used in aircraft connection. In this paper, the single shear lap joint of composite material and titanium alloy countersunk bolt is studied. Two models of single nail and double nail are established, and the modified Tserpes failure criterion is adopted to fully consider the matrix damage and fiber fracture under the condition of tensile and extrusion. The matrix fiber shear and delamination failure modes are adopted, and the improved degradation criterion of material properties is adopted. The ultimate failure criterion of the joint is fiber damage extending to the width of the plate or the edge of the end of the plate. The ultimate failure criterion of composite plate caused by increasing the local extrusion damage at the hole edge is also taken into account as a criterion of ultimate failure of joint, and the shear fracture of countersunk bolt is also taken into account. The above criteria are programmed and embedded into the main program by using the secondary development language APDL of ANSYS, and the parameterized modeling is realized, and the correctness of the simulation model is verified by experiment and comparison. This paper discusses the influence of the joint parameters, such as laying mode, countersink depth, tightening torque, plate width and end distance, on the connection strength and initial damage, and optimizes the relationship between each parameter and the ultimate failure strength by using MATLAB software. The optimal parameters of the joint are further selected. The progressive damage process of joints with optimal parameters is analyzed visually, and the initial damage is compared between 0 掳, 45 掳, -45 掳and 90 掳laying angles of single nail joints, respectively. In the process of damage propagation which leads to the ultimate failure of the joint, the damage propagation in different positions along the thickness of the composite plate is compared and analyzed in more detail, while the different angles of the double nailed joint are analyzed.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;TH131.3

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