复合材料机械连接强度分析及影响因素研究

【作者】 顾亦磊；

【导师】 赵美英；

【作者基本信息】 西北工业大学 ， 飞行器设计， 2006， 硕士

【摘要】 随着复合材料在航空结构中应用的日益广泛,不可避免地会出现许多连接问题,其中主要是机械连接。由于复合材料的各向异性及脆性,机械连接的破坏模式复杂且难以分析,这往往需要耗费大量的时间和财力进行试验。使用高精度的仿真来代替部分试验一直是研究人员和设计者所期待的。本文从工程实用角度出发,对复合材料机械连接进行了大量细致的研究工作。 本文第一部分重点是建立复合材料机械连接高精度仿真接触模型,根据研究目的及研究对象的不同,对复合材料多钉连接分别采用二维及三维接触模型,研究了搭接方式、螺栓预紧力、沉头螺栓锪窝及螺栓间距等因素对钉载比例的影响。针对工程中大量存在的多钉连接问题,开发出适合工程应用的钉群载荷分配计算软件,软件经多个算例验证具有较高的可信度。 第二部分针对复合材料机械连接的特点,结合复合材料破坏机理,在研究国外试验数据及数值模拟结果的基础上,改进了Hashin失效准则,并考虑到复合材料的累积损伤,提出了相应的刚度退化模型。论文中根据螺栓连接侧压的影响,提出对垫圈下单元的刚度退化处理方法,改善了螺栓连接强度预测精度。经与多个模型的试验数据对比,采用本文改进后的失效准则及相应刚度退化模型能较准确地预测螺栓孔的挤压强度。 本文第三部分开展了多钉连接强度分析工作,分析内容包括层合板铺层顺序、螺栓预紧力、沉头螺栓锪窝、紧固件材料、螺栓间距、单搭接次弯曲等因素对层合板多钉连接强度的影响。其中部分计算结果经过试验验证,对工程实践具有参考价值。更多还原

【Abstract】 With the extensive use of composite materials in aircraft structures, bolting and riveting are extensively used as a primary method of forming structural joints. However, designing bolted joints in composite structures is more complex than in metallic structures due to anisotropic material properties, complex failure modes and the inability of the composite to yield and a lot of expansive experiments are needed. Advanced numerical design methods for bolted joints in composite aircraft structures are expected by joints designers. To increase the efficiency of whole structures, the author performed the research on the composite bolted joints.According to different intention 2D and 3D FEM model were built respectively. Clamping force, countersunk head bolts, different distance between the fasteners and lap modes were considered to analyze the load distribution on the bolts. For the purpose of determining the load distribution on each bolt a computer program was developed. The results were compared with available experimental data and good correlation observed.Hashin criteria was improved based on damage mechanics, the experimental data and simulation results obtained from foreign thesis. The related material property reduction rules were proposed and cumulative damage was taken into account. Parametric studies were carried out to evaluate the effect of the new method.The obtained results were compared with experimental data and comparison showed good agreement between numerical and experimental method.In the last part, strength prediction for multi-bolted joints was discussed, and stack sequence, clamping force, countersunk head bolt, fastener material, distance between bolts and effect of secondary bending were taken into account.Except bolt-hole clearance, wash size etc. a major of parameters related to joints were considered, and some of them were validated by experimental data.更多还原