纤维增强树脂基复合材料连接结构强度与失效分析

采用拉伸试验和有限元分析方法研究纤维增强树脂基复合材料螺栓连接与胶–螺混合连接结构的失效机理。通过拉伸–剪切试验分析其载荷–位移曲线,结合有限元仿真结果及断面微观结构变化分析其结构强度和失效机理。结果表明,螺栓连接结构孔周碳纤维丝束受到螺栓挤压力变形后传递给树脂基体。因此,呈现纤维屈曲变形,树脂基体由均匀分布状被断裂的纤维短束挤压变成团簇状,形成结构不均匀而出现薄弱区域。胶–螺混合连接结构呈现拉伸断裂式破坏,断口处碳纤维丝束在拉伸–剪切作用下从环氧树脂基体中拔出并损伤断裂,丝束方向杂乱排布。附着在碳纤维丝束周围的树脂基体从均匀分布状变为团聚状,连接结构在达到极限载荷之后出现拉伸断裂,呈现净截面破坏,并且在重新分配载荷之后板材之间的胶粘剂对纤维的破坏会起延滞作用。材料强度、螺栓强度、胶层强度及螺栓宽径比等因素均会成为影响连接结构失效破坏的因素。

Research on Strength and Failure Analysis of Fiber Reinforced Resin Matrix Composites

Experimental methods and finite element are used to study the failure mechanism of mechanical joints and adhesive-bolt hybrid joints.The load-displacement curve is analyzed by tensile-shear test,and the microstructure of the section is analyzed combining the stress distribution of the finite element simulation results.The results show that the perforated carbon fiber tow of the bolted joint structure is deformed by the bolt pressing force,which is passed to the resin matrix,so the fiber is subjected to buckle deformation,and the resin matrix is squeezed into a cluster by a short bundle of fibers that are uniformly distributed.Therefore the formed weak structure is due to uneven structure.Adhesive-bolt hybrid joints exhibits tensile fracture failure,the carbon fiber tow at the fracture is pulled out from the epoxy resin matrix under tensile-shearing and damages the fracture,and the direction of the tow is disorderly arranged.The resin matrix attached to the fiber changes to be agglomerated,and the joint structure fractures after reaching the ultimate load.And the adhesive between the sheets has a retarding effect on the destruction of the fibers after the redistribution of the load.Factors such as material strength,bolt strength,adhesive strength and bolt width to diameter ratio will be factors that affect the failure of the joint structure.