复合材料单搭胶接接头静力与疲劳裂纹扩展研究

Study on Static and Fatigue Cracks Propagation of Single-lap Bonded Composite Joints

胶层裂纹是复合材料胶接接头的常见损伤形式之一,严重影响复合材料结构的完整性。以胶接结构中常见的复合材料单搭胶接接头为研究对象,建立其三维数值模型,采用双线性内聚力本构关系表征静态裂纹扩展,并将静态模型扩展至疲劳裂纹扩展模型;结合静力与疲劳试验,对单搭胶接接头的应力应变分布规律、裂纹扩展与破坏机理展开研究。结果表明:单搭胶接接头在静力和疲劳载荷下,由于偏心拉伸应变呈非线性变化,搭接区域两端由于应力集中首先出现裂纹,由两端向中央区域扩展并迅速贯穿整个搭接区域,静力失效模式为内聚破坏,疲劳断面为界面脱胶。

The crack in adhesives is one of the common damage patterns in composite adhesive structures,which will affect the integrity of composite structures.In this paper,the single-lap bonded composite joints which are the common adhesive structures in aircraft are chosen as the study object.The three-dimensional numerical model is es⁃tablished with the bilinear cohesive constitutive relation characterizing the static crack propagation,and then the static model is extended to fatigue crack propagation model.The distribution of stress and strain,crack propagation and failure mechanism are studied by using the experiment and numerical methods.The results show that the strain of single-lap adhesive joints varies nonlinearly under static and fatigue loadings because of the eccentric tension.Due to the stress concentration,fatigue cracks appear on both ends of the lapped area firstly,and then extend to the central area until cover the whole lapped area.The static failure mode is cohesive failure,and the interface debond⁃ing failure is observed in fatigue fracture.