关键词: 层合板, 单搭接, 胶接界面, 虚拟裂纹闭合技术, 疲劳, 复合材料

Abstract: The mechanical properties and fatigue characteristics of the single lap bonded surface made of two different thicknesses of composite materials were studied through a combination of experimental research and numericalsimulation. Virtual crack closure technique (VCCT) was used to simulate the bond interface, and the crack initiation and propagation principle of single lap specimens under axial tensile load was studied. It was found that at the damage initiation time G_Ⅲ was much smaller than G_Ⅰ and G_Ⅱ, while G_Ⅰ decreased and G_Ⅱ increased with increasing crack length. The out-of-plane peeling stress mainly affected the interface damage initiation, while the sliding shear stress mainly affected the crack propagation. Fatigue tests were designed for the composite single lap specimens of two thicknesses to determine their fatigue life under different fatigue loads. The values of G_Ⅰ/G_ⅠC and G_Ⅱ/G_ⅡC of the corresponding crack tips were given. N-G_Ⅰ/G_ⅠC and G_Ⅱ/G_ⅡC curves are drawn, and it was found that the range of life decrease with the increase of G_Ⅰ/G_ⅠC was much larger than that of G_Ⅱ/G_ⅡC. The failure forms of the adhesive interface were compared, and it was found that the failure forms of the test pieces with thicker adhesive layers were smoother than those with thinner adhesive layers, and the failure area of the adhesive layer accounted for a higher proportion. With an increase in fatigue load value, the proportion of the failure area of the adhesive layer in the lap area decreased, while the tear area of the bonded composite fiber layer increased.

Key words: laminates, single lap joint, bonding interface, VCCT, fatigue, composites