Numerical analysis of the strength and interfacial behaviour of adhesively bonded joints with varying bondline thicknesses

A new model of adhesive joints with varying bondline thicknesses is proposed and explored numerically in this paper. Three types of roughness morphology are considered, including triangular, circular and trapezoidal protuberances. With the help of cohesive zone model and a user subroutine USDFLD code implemented in finite element method, the ultimate load, the fracture energy as well as the interface damage are calculated. The effect of protuberance's geometric parameters, adhesive type as well as interfacial defect are comprehensively studied. It is found that by introducing protuberances, a gradient change of the adhesive thickness is formed, thus changing the load bearing capacity of adhesive joints. Proper tuning the protuberance's geometric parameters will effectively improve the strength and interfacial behavior of bonded joints. What is more, defects must be carefully removed in order to use protuberances to improve a SLJs' strength. The findings should be useful for the design of novel adhesive structures and enlighten new adhesively bonded strategies.