Finite element analysis of competitive damage mechanisms of composite scarf adhesive joints by considering thickness effect

Cohesive zone models are demonstrated to fail to predict damage mechanisms of adhesive layer with the increase of thickness, although the load response and ultimate failure strength of adhesive joints are evaluated well to some extent. This paper attempts to explore damage mechanisms of composite scarf adhesive joints with brittle adhesive material under quasi-static loading, where the competitive relationships between the damage behaviors of adhesive layer and the interface debonding between the adhesive layer and composite laminates are investigated. For the epoxy adhesive layer, the damage initiation criteria are developed by considering the hydrostatic pressure, the tension/compression asymmetry and frictional effects, and the damage evolution law is derived using continuum damage mechanics. The bilinear cohesive model and the modified Xu and Needleman's exponential cohesive model are used to predict the interface debonding between the epoxy adhesive layer and glassy fiber/epoxy composite laminates, respectively. FEA is performed to study two competitive damage mechanisms of composite scarf adhesive joints by discussing the effects of the scarf angle, the thickness of adhesive layer and the shape of cohesive models. Results show that 1. two approaches with/without considering damage mechanisms of adhesive layer can be chosen alternatively within the thickness of adhesive layer 0.5-1.0 mm, by weighing calculation efficiency and precision appropriately; 2. damage features of adhesive layer deserve more attention as the thickness increases beyond 1.0 mm.

Automated summary

This paper investigates the damage mechanisms of composite scarf adhesive joints with brittle adhesive material and explores the competitive relationships between the damage behaviors of the adhesive layer and interface debonding. The study develops damage initiation criteria and damage evolution laws for the epoxy adhesive layer. Finite element analysis is performed to study the two competitive damage mechanisms of the adhesive joints. The results show that the damage features of the adhesive layer become more important as the thickness increases beyond 1.0 mm.