On the analysis of adhesively bonded structures: A high order semi-elastic adhesive layer model

Several fundamental questions remain open regarding the behavior of adhesive layers in axially loaded lap shear joints. These issues are: the existence and magnitude of longitudinal tensile stresses, the appropriateness of an assumed state of plane stress versus a state of plane strain and the relevance of these two states with regards to failure mode prediction. To investigate these issues, a high-order approximate elasticity solution for the adhesive layer is developed. This linear elastic model satisfies all natural and essential boundary conditions for the adhesive layer. Using this model, it is found that the longitudinal tensile stresses are negligible and that the shear stress state does not vary through the thickness of the adhesive layer. It is also found that the prevailing plane stress adhesive layer models underestimate the adhesive peel stresses by nearly 10%.