On the intralaminar and interlaminar stress analysis of adhesive joints in plated beams

Abstract

An improved bimaterial adhesive joint model is proposed for the intralaminar and interlaminar stress analysis of adhesively-bonded interfaces in plated beams with thin or moderately thick adhesive layer. To overcome the limitations or unreasonable assumptions in the existing theoretical joint models, both the shear and normal stresses along two adherend–adhesive interfaces are assumed to be different in the present model, and the adhesive layer is modeled as a simplified 2-D elastic continuum. Deformable interfaces are assembled to establish the continuity conditions between the adherend–adhesive interfaces, and the local deformations near the end of the adhesive layer are fully captured. The longitudinal and transverse displacements of the adhesive layer are introduced as two new independent parameters, and the missing “degrees of freedom” in the conventional elastic foundation models are retrieved. Differential governing equation of an adhesively-bonded bi-layer beam is established, and explicit closed-form expressions of beam forces and interface stresses are derived. Comparisons of the present solution with the existing elastic foundation models as well as the full 2-D continuum elastic solutions by the finite element analysis are conducted to validate the presented model. Parametric studies are then conducted to reveal the roles of the adhesive thickness and local interface deformations on the stress distributions both along the adherend–adhesive interfaces (interlaminar) and through the adhesive layer thickness (intralaminar), from which a feasible measure to reduce the strain or stress concentrations is obtained. The present improved adhesive joint model in plated beams sheds light on the effect of adhesive layer thickness in bimaterial bonding assembly and provides a better understanding of potential interface debonding initiation and its propagation path.