Damage Analyses of Adhesively Bonded Single Lap Joints Due to Delaminated FRP Composite Adherends

Three-dimensional non-linear Finite Element Analyses (FEA) due to an in-plane loading have been performed to evaluate the out-of-plane normal and shear stresses over the overlap region of a Single Lap Joint (SLJ) on different surfaces. These surfaces have been considered as; (i) two interfacial surfaces between the adherends and the adhesive layer, (ii) the mid-surface of the adhesive layer and (iii) two surfaces beneath the surface ply of both the adherends adjacent to the adhesive layer. The critical locations of onset of adhesion, cohesion and delamination failures on the above mentioned surfaces of the SLJ have been determined using suitable damage criteria. A comparative study due to adhesion, cohesion and delamination failures in the SLJ with Fiber Reinforced Polymeric (FRP) composite adherends have been presented. The effects of simultaneous variations of the delamination positions on the out-of-plane peel and shear stress components have been studied by pre-embedding the delamination damages at the critical locations in both the adherends. It has been observed that the possibilities of onset of cohesion failures in the adhesive layer are higher compared to the adhesion and delamination failures. The detailed analyses showed that secondary peaks of out-of-plane stress components (σ z , τ yz and τ xz ) on the mid surface of the adhesive layer appeared at the locations closer to the delamination fronts due to pre-embedded delamination damages. The highest stress magnitudes on the overlap edge of the SLJ have been reduced significantly when the centers of the delamination damages are exactly aligned with the overlap ends of the joint. No significant variations of stress magnitudes have been noticed either when the delaminations are pre-embedded outside the overlap regions or when the delamination damages are completely entrapped within the overlap region.