Evaluation of stress concentration effects in single-lap bonded joints of laminate composite materials

This paper presents a two-dimensional finite element analysis of composite bonded single-lap joints. The model uses six-node interface elements compatible with eight-node isoparametric plane solid elements. The interface finite elements were placed between the adherends and the adhesive, at the midplane of the adhesive and at the interfaces between different oriented layers of the adherends. The main objective of the interface elements is to obtain stress fields at interfaces between different materials, which is not possible with conventional solid finite elements. Normalised shear and peel stresses were calculated at those interfaces along the overlap length considering a material linear elastic and geometric nonlinear analysis. Joints made of adherends with both the same and different material properties were studied. The results show important stresses variation along the adhesive thickness near the extremities of the overlap length. The influence of these stress concentrations in damage initiation of bonded composite lap-shear joints is also discussed.