Effect of Material Anisotropy on Delamination Damage in Adhesive Bonded Lap Shear Joints Made with Curved Laminated FRP Composite Panels

Abstract

This paper deals with mixed mode fracture behaviour of embedded delaminations in lap shear joints (LSJs) made with curved laminated FRP composite panels under uniform applied extension. The delaminations are presumed to be pre-existed at the interface of the first and second plies of the strap adherend of the LSJ at a location more prone to failure as per Tsai-W� failure criterion. Three-dimensional nonlinear finite element analyses of several LSJs have been carried out using contact and multi-point constraint (MPC) elements. Progressive growth of embedded delamination has been simulated by sequential release of the MPC elements. Strain energy release rate (SERR), being an indicative parameter, has been computed using virtual crack closure technique for assessment of structural integrity of the LSJs. The inter-laminar stresses and the three individual modes of the SERR in the vicinity of either end of the delamination front are found to be much different from each other indicating dissimilar rates of growth of delamination. The degree of anisotropy of the materials of the curved adherend panels influences the inter-laminar stresses and therefore the SERRs in the vicinity of the delamination fronts. Thus, a choice can be made in favour of use of some particular type of FRP composite materials wherein the SERR values would be less, thereby enhancing the overall strength and structural integrity of the LSJs. Here in this paper, it has been found that glass/epoxy material is better suited either to prevent or slow down the delamination propagation if the strength requirement is met. � 2016 Shiraz University.