An evaluation of the influence of geometry and of material properties at free edges and at corners of composite laminates

Characteristic of multilayered structures is the edge-stress problem, where interlaminar shear and normal stresses are responsible for delamination. Whereas analyses implicitly accounting for the singularity at the edge interface and which prove its existence numerically can be found in the literature, analyses which explicitly account for it are lacking. To make up for this deficiency and at the same time to assess the effect of material properties and layer orientation, the slope of inclined edges and the angle at corners, a three-dimensional, finite element stress singularity analysis is carried out. A three-dimensional singular wedge element with variable singularity power shape functions based on a displacement formulation is used for this purpose. A predictor-corrector procedure is employed to fulfill the stress contact and traction-free conditions. The present numerical results confirm the existence of the singularity for all the lay-ups investigated. They show a negligible effect of material properties, lay-up and slope at the free edge. On the contrary, a considerable effect of the lay-up and of the vertex angle is focused at corners.