Stress and Delamination Analysis on Overlapped-Grouped and Overlapped-Dispersed Tapered Composite Laminate

A modern aeronautical structure is made of a laminated composite in which plies are terminated at discrete position to provide taperness. Ply termination is called ply-drop. Thickness variation in laminated composite is achieved by changing the number of plies in proportion to the thickness change. It requires the termination of plies within the laminate. In the present study, two different ply-drop configurations are taken for the analysis under tensile loading: overlapped-grouped and overlapped-dispersed. Commercial finite-element software ANSYS 14.0 is used for the analysis. To construct the model geometry, layered 3-D finite element (SOLID 20 node 186) is considered which have six degrees of freedom at each node. The Tsai–Wu criterion is implemented to obtain the value of the failure factor for separate plies. Interlaminar stress variations along the interface of plies are determined to initialize possible delamination sites. For both configurations the value of the failure factor is found to be maximum at the position of the first resin pocket tip. In case of overlapped-grouped, delamination growth occurs at a position near the thin section but in case of overlapped-dispersed it is spread over discrete positions over the laminate.