Response and failure analysis of a graphite-epoxy laminate containing terminating internal plies

A change in laminate thickness due to terminating internal plies acts as a str-ess riser for both intralamina and interlamina stresses. This laminate configuration is referred to as a ply drop. The linear elastic, three-dimensional stress distributions in the vicinity of a ply drop are determined for a graphite-epoxy laminate subject to axial tension and compression by a finite element analysis. It is shown that the interlaminar stresses have a maximum magnitude at the ply drop-off, and decrease proceeding away from the drop. The interlaminar stresses vanish in regions sufficiently removed from the ply dropoff. Two modes of failure initiation are analyzed. In the pure resin regions surrounding the dropped plies, the maximum stress criterion is assumed to govern failure. The Tsai-Wu criterion is used for intralamina failure prediction. The influence of two laminate lay-ups and a variety of ply drop geometries on the rbsponse and failure are presented.