Effects of ply-arrangement on compressive failure of layered structures

Using detailed finite element models, compressive failure mechanisms of com posite structures consisting of many laminae are analyzed. It is assumed th at the structures contain interlaminar delamination and their failure mode to be characterized by either buckling or delamination growth. Our primary goal is to identify the effects of delamination and ply-arrangement on the multi-layered structures. Up to 32 laminae are distinctly modeled in this i nvestigation. Our study considers two most basic geometry; one is flat pane ls under compressive load and the other is cylindrical shells subjected to external pressure. In both cases, the energy release rate and mixed-mode st ress intensity factors are computed to quantify the crack driving force. Th e results are used to determine dominant failure initiation mode, structura l buckling or delamination growth. Regardless of the structural type and to tal number of layers, a significant reduction in the load carrying capacity may occur when interlaminar delamination exists. In the flat panels, inter laminar delamination can generate unstable post-buckling behavior and lower the steady-state post-buckling load. However, delamination growth does not likely to occur during the pre-buckling stage. For the cylindrical shells, delamination growth may initiate prior to structural buckling. The locatio n of delamination also plays an important role in defining the critical cra ck initiation load. When the delamination is located within 25% to 40% of s hell thickness measured from the outer surface, the crack initiation load c an be as low as half of the buckling load. In both types of structures, as the total number of plies increases, the layer effort diminishes. The overa ll deformation and failure behaviors of panels with large number of layers approach those of the infinite-layer model with homogenized material proper ties. (C) 2000 Published by Elsevier Science Ltd.