This research studied the effects of an inserted circular delamination on the strength of an eight-ply, quasi-isotropic composite laminate. Cylindrical panels were loaded compressively, and the global buckling load of the delaminated plies were examined. It was found that, for the level of delamination defect investigated, a linear bifurcation analysis gave fairly accurate predictions of the global panel strength. Load values, which caused local instabilities in the region of panel damage, were also recorded and compared to an approximate analysis.

During the experimental phase of this research, certain physical responses of the panels led to a set of simplifying assumptions. It was thought that there existed a value of strain that when applied to a circular delamination would cause the sublaminate to buckle. The value of strain in the sublaminate should be related to a value of strain in the curved panel. Some method of relating these two values of strain was suggested by the results of experimental tests.