Failure of delaminated carbon/epoxy composite plates under compression

The purpose of this work is to study the buckling loads, buckling modes, po stbuckling behavior, and critical loads of delamination growth for delamina ted unidirectional carbon/epoxy composites. Nonlinear buckling analysis, wh ich is a finite-element method including contact elements to prevent the ov erlapping situation, was applied to predict the delamination buckling loads . In order to predict the delamination growth loads, the total strain-energ y release rate criterion, the strain-energy release rate component criterio n, and the inerlaminar stress criterion were used in the postbuckling analy sis. Experimental results were also provided to compare with the prediction . The results indicate that nonlinear buckling analysis has very good agree ment on the buckling loads with the experiments except for the global buckl ing case. For global buckling mode, the buckling loads are suggested to rep resent the failure loads of delaminated composites, and postbuckling analys is may not be necessary. For mixed and local buckling modes, the postbuckli ng behavior is in the mixed mode, and the failure of the delaminated compos ite is due to the growth of delamination. The errors of the three different criteria in predicting delamination growth loads are from 10% to 22% for d ifferent cases.