Analytical prediction of damage growth in notched composite panels loaded in compression

A progressive failure analysis method based on shell elements is developed for the computation of damage initiation and growth in stiffened, thick-skin, stitched graphite-epoxy panels loaded in axial compression. The analysis method involves a step-by-step simulation of material degradation based on ply-level failure mechanisms. High computational efficiency is derived from the use of superposed layers of shell elements to model each ply orientation in the laminate. Multiple integration points through the thickness are used to obtain the correct bending effects through the thickness without the need for ply-by-ply evaluations of the state of the material. The analysis results are compared with experimental results for three stiffened panels with notches oriented at 0, 15, and 30 deg to the panel width dimension. A parametric study is performed to investigate the damage growth retardation characteristics of the Kevlar(R) stitch lines in the panels.