Damage Tolerance Analysis of Cracked Stiffened Composite Panels

Abstract

An approach based on a displacement compatibility model is developed for stiffened composite panels with a crack. Some important improvements on the damage tolerance analysis of the stiffened composite panels have been made in comparison with previous work. Some new results are obtained regarding the effects of adhesive nonlinearity, stringer stiffness and bending, and stringer spacing on strengths and crack growth behaviours of bonded skin/stringer panels. The study indicates that the adhesive nonlinearity benefits the load bearing capacity of the panels. When the stringer is quite thick in comparison to the skin thickness, its out-of-plane bending will lower panel failure strains. Increasing stringer stiffness can not often guarantee the high failure strains of bonded skin/stringer composite panels. As the stringer stiffness exceeds some value, its increase has a negative effect on the load bearing capacity of the panels. For a given ratio of stringer stiffness to panel stiffness, the failure strains of the panels increase as stringer spacing, Wa, decreases. Predictions for failure strains and crack arrest capability agree well with experimental results for several composite panel configurations.