Postbuckling strength of stiffened composite plates with impact damage

Abstract

The buckling and postbuckling strengths for unstiffened and stiffened composite plates with various impact damages were studied numerically and experimentally. To predict the residual strength, a progressive failure model with the degradation of elastic moduli in the damaged regions was adopted in a nonlinear finite element method. The progressive failure analysis used the maximum stress criterion and the complete unloading model. The degradation ratio in each sublaminate was determined by delamination distributions through the thickness of laminates. The ply-by-ply delamination was detected by an improved ultrasonic technique. The predicted buckling and postbuckling strength showed good agreement with experimental results. The correlation between the impact damage and the postbuckling strength is discussed. The delamination growth was also observed for I-stiffened composite plates under the cyclic compressive load.