In this study, the structural behavior of composite structures considering damage tolerance was investigated by the finite element analysis and experiments. The impact damage of the stiffened composite plate was predicted by the finite element analysis implemented by modified failure criterion. An improved C-SCAN technique proved the damage prediction for stiffened composite structures. The ply-by-ply delamination predicted by the present analysis showed good agreements with experiments.
The buckling and postbuckling strengths for unstiffened composite plates and stiffened composite plates with various impact energies were studied numerically and experimentally. To predict residual strengths, a progressive failure model with the degradation of elastic moduli in the damaged region was adopted in a nonlinear finite element analysis. 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 predicted buckling and postbuckling residual strengths showed good agreements with experiments. The impact damage characteristics and the postbuckling strengths of blade stiffened composite plates were discussed. In experiments, the fiber optic sensor was successfully inserted to the filler of the stiffener with a view to detect buckling and postbuckling behavior. The delamination growth was also observed for I-stiffened composite plates with different impact locations under the cyclic compressive load.