Compressive property degradation of composite stiffened panel due to debonding and delaminations
The effect of localized damage due to impact on compressive buckling as well as postbuckling behaviors of blade stiffened composite plates was numerically studied. A partial debonding between a skin panel and a flange and multiple delaminations in the skin panel were chosen as the localized
damage. The three-dimensional composite elements used to analyze the compressive behavior of the stiffened panel with multiple delaminations was found to be suitable for this kind of complex composite structure. The contact problem between the skin and flange panels was approximated by a spring
element with no restraint of the positive relative displacement and a strong restraint of the negative displacement. At the delaminations in the skin panel, which tended to close during compression, the normal relative displacement was constrained to prevent the delaminated portions from overlapping;
this constraint made the convergence of the solution quite smooth compared to the case where the contact problem was exactly considered. When a debonded area only was located at the edge of the flange, no notable reduction of compressive buckling load was found until the size of the debonding
reached a half wavelength of the buckling mode. The compressive buckling load dropped significantly when multiple delaminations, which were small in comparison to the half wavelength of the buckling mode, accompanied the skin-flange debonding. The energy release rate distributions at the damage
edges, calculated using the virtual crack closure technique, increased quite rapidly, particularly in the transverse direction after buckling became sufficient to increase the delamination.