The initial post-buckling behavior of face-sheet delaminations in sandwich composites

Should an interface crack between the layers of the composite face-sheet or between the core and the composite face-sheet of a sandwich beam/plate exists, local buckling and possible subsequent growth of this interface crack (delamination) may occur under compression. In this study, the buckling, and initial post-buckling behavior is studied through a perturbation procedure that is based on the nonlinear beam equations with transverse shear included. Closed-form solutions for the load and midpoint delamination deflection versus applied compressive strain during the initial postbuckling phase are derived. Illustrative results are presented for several sandwich construction configurations, in particular with regard to the effect of material system and transverse shear.