Fiber-reinforced composite materials have been increasingly used over the past few decades in a variety of applications in which a fairly high ratio of stiffness/strength to weight is required. However, these materials are prone to wide range of defects and damages that can cause significant reductions in stiffness and strength. In particular, when the laminated composites are subjected to compressive loads, delamination becomes a constraint in the design process. Various methods have been proposed for the analysis of a plate that contains through-the-width delaminations. In the current paper, a continuous method of analysis is developed for determining the buckling loads of delaminated plates. The system is modeled as a plate on an elastic foundation. The elastic adhesive layer between the buckled sublaminates is represented by some parallel springs. The plate on a discontinuous foundation is treated as a continuous foundation but with added transverse forces at a number of discrete points in the delamination regions to make the net transverse force at each of these points to vanish. The delaminated plates which contain one or two through-the-width delaminations are analyzed. In the cases where two delaminations are located at different depths across the thickness of the laminate, the governing differential equations of each sublaminates become coupled, resulting in a more challenging analysis. Some representative results are shown in the figure below.
Buckling load of a simply supported laminate with a single delamination (Pe: Buckling load of a laminate with a centrally located delamination)