Compressive failure of sandwich beams with debonded face-sheets

Axial compression tests were performed on debonded sandwich composites made of graphite/epoxy face-sheets and aramid fiber honeycomb core. The sandwich beams were manufactured using a Vacuum bagging process. The face-sheet and the sandwich beam were cocured. Delamination between one of the face-sheets and the core was introduced by using a Teflon(R) layer during the curing process. Axial compression tests were performed to determine the ultimate load carrying capacity of the debanded beams. Flatwise tension tests and Double Cantilever Beam tests were performed to determine, respectively, the strength and fracture toughness of the face-sheet/core interface. From the test results semi-empirical formulas were derived for the fracture toughness and ultimate compressive load carrying capacity in terms of the core density, core thickness, face-sheet thickness and debond length. Four different failure modes and their relation to the structural properties were identified. Linear buckling analysis was found to be inadequate in predicting the compressive load carrying capacity of the debonded sandwich composites.