Flexural strength of curved sandwich beams with face/core debond

The influence of a face/core (F/C) debond on the flexural stiffness and strength of curved sandwich beams under opening bending moments has been experimentally examined. The sandwich beams consisted of glass/polyester face sheets over a PVC foam core. Debonds of various sizes were defined by inserting thin non-stick Teflon films at the outer F/C interface in the curved region of the beam prior to processing. The beams were tested in flexure in a specially designed four-point bend test fixture. The load versus displacement and surface strains at the apex of the beam were recorded to examine the response. It was observed that the debonded face sheet lifted off of the core and underwent a bifurcation associated with strain reversal. Beam failure occurred by propagation of the debond. It was observed that the beams suffered marginal reductions in stiffness, but substantial reductions in strength due to the presence of a debond. Linear finite element analysis was performed to examine the initial response of the beams.