The role of the resin fillet in the delamination of honeycomb sandwich structures

In this study, the mechanism of peel fracture (or core/skin delamination) in honeycomb-core sandwich panels was investigated, and the role of resin fillets on energy absorption was elucidated. Fillet deformation and fracture were shown to control the delamination resistance of sandwich panels, to a great extent. In fact the area fraction of fillets on the fracture surface proved to be very important. The delamination resistance data for a variety of panels, made with various materials, cores etc., collapsed to a single master curve when the peel energy was normalized by the delamination energy of the skin material, and this ratio was plotted against the residual area fraction of the resin remaining on the core side after the peel test. A detailed stick/slip mechanism for crack advance was proposed, and its existence was supported by both the load traces and by fractography.