The interface of CFRP face sheets and aluminum foam cores in hybrid sandwich panels manufactured by a PUR spraying process

Hybrid sandwich panels with aluminum foam core structures and face sheets made of carbon fiber reinforced plastic (CFRP) were manufactured by means of an automated polyurethane (PUR) spraying process with low pressure during the curing of the resin. Face sheets and core were combined by an integrated interface of PUR foam, which also acts as the face sheet matrix. Prior to the extraction of specimens, the sandwich panels were investigated by X-ray radiography, in order to detect local inhomogeneities. The interfacial properties of face sheets and core structure, determined by the two interlocking foam structures of the PUR matrix and the aluminum core, was characterized by the climbing drum peel test and by optical analysis. The influence of the process parameters, such as the face sheet architecture, the area weight of fibers, the amount of applied PUR and the core cell structure, were investigated. The results show a correlation of the PUR penetration depth and the failure mechanisms occurring in the climbing drum peel test.