Impact damaging of polypropylene-glass composites

The damage tolerance of multi-layer structures is strongly related to the assembly stacking sequence and properties of constituent plies. This contribution deals with interlaminar graded interface strength (IGIS) laminated structures, prepared by properly alternating layers of a woven glass fabric with peculiar sequences of compatibilized and not compatibilized polypropylene film layers, symmetrically arranged with respect to the structure mid-plane. The behaviour at two impact energies (namely 6 and 25 J) of all configurations is investigated. Impacted and not impacted specimens are non-destructively evaluated with lockin thermography (LT), which is a remote and non-destructive technique. Results show that the impact damage type is strongly related to the used layer sequence in the IGIS laminate and to its symmetry.