Effects of interface strength gradation on impact damage mechanisms in polypropylene/woven glass fabric composites

The attention of the present work is focused on the behaviour of interlaminar graded interface strength (IGIS) laminated structures under impact. IGIS structures are made of layers of a woven glass fabric alternated with compatibilized and not compatibilized polypropylene film layers, symmetrically and asymmetrically arranged with respect to the middle plane. For each configuration some specimens are subjected to impact tests at energies of 6 and 25 J while one specimen is left unloaded. Impacted and not impacted specimens are non-destructively evaluated with lock-in thermography (LT). Results highlight the role played by the stacking sequence in the IGIS laminate and confirm data previously obtained through mechanical characterization.