Effect of the compatibilizer agent on the quasi-static and low velocity impact responses of glass woven fabric/polypropylene composites

Glass woven fabric/polypropylene laminates have been studied given their outstanding performance/cost ratio. Their flexural properties, mainly influenced by the adhesion between matrix and reinforcing fibers, have been investigated for systems containing maleated polypropylene (PP-g-MA) amounts ranging from 0% to 10% by weight. Results have shown that the presence of the compatibilizer improves both flexural modulus and strength, achieving plateau values approximately for 5 and 2 wt% of PP-g-MA, respectively. On the contrary, an inverse proportion between the compatibilizer content and the energy dissipated at perforation emerged from low velocity impact tests. The different dependence can be related to the failure mechanisms occurring at the fiber/matrix interface. These mechanisms are able to dissipate large amounts of energy through friction phenomena, and are pronounced when the fiber/matrix adhesion is weak. Pull-out of fibers from the matrix has been detected, in particular, in systems containing low contents of compatibilizer and evidenced by the morphological analysis of fracture surfaces after failure. The large amount of energy dissipation allowed by the relative motion of fibers and matrix occurred before fiber breakage, as confirmed by the evaluation of the laminates ductility index.