Strengthening and toughening mechanisms for polypropylene/glass fiber composite foams under three-phase coexistence

Composite foams were obtained through a two-step molding process in an injection molding machine. Gas phase was introduced into the mixture of molten polypropylene (PP) and solid glass fiber (GF). The interfacial behavior was investigated, and the strengthening and toughening mechanisms for PP/GF composites under three-phase coexistence were discussed. The incorporation of gas phase significantly increased the tensile strength by 112 % and impact toughness by 105 % in comparison to its unfoamed counterpart. The resulting mechanical properties of the PP/GF composite foams were found to depend considerably on the coexistence state of solid (GF) and gas (cells) phases and the cell structure of the foams.