Toughening of carbon fiber/thermoset composite by the morphology spectrum concept

Morphology spectrum toughening, a novel technique for toughening brittle carbon fiber/thermoset composites, was applied to a polyetherimide-modified carbon fiber/dicyanate composite. Composites were prepared by inserting a polyetherimide film between the prepregs of carbon fabric impregnated by dicyanate alone, and by controlling both the relative rates of dissolution of the polyetherimide and the polymerization of the dicyanate by adding zinc stearate catalyst. A composite with 13 wt% polyetherimide afforded a mode I interlaminar fracture toughness of 1.4 kJ/m(2), almost 1.8 times higher than that of a control composite containing same composition of polyetherimide. Two effects were observed. First, a thermoplastic continuous morphology formed in the center interply zone, where the concentration of polyetherimide was high, provided good fracture toughness. Second, a thermosetting continuous morphology formed in the fiber-rich zone, where the concentration of polyetherimide was low, maintained good interfacial shear strength between the fiber and the matrix.