Interfacial toughening and consequent improvement in fracture toughness of carbon fiber reinforced epoxy resin composites: induced by diblock copolymers

Carbon fibers chemically grafted with hydroxyl-terminated diblock copolymer poly (n-butylacrylate)-b-poly (glycidyl methacrylate) (OH-PnBA-b-PGMA), were used as the reinforcement for epoxy composites. The multi-filament composite specimens were prepared and measured by dynamic mechanical analysis (DMA), to study the interfacial toughness of carbon fiber reinforced epoxy composites with the diblock copolymers. The loss modulus and loss factor peaks of beta-relaxation indicated that composites with diblock copolymers could dissipate more energy at small strain and possess better interfacial toughness, whereas composites without the ductile block PnBA having the worse interfacial toughness. The glass transition temperature and the apparent activation energy calculated from the glass transition showed that the strong interfacial adhesion existed in the composites with diblock copolymers, corresponding with the value of interfacial shear strength. Therefore, a strengthening and toughening interfacial structure in carbon fiber/epoxy composites was achieved by introducing the diblock copolymer OH-PnBA-b-PGMA. The resulting impact toughness, characterized with an Izod impact tester, was better than that of composite without the ductile block PnBA.