On toughening of epoxies and their carbon fibre-reinforced composites

Epoxy resins were introduced commercially in the late 1940s and have been used widely in industrial applications, including fib re-reinforced pol)'lner matrix composites, adhesives and coatings. While epoxies have numerous advantages, they suffer from brittleness as a result of their high crosslink polymer structure. The present work is a brief review of the toughening methods used previously to improve the crack growth resistance of epoxies and their fibre reinforced composites. Toughening agents discussed include rubbers, inorganic fillers, thermoplastics and hyperbranched polymers. The chapter provides the state-of-the-art knowledge in this field as well as indicates the future directions towards improving the fracture toughness of epox ies.