Abstract
The definition of toughness is the first issue that must be clarified in describing toughness in thermoset resins. This review is focused on toughness as measured by resistance of a material to the propagation of cracks. First, toughness obtained by fracture toughness tests has been reviewed. Toughness under crack propagation condition is achieved in polymers by the involvement of a significant volume of material in the deformation zone. For maximum toughness, the crack tip deformation processs is shear yielding. The addition of dispersed rubber particles can enhance shear yielding due to local stress concentrations around the particle. The onset and development of shear yielding around the rubber particles have been discussed on the basis of FEM calculations.
