Mode I fracture modeling of elastomer toughened epoxy adhesive joints

An analytical model is developed to correlate the mode I fracture energy of toughened epoxy adhesive joints with microdamage mechanisms generated around a crack tip. The analytical expression for the mode I fracture energy is derived on the basis of total energy dissipation during crack extension. Three dominant damage modes, plastic shear band formation, plastic void growth, and plastic deformation of the entire matrix resin in a crack-tip region, are identified in the proposed model as the primary energy dissipation mechanisms. Numerical results show that the models can predict the effects of adhesive thickness on the mode I fracture energy of toughened adhesive joints. The analytical model involving material constants and microstructural variables should provide some guidelines toward achieving optimum fracture toughness for these types of adhesive joints.