A study of the fracture, mechanical behaviour and morphology of an epoxy resin system

The fracture and mechanical properties of an epoxy resin system have been investigated as a function of changes in stoichiometry and heat treatment. Relationships between the various macroscopically measured properties and the microscopic characteristics of the cured resin are described. The investigation shows that the concept of fracture surface work, Ƴ , measured by a cleavage technique, is a sensitive parameter for monitoring changes in the resin's fracture properties and that the Irwin-Kies and Berry analyses can provide a more sensitive monitor of Ƴ than the Gurney method, in some circumstances. The investigation also demonstrates how the elastic and visco-elastic properties of the resin can effect plasticisation at the tip of a crack, with consequent improvement in fracture toughness. To aid the interpretation of the mechanical data, a morphological characterisation of the cured resin will be described in which quantitative infrared spectroscopy, thermo-mechanical analysis, solvent. uptake resistance, chemical and ion-beam etching methods have been used.