TENSILE FATIGUE MECHANISMS IN UNIDIRECTIONAL POLYMER MATRIX COMPOSITE-MATERIALS

Tensile fatigue tests on unidirectional (UD) polymer matrix composites have confirmed that tougher materials are more sensitive to fatigue. Damage studies have revealed that splitting along the fibres is the primary damage growth mechanism. Model tests to study split growth in detail were performed which confirmed that the tougher composites exhibited faster split growth rates than the standard materials. An expression based on simple fracture mechanics was derived and used to show that the growth of splits followed the Paris relationship.