Matrix Toughness, Long-Term Behavior, and Damage Tolerance of Notched Graphite Fiber-Reinforced Composite Materials

The emergence of new toughened-matrix composites with improved durability has resulted in the need to understand the influence of increased toughness on long-term damage tolerance. Several graphite fiber-reinforced composite material systems with epoxy and thermoplastic matrices and unidirectional tape and woven cloth fiber architectures are compared in the present investigation of the fatigue response of notched laminates. Through the evaluation of damage and measurement of residual strength during fatigue damage development, it was concluded that long-term behavior and damage tolerance are controlled by a number of interacting factors such as matrix toughness, fiber architecture, loading levels, and damage types and distributions. Deficiencies associated with the prediction of long-term behavior from common measures of damage tolerance are discussed.