Defect and Damage Characterization in Composite Materials

Abstract

Defects may be introduced in composites during processing and fabri- cation. They include contaminants, porosity, inclusions, delaminations, and nonuniform fiber and matrix distributions. Damage induced in service under loading and environmental variations includea matrix cracking, de- lamination, fiber breakage, and dispersed defecta, such as matrix ageing and degradation. A variety of nondestructive evaluation methods have been used for composites, but the most effective and practica! ones are ultrasonic and radiographic methods. These methods can be supplemented by others, such as acoustic emission, interferometric, and wave propagation techniques. The sensitivity and effectiveness of such NDE methods are discussed in connection with three applications: thick composites, metal-matrix com- posites, and fatigue damage. THICK