Nondestructive evaluation of damage accumulation processes in composite laminates

This paper presents results from several interdisciplinary studies of the mechanical response of composite materials, in which mechanics and materials science were used in concert with nondestructive evaluation (NDE) to investigate the damage accumulation process. Specific examples are cited for the initiation and growth of damage in notched and unnotched laminates subjected to cyclic loading histories. The process of damage accumulation in composite materials involves a number of damage modes, including matrix cracking, delamination, and fiber fracture, which initiate, grow, and interact to form a complex network of damage details called the damage state. Nondestructive techniques, including replication, light and electron microscopy, X-ray radiography, ultrasonics, stiffness change, and thermography, are used to detect and monitor the progressive development of damage throughout the fatigue life and to evaluate its effect on fatigue response of the laminates.