Thermography-Applications To The Manufacture And Nondestructive Characterization Of Composites

The increasing use of composite materials in military and commercial aircraft requires the development of improved quality control and nondestructive inspection techniques to assure their structural integrity and reliability. Infrared thermography is particularly useful for rapid scanning and detection of manufacturing inhomogeneities and inservice damage states in composites. The relationship between the surface thermal patterns and the interior damage is governed by the type of damage, thermal conductivity of the material and the distance between the surface and the damaged region. Applications of real-time thermography as a quality control technique for processing fiber reinforced composites, and as a nondestructive technique for monitoring growth and development of defects in composite laminates and rotor blades during low-frequency, high amplitude fatigue tests will be discussed. Applications of high frequency vibrothermography for characterizing composite structures will also be presented. This latter technique involves the use of high-frequency, low amplitude ultrasonic excitation of a sample.