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31 March 1998 Microwave and ultrasonic NDE of thick glass-fiber-reinforced composites
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Both microwave and ultrasonic techniques for NDE are based on wave propagation and scattering from discrete defects in materials. Conventional ultrasound provides good separation of refections from material boundaries and defects by using short-pulse excitation for transducers of wide bandwidth and damping. Microwave propagation and scattering in nonmetallic composites follow similar principles as ultrasound, with the important difference that the intrinsic difference in wave impedance between material and small voids are less here than in ultrasound. As a consequence, in thick, highly inhomogeneous and somewhat porous composites, microwave NDE may be a good alternative to ultrasound which may suffer from large signal loss due to scattering from voids over a long path length. In this paper we present microwave and ultrasound pulse-echo data in thick composites to illustrate the capabilities of microwave techniques to provide defect information generally sought after by ultrasound, viz. defect location, size, and shape.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John M. Liu "Microwave and ultrasonic NDE of thick glass-fiber-reinforced composites", Proc. SPIE 3396, Nondestructive Evaluation of Materials and Composites II, (31 March 1998);

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