Ultrasonic Evaluation of Thermal Fatigue of Composites

[+] Author and Article Information
S. O. Kasap, V. Mirchandani

Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0

S. Yannacopoulos, J. R. Hildebrandt

Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0

J. Eng. Mater. Technol 114(2), 132-136 (Apr 01, 1992) (5 pages) doi:10.1115/1.2904151 History: Received March 01, 1991; Revised September 21, 1991; Online April 29, 2008


Results are presented on the evaluation of thermally fatigued E-glass composite specimens using ultrasonic techniques. The changes of the acoustic velocity and the attenuation coefficient in the ultrasonic range have been examined as a function of accumulated damage in various thermally fatigued composites. Three types of E-glass fiber reinforced composites have been used in this study having the following fiberglass weaves: (a) randomly oriented short fiber, (b) uniaxial fiber mat with continuous fiber bundles, (c) bidirectional continuous glass fiber mat. Representative specimens were subjected to thermal fatigue by thermal cycling between 25°C and 75°C. The structural integrity of these specimens was evaluated by determining the flexural strength after a number of thermal cycles via three point bending tests. It was observed that both the acoustic velocity and the flexural strength decreased whereas the ultrasonic attenuation increased with the number of thermal cycles which have been attributed to an accumulation of defects in the material and especially to debonding at the fiber-matrix interface. It has been observed that the use of ultrasonics may be very appropriate in evaluating composites in service since a good correlation has been noted between changes in the flexural strength, acoustic velocity and the attenuation coefficient in thermally fatigued composites.

Copyright © 1992 by The American Society of Mechanical Engineers
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