Shearographic and Holographic Assessment of Defective Laminates With Bond-Lines of Different Elasticities

[+] Author and Article Information
H. M. Shang, L. M. Tham, F. S. Chau

Department of Mechanical and Production Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 0511

J. Eng. Mater. Technol 117(3), 322-329 (Jul 01, 1995) (8 pages) doi:10.1115/1.2804546 History: Received March 24, 1994; Revised October 06, 1994; Online November 27, 2007


While defects in laminated plates are readily revealed using double-exposure shearography and holography, when an incremental vacuum pressure is applied between the exposures, the apparent defect size, measured from the boundary of the perturbed fringes, may over-estimate the actual defect size depending on the elasticity of the bond-line. In this paper, the perturbed fringes were described by a mathematical model derived from the theory of thin plates supported by a Winkler type elastic foundation which takes into consideration the elasticity of the bond-line. An iterative technique is subsequently presented for estimating the size and depth of the defect from the fringe pattern without the need to pre-determine the current elasticity of the bond-line. Laminates with a thick and highly elastic bond-line, found in foam-adhesive bonded metal laminates, and those with a thin and brittle bond-line, found in multi-layered glassflbre reinforced plastic plates, were tested. Results have shown that the defects in these laminates were accurately assessed.

Copyright © 1995 by The American Society of Mechanical Engineers
Topics: Laminates
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