Authors:

Timothy Emge

,

Oral Buyukozturk

Publication:

Materials Evaluation, Volume 70, Issue 12

Publication Date: 1 December 2012Testing Method:

Laser Testing

Composite fiber reinforced polymer (FRP) materials are increasingly being used in both civil and ship structures. Both uses of FRP are usually in conjunction with some other material, oftentimes steel. When FRP and steel are joined adhesively, the most common failure mode is debonding or delamination at the interface of the adhesive with the steel and composite materials. These discontinuities are often visually obscured by the FRP and require the aid of some form of nondestructive testing (NDT). Acoustic laser vibrometry is a novel NDT technique in which an airborne acoustic wave is utilized to excite the location of the damage underneath the FRP sheets/plates, causing a vibration like a drum head, which can be measured with a laser vibrometer. To study the acoustic laser technique, a discontinuous specimen was created from a plate of stainless steel adhesively bonded to a plate of glass FRP on their faces with a purposely-placed elliptical debonding discontinuity. A number of parameters of the acoustic laser vibrometry system were studied. Additionally, grid data were collected from the discontinuity specimen and a discontinuity mapping was created. Theoretical and numerical models were produced and compared to measured results.

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