Location

La Jolla, CA

Start Date

1-1-1989 12:00 AM

Description

This paper describes the results of work on the feasibility of using high frequency ultrasound to determine the degree of bondedness of multilayer structures. A sandwich structure of two identical metal sheets of thickness on the order of 25 µm, bonded together by a dissimilar third layer of thickness 10 µm was examined. The primary disbond was expected to be in the region of the interface between the top two metal layers. Frequency domain analysis using a Wiener-filtered FFT was used to extract a signature related to the properties of the upper metal strip as an acoustic resonator, which is strongly dependent on the boundary conditions on its back surface. The frequency range of 200 to 300 MHz was determined to be the appropriate range at which to perform the inspections. The sandwich structure was modelled for varying degrees of bondedness, and frequency domain measurements were made on a number of samples using a 300 MHz acoustic transducer and electronic setup. Experimental results have indicated strong correlation between the depth and width of nulls in the Wiener-filtered spectrum and the state of bondedness. The results correspond well to the acoustic resonance of the disbonded upper metal layer as predicted by the theory.

Volume

8B

Chapter

Chapter 7: Engineered Materials

Section

Adhesive Bonds

Pages

1425-1430

DOI

10.1007/978-1-4613-0817-1_178

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Application of Ultrasonic Resonance Technique at 300 MHz to the Detection of Disbonds in a Multilayer Structure

La Jolla, CA

This paper describes the results of work on the feasibility of using high frequency ultrasound to determine the degree of bondedness of multilayer structures. A sandwich structure of two identical metal sheets of thickness on the order of 25 µm, bonded together by a dissimilar third layer of thickness 10 µm was examined. The primary disbond was expected to be in the region of the interface between the top two metal layers. Frequency domain analysis using a Wiener-filtered FFT was used to extract a signature related to the properties of the upper metal strip as an acoustic resonator, which is strongly dependent on the boundary conditions on its back surface. The frequency range of 200 to 300 MHz was determined to be the appropriate range at which to perform the inspections. The sandwich structure was modelled for varying degrees of bondedness, and frequency domain measurements were made on a number of samples using a 300 MHz acoustic transducer and electronic setup. Experimental results have indicated strong correlation between the depth and width of nulls in the Wiener-filtered spectrum and the state of bondedness. The results correspond well to the acoustic resonance of the disbonded upper metal layer as predicted by the theory.