Location

La Jolla, CA

Start Date

1979 12:00 AM

Description

The problem of detecting weak adhesion in completed adhesive bonds can be considered a problem in measuring the effective acoustic impedance of a thin layer at the adherend to adhesive interface. By calculating the ultrasonic reflection coefficient of the entire sandwich structure as a function of frequency including an interfacial layer, it can be shown that quite obvious changes in the reflection spectrum can be produced by minor changes in the properties of the thin layer. The inverse problem of deducing the properties of the thin layer from experimental measurements is more difficult because of the sensitivity of the results to small experimental errors in the data. However, special procedures based on estimation theory are being.developed for use on actual ultrasonic data obtained from specimens with both optimum and degraded adhesive bonds. Once the elastic properties of the interfacial layer have been deduced from ultrasonic or other nondestructive measurements, they can be used to infer the physical state of the material at the interface. Models that relate the physical state of polymers to their failure probability such as that being developed by D. H. Kaelble can then be used to predict the strength and reliability of the adhesive bond.

Book Title

Proceedings of the ARPA/AFML Review of Progress in Quantitative NDE

Chapter

7. NDE for Advanced Materials

Pages

266-271

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Ultrasonic Measurement of Interfacial Properties in Completed Adhesive Bonds

La Jolla, CA

The problem of detecting weak adhesion in completed adhesive bonds can be considered a problem in measuring the effective acoustic impedance of a thin layer at the adherend to adhesive interface. By calculating the ultrasonic reflection coefficient of the entire sandwich structure as a function of frequency including an interfacial layer, it can be shown that quite obvious changes in the reflection spectrum can be produced by minor changes in the properties of the thin layer. The inverse problem of deducing the properties of the thin layer from experimental measurements is more difficult because of the sensitivity of the results to small experimental errors in the data. However, special procedures based on estimation theory are being.developed for use on actual ultrasonic data obtained from specimens with both optimum and degraded adhesive bonds. Once the elastic properties of the interfacial layer have been deduced from ultrasonic or other nondestructive measurements, they can be used to infer the physical state of the material at the interface. Models that relate the physical state of polymers to their failure probability such as that being developed by D. H. Kaelble can then be used to predict the strength and reliability of the adhesive bond.