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Proceedings Paper

Use of high and low frequency dielectric measurements in the NDE of adhesively bonded composite joints
Author(s): R. A. Pethrick; D. Hayward; B. K. McConnell; R. L. Crane
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Paper Abstract

Dielectric spectroscopy has been developed as a non-destructive technique for assessment of moisture content and structural integrity of adhesively bonded joints. Knowledge of these parameters is particularly crucial for the aerospace industry, since environmental degradation of adhesive joints presents a major limit on their utilization. High and low frequency measurements have been carried out on joints assembled from CFRP adherend, and a commercially available adhesive (AF 163-2K). The samples have been aged in deionised water at 75oC to chart the effect water ingress has on bond durability. In addition, some joints have been exposed to cryogenic temperatures to mimic the conditions joints experience whilst an aircraft is in flight. In this way it has been possible to determine the extent of degradation caused by freezing of water within the joint structure. Dielectric behaviour of the joints was studied in both the frequency and in the time domain. Frequency domain analysis allows the amount and effects of moisture ingress in the bondline to be assessed, whereas the time domain highlights the onset of joint defects with increasing exposure time. Mechanical testing of the joints has been carried out to enable correlation between changes in strength and failure mechanism due to moisture ingress, with changes in the dielectric data. In addition, dielectric studies of the neat adhesive have been undertaken, as have gravimetric and dynamic mechanical thermal analysis. These have helped reveal the effects of ageing upon the adhesive layer itself.

Paper Details

Date Published: 19 May 2005
PDF: 11 pages
Proc. SPIE 5767, Nondestructive Evaluation and Health Monitoring of Aerospace Materials, Composites, and Civil Infrastructure IV, (19 May 2005); doi: 10.1117/12.599600
Show Author Affiliations
R. A. Pethrick, Univ. of Strathclyde (United Kingdom)
D. Hayward, Univ. of Strathclyde (United Kingdom)
B. K. McConnell, Univ. of Strathclyde (United Kingdom)
R. L. Crane, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 5767:
Nondestructive Evaluation and Health Monitoring of Aerospace Materials, Composites, and Civil Infrastructure IV
Peter J. Shull; Andrew L. Gyekenyesi; Aftab A. Mufti, Editor(s)

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