Regeneration of Adhesive Bonding in Fiber/Resin Systems

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Abstract
The bond between a fiber and a surrounding polymer matrix can be weakened or completely broken by mechanical shearing. In some cases bond strength can be reduced by exposure to active environments (for example, hot water or steam). Obviously, it would be of considerable practical value if weakended or lost bonding could be regenerated. This paper presents the first results of an ongoing study of the possibility of bond repair in fiber/resin systems. The use of the TRI microbond shear strength measurement technique makes it possible to study bond regeneration with individual fiber/resin specimens. Since the microdrop is displaced only a very short distance along the fiber during the shear strength measurement, it is a simple matter to treat a sheared drop without removing it from the fiber and then perform a second shear strength evaluation. Several systems have been studied in this manner, involving both thermosetting and thermoplastic resins. Examples of significant regeneration of both mechanically-sheared and hydrolytically-weakened bonds are given, and possible mechanisms for the bond strength regeneration are discussed.