Measurement of the cure of resins by ultrasonic techniques

An ultrasonic critical-angle method and an ultrasonic resonance method have been successfully used to monitor the cross-linking reaction in amine-cured epoxide resins in both unfilled and filled states by measuring the ultrasonic velocity. Glass beads and glass fibre have been used as fillers to produce isotropic and unidirectional glass-fibre composites. The values of modulus measured on the isotropic composite were in agreement with an exact theory developed by Kerner. Theoretical results are also presented over a range of fibre loading showing how the modulus changes for the uncured and cured glass-fibre composites, with the fibre in a variety of geometrical arrays.