The Development of Shear and Compression Elastic Moduli in Curing Epoxy Adhesives Measured Using Non-Contact Ultrasonic Transducers

Thin epoxy resin adhesive samples were ultrasonically measured using normal incidence radially polarised. shear wave ElectroMagnetic Acoustic Transducers (EMATs) that also generate a significant compression wave. This allows us to make simultaneous measurement of the shear and compression wave propagation through the polymer, although the signal to noise ratio is significantly higher for the shear wave measurements. The adhesive thickness examined in the experiments was 1 mm, which was chosen to be the optimum thickness for experimental measurement using our apparatus. The epoxy resin systems ('rapid' cure and a 'standard' cure time) described in this paper were supplied in a 2-part cartridge form, mixed by through a special nozzle. Although the number of samples investigated at this stage is small, there does appear to be a fundamental difference in the way in which the elastic moduli develop as cure rate is increased.