Modelling guided acoustic waves for monitoring epoxy curing

It has been observed that the attenuation of some acoustic modes propagating in a thin copper rod embedded in a curing epoxy resin varies as the epoxy cures. This case is modeled as a rod embedded in an infinite medium. Possible acoustic modes propagating with complex propagation constants are found by matching the stress and strain fields at the rod-medium interface. The frequency and velocity of modeled modes correspond to experimental values. The attenuation of these modes decreases as the resin shear and longitudinal velocities increases which agrees with experiment. This makes possible the identification of the modes and a determination of the acoustic properties of the media surrounding the rod from the attenuation in the rod. The technique is therefore useful for characterization of resin cure as well as suggesting the acoustic properties of the rod that increase its sensitivity