Modelling of ultrasonic attenuation in unidirectional FRP - Formulation and analysis for longitudinal wave

Abstract

A theoretical model for attenuation behavior of ultrasonic waves is formulated for unidirectional fiber-reinforced polymer-based composites consisting of viscoelastic matrix and elastic fibers. The model accounts for energy losses due to wave scattering by the fibers and viscous absorption in the matrix, where the scattering loss is evaluated on the assumption of single and independent scattering. Using this theoretical model, the overall attenuation coefficient of the composite can be connected to its microstructure and the constituent properties. Numerical analysis is carried out for attenuation behavior of longitudinal wave in a unidirectional CFRP. When the frequency is sufficiently low or when the incident wavelength is sufficiently large compared to the fiber diameter, the analysis reveals that the CFRP exhibits less attenuation than the epoxy matrix. On the other hand, as the frequency is increased so that the fiber diameter approaches the wavelength, the attenuation of the CFRP may exceed that of the matrix due to significant scattering. The frequency dependence of attenuation in the CFRP is described in detail based on the findings of the present analysis and discussed in the light of the corresponding experimental results.