Analysis of wave attenuation in unidirectional viscoelastic composites by a differential scheme

Wave attenuation characteristics of unidirectional fiber-reinforced polymer composites are analyzed theoretically by a micromechanical differential (incremental) scheme for their macroscopic acoustic properties. In this approach, the effect of neighboring fibers on the wave scattering by a single fiber is accounted for in an approximate and averaged sense. The analysis also takes into account the viscoelastic nature of the matrix, so it yields the attenuation of the composite due to both wave scattering loss and the viscoelastic absorption loss. As an example, frequency-dependent attenuation coefficients of the longitudinal and transverse waves are computed for unidirectional carbon/epoxy composites. The computed results are favorably compared to the experimental data regarding their dependence on the frequency and the fiber volume fraction. The analysis shows that the attenuation in these composites is principally governed by the wave absorption of the epoxy matrix for a practical frequency range.