Experimental Study on the Acoustoelastic Effect in Composites Using Ultrasonic Waves

The state of stress in a structural composite component can influence its integrity, reliability, and safety. In this sense, ultrasonic waves can be used for non-destructive stress measurements based on the acoustoelastic effect that relates wave velocity to the material's stress state. This work aims to evaluate the acoustoelastic behavior of four types of composite samples made of epoxy resin and carbon fiber. Critically refracted longitudinal (Lcr) ultrasonic waves were employed to obtain the acoustoelastic constants, which relate wave velocity to the stress applied to the samples. PMMA wedges, specially designed for each type of sample, were used to generate the Lcr waves. The results showed that the acoustoelastic constants' values are higher for samples with more layers of laminate with fiber direction coinciding with the wave propagation direction. The acoustoelastic constants obtained experimentally in this paper can be used in the future for stress evaluations of the composites studied in this work.