Ultrasonic guided wave technique for monitoring cure-dependent viscoelastic properties of carbon fiber composites with toughened interlaminar layers

Abstract

This study presents an ultrasonic guided wave technique for real-time monitoring of the viscoelastic properties of curing carbon fiber-reinforced plastics (CFRPs) with toughened interlaminar layers. The guided wave propagating in a unidirectional CFRP prepreg was measured. The energy velocity and attenuation of the guided wave were acquired by the Hilbert transform and continuous wavelet transform. The micromechanics of fiber composite and rule of mixtures for a slab model were used to express the material properties of the CFRP as functions of only the complex Young’s modulus of the resin. A transfer matrix method was performed to obtain the relationship between the energy velocity and the resin complex modulus and that between the attenuation and the resin complex modulus. The development of the Young’s modulus during curing was estimated from the measurement results using the relationship obtained in the transfer matrix method. The estimated complex modulus was compared with that measured by a dynamic mechanical analyzer to verify the validity of the proposed method.