Evaluation of interlayer interfacial stiffness and layer wave velocity of multilayered structures by ultrasonic spectroscopy

Abstract

An ultrasonic evaluation procedure for the interlayer interfacial normal stiffness and the intralayer longitudinal wave velocity of multilayered plate-like structures is proposed. Based on the characteristics of the amplitude reflection spectrum of ultrasonic wave at normal incidence to a layered structure with spring-type interlayer interfaces, it is shown that the interfacial normal stiffness and the longitudinal wave velocity in the layers can be simultaneously evaluated from the frequencies of local maxima and minima of the spectrum provided that all interfaces and layers have the same properties. The effectiveness of the proposed procedure is investigated from the perspective of the sensitivity of local extremal frequencies of the reflection spectrum. The feasibility of the proposed procedure is also investigated when the stiffness of each interface is subjected to small random fluctuations about a certain average value. The proposed procedure is applied to a 16-layered cross-ply carbon-fiber-reinforced composite laminate. The normal stiffness of resin-rich interfaces and the longitudinal wave velocity of plies in the thickness direction evaluated from the experimental reflection spectrum are shown to be consistent with simple theoretical estimations.

Second-harmonic generation in an infinite layered structure with nonlinear spring-type interfaces

“…Elastic wave propagation in multilayered structures with spring-type interlayer interfaces has also been analyzed in order to clarify the effect of thin interlaminar resin-rich regions in fiber-reinforced composite laminates [18][19][20][21][22][23].…”

Effective spring boundary conditions for a damaged interface between dissimilar media in three-dimensional case

“…e.g. by measuring the group velocity to find a damaged part of an interface (Balvantin et al, 2012;Mezil et al, 2014) or by using wave velocities from local maximum and minimum frequencies of the reflection spectrum to obtain a normal interfacial stiffnesses for multilayered structures (Ishii and Biwa, 2014).…”

Ultrasonic bandgaps in composite laminates: Experimental observation and Floquet-Bloch wave analysis

“…10 In assessing the structural integrity of composite laminate structures, the quality of interlaminar interfaces is of equal or higher importance compared to the mechanical properties of plies themselves. In recent investigations, a method has been proposed [11][12][13][14][15] to evaluate the equivalent stiffnesses of interlaminar interfaces of composite laminates based on the reflection or transmission spectra of ultrasonic waves in the frequency range where the wavelength is comparable to the double ply thickness. Furthermore, it has been shown that the porosity content in the laminate can be evaluated from the characteristics of interlaminar interface echoes in the frequency range of bandgap.…”