Ultrasonic evaluation of interlayer interfacial stiffness of multilayered structures

Abstract

A procedure for the ultrasonic evaluation of the interlayer interfacial stiffness of multilayered structures is proposed. As a theoretical background to this proposal, the elastic wave propagation in a multilayered structure, in which the layers are bonded with spring-type interfaces, is analyzed theoretically based on the transfer-matrix method. Using the notion of the Bloch phase which characterizes wave transmission in the corresponding infinite periodic structure, some explicit relations are derived for the reflection coefficient of the multilayered structure. Based on the features clarified theoretically, the interlayer interfacial stiffness of the multilayered structure can be evaluated from the locations of local minima and maxima of the amplitude reflection spectrum. By numerical analysis, the proposed procedure is shown to apply even when the viscous property of the layers is not known precisely, and when a transient waveform of a limited length is used. Using the proposed procedure, the stiffness of interlayer resin-rich regions in a carbon-epoxy cross-ply composite laminate is identified from the experimental reflection spectrum. The identified stiffness is shown to lie within the range as expected from the micrographic observation and a simple estimate for a thin resin layer. V

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

“…The band structure of the layered structure with spring-type interfaces is governed by the non-dimensional parameter  [21]. When 0 Λ  , the interfaces become perfectly bonded and the dispersive nature disappears.…”

“…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].…”

Investigation on Ultrasonic Welding Attributes of Novel Carbon/Elium® Composites

“…Welding attributes of thermoplastics aids in the cost-effectiveness of the composite part to be manufactured in an industrial environment from forming until the finishing steps [3][4][5][6]. The most feasible welding techniques available for fusion bonding of thermoplastic composites are resistance [7][8][9], induction [8,[10][11][12][13][14][15] and ultrasonic welding [6,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. These behave differently in the way the heat is generated at the welding interface.…”

Influence of porosity on ultrasonic wave velocity, attenuation and interlaminar interface echoes in composite laminates: Finite element simulations and measurements

“…The spring boundary conditions [35][36][37][38][39][40][41] are applied to the double nodes on the interlaminar interfaces located at x2 = Hw + mh (m = 1, 2,…, N -1, h = H/N: ply thickness). The material properties used in the present analysis are summarized in Table 2.…”

“…This is of particular advantage when incorporating the viscoelastic properties of CFRP exhibiting nearly linear frequency dependence of the attenuation coefficients [32][33][34]. Thin interlaminar resin-rich regions are modeled as spring-type interlayer interfaces with equivalent normal and shear stiffnesses [35][36][37][38][39][40][41].…”