Phononic band gaps and phase singularities in the ultrasonic response from toughened composites

Robert A. Smith*, Luke J. Nelson, Martin J. Mienczakowski

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

2 Citations (Scopus)

Abstract

Ultrasonic 3D characterization of ply-level features in layered composites, such as out-of-plane wrinkles and ply drops, is now possible with carefully applied analytic-signal analysis. Study of instantaneous amplitude, phase and frequency in the ultrasonic response has revealed some interesting effects, which become more problematic for 3D characterization as the inter-ply resin-layer thicknesses increase. In modern particle-toughened laminates, the thicker resin layers cause phase singularities to be observed; these are locations where the instantaneous amplitude is zero, so the instantaneous phase is undefined. The depth at which these occur has been observed experimentally to vary with resin- layer thickness, such that a phase-singularity surface is formed; beyond this surface, the ultrasonic response is reduced and significantly more difficult to interpret, so a method for removing the effect would be advantageous. The underlying physics has been studied using an analytical one-dimensional multi-layer model. This has been sufficient to determine that the cause is linked to a phononic band gap in the ultrasound transmitted through multiple equally-spaced partial reflectors. As a result, the phase singularity also depends on input-pulse center frequency and bandwidth. Various methods for overcoming the confusing effects in the data have been proposed and subsequently investigated using the analytical model. This paper will show experimental and modelled evidence of phase-singularities and phase-singularity surfaces, as well as the success of methods for reducing their effects.

Original languageEnglish
Title of host publication44th Annual Review of Progress in Quantitative Nondestructive Evaluation, Volume 37
PublisherAmerican Institute of Physics (AIP)
Volume1949
ISBN (Electronic)9780735416444
DOIs
Publication statusPublished - 20 Apr 2018
Event44th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2017 - Provo, United States
Duration: 16 Jul 201721 Jul 2017

Conference

Conference44th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2017
CountryUnited States
CityProvo
Period16/07/1721/07/17

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