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

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

Mienczakowski

et al. 2018

Self Cite

Ultrasound has been used to inspect composite laminates since their invention but only recently has the response from the internal plies themselves been considered of interest. This paper uses modeling techniques to make sense of the fluctuating and interfering reflections from the resin layers between plies, providing clues to the underlying inhomogeneities in the structure. It shows how the analytic signal, analyzed in terms of instantaneous amplitude, phase, and frequency, allows 3-D characterization of the microstructure. It is found that, under certain conditions, the phase becomes locked to the interfaces between plies and that the first and last plies have characteristically different instantaneous frequencies. This allows the thin resin layers between plies to be tracked through various features and anomalies found in real composite components (ply drops, tape gaps, tape overlaps, and out-of-plane wrinkles), giving crucial information about conformance to design of as-manufactured components. Other types of defects such as delaminations are also considered. Supporting evidence is provided from experimental ultrasonic data acquired from real composite specimens and compared with X-ray computed tomography images and microsections.

Section: Discussionmentioning

confidence: 99%

Ultrasonic Analytic-Signal Responses From Polymer-Matrix Composite Laminates

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

Mienczakowski

et al. 2018

Self Cite

“…Analytical modelling work [18][19][20] has provided a thorough understanding of the interaction of ultrasound with a uni-directional monolithic composite. Such composites contain a number of plies, on which fibres of a common orientation are constrained, each ply being separated from its neighbours by a thin (typically 5-50 µm) resin-rich layer.…”

Section: Ultrasonic Pulse-echo Interaction With Cfrpmentioning

confidence: 99%

Fibre direction and stacking sequence measurement in carbon fibre composites using Radon transforms of ultrasonic data

Composites Part A: Applied Science and Manufacturing

2019

Stacking sequence and, more generally, fibre orientation, are critical parameters in fibrous composite materials since they govern mechanical performance. This paper presents a method, based on the ultrasonic pulse-echo non-destructive technique, that can map the stacking sequence in unidirectional carbon-fibre composites. In-plane fibre orientation is measured using a Radon-transform method applied to local 2D images extracted from the 3D dataset formed from a 2D scan of pulse-echo responses. The ability to align these local 2D images to the plies in the region being assessed makes this technique suitable even in laminates where out-of-plane ply wrinkling is present. The Radon-transform method is shown to provide interpretable stacking-sequence maps, allowing ply lay-up sequence and both in-plane waviness and out-of-plane wrinkling to be visualised and quantified.

“…The carbon-fibre laminate studied in this paper was manufactured from an IMA/M21 carbon-fibre/resin pre- giving a high signal-to-noise ratio [22]. The authors' experience with fibre-resin systems exhibiting thinner resin layers shows that, although these produce weaker reflections, sufficient signal is obtained to allow the orientation measurement techniques described in this paper to be applied [56]. Out-of-plane wrinkles in the 0°direction were induced through a process of introducing tape overlaps and gaps in the 90°plies at specific locations [57].…”

Section: Cfrp Sample Detailsmentioning

confidence: 99%

Ply-orientation measurements in composites using structure-tensor analysis of volumetric ultrasonic data

Composites Part A: Applied Science and Manufacturing

Mienczakowski

2018

Ply wrinkling in carbon fibre reinforced polymer (CFRP) laminates is often geometrically complex and difficult to quantify using non-destructive techniques. In this paper, an ultrasonic technique for mapping ply wrinkling is presented. The instantaneous-phase three-dimensional dataset obtained from a pulse-echo ultrasonic inspection is processed using the structure-tensor image processing technique to quantify the orientations of the internal plies of a CFRP laminate. It is shown that consideration must be given to the wrapped nature of the phase dataset during processing to obtain accurate orientation maps. Three dimensional ply orientation and ply-location maps obtained from a test coupon are compared with true ply angles and locations by overlaying the ultrasonically-derived results on X-ray CT image slices, showing that accurate orientation maps can be obtained using the proposed technique.