256 shades of gray: Application of image processing to evaluate the effect of sample geometry and constant shear strain rates in the picture-frame test

Christian Krogh, Lisa M. Dangora, Kari D. White, Johnny Jakobsen, James A. Sherwood

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Abstrakt

Shearing or trellising is recognized as the primary deformation mechanism in textile-reinforced composite forming processes. A popular method for characterization of the shear properties of a ply is the picture-frame test. The test setup involves the clamping of a cruciform shaped specimen in a frame hinged at its corners. During the processing of the test results, it is often assumed that the shear distribution in the central square of the sample is uniform, such that a shear force vs. shear angle relation can be calculated based on kinematics. One thing to note is that a constant displacement rate of the frame yields a nonlinear shear-strain rate throughout the test. Relying on Digital Image Correlation (DIC), this study considers two concepts in relation to the picture-frame test: First, the effect of sample geometry is tested, i.e. whether modifications of the standard cruciform shape influence the uniformness of the shear-strain field. Two different materials are considered: a woven carbon-fiber prepreg and a thermoplastic cross-ply sheet. Second, methods of obtaining constant shear rate data are explored. The methods involve programming of a universal testing machine with a multi-linear approximation of a nonlinear crosshead displacement rate and post-processing data obtained with a constant crosshead rate.
OriginalsprogEngelsk
TitelProceedings of the 22nd International ESAFORM Conference on Material Forming, ESAFORM 2019
RedaktørerPedro Arrazola, Eneko Saenz de Argandona, Nagore Otegi, Joseba Mendiguren, Mikel Saez de Buruaga, Aitor Madariaga, Lander Galdos
Antal sider6
ForlagAmerican Institute of Physics
Publikationsdato2 jul. 2019
Artikelnummer020001
ISBN (Elektronisk)9780735418479
DOI
StatusUdgivet - 2 jul. 2019
BegivenhedESAFORM 2019 - Vitoria-Gasteiz, Spanien
Varighed: 8 maj 201910 maj 2019
Konferencens nummer: 20

Konference

KonferenceESAFORM 2019
Nummer20
LandSpanien
ByVitoria-Gasteiz
Periode08/05/201910/05/2019
NavnAIP Conference Proceedings
Nummer1
Vol/bind2113
ISSN0094-243X

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Citationsformater

Krogh, C., Dangora, L. M., White, K. D., Jakobsen, J., & Sherwood, J. A. (2019). 256 shades of gray: Application of image processing to evaluate the effect of sample geometry and constant shear strain rates in the picture-frame test. I P. Arrazola, E. Saenz de Argandona, N. Otegi, J. Mendiguren, M. Saez de Buruaga, A. Madariaga, & L. Galdos (red.), Proceedings of the 22nd International ESAFORM Conference on Material Forming, ESAFORM 2019 [020001] American Institute of Physics. AIP Conference Proceedings, Nr. 1, Bind. 2113 https://doi.org/10.1063/1.5112506