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Design of an Uncontaminated Textile CFRP Specimen Optimised for both Mechanical Testing and X-ray Microtomography

Chowdhury, N.T., Tao, C., Pearce, G.M., Walsh, S.D.C., Latham, S.J., Middleton, J.P., Beeching, L.
Composites 2019
carbon fibers, composite materials, epoxides, fabrics, mechanical testing, micro-computed tomography, models, physics, polymers
The aim of this paper is to develop a novel specimen configuration optimised for developing and validating structure-property relationships for textile carbon fibre reinforced polymers (CFRPs). The specimen is designed to be imaged non-destructively using X-ray Microtomography (μCT), but is also optimised for in- and ex-situ mechanical testing. The investigation bridges a gap in current research where modified/enhanced (i.e. contaminated) CFRPs are often used to obtain suitable reconstructions to analyse. This paper looks at identifying the textile architecture of composites at the meso-level without the use of contrast enhancement agents (i.e. uncontaminated) and then proposes the optimum specimen size and scanning parameters to achieve successful reconstructions of the materials system. It was found that the Histogram of Oriented Gradients (HOG) gave the best segmentation outcome when the specimen was sized to fit at least two voxels within a fibre width. In addition to this prepping the specimen to include a cast epoxy jacket prevented CT artefacts during reconstruction. The application of these results will assist researchers in better understanding the evolution of microcracks and damage in textile composites while enabling physics based multiscale modelling approaches to be validated with realistic textile architectures.