7.6 Computed Tomography of Composites

Wang, Ying; Garcea, Serafina; Withers, Philip J.

doi:10.1016/b978-0-12-803581-8.10250-4

Cited by 10 publications

(8 citation statements)

References 47 publications

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“…Moreover, it is possible to scan a sample while it is loaded in-situ in compression so that the evolution in fibre orientation under load can be observed in 3D from no load towards failure. Conventional tomography, even at synchrotron sources, is too slow to capture the onset of micro-buckling [18,19]. However, ultra-fast imaging (∼ 500 − 10, 000 2D images per second) is now possible on some beamlines, which enables the events leading up to failure to be captured by X-ray CT [20].…”

Section: Introductionmentioning

confidence: 99%

Quantifying fibre reorientation during axial compression of a composite through time-lapse X-ray imaging and individual fibre tracking

Emerson

Wang

Withers

et al. 2018

Composites Science and Technology

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The sudden compressive failure of unidirectional (UD) fibre reinforced composites at loads well below their tensile strengths is a cause of practical concern. In this respect and more generally, analytical and numerical models that describe composite behaviour have been hard to verify due to a lack of experimental observation, particularly in 3D. The aim of this paper is to combine fast in-situ X-ray computed tomography (CT) with advanced image analysis to capture the changes in fibre orientation in 3D during uninterrupted progressive loading in compression of a UD glass fibre reinforced polymer (GFRP). By analysing and establishing correspondence between a sequence of time-lapse X-ray CT images of the composite, we are able for the first time to follow each fibre and quantify the progressive deflection that takes place during axial compression in the steps leading up to fibre micro-buckling and kinking. Even at just 25% of the failure load, fibres have started to tilt in approximately the direction of the ultimate kink band. The rate of tilting increases as the composite approaches the collapse load. More generally, our approach can be applied to investigate the behaviour of a wide range of fibrous materials under changing loading conditions.

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Section: Introductionmentioning

confidence: 99%

Quantifying fibre reorientation during axial compression of a composite through time-lapse X-ray imaging and individual fibre tracking

Emerson

Wang

Withers

et al. 2018

Composites Science and Technology

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“…X-ray computed tomography (CT), which has been applied increasingly to materials characterisation [2,3], is superior to most non-destructive techniques in that three-dimensional (3D) information can be obtained non-destructively at a high spatial resolution. Unlike fatigue crack initiation and propagation in homogeneous materials, various damage mechanisms occur cooperatively in composites under cyclic loading, including fibre fracture, matrix cracking, debonding and delamination [4].…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, helical CT is well suited to the characterisation of unidirectionally reinforced fibre composites, allowing us to observe the overall damage distribution and to detect localised damage events such as individual fibre fractures. In addition, dye penetrant with high atomic number (e.g., zinc iodide) can be used as stains to improve the detectability of cracks by enhancing the contrast between damage and the bulk material [2,3]. Although the use of staining has limitations in that only cracks connected to the outer surface could be stained and that it could affect the growth of matrix crack/splitting under fatigue [10], Yu et al [11] assessed the effect of four methods to increase detectability of cracks in X-ray CT imaging and suggested that staining was perhaps the most effective in terms of increasing the sensitivity of cracks to better than 1/10 the spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

Time-Lapse Helical X-ray Computed Tomography (CT) Study of Tensile Fatigue Damage Formation in Composites for Wind Turbine Blades

et al. 2018

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Understanding the fatigue damage mechanisms in composite materials is of great importance in the wind turbine industry because of the very large number of loading cycles rotor blades undergo during their service life. In this paper, the fatigue damage mechanisms of a non-crimp unidirectional (UD) glass fibre reinforced polymer (GFRP) used in wind turbine blades are characterised by time-lapse ex-situ helical X-ray computed tomography (CT) at different stages through its fatigue life. Our observations validate the hypothesis that off-axis cracking in secondary oriented fibre bundles, the so-called backing bundles, are directly related to fibre fractures in the UD bundles. Using helical X-ray CT we are able to follow the fatigue damage evolution in the composite over a length of 20 mm in the UD fibre direction using a voxel size of (2.75 µm)3. A staining approach was used to enhance the detectability of the narrow off-axis matrix and interface cracks, partly closed fibre fractures and thin longitudinal splits. Instead of being evenly distributed, fibre fractures in the UD bundles nucleate and propagate locally where backing bundles cross-over, or where stitching threads cross-over. In addition, UD fibre fractures can also be initiated by the presence of extensive debonding and longitudinal splitting, which were found to develop from debonding of the stitching threads near surface. The splits lower the lateral constraint of the originally closely packed UD fibres, which could potentially make the composite susceptible to compressive loads as well as the environment in service. The results here indicate that further research into the better design of the positioning of stitching threads, and backing fibre cross-over regions is required, as well as new approaches to control the positions of UD fibres.

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“…However, the 0% TCP group was difficult to scan with live-CT due to its low contrast and fine fiber diameter. The ability to scan with live-CT is affected by the signal-to-noise ratio, the phase difference, and the tissue around the artifact [33][34][35][36]. Table 2 lists the volume differences of samples that were estimated by Equation (3) by subtracting the volume before implantation by micro-CT from the volume at one day after implantation by live-CT.…”

Section: Evaluation Of Filament Degradation In the Subcutaneousmentioning

confidence: 99%

The Influence of Electron Beam Sterilization on In Vivo Degradation of β-TCP/PCL of Different Composite Ratios for Bone Tissue Engineering

et al. 2020

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We evaluated the effect of electron beam (E-beam) sterilization (25 kGy, ISO 11137) on the degradation of β-tricalcium phosphate/polycaprolactone (β-TCP/PCL) composite filaments of various ratios (0:100, 20:80, 40:60, and 60:40 TCP:PCL by mass) in a rat subcutaneous model for 24 weeks. Volumes of the samples before implantation and after explantation were measured using micro-computed tomography (micro-CT). The filament volume changes before sacrifice were also measured using a live micro-CT. In our micro-CT analyses, there was no significant difference in volume change between the E-beam treated groups and non-E-beam treated groups of the same β-TCP to PCL ratios, except for the 0% β-TCP group. However, the average volume reduction differences between the E-beam and non-E-beam groups in the same-ratio samples were 0.76% (0% TCP), 3.30% (20% TCP), 4.65% (40% TCP), and 3.67% (60% TCP). The E-beam samples generally had more volume reduction in all experimental groups. Therefore, E-beam treatment may accelerate degradation. In our live micro-CT analyses, most volume reduction arose in the first four weeks after implantation and slowed between 4 and 20 weeks in all groups. E-beam groups showed greater volume reduction at every time point, which is consistent with the results by micro-CT analysis. Histology results suggest the biocompatibility of TCP/PCL composite filaments.

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7.6 Computed Tomography of Composites

Cited by 10 publications

References 47 publications

Quantifying fibre reorientation during axial compression of a composite through time-lapse X-ray imaging and individual fibre tracking

Quantifying fibre reorientation during axial compression of a composite through time-lapse X-ray imaging and individual fibre tracking

Time-Lapse Helical X-ray Computed Tomography (CT) Study of Tensile Fatigue Damage Formation in Composites for Wind Turbine Blades

The Influence of Electron Beam Sterilization on In Vivo Degradation of β-TCP/PCL of Different Composite Ratios for Bone Tissue Engineering

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