Contrast enhancement in visualisation of woven composite architecture using a MicroCT Scanner. Part 2: Tow and preform coatings (original) (raw)
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Composites Part A-applied Science and Manufacturing, 2009
MicroCT scanning is a non-destructive inspection method which was used to visualise tow architecture in woven composites with the ultimate goal of three-dimensional model generation. This has been achieved in the past for glass fabric composites, but is problematic when applied to carbon fabrics. Using X-rays, it is difficult to discriminate between elements of the composite, particularly the region between co-aligned neighbouring tows. This presents difficulty when viewing such composites using X-ray MicroCT scanning. Additives were used to enhance contrast during scanning. The most successful techniques were coating of fabrics with gold, copper, and an iodine contrast agent. Resin particle additive techniques were also trialled, with limited success. Good visualisations of glass fabrics were possible without contrast enhancement. Three-dimensional reconstructions of interior tow architectures were then made from the scans of contrast enhanced specimens. This research can be viewed as a starting point in developing methods for generating contrast between neighbouring tows within a three-dimensional woven preform using MicroCT scanning.
Preliminay Obeservations on the Architecture of Textile Composites Using Micro-Xray-CT
2017
Understanding failure within composite materials has been an ongoing area of research over the last several decades. A lot of newly emerging failure theories are starting to acknowledge this nonhomogeneity using Representative Volume Elements (RVEs) where the properties of the fibre and matrix constituents are retained throughout the modelling process. To create meaningful RVEs at the meso-mechanical level, suitable methods need to be established that can capture the key geometric features within the material. Micro-Xray CT has been used in the past to visualise the textile architecture without destroying the material in the scanning process. However, there have been a lot of advancements in the technology since its first use within composites where contrast enhancement agents were used. This paper looks at identifying the textile architecture of composites at the meso-level without the use of contrast enhancement agents. Obtaining successful results without the use of any modificat...
Journal of the American Ceramic Society, 2012
Three-dimensional (3-D) images of two ceramic-matrix textile composites were captured by X-ray micron-resolution computed tomography (lCT) on a synchrotron beamline. Compared to optical images of sections, CT data reveal comprehensive geometrical information about the fiber tows; information at smaller scales, on matrix voids, individual fibers, and fiber coatings, can also be extracted but image artifacts can compromise interpretation. A statistical analysis of the shape and positioning of the fiber tows in the 3-D woven architecture is performed, based on a decomposition of the spatial variations of any geometrical characteristic of the tows into non-stochastic periodic trends and non-periodic stochastic deviations. The periodic trends are compiled by exploiting the nominal translational invariance of the textile, a process that maximizes the information content of the relatively small specimens that can be imaged at high resolution. The stochastic deviations (or geometrical defects in the textile) are summarized in terms of the standard deviation of any characteristic at a single point along the axis of a tow and correlations between the values of deviations at two different points on the same or different tows. The tow characteristics analyzed consist of the coordinates of the centroids of a tow, together with the area, aspect ratio, and orientation of its cross-section. The tabulated statistics are sufficient to calibrate a probabilistic generator (detailed elsewhere) that can create virtual specimens of any size that are individually distinct but share the statistical characteristics of the small specimens analyzed by X-ray lCT. The data analysis presented herein forms the first step in formulating a virtual test of textile composites, by providing the statistical information required for realistic description of the textile reinforcement.
Micro-CT Analysis of Glass Knitted Fabric Structure
2013
Micro-CT scanning (X-ray microtomography) is a non-destructive analysis technique that provides visualization of the internal structure of materials and it has been widely used in recent years for inspection of different types of materials. Unlike the traditional microstructure observation, X-ray microtomography does not require sample significant and time consuming pre-treatments as cutting and polishing. The objective of this study is to demonstrate the potential of the micro-CT technique for geometrical analysis of textiles. A technique for determining initial geometry of glass knitted fabric at a mesoscopic scale is presented. Geometrical parameters, namely the yarn positional information, shape and dimensions of cross-sections are determined using the X-ray microtomography experimental data. A structural model of the studied textiles is build. The obtained information can be used for further micromechanical modelling.
Case Studies in Nondestructive Testing and Evaluation, 2016
In recent years, advanced composite materials such as carbon fiber reinforced polymers (CFRP) are used in many fields of application (e.g., automotive, aeronautic and leisure industry). These materials are characterized by their high stiffness and strength, while having low weight. Especially, woven carbon fiber reinforced materials have outstanding mechanical properties due to their fabric structure. To analyze and develop the fabrics, it is important to understand the course of the individual fiber bundles. Industrial 3D X-ray computed tomography (XCT) as a nondestructive testing method allows resolving these individual fiber bundles. In this paper, we show our findings when applying the method of Bhattacharya et al. [6] for extracting fiber bundles on two new types of CFRP specimens. One specimen contains triaxial braided plies in an RTM6 resin and another specimen woven bi-diagonal layers. Furthermore, we show the required steps to separate the individual bundles and the calculation of the individual fiber bundles characteristics which are essential for the posterior visual analysis and exploration. We further demonstrate the classification of the individual fiber bundles within the fabrics to support the domain experts in perceiving the weaving structure of XCT scanned specimens.
Micro-CT characterization of variability in 3D textile architecture
Composites Science and Technology, 2005
In the present work, we explore the potential of X-ray micro-computed tomography (X-ray micro CT) to characterize the microstructural variation of four different 3D warp-interlaced fabrics. The accuracy of the technique was determined quantitatively by comparing measured values of yarn thickness, width and spacing between the yarns from X-ray micro CT images with measurements obtained from optical micrographs of the same textile. This comparison indicates that the difference between the two techniques is not statistically significant, lending credence to X-ray micro CT as a means to acquire input for models of textiles and textile composites. Micro-structural variation in a given fabric was found to be quite large (standard deviation of the geometrical parameters up to 16%). A comparison of similar yarns in different directions and fabrics also resulted in large variations. Variability of the fabric parameters is implemented in a ''virtual textile'' model of 3D fabrics. The influence of the variability of the fabric internal geometry on the mechanical properties of the composite is estimated using a micro-mechanical model.
X-ray analysis of sheared textile composite reinforcement
2014
The micro-CT(X-ray micro computed tomography) technique is used to show the mesoscopic internal structure of the woven fabric in this paper. Simple shear is an interesting deformation mechanism for woven fabric for example during covering the mould. The internal structure change of the fabric after shear deformation is chosen as a subject of this paper. The cross section shape, area, and middle line coordinate are the main parameters that can be obtained from micro-CT scanning and image processing procedures. Change of yarns parameters during shear of a carbon fibre twill fabric is quantified. Details of the image data processing for sheared fabric cross sections are discussed.
Applied Composite Materials, 2016
The EU-project EVITA (Non-Destructive EValuation, Inspection and Testing of Primary Aeronautical Composite Structures Using Phase Contrast X-Ray Imaging) aims at bringing Grating-based Phase Contrast X-ray imaging technology to Non-Destructive Evaluation and Inspection of advanced primary and/or complex aerospace composite structures. Grating-based Phase Contrast X-Ray Imaging is based on the so-called Talbot-Lau interferometer, which is made of the combination of a standard X-ray apparatus with three transmission gratings as documented in the literature. This paper presents a comparison of two traditional non-destructive techniques (NDT): ultrasonic through transmission (immersed and water jet) and ultrasonic phased-array pulse echo, with the developed phase contrast X-Ray Imaging applied to advanced aerospace carbon fibre reinforced polymer. Typical defects produced during manufacture is examined as part of the testing and validation procedure. The following defects have been identified as being those most likely to be detected more effectively by the Grating-based Phase Contrast X-Ray Imaging process than other state of the art industrial NDT techniques: porosity, foreign objects, cracks, resin rich, cut fibres, and wavy fibres. The introduction of this innovative methodology is expected to provide the aeronautical industry with a reliable and detailed insight of the integrity of thin and thick
Composites Part A-applied Science and Manufacturing, 2008
X-ray microtomographs of samples cut from non-deformed and compression moulded Sheet Moulding Compounds (SMC) plates have been analysed using the phase contrast mode. Results emphasise a significant decrease of the porosity after moulding, this phenomenon being enhanced with increasing the initial SMC temperature. They also show that pronounced migration of the polymer–matrix occurs through the thickness of the plates during
Investigation of Carbon Fiber Architecture in Braided Composites Using X-Ray CT Inspection
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During the fabrication of braided carbon fiber composite materials, process variations occur which affect the fiber architecture. Quantitative measurements of local and global fiber architecture variations are needed to determine the potential effect of process variations on mechanical properties of the cured composite. Although non-destructive inspection via X-ray CT imaging is a promising approach, difficulties in quantitative analysis of the data arise due to the similar densities of the material constituents. In an effort to gain more quantitative information about features related to fiber architecture, methods have been explored to improve the details that can be captured by X-ray CT imaging. Metal-coated fibers and thin veils are used as inserts to extract detailed information about fiber orientations and inter-ply behavior from X-ray CT images.