Abstracts: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.

Abstracts:Additive manufacturing (AM) allows for fast fabrication of three dimensional objects with the use of considerably less resources, less energy consumption and shorter supply chain than would be the case in traditional manufacturing. AM has gained significance due to its cost effective method which boasts the ability to produce components with a previously unachievable level of geometric complexity in prototyping and end user industrial applications, such as aerospace, automotive and medical industries. However these processes currently lack reproducibility and repeatability with some ‘prints’ having a high probability of requiring rework or even scrapping due to out of specification or high porosity levels, leading to failure due to structural stresses. It is therefore imperative that robust quality systems be implemented such that the waste level of these processes can be significantly decreased. This study presents an artefact that is optimised for characterisation of form using computed tomography (CT) with representative geometric dimensioning and tolerancing features and internal channels and structures comparable to cooling channels in heat exchangers. Furthermore the optimisation of the CT acquisition conditions for this artefact are presented in light of feature dimensions and form analysis. This paper investigates the accuracy and capability of CT measurements compared with reference measurements from coordinate measuring machine (CMM), as well as focus on the evaluation of different AM methods.

Abstracts:We compare the quality of reconstruction obtainable using various laminographic system trajectories that have been described in the literature, with reference to detecting defects in composite materials in engineering. We start by describing a laminar phantom representing a simplified model of composite panel, which models certain defects that may arise in such materials, such as voids, resin rich areas, and delamination, and additionally features both blind and through holes along multiple axes. We simulate ideal cone-beam projections of this phantom with the different laminographic trajectories, applying both Simultaneous Iterative Reconstruction Technique (SIRT) and Conjugate Gradient Least Squares (CGLS) reconstruction algorithms. We compare the quality of the reconstructions with a view towards optimising the scan parameters for defect detectability in composite NDT applications.

Abstracts:Internal defects such as voids and porosity directly influence mechanical properties, durability, service life and other characteristics of industrial parts. There are several non-destructive and destructive methods for defects detection and evaluation. Recently, X-ray Computed Tomography (CT) has emerged as an effective tool for geometrical characterization of internal defects. 3D information about internal voids/porosity extracted from CT datasets can be utilized in many applications, such as production processes optimization and quality control. However, there are still challenges in using CT as a traceable method for internal voids dimensional measurements. In order to enhance the accuracy and reliability of CT porosity measurements, a metrological validation method is required.

Abstracts:This work is focused on the inspection of carbon fibre reinforced plastic composites (CFRP) combined with metal components. It is well known that the high absorption of metallic parts degrades the quality of radiographic measurements (contrast) and causes typical metal artefacts in X-ray computed tomography (CT) reconstruction. It will be shown that these problems can be successfully solved utilizing the dual energy CT method (DECT), which is typically used for the material decomposition of complex objects. In other words, DECT can help differentiate object components with a similar overall attenuation or visualise low attenuation components that are next to high attenuation ones. The application of DECT to analyse honeycomb sandwich panels and CFRP parts joined with metal fasteners will be presented in the article.

Abstracts:This paper presents a comparison of surface-based and image-based quality metrics for dimensional X-ray computed tomography (CT) data. The chosen metrics are used to characterize two key aspects in acquiring signals with CT systems: the loss of information (blurring) and the adding of unwanted information (noise). A set of structured experiments was designed to test the response of the metrics to different influencing factors. It is demonstrated that, under certain circumstances, the results of both types of metrics become conflicting, emphasizing the importance of using surface information for evaluating the quality dimensional CT data. Specific findings using both types of metrics are also discussed.

Abstracts:In many industrial applications, components characterized by high surface roughness are measured by X-ray computed tomography (CT). This is the case, for example, of additive manufactured parts. Surface roughness has a strong influence on CT dimensional measurements, causing relevant measurement deviations with respect to tactile reference measurements by coordinate measuring machines (CMMs), especially for parts characterized by high surface roughness. It comes that roughness effects on CT dimensional measurements must be quantified.

Abstracts:Laser Sintering (LS) is an Additive Manufacturing (AM) technology for polymers processing which is increasingly being used to produce functional products with designs not achievable with traditional manufacturing technologies. Lightweight cellular structures are a good example of complex designs which are increasingly finding applications in AM parts. However, it is not yet clear how the LS process affects the porosity and geometrical characteristics of the cell structural elements. Getting this information allows to perform quality control of the LS process, gives insights into how to improve it, and might help to take into account manufacturing process variability during the design phase.