Abstract:Ensuring the correct fiber orientation in draped textiles and 3D preforms is one of the current challenges in the production of carbon-fiber reinforced plastics (CFRP), especially in resin transfer molding (RTM). Small deviations in fiber angle during preforming have a considerable effect on the mechanical properties of the final composite. Therefore, this paper presents an automated method for determining local yarn orientation in three-dimensionally draped, multi-layered fabrics. The draped fabric is scanned… Show more
“…This issue, which could obscure smaller peaks resulting from ply misalignments, is not observed in the RT analysis method. The FWHM will scale inversely with the number of pixels in the analysed data as demonstrated by Bardl et al [16], tending towards a minimum limit that will depend on the diameter of the inspection coil.…”
Section: Technique Comparisonmentioning
confidence: 82%
“…and use the signal strength at particular orientations to infer stacking sequences making the assumption that weaker orientation signals are deeper in the material [28,16]. This approach overlooks the full information encoded into the complex values and could misrepresent the structure of more complex stacking sequences.…”
Section: Ply Structurementioning
confidence: 99%
“…The center pixel is removed from the F(u, v) image and the image re-sampled in polar coordinates using cubic interpolation at radial increments of 0.2 mm and angular increments of 0.1 • to give the polar 2D-FFT, F(u , θ), (Figure 4.ii) [32]. Angular distributions, α(θ), were calculated by summing along the radial axis, u , for each angle, θ, as performed by Bardl et al [16]. The 2D-FFT images are shown in Figure 5.b and the resulting angular-distributions, α(θ) FFT , are shown in Figure 5…”
Maintaining the correct fibre orientations and stacking sequence in carbon-fibre reinforced polymers (CFRP) during manufacture is essential for achieving the required mechanical properties of a component. This paper presents and evaluates a method for the rapid characterisation of the fibre orientations present in CFRP structures, and the differentiation of different stacking sequences, through the Radon-transform analysis of complex-valued eddy-current testing (ECT) inspection data. A high-frequency (20 MHz) eddy-current inspection system was used to obtain 2D scans of a range of CFRP samples of differing ply stacking sequences. The complex electrical impedance scan data was analysed using Radon-transform techniques to quickly and simply determine the dominant fibre orientations present in the structure. This method is compared to 2D-fast Fourier transform (2D-FFT) analysis of the same data and shown to give superior quantitative results with comparatively fewer computational steps and corrections. Further analysis is presented demonstrating and examining a method for preserving the complex information inherent within the eddycurrent scan data during Radon-transform analysis. This investigation shows that the real and imaginary components of the ECT data encode information about the sacking sequence allowing the distinction between composites with different stacking structures. This new analysis technique could be used for in-process analysis of CFRP structures as a more accurate characterisation method, reducing the chance of costly manufacturing errors.
“…This issue, which could obscure smaller peaks resulting from ply misalignments, is not observed in the RT analysis method. The FWHM will scale inversely with the number of pixels in the analysed data as demonstrated by Bardl et al [16], tending towards a minimum limit that will depend on the diameter of the inspection coil.…”
Section: Technique Comparisonmentioning
confidence: 82%
“…and use the signal strength at particular orientations to infer stacking sequences making the assumption that weaker orientation signals are deeper in the material [28,16]. This approach overlooks the full information encoded into the complex values and could misrepresent the structure of more complex stacking sequences.…”
Section: Ply Structurementioning
confidence: 99%
“…The center pixel is removed from the F(u, v) image and the image re-sampled in polar coordinates using cubic interpolation at radial increments of 0.2 mm and angular increments of 0.1 • to give the polar 2D-FFT, F(u , θ), (Figure 4.ii) [32]. Angular distributions, α(θ), were calculated by summing along the radial axis, u , for each angle, θ, as performed by Bardl et al [16]. The 2D-FFT images are shown in Figure 5.b and the resulting angular-distributions, α(θ) FFT , are shown in Figure 5…”
Maintaining the correct fibre orientations and stacking sequence in carbon-fibre reinforced polymers (CFRP) during manufacture is essential for achieving the required mechanical properties of a component. This paper presents and evaluates a method for the rapid characterisation of the fibre orientations present in CFRP structures, and the differentiation of different stacking sequences, through the Radon-transform analysis of complex-valued eddy-current testing (ECT) inspection data. A high-frequency (20 MHz) eddy-current inspection system was used to obtain 2D scans of a range of CFRP samples of differing ply stacking sequences. The complex electrical impedance scan data was analysed using Radon-transform techniques to quickly and simply determine the dominant fibre orientations present in the structure. This method is compared to 2D-fast Fourier transform (2D-FFT) analysis of the same data and shown to give superior quantitative results with comparatively fewer computational steps and corrections. Further analysis is presented demonstrating and examining a method for preserving the complex information inherent within the eddycurrent scan data during Radon-transform analysis. This investigation shows that the real and imaginary components of the ECT data encode information about the sacking sequence allowing the distinction between composites with different stacking structures. This new analysis technique could be used for in-process analysis of CFRP structures as a more accurate characterisation method, reducing the chance of costly manufacturing errors.
“…The detailed approaches are depicted in Figure 5. 16,17 Figure 5.Procedure for determination of (a) cross section and void content; (b) fiber angle distribution – from micro-CT images.…”
Coreless filament winding technologies possess the potential to flexibly produce lightweight rigid frame structures at comparably low costs. The key to versatility, geometrical freedom and cost-effectiveness is the avoidance of core elements. Existing research on the filament winding of rigid frames focusses primarily on “isotruss” or “lattice” structures, manufactured by depositing fibers on polygon-shaped mandrels with carved-out gaps. Therefore, an investigation into the performance of coreless wound laminates and their material characteristics under process conditions is performed. Therefore, generic 2D specimens were manufactured on a new fully automated 3D winding equipment and successively exposed to incineration, micro-CT analysis and tensile testing. The benefits of core elements are evaluated by additional reference samples and opposed to coreless winding methods. The research demonstrates the potential of coreless filament winding and inductively quantifies the positive influence of fiber pretension and core/die elements on the material properties at cost of decreased versatility, costs and design degrees of freedom.
“…Studies [106] have been conducted to show the capabilities of Eddy currents for defect detection in dry preforms. In 2014, Schmidt [31] investigated high frequency Eddy Current testing for online quality control of AFP parts.…”
A literature review of quality control for automated lay-up processes of CFRP Automated lay-up of carbon fiber reinforced polymers is an established method for producing large parts in the aerospace industry. Currently, the quality control for this automated manufacturing process is performed by humans. In the last years, research has focused on increasing productivity of automated lay-up, thus the automation of the quality control has been taken into consideration. The objectives of the paper are to review the requirements for quality control based on an overview of the possible defects in automated lay-up and to evaluate their fulfilment by both visual quality control by humans and automated quality control systems. Literaturübersicht zur Qualitätskontrolle von automatisierten Ablegeverfahren von CFK Automatisiertes Ablegen von kohlenstofffaserverstärkten Kunststoffen ist eine etablierte Methode zur Herstellung großer Flugzeugteile. Zurzeit wird die Qualitätskontrolle dieses automatisierten Fertigungsverfahrens noch von Menschen durchgeführt. In den letzten Jahren hat sich die Forschung auf die Automatisierung der Qualitätskontrolle fokussiert um die Produktivität zu erhöhen. Die Ziele dieser Literaturübersicht sind, die Anforderungen für die Qualitätskontrolle basierend auf den vorkommenden Fehlern festzulegen und die Erfüllung dieser Anforderungen durch die visuelle Qualitätskontrolle durch den Mensch als auch durch automatisierte Systeme zu bewerten.
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