Capabilities of Macroscopic Forming Simulation for Large-Scale Forming Processes of Dry and Impregnated Textiles

Kärger, Luise; Galkin, Siegfried; Dörr, Dominik; Poppe, Christian

doi:10.1016/j.promfg.2020.04.155

Cited by 10 publications

(16 citation statements)

References 36 publications

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“…Line segment 20 corresponds to the direction of the stitching, cf. on [11], [15] on [11], [15] In the corresponding alternative intermediate configuration, the nominal stress tensor ̲ * can be formulated based on an orthogonal material stiffness matrix by:…”

Section: /2mentioning

confidence: 99%

“…In addition to fibre orientation, shear angle and FVC, the modelling approach provides indication to analyse three further forming effects: gapping, transverse compaction and fibre waviness [15], [17]. Thereby, observations based on extensive OAT tests have shown, that the non-orthogonal tensile strain component 2 (stitching) is not suitable for indicating gapping nor transverse in-plane compressive behaviour.…”

Section: /4mentioning

confidence: 99%

“…However, it depends on the compressive stiffness of the fibre yarn, which has not been measured and thus impedes a quantitative evaluation. Nevertheless, a qualitative evaluation of the susceptibility to waviness can be conducted, e.g., for varying process conditions [15]. An L-shaped geometry as shown in Fig.…”

Section: /4mentioning

confidence: 99%

“…In contrast to mesoscopic modelling, macroscopic approaches are not able to discretely predict local forming effects. Nevertheless, they need to capture the relevant forming mechanisms occurring on meso-scale in a homogenized way and consequently indicate areas with a high likelihood of local effects like waviness, transverse compaction or gapping [15]. This desired capability of macroscopic forming simulation of UD-NCF has not yet been addressed in the literature.…”

Section: Intr Introduction Oductionmentioning

confidence: 99%

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Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations

Kärger¹,

Galkin²,

Kunze³

et al. 2021

Esaform 2021

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Unidirectional non-crimp fabrics (UD-NCF) provide the highest lightweight potential among dry textile materials. Compared to multiaxial NCF, the fabric layers in UD-NCF enable a more targeted tailoring. Compared to woven fabrics, the fibres of UD-NCF are straight without weakening undulations. However, the formability of UD-NCF is more challenging compared to woven fabrics. The yarns are bonded by a stitching and the deformation behaviour highly depends on this stitching and on the slippage between the stitching and the fibre yarns. Moreover, distinct local draping effects occur, like gapping and fibre waviness, which can have a considerable impact on the mechanical performance. Such local effects are particularly challenging or even impossible to be predicted by macroscopic forming simulation. The present work applies a previously published macroscopic UD-NCF modelling approach to perform numerical forming analyses and evaluate the prediction accuracy of forming effects. In addition to fibre orientations and shear angles, as investigated in previous work, the present work also provides indication for fibre area ratios, gapping, transverse compaction and fibre waviness. Moreover, the prediction accuracy is validated by comparison with experimental tests, where full-field strains of inner plies are captured by prior application of dots onto the fibre yarns, by measuring them via radiography and applying a photogrammetry software. The modelling approach provides good prediction accuracy for fibre orientations, shear strains and fibre area ratio. Conversely, normal fibre strains, indicating fibre waviness, and transverse strains, indicating gapping, show some deviations due to the multiscale nature of UD-NCF that cannot be captured entirely on macroscopic scale.

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Section: /2mentioning

confidence: 99%

Section: /4mentioning

confidence: 99%

Section: /4mentioning

confidence: 99%

Section: Intr Introduction Oductionmentioning

confidence: 99%

See 2 more Smart Citations

Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations

Kärger¹,

Galkin²,

Kunze³

et al. 2021

Esaform 2021

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“…The degree of the deformation is defined by the composition of the fabric itself. While forming simulations on a macroscopic level provides reliable results regarding the local fabric deformations [ 4 ], the actual material properties of the composite are defined after the infiltration step as soon as the laminate is fully cured. As shown in a previous study [ 5 ], fabric deformations have a strong impact on the resulting FVC.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Draping Effects on the Stiffness and Failure Behavior of Unidirectional Non-Crimp Fabric Fiber Reinforced Composites

et al. 2020

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Unidirectional non-crimp fabrics (UD-NCF) are often used to exploit the lightweight potential of continuous fiber reinforced plastics (CoFRP). During the draping process, the UD-NCF fabric can undergo large deformations that alter the local fiber orientation, the local fiber volume content (FVC) and create local fiber waviness. Especially the FVC is affected and has a large impact on the mechanical properties. This impact, resulting from different deformation modes during draping, is in general not considered in composite design processes. To analyze the impact of different draping effects on the mechanical properties and the failure behavior of UD-NCF composites, experimental results of reference laminates are compared to the results of laminates with specifically induced draping effects, such as non-constant FVC and fiber waviness. Furthermore, an analytical model to predict the failure strengths of UD laminates with in-plane waviness is introduced. The resulting stiffness and strength values for different FVC or amplitude to wavelength configurations are presented and discussed. In addition, failure envelopes based on the PUCK failure criterion for each draping effect are derived, which show a clear specific impact on the mechanical properties. The findings suggest that each draping effect leads to a “new fabric” type. Additionally, analytical models are introduced and the experimental results are compared to the predictions. Results indicate that the models provide reliable predictions for each draping effect. Recommendations regarding necessary tests to consider each draping effect are presented. As a further prospect the resulting stiffness and strength values for each draping effect can be used for a more accurate prediction of the structural performance of CoFRP parts.

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Advances in composite forming through 25 years of ESAFORM

et al. 2022

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The increase in the number of structural applications of composite materials, especially in the aerospace and automotive industries, has led to a demand for robust models to simulate composite forming processes. The mechanical behaviour of composite materials during forming is relatively complex due to their fibre-matrix composition. Many research studies have been conducted in the past 25-plus years into experimental methods for the characterization of the mechanical behaviours that are exhibited by textile-reinforced composite material systems during forming and into the development of material models to be used in computer codes for forming simulations. These studies have been presented and discussed in the ESA-FORM conferences since 1997 and especially in the 'Composite Forming Processes' mini-symposium launched in 2001. This article presents a survey of the research carried out in this context. Mechanical characterization tests specific to composite forming are presented as well as recent analysis techniques such as digital image correlation and X-ray tomography. Threedimensional mechanical behaviour laws, in particular hypo-and hyperelastic, have been developed and extended to second gradient models. Specific shell approaches have been presented and their application to wrinkling analysis. Resin flow and permeability analysis is another area of research in composite forming processes which are discussed in this article. Research on certain processes is also presented, in particular thermoforming of thermoplastic composites, wet compression moulding, pultrusion, automated fibre placement and three-dimensional printing. This comprehensive review of the works of multiple research groups is a recognition of the breadth and depth of efforts that have been invested into the understanding of the manufacturability of textile-reinforced composite materials.

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Capabilities of Macroscopic Forming Simulation for Large-Scale Forming Processes of Dry and Impregnated Textiles

Cited by 10 publications

References 36 publications

Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations

Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations

The Impact of Draping Effects on the Stiffness and Failure Behavior of Unidirectional Non-Crimp Fabric Fiber Reinforced Composites

Advances in composite forming through 25 years of ESAFORM

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