Formability Evaluation of Non-Crimp Carbon Fabric by Non-Contact 3D Deformation Measurement System

2012 ◽  
Vol 525-526 ◽  
pp. 493-496
Author(s):  
Kazuto Tanaka ◽  
Kazuya Kanazawa ◽  
Shinichi Enoki ◽  
Tsutao Katayama
Keyword(s):  
Measurement System ◽  
Woven Fabrics ◽  
Shear Angle ◽  
Deformation Measurement ◽  
Evaluation Index ◽  
Regular Tetrahedron ◽  
Carbon Fabric ◽  
Bias Extension Test ◽  
3D Deformation ◽  
Bias Extension

Non-Crimp Carbon Fabric (NCF) consists of unidirectional plies which are kept together by stitching yarns arranged in a number of different orientations relative to the fabric production direction. It is reported that NCF possesses excellent drape performance compared to woven fabrics. However there is not a clear criterion of a drape evaluation on the drape characteristic of the NCF. In addition, it is not clarify that stitch pattern and stitch tension influence on the drape characteristic of the NCF. Moreover, in existing bias extension test, measurement of shear angle is based on the pin-jointed net (PJN) approximation. The PJN approximation doesnt takes into consideration the fiber sliding and the effect of the stitched parameters of the NCF. In this study, the bias extension test based on the measurement of shear angle by non-contact 3D deformation measurement system was conducted to evaluate the drape performance of the NCF. We made a proposal of the formability evaluation index based on the measurement results. Moreover, the 3D draping tests were conducted onto hemisphere geometry and regular tetrahedron, in order to verify availability of the formability evaluation index. The availability of the formability evaluation index was verified.

scholarly journals Bias extension test on an unbalanced woven composite reinforcement: Experiments and modeling via a second-gradient continuum approach

2016 ◽  
Vol 51 (2) ◽  
pp. 153-170 ◽  
Author(s):  
Gabriele Barbagallo ◽  
Angela Madeo ◽  
Ismael Azehaf ◽  
Ivan Giorgio ◽  
Fabrice Morestin ◽  
...  
Keyword(s):  
Constitutive Expression ◽  
Woven Fabrics ◽  
Woven Composite ◽  
Plane Shear ◽  
Second Gradient ◽  
Proposed Model ◽  
Bias Extension Test ◽  
Bias Extension ◽  
Deformation Patterns ◽  
Second Gradient Continuum

The classical continuum models used for the woven fabrics do not fully describe the whole set of phenomena that occur during the testing of those materials. This incompleteness is partially due to the absence of energy terms related to some microstructural properties of the fabric and, in particular, to the bending stiffness of the yarns. To account for the most fundamental microstructure-related deformation mechanisms occurring in unbalanced interlocks, a second-gradient, hyperelastic, initially orthotropic continuum model is proposed. A constitutive expression for the strain energy density is introduced to account for (a) in-plane shear deformations, (b) highly different bending stiffnesses in the warp and weft directions, and (c) fictive elongations in the warp and weft directions which eventually describe the relative sliding of the yarns. Numerical simulations which are able to reproduce the experimental behavior of unbalanced carbon interlocks subjected to a bias extension test are presented. In particular, the proposed model captures the macroscopic asymmetric S-shaped deformation of the specimen, as well as the main features of the associated deformation patterns of the yarns at the mesoscopic scale.

A Finite Element Based Approach for the Accurate Determination of the Shear Behaviour of Textiles with the Picture-Frame Shear Test

2013 ◽  
Vol 554-557 ◽  
pp. 1105-1115 ◽  
Author(s):  
Oliver Döbrich ◽  
Thomas Gereke ◽  
Chokri Cherif
Keyword(s):  
Finite Element ◽  
Shear Force ◽  
Shear Test ◽  
Input Parameter ◽  
Woven Fabrics ◽  
Shear Angle ◽  
Shear Behaviour ◽  
Drape Simulation ◽  
Bias Extension ◽  
Picture Frame

Picture frame shear tests are state of the art for determining the shear force vs. shear angle behaviour for in-plane deformation of most technical textiles, such as woven fabrics. Many publications describe this test and the used picture frames. Benchmark tests showed that the measured shearing behaviour for one sample depends on the picture frame used. The shearing rigidity of most textiles is very small compared to the in-plane tensile stiffness, so slight imperfections on the experimental setup have a significant effect on the measured results. During the picture frame test, wrinkles may form on the sample surface during the motion of the picture frame above a critical shear angle. These wrinkles can be described as local fabric buckling. If forming of wrinkles leads to a lower level of internal energy compared to a further shearing of the fabric, local wrinkles occur due to the principle of least action. Because of this effect, the measured shear force above the first formation of wrinkles is inaccurate for describing the exact shearing behaviour of textiles. Another possibility for measuring the shear force vs. shear angle behaviour is the bias-extension test. Here, higher shear angles can be achieved without the formation of wrinkles. Both methods are compared in this paper for different textile samples. The relationship of the shear angle and the applied shear force is an important mechanical value and one of the most important input parameter in numerical drape simulations. The analysis of wrinkles, which occur during textile draping, demands exact input parameters for the simulation. Most important for the drape simulation of technical high-performance textiles are accurate values for the bending and shear behaviours. This paper presents simulation results of the wrinkling during a picture frame shear test. Results show that the input parameter for the shear rigidity delivered by the picture frame shear test do not exactly reproduce the formed wrinkles and are, therefore, not suitable for an exact drape simulation. The underestimation of the shear force vs. shear angle behaviour will be shown with a finite element simulation model. The adaptation of the picture-frame and bias-extension parameters for a proper use in numerical drape simulations are examined.

Analysis of Non-Crimp Fabric Composite Reinforcements Forming

2012 ◽  
Vol 504-506 ◽  
pp. 219-224
Author(s):  
Sylvain Bel ◽  
Nahiene Hamila ◽  
Philippe Boisse
Keyword(s):  
Shear Stiffness ◽  
Middle Surface ◽  
Woven Fabrics ◽  
Woven Fabric ◽  
Shear Behaviour ◽  
Fabric Reinforcement ◽  
Fabric Composite ◽  
Bias Extension Test ◽  
Bias Extension ◽  
Composite Reinforcements

Abstract Two experimental devices are used for the analysis of the deformation mechanisms of biaxial non-crimp fabric composite reinforcements during preforming. The bias extension test, commonly use for the shear behaviour characterisation of woven fabrics, allows to highlight the sliding between the two plies of the reinforcement. This sliding is localized in areas of high gradient of shearing. This questions the use of bias extension test in determining the shear stiffness of the studied reinforcement. Then a hemispherical stamping experiment, representative of a preforming process, allows to quantify this sliding. The slippage is defined as the distance, projected onto the middle surface, of two points initially opposed on both sides of the reinforcement. For both experiments, the characteristic behavior of the non-crimp fabric reinforcement is highlighted by comparison with a woven textile reinforcement. This woven fabric presents only a very little sliding between warp and weft yarns during preforming. This aspect of the deformation kinematics of the non-crimp fabric reinforcement must be considered when simulating the preforming.

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