23 research outputs found
Stitch modeling of non crimp fabric in forming simulations
No full text21st International ESAFORM Conference on Material Forming (ESAFORM), Univ Palermo, Palermo, ITALY, APR 23-25, 2018International audienceThe use of Non Crimp Fabric composite has increased during the last years due to cheaper cost of manufacturing and high mechanicals properties suitable for applications such as aeronautic, automotive and wind turbines. The main difference between Non Crimp Fabric (NCF) and textile reinforcement is the mean of manufacturing: where in textile fibers are woven, in NCF layers of unidirectional oriented fibers are assembled with a stitch. As a consequence, the stitch especially its geometry (stitch pattern) will have a major influence on the deformation of this type of reinforcement during forming process. Experimental campaigns on NCF samples compared to textile with the same fibers orientation have showed that the stitch affects the shear behavior of the reinforcement which is the main mode of deformation in the forming process. A description of the stitch has been implemented in a shell element for macro scale forming simulation as a first approach based on simple hypothesis. Further works are focus on the specific behavior of the stitch along the fabric and interaction with the fibers layers during shear deformation of the reinforcement and a method to implement the stitch in a more refined model of the fabric
Forming tests of a uni- and a bidirectional non-crimp fabric for different orientations and geometries (hemisphere, tetrahedron, square box)
No full textReference: The data is published as supplementary data for publications and for other researchers to incorporate the data in their work. Details behind the experimental procedure and the methods applied to analyze the tests are published in (please use to reference this data):
“B. Schäfer, R. Zheng, J. Colmars, A. Platzer, N. Naouar, P. Boisse, L. Kärger. Experimental analysis of the forming behavior of uni- and bidirectional non-crimp fabrics for different geometries, Composites Part B: Engineering, 287:111765, 2024. https://doi.org/10.1016/j.compositesb.2024.111765”
Description: This dataset contains high-resolution images and analyzed numerical data (punch forces, outer contour after forming, local strains measured with DIC) of forming tests on a unidirectional non-crimp fabric (UD-NCF) and a bidirectional non-crimp fabric (Biax-NCF) for different layup configurations and punch shapes (hemisphere, tetrahedron, square box). The tests were conducted for various single- and double-layer configurations with different relative fiber orientations. The experiments were conducted at the “LaMCoS – Laboratoire de Mecanique des Contacts and des Structures” from the “Institut National des Sciences Appliquées de Lyon (INSA Lyon)” in France. The analysis of the data was performed at the “Institute of Vehicle System Technology, Division Lightweight Engineering” from the “Karlsruhe Institute of Technology (KIT)” in Germany. The work was part of the international collaborative research project AMECOMP funded by the ANR in France and the DFG in Germany (DFG: 431354059, ANR: ANR-19-CE06-0031) - https://doi.org/10.5445/IR/1000172090
Irreversibility during forming process of woven reinforcements
No full text21st International ESAFORM Conference on Material Forming (ESAFORM), Univ Palermo, Palermo, ITALY, APR 23-25, 2018International audienceToday, numerical simulations of shaping fibrous reinforcements are based on continuous material models that have been assumed to be nonlinear elastic thypoelastie [1] or hyperelastic [2, 3]). Nevertheless, it is also believed that during the shaping process, there is a possible non reversibility of behavior that plays a significant role. In this work, we are interested in quantifying the importance of these phenomena by doing a group of tests (flexion, shear, compression) and then afterwards by proposing models compatible with the simulation of industrial parts when irreversibility is significant
A shell formulation for fibrous reinforcement forming simulations
No full textThe fibrous nature of continuous fiber textile composite reinforcements strongly modifies their mechanical behavior, in particular for bending. The basic assumptions of classical plate and shell theories are not verified by these materials during a deformation because of the slippage between fibers. However, simulations of reinforcement forming generally use shell finite elements. A shell formulation is proposed for the forming of continuous fiber reinforcements. The large tensile stiffness leads to the quasi inextensibility in the fiber directions. The fiber bending stiffness determines the curvature of the reinforcement. The calculation of tensile and bending virtual works are based on the precise geometry of the single fiber. A simple way to consider friction between fibers is to take it into account in the flexion bending. Simulations and experiments are compared for different reinforcements. It is shown that the proposed fibrous shell approach not only correctly simulates the deflections but also the rotations of the through thickness material vectors. This is particularly interesting in the case of thick interlock reinforcements. (C) 2017 Elsevier Ltd. All rights reserved
The importance of taking into account behavior irreversibilities when simulating the forming of textile composite reinforcements
No full textInternational audienc
A shell approach for fibrous reinforcement forming simulations
No full text21st International ESAFORM Conference on Material Forming (ESAFORM), Univ Palermo, Palermo, ITALY, APR 23-25, 2018International audienceBecause of the slippage between fibers, the basic assumptions of classical plate and shell theories are not verified by fiber reinforcement during a forming. However, simulations of reinforcement forming use shell finite elements when wrinkles development is important. A shell formulation is proposed for the forming simulations of continuous fiber reinforcements. The large tensile stiffness leads to the quasi inextensibility in the fiber directions. The fiber bending stiffness determines the curvature of the reinforcement. The calculation of tensile and bending virtual works are based on the precise geometry of the single fiber. Simulations and experiments are compared for different reinforcements. It is shown that the proposed fibrous shell approach not only correctly simulates the deflections but also the rotations of the through thickness material normals
The Dahl’s Model for the Inelastic Bending Behavior of Textile Composite Preforms. Analysis of its Influence in Draping Simulation
No full textMost of the numerical simulations of dry textile reinforcements forming are based on a macroscopic approach and continuous material models whose behavior is assumed to be elastic (linear or nonlinear). On the one hand, the experience shows that under loading/unloading stresses, residual inelastic deformations are observed. On the other hand, among the deformations that a woven reinforcement undergoes during forming, in most cases, only bending is subject to loading/unloading stresses. The first objective of this work is to highlight the inelastic bending behavior of textile reinforcements during a forming process and to find the possible origins of inelasticity. The second objective is to find the cases generating bending loading/unloading during forming as well as to study the influence of the bending inelasticity on forming simulation. For this purpose, the inelastic bending behavior was characterized by three-point bending tests. Then, the Dahl friction model was adapted to bending to describe the inelastic behavior. Finally, this model was implemented in a finite element code based on shell elements allowing the study of the influence of taking into account the inelastic behavior in bending on the numerical simulation of forming
Approche de coque fibreuse pour la simulation du drapage des renforts de composites avec une orientation pertinente des normales
No full textInternational audienceLes simulations de drapage de renforts textiles composites utilisent des éléments finis de coques pour lesquels le comportement en flexion est très particulier. La composition fibreuse des renforts réduit significativement la rigidité en flexion. De plus, la cinématique de la déformation est fortement modifiée et ne suit pas les théories classiques telles que celle de Kirchhoff. Une approche de coque fibreuse basée sur la quasi-inextensibilité des fibres permet de modéliser correctement la déformation lors du drapage avec une rotation pertinente de la normale matérielle
