Prediction of Bending, Buckling and Free-Vibration Behaviors of 3D Textile Composite Plates by Using VAM-Based Equivalent Model

To solve the microstructure-related complexity of a three-dimensional textile composite, a novel equivalent model was established based on the variational asymptotic method. The constitutive modeling of 3D unit cell within the plate was performed to obtain the equivalent stiffness, which can be inputted into the 2D equivalent model (2D-EPM) to perform the bending, free-vibration and buckling analysis. The correctness and effectiveness of the 2D-EPM was validated by comparing with the results from 3D FE model (3D-FEM) under various conditions. The influence of yarn width and spacing on the equivalent stiffness was also discussed. Finally, the effective performances of 3D textile composite plate and 2D plain-woven laminate with the same thickness and yarn content were compared. The results revealed that the bending, buckling and free-vibration behaviors predicted by 2D-EPM were in good agreement with 3D-FEM, and the local field distributions within the unit cell of 3D textile composite plate were well captured. Compared with the 2D plain-woven laminate, the displacement of 3D textile composite plate was relatively larger under the uniform load, which may due to the fact that the through-the-thickness constrains of the former are only dependent on the binder yarns, while the warp yarns and weft yarns of the latter are intertwined closely.

ACHIEVING REALISTIC TOW FIBER VOLUME FRACTIONS IN TEXTILE COMPOSITE MODELS BY INDUCING FIBER ENTANGLEMENT

Modeling composites can be an effective way to understand how a part will perform without requiring the destruction of costly specimens. By combining artificial fiber entanglement with manufacturing process simulation, a method was developed to create fiber bundle models using entanglement to control the fiber volume fraction. This fiber entanglement generation uses three parameters, probability of swapping (p_(r_S )), swapping radius standard deviation (r_(σ_S )), and the swapping plane spacing (l_S), to control the amount of entanglement within the fiber bundle. A parametric study was conducted and found that the more entanglement within a fiber bundle, the more compression mold pressure required to compact the fiber bundle to the same fiber volume fraction as that required for a less entangled bundle. This artificial fiber entanglement and manufacturing process simulation method for creating fiber bundles shows the potential to be able to create bundles with controlled final volume fraction using a desired mold compression pressure.

FINITE ELEMENT ANALYSIS FOR TEXTILE COMPOSITES USING FIBER-BUNDLES/MATRIX-RESIN SEPARATED MESH

This paper proposes a finite element modeling method for textile composite, in which fiber bundle and matrix resin are separately meshed, and they are connected by using discontinuous Galerkin (DG) method. The fiber bundle geometry is often complex in the textile composite. In the conventional FEM, it causes small, distorted resin elements surrounded by the fiber bundles, because the resin must be meshed along the fiber bundle geometry. These distorted elements result in the increased effort to meshing, computing cost, and degraded accuracy. In the proposed method, we apply the DG method to the 3-dimensional analysis of the textile composite. DG method is a method which can connect two separately divided meshes in the FEM. The method proposed in this paper has a distinct advantage, because matrix resin has not to be meshed along the fiber bundle geometry. Moreover, regular cubic grid mesh can be used for matrix resin. In the present paper, the formulation of the DG method is presented first. The method and results of the microscopic stress analysis for textile composite is then described. The results agree well with those of conventional FEM, and validity of the proposed method is demonstrated.

The Dahl’s Model for the Inelastic Bending Behavior of Textile Composite Preforms. Analysis of its Influence in Draping Simulation

Most 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.