Louise P. Brown

Modelling and Simulating Textile Structures Using TexGen

This paper provides an overview of TexGen, the open source software package for 3D modelling of textiles and their composites developed at the University of Nottingham. The underlying modelling theory is briefly discussed followed by descriptions of applications utilising TexGen in the fields of textile mechanics, textile composite mechanics and permeability. The limitations and further development of the approach are also considered.

Modelling the geometry of textile reinforcements for composites: TexGen

Abstract This chapter provides an overview of TexGen, the open-source software package for 3D modeling of textiles and their composites developed at the University of Nottingham. The modular design of the cross-platform software and its modules (Core, Renderer, Export, Python Interface, and Graphical User Interface) are described. The underlying modeling theory is then discussed, followed by descriptions of applications utilizing TexGen in the fields of textile mechanics, textile composite mechanics, and permeability. Developments for creation of models for 3D weaves are described including the extension of modeling to more complex shapes such as T-pieces and a framework for optimization of these geometries. Finally, future developments, including further automation of the modeling process, improvements to methods of dealing with yarn interpenetration, issues of variability and optimization of complex structures are considered, all of which will enable a more robust design process for new, complex 3D woven structures.

Prediction of textile geometry using an energy minimization approach

In this article, a numerical method to predict textile geometry is derived using a technique based on finite elements (FEs). A geometric modeling package is used to represent an initial geometry of the yarns within the textile. The yarn mid-surface is then represented using plate elements, with the yarn thickness and cross-section being reconstructed from this mid-surface. The bending and tensile aspects of the yarn behavior are represented by separate features of the plate elements and the total energy for the system is minimized. Contacts are modeled using a penalty method, where the contact force is proportional to penetration distance. Once geometry correction has been achieved by solving the FE problem, the geometric model of the textile is corrected to take into account the predicted movements of the yarns. For validation purposes, the method is applied to two-dimensional (2D) and three-dimensional (3D) weaves and compared against images of the real fabrics. Agreement between predictions and images is good for the 3D weave and excellent for the 2D weave.

Effects of layer shift and yarn path variability on mechanical properties of a twill weave composite

Experimental and numerical analyses of a woven composite were performed in order to assess the effect of yarn path and layer shift variability on properties of the composite. Analysis of the geometry of a 12 K carbon fibre 2 × 2 twill weave at the meso- and macro-scales showed the prevalence of the yarn path variations at the macro-scale over the meso-scale variations. Numerical analysis of yarn path variability showed that it is responsible for a Young’s modulus reduction of 0.5% and CoV of 1% which makes this type of variability in the selected reinforcement almost insignificant for an elastic analysis. Finite element analysis of damage propagation in laminates with layer shift showed good agreement with the experiments. Both numerical analysis and experiments showed that layer shift has a strong effect on the shape of the stress–strain curve. In particular, laminates with no layer shift tend to exhibit a kink in the stress–strain curve which was attributed solely to the layer configuration.

Quantification of mesoscale variability and geometrical reconstruction of a textile

Automated image analysis of textile surfaces allowed determination and quantification of intrinsic yarn path variabilities in a 2/2 twill weave during the lay-up process. The yarn paths were described in terms of waves and it was found that the frequencies are similar in warp and weft directions and hardly affected by introduced yarn path deformations. The most significant source of fabric variability was introduced during handling before cutting. These resulting systematic deformations will need to be considered when designing or analysing a composite component. An automated method for three dimensional reconstruction of the analysed lay-up was implemented in TexGen which will allow virtual testing of components in the future.

Geometric modeling of 3D woven preforms in composite T-joints

A common method to fabricate net-shaped three-dimensional (3D) woven preforms for composite T-joints is to weave flat 3D preforms via a standard weaving machine with variation in binder yarn path and then separate the preform in the form of a bifurcation. Folding introduces fiber architecture deformation at the 3D woven bifurcation area. In this paper, a geometric modeling approach is proposed to represent the realistic fiber architecture, as a preprocessor for finite element analyses to predict composite structural performance. Supported by X-ray micro-computed tomography (µCT), three important deformation mechanisms are observed including yarn stack shifting, cross-section bending, and cross-section flattening resulting from the folding process. Furthermore, a set of mathematical formulae for simulation of the deformations in the junction region are developed and satisfactory agreement is observed when compared with μCT scan results.