This document summarizes ongoing and future work using a discrete modelling approach to simulate non-crimp fabric composite manufacturing processes. The model aims to capture deformations through multi-layer forming and further understand deformation mechanisms. It has been developed to represent individual yarns with shell elements and cross-sectional supports. Comparisons to X-ray CT scans show the model predicts compressive deformations well during multi-layer compaction, including tow spreading and waviness. Initial results also indicate potential for modelling more complex forming processes like a tetrahedron shape.

1. Discrete Modelling of NCF Forming Processes
Adam Thompson  adam.thompson@bristol.ac.uk Supervisor: Prof. Stephen Hallett, Dr Jonathan Belnoue
The continuation of this work aims to:
• Explore methods ability at capturing deformations induced through multi-layer forming processes
• Use the model to further understand and characterise deformation mechanisms, specifically those which occur through the
thickness
• Use this model as a benchmark for the development of more computationally efficient models
Future work
A discrete modelling process has been developed to capture
local and global deformations induced through the preforming
stage of non-crimp fabric (NCF) composite manufacture.
Introduction
Unit Cell to Macro-scale Modelling
Mesh for 3D yarn representation with one yarn surface hidden to show cross-section support
Tow Surface
Stitch Yarn
Cross Section
Support
The geometry is then extracted from the Digital Element model and
tessellated to form a feature or component scale fabric.
At this scale, the individual tows are described by shell elements
which act as contact surfaces, this enables inter tow interactions to
be simulated.
Cross sectional supports are placed along the length of the tows,
prescribed with visco-elastic material properties to simulate cross-
section deformation as a shear dominated phenomenon.
Modelling Compaction Processes
Generating Accurate Initial Geometry
The process begins by generating an accurate as manufactured
geometry of an NCF utilizing the Multi-Chain Digital Element
technique. The foundation of this method is the discretization of the
tows into multiple 1D element chains, where each element chain
homogenises the behaviour of a bundle of fibres.
By applying tension to the element chain representing the stitch
yarn, the fibrous tows are drawn together generating an accurate as
manufactured fabric geometry .
Predicted as manufactured geometry (post tension)
Comparisons with X-ray CT scans show the discrete method to make
good predictions for the compressive deformations experienced in
multi-layer compaction processes, capable of capturing both tow
spreading and waviness.
Experiment Prediction
Shearstrain
Experiment
Prediction
Modelling Forming Processes
CT Observations
Model Prediction
The method also shows good potential for use in forming
simulations when compared to experimental results of a
tetrahedron forming process.
Initial geometry representation
Planar View of Tetrahedron Forming Results