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 capturelocal and global deformations induced through the preformingstage 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 andtessellated to form a feature or component scale fabric.

At this scale, the individual tows are described by shell elementswhich act as contact surfaces, this enables inter tow interactions tobe 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 manufacturedgeometry of an NCF utilizing the Multi-Chain Digital Elementtechnique. The foundation of this method is the discretization of thetows into multiple 1D element chains, where each element chainhomogenises the behaviour of a bundle of fibres.

By applying tension to the element chain representing the stitchyarn, the fibrous tows are drawn together generating an accurate asmanufactured fabric geometry .

Predicted as manufactured geometry (post tension)

Comparisons with X-ray CT scans show the discrete method to makegood predictions for the compressive deformations experienced inmulti-layer compaction processes, capable of capturing both towspreading and waviness.

Experiment Prediction

Shear strain

Experiment

Prediction

Modelling Forming Processes

CT Observations

Model Prediction

The method also shows good potential for use in formingsimulations when compared to experimental results of atetrahedron forming process.

Initial geometry representation

Planar View of Tetrahedron Forming Results