Slide 1

Xueliang Xiao

Prof. Andrew LongDr. Xuesen ZengModelling the Structure-Permeability Relationship for Woven FabricsDivision of Materials, Mechanics and StructuresFaculty of Engineering

What degree did I do before my PhD? What made I choose this topic? Four years, Bachelor's degree on Textile Science and Engineering(China) Two years, Masters study on Surface Coating and Nano Technique(China)PhD, come to a new field, original topic Modelling impact performance of wearable airbag for fall protection. (UK)Where to start? How to start? What methodology? Keywords in the topic? Challenging

Requirement: Low gas permeabilityMain jobs on: woven fabric, permeability, fabric structure, analytical modelling

2Division of Materials, Mechanics and StructuresFaculty of Engineering

Summary of main work (discoveries, contributions) during PhD studyAn analytical static permeability model developed without fitting factor for woven fabric in through-thickness, excellent accuracy!Studied fabric dynamic permeability experimentally, compared it with corresponding fabric static permeability and found their difference;Modelled fabric deformation under high pressure load and its effect on the fabric through-thickness permeability;Studied the nonlinear relationship of pressure and flow velocity when high speed flow through the fabric structure; Tried to understand which effect has more contribution on the fabric permeability? fabric deformation or nonlinear flow;

3Division of Materials, Mechanics and StructuresFaculty of Engineering

4

Fabric static through-thickness permeability (unit cell level)

P

Ohms LawK is similar with R

Laminar Flow

Darcys law for low Re values

The Forchheimer equation for high Re values

Where ,

Kg ? & Ky ?

5

Previous model

The Gebart modelThe Kulichenko modelCurrent model

Yarn permeabilityGap permeabilityFabric static through-thickness permeability (unit cell level)6

Yarn permeability model

Yarn permeability

Flow parallel and perpendicular to filamentsFabric static through-thickness permeability (unit cell level)

Matrix transpose

7

Fabric static through-thickness permeability (unit cell level)

Gap permeability model

xyParabola fitted gap cross section

Hagen-Poiseuille flowGap flow

(Gradual converging-diverging flow channel)(straight flow channel)

8

3D woven fabric--- static through-thickness permeability

K1h1P1KihiPiKnhnPnP, H, v, v

homogenization

Real 3D fabric by CT scanning9

Fabric dynamic through-thickness permeability

High initial pressure impact + fabric deformationTransient pressure

10

Fabric deformation under high pressure load

Dial gaugeVernier caliperDeformed fabric under high pressure load11

Fabric deformation under high pressure load

rzaa

D:bending rigidityE: Youngs modulus12

Effect of fabric deformation on its permeability

Ly2a

Input new predicted geometric parameters into yarn and gap permeability models to get deformed fabric permeability valuesAssume all yarns have the same value

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Modelling nonlinear flow in gaps of woven fabricWithout fabric deformation, both increased pressure and flow velocity display a nonlinear relationship.

PV

Nonlinear flow based on the Navier-Stokes Equation

(body force is 0)

xy

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Modelling nonlinear flow in gaps of woven fabric

A1 V1 P1A2 V2 P2

BC

BC

BC

If C=8, the equation is for a circular tube;

If , the equation is for gradual converging-diverging flow channel.

The Forchheimer Eq.ABC

CFD simulationForchheimer style Eq. for woven fabric15

Nonlinear flow model with fabric deformationFabric U2

Future research based on current modelsRd, ad and d can be predicted by the deformation model in Chapter 5.

To develop rectangular gap permeability model.To study fluid flow in twisted yarns (staple fibres).To simulate flow behaviour in real woven fabric by CFD.To understand why Forchheimer factors varying under high Re valuesTo develop a nonlinear flow model for yarns or tight fabrics.

16Division of Materials, Mechanics and StructuresFaculty of Engineering

Thank you very much!