Meso Scale Modelling of geometry and mechanical properties ... · properties of the final...

Guillaume PERIE Stepan LOMOV Ignaas VERPOEST

(MTM KULeuven)

David MARSAL (SNECMA)

Meso Scale Modelling of geometry and mechanical

properties of an interlock reinforced composite

Geometrical and mechanical modelling of 3D Interlock Fabrics

Introduction

07/04/2009 2nd World conference on 3D fabrics 2

Snecma Fan blade Project

Carbon / epoxy composite, 3D reinforcement, RTM process

3D = Better resistance to impact and fatigue

The fan blade

1m long, complex shape

Thickness, Vf and Weave pattern change along the length of the blade


Snecma 3D interlock Fabric


3D angle Interlock :

Several weft layers linkes by warp yarns

Shifted weft layers

Thick Fabrics

Parameters of the fabric:

Weave pattern

Spacing between yarns

Type of yarns

Fiber volume fraction

Shear angle

Impossible to perform mechanical

tests on all configurations

Need of a modeling tool

WiseTex + TexComp


Objectives :


Geometrical modelling of Interlock fabrics :

Modification of WiseTex

Input data : compression behavior of carbon yarns

Validation of the models with image analysis on samples

Mechanical modelling of Interlock fabrics :

Calculation of static mechanical properties

producing database of mechanical properties

Damage modelling ?


WiseTex : Modeling of internal geometry of relaxed & deformed textiles


Model a RVE (Representative Volume Element) using the minimum energy principle,

calculating the equilibrium of yarn interactions

Covers a wide range of textile structures (2D, 3D, Braided, Knitted, Laminates, non

crimp)


WiseTex Modifications

1. « Missing Wefts »

Possibility to remove weft yarns In order to model shifted weft layers


Modification of the mathematical coding of the weave pattern with

negative values

4

1 2 3

1 2 3 4 layer 1

layer 2

level 0

level 1

level 2

1210

0121

1012

2101warp 1

warp 2

warp 3

warp 4

WiseTex WiseTex modified


WiseTex Modifications

2. Modification of interaction algorithm between warp and weft


Different definitions of bending intervals for calculation of bending energy

Interval n°2 Interval n°7




N°1 N°2 N°3

• Interpenetrations between

yarns

• No crimp on weft yarns

• Low Vf

• Interpenetrations between

yarns

• Bad contact zones between

warp and weft

• Good modelisation of undulation

of yarns for warp and weft

• reduced interpenetration


Input Data : Compression behaviour of carbon yarns


Critical data for prediction of deformation of the fabric

Standard tests (Kawabata) not designed for heavy yarns Fmax= 10N and no

measurment of yarn width

Compression set up developed in LPMT

(Laboratoire de Physique et Mecanique des

Textiles, Mulhouse, France)

First designed for polymer monofilaments

Fmax= 1.5 kN

Compression between glass plates = width

measurement

G. Stamoulis , Ch. Wagner-Kocher and M. Renner

An experimental technique to study the transverse mechanical behaviour of

polymer monofilaments,vExperimental Techniques, vol.29, issue 4, 2005




Matlab routine developed to analyse automaticaly pictures and

measurements

Greyscale to binary image

Correction of angle of the yarn axis

Measurment of width on each pixel row and averaging

Synchronization of the image with force and thickness




Force kN 0.01 0.025 0.05 0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.9 1.1 1.3 1.48

Mean 0.68 0.70 0.72 0.74 0.75 0.76 0.78 0.79 0.80 0.81 0.81 0.82 0.83 0.84 0.85

Std 0.53 0.52 0.50 0.49 0.48 0.47 0.46 0.46 0.46 0.45 0.45 0.45 0.45 0.45 0.45

CV % 15.10 14.39 13.60 12.88 12.47 12.10 11.69 11.42 11.20 11.06 10.92 10.77 10.58 10.47 10.39

Normalized Width measurements made on 20 samples

Force kN 0.01 0.025 0.05 0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.7 0.9 1.1 1.3 1.48

Mean 0.82 0.70 0.62 0.54 0.50 0.47 0.44 0.42 0.40 0.39 0.38 0.36 0.35 0.34 0.33

Std 0.10 0.07 0.06 0.05 0.04 0.04 0.04 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03

CV % 10.70 9.48 8.76 8.08 7.83 7.59 7.39 7.27 7.18 7.19 7.11 7.04 7.04 6.99 6.94

Normalized Thickness measurements made on 20 samples




Deviation between samples in the same serie of tests but also

between different series of test :

Slope of the curves is similar for every test but curves look shifted up

or down which shows a strong dependency on the initial dimensions

of the yarns

Initial thickness d10 and width d20 :

It is not possible to measure accurately d10 and d20, as the yarn begins to

flatten before the measurments starts (when the load cell mesure 0.01 kN

D10 depends a lot on how the yarn is fixed on the glass plate by the operator

(different tension and torsion of the yarn)

A proposed solution would be to add tension to the yarn during the

compression test

A modification of the set up is needed to introduce tension


20

25

30

35

40

45

50

55

60

65

70

Vf %

Pressure

Specimen

WiseTex



d1

d2

Average behaviour = WiseTex Input:

Improvment in the prediction of the fabric

compression

Overestimation due to interpenetration of

yarns in WiseTex

In the fabric widening of one yarns is

constrained by the other yarns

• Need to make tests with side boundaries

Yarns compresion

Fabric Compresion


Validation of models with image analysis


1. Transverse Yarns

Filtering on grey scale levels to isolate the yarns and clean the image

Manual separation of contours in Photoshop

Measurments made with image analysis softwares

Measurements :

Spacing between yarns

Vf inside yarns

Orientation of cross sections


Validation of models with image analysis


2. Longitudinal yarns

Filtering on grey scale levels to isolate the yarns and clean the image

Manual separation of contours in Photoshop

Matlab routines to calculate crimp and orientation of the yarn

In Matlab :

Isolation of contours and center line for each yarn

Smoothing of lines using cubic smoothing splines, in order to avoid pixel effect

Measurement of the length of the spline, and orientation of spline at different

points


Image analysis results


Warp

Weft

Sample WiseTex Model

Warp d1 1 0.89

Warp d2 1 1.12

Warp Vf % 77.1 70

Warp Crimp % 1.17 1.5

Weft d1 1 0.87

Weft d2 1 1.08

Weft Vf % 69.6 63.9

Weft crimp % 1.01 1.2

FabricThickness 1 1.02

Conclusion:

Yarns are flatenning too much

Crimp is overestimated due to local

changes of curvature on the models

Crimp is not enough accurate :

Need to compare histograms of yarns

orientation for better characterization

of the fabric.

Normalized measurments


Calculation of mechanical properties


Tex comp routines are used to calculate homogenized mechanical

properties of the final composites:

Inputs : WiseTex model for reinforcement and matrix properties

Calculation of mechanical properties by method of inclusions with different

calculation schemes implemented (Mori-Tanaka, Iso-Strain..)

Results are compared with measurements made by UTC

(Université de Technologie de Compiegne)

Implementation of a tool to produce databases of material

Unique interface linking WiseTex and TexComp

Automatic Production of several WiseTex models based on a range of

weaving parameters specified by the user and calculation of mechanical

properties with export to excel file.


Iso-Strain

MoriTanaka

Experiment

Results


E11 and E22 measured on tensile tests

in warp and weft directions

E33 measured on samples cut in the

thickness direction

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

Normalized Pick spacing

E1 58%

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


E2 58%

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


E3 58%


Iso-Strain

MoriTanaka

Experiment

Results


G12 measured on tensile tests in bias

direction

Techniques are developed in UTC for

measurment of G13 and G23 based on

torsion tests and strain mapping on

bending tests

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


G12 58%

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


G13 58%

0.00

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


G23 58%


Errors on E1


There are still some significant errors in E1 results (up to 15%)

These errors can be explained by the errors on fiber orientation in WiseTex

Models

For small Pick spacing:

in WiseTex crimp is overestimated and we can

observe too important changes of curvature in the

yarn path which can explain the low E1 calculated

For high Pick spacing:

The higher pressure applied on this material

makes the yarn expand between weft rows,

leading to a local disorientation of fibers. This is

not modeled in WiseTex, and can explain that

wiseTex values are higher


Errors on E1


Proof of the effect of crimp on E1 :

We can artificially reduce crimp by reducing the number of points between

contacts, which leads to straight warp yarns (but it introduces

interpenetration between warp and weft)

You can see on the graph that reducing crimp leads to an increase of E1

0.20

0.40

0.60

0.80

1.00

0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00


E1 58%Crimped Yarns

Experiment

Straight Yarns

« Straight » yarns

« crimped » yarns

A solution to decrease crimp without introducing interpenetration, would be

to implement tilt of the weft cross sections to fit the interlock angle.


Conclusion


Prediction of mechanical properties is quiet good:

Most of the properties calculated are close to the mechanical tests (in the

standard deviation range)

The errors can be linked to the errors in modelling the geometry of the

reinforcement

Further Work:

Improve compression test to reduce deviation, tests with side boundaries

should also help to get more accurate modeling of the yarn geometry

Implement tilt of the weft cross section to get a more accurate modelling of

warp path (we can see on pictures that weft yarn tilt to fit the interlock angle)



Thank you for your attention

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