Testing Solution for the CF Industry - Fraunhofer IGCV...Precise determination of modulus and...

© Textechno Germanywww.textechno.com

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Dr. Stefan Fliescher

–

reTHINK Travelling Conference

“CFRP – Recycling and Sustainability”

Textechno –

Testing Solutions for the

Carbon Fibre Industry


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About Textechno Herbert Stein GmbH & Co. KG

Founder: Herbert Stein

Textechno’s Headquarter in Germany Lenzing Instruments in Austria

Founded in 1949 in Mönchengladbach, Germany

Family business, operating world-wide

Since the 1960ies market- and technology leader in

testing instruments for man-made fibres and yarns

In 2004 Textechno founded Lenzing Instruments in

Austria as specialist for online testing equipment

Since 2010 additional focus on testing solutions for

composite materials


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Textechno: 100% Made in Germany


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FAVIMAT+ Single Fibre Testing

Vibroscopic

head

Situation

Precise determination of modulus and breaking stress

of CFs is also possible on single filaments

Requires precise determination of the cross-section

per filament

Microscopic determination of

cross-section is time-consuming

and cumbersome


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FAVIMAT+ Single Fibre Testing

Vibroscopic

head

Approach

Integrate measurement of cross

section and breaking force into

one device: FAVIMAT+

Speed up the test with an

automatic single-fibre feeding

device: ROBOT 2

Use vibroscopic method to

determine cross section


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FAVIMAT+ Cross Section from Vibroscopic Method

Vibroscopic

head

Search the resonance frequency 𝑓 of the fibre

Given a know tension 𝐹, gauge length 𝐿and density of the fibre 𝜌 the cross section 𝐴 is calculated as:

𝐴 =𝐹

4𝜌𝐿2𝑓2

Jaws of

FAVIMAT+


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FAVIMAT+ Determination of Modulus

Precise determination of modulus as

derivative of the stress-elongation diagram

Here: Modulus = 275 GPa

Example: 20 tested Carbon Fibres

Force is translated to stress using the individual fibre cross sections


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Fast Fibre Diameter Distribution:

Situation

Diameter distribution is important e.g. to check homogeneity of rovings

Regular microscopic determination is cumbersome and time-consuming

Even with FAVIMAT+ limited statistics

Approach

Cut fibres into short sections

Dissolve and disperse in water

Scan with microscopic camera and

high-speed image analysis

Equipment developed and produced in Australia

Measures up to 20.000 fibres per minute

Fast and easy to use


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Fast Fibre Diameter Distribution:

Approach

Cut fibres into short sections

Dissolve and disperse in water

Scan with microscopic camera and

high-speed image analysis

Equipment developed and produced in Australia

Measures up to 20.000 fibres per minute

Fast and easy to use

Example: Distribution within a CF roving

Measured: 10000 fibres

Mean diameter: 5.8 µm


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FIMATEST: Fibre-Matrix Adhesion Testing

Performance of composites:

Strongly depends on fibre-matrix

adhesion, influenced by:

surface structure

sizing of the fibre

the matrix material

Macroscopic tests (e.g. ILSS) have

limited precision due to large influence of

the operator

Up to now tests on micro-level are time

consuming and not commercially

available

A single CF composite:

A single

carbon

fibreEpoxy matrix


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A single CF composite:

A single

carbon

fibreEpoxy matrix

Approach:

Pull-out tests based on single fibre

composites have been researched at IPF

Dresden for the past 20 years

Pull-out most versatile of all

micromechanical tests –

suited for all kinds of fibres and matrices

Make microscopic pull-out test into a

commercial system

Cooperation with IPF Dresden and

Faserinstitut Bremen (FIBRE) for

knowledge transfer and automation

Use FAVIMAT+ for pull-out tests AND

cross-section AND tensile properties


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A pull-out testing device

as accessory to FAVIMAT+

FIMATEST consists of:

The FIMABOND

embedding station

FIMATEST has

won the JEC

WORLD

Innovation

Award 2016

Many important

measurements for

CF in one system

fibre-matrix adhesion

and diameter,

breaking strength,

modulus of fibres


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FIMATEST: Embedding Station FIMABOND

Insert a fibre into the FIMABOND


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Example:

Embedding a fibre in PP

Matrix is placed in an

aluminum crucible

Freely-programmable

heater (max. 400°C)

Adjustable embedding

speed and depth

Inert atmosphere possible

(flushing with nitrogen,

argon etc.)

As seen by FIMABOND (time lapse)

Melting

Embedding

Cooling


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Example:



aluminum crucible

Freely-programmable



speed and depth



argon etc.)


Melting

Embedding

Cooling


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Example:



aluminum crucible

Freely-programmable



speed and depth



argon etc.)


Melting

Embedding

Cooling


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FIMATEST: Pull-out Test in FAVIMAT+

As seen by FAVIMAT+

Direct clamping of the

fibre huge speed up

in comparison to

previous lab setup

Measure the force-

displacement curve

using FAVIMAT+’s

excellent force and path

resolution (1µN, 0.1µm)


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FIMATEST: Pull-out Test Evaluation

The FIMATEST analysis software

automatically determines the

relevant parameters from the

force-displacement curve…

…and calculates the sought-after

quantities 𝜏f, 𝜏app, 𝜏d and Gic

Fd

Fmax

Fb

le

E. Mäder

F

Example: Pull-out from a epoxy resin

𝜏d : Local interfacial shear strength – based on Fdabsolute measure of the fibre-to-matrix adhesion,

independent from friction,

corrected for deformation of fibre and matrix during the pull-out test


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FIMATEST: Pull-out Test Evaluation

Calculated parameters:

Apparent interfacial shear strength………….….τapp [MPa]

Local interfacial shear strength………………τd [MPa]

Interfacial frictional stress…………………….….τf [MPa]

Critical interfacial energy release rate…..…. Gic [J/m2]

Meaning of the most important parameters:

τapp : based on the maximum force Fmax.Good for a first relative comparison of the fibre-to-maxtrix adhesion

(influence of fibre-to-matrix friction)

τd : based on the debonding force Fd.Absolute measure of the fibre-to-matrix adhesion, independent from friction

and corrected for deformation of fibre and matrix during the pull-out test

Gic : Describes the energy required to debond the fibre per unit contact surface area.


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waviness

Situation:

Defects in fabric structure occur in draping and forming

and lead to bad performance of composite parts.

Classical drapability testing as for textile applications is

not suited for reinforcement fabrics

Picture-frame test is used, but not standardized,

not suited for other than 0/90° geometries,

no automatic/objective detection of defects.

Partners: SAERTEX, FIBRE Bremen, Schilgen

DRAPETEST: Drapability Testing

Typical defects during draping:

undulations and loops gaps


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Approach:

Cricular sample deformed by

reference body

Clamping mechanism with

computer-controlled pressure

holds back the sample

Force to deform the sample is

recorded



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Approach:

Cricular sample deformed by

reference body

Clamping mechanism with

computer-controlled pressure

holds back the sample

Force to deform the sample is

recorded

Defects are detected and

analyzed: Gaps, undulation,

loops, waves, wrinkles


DIN-SPEC 8100 established

since November 2015

Project has been introduced

to ISO committee

Example: Gaps in a NCF


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NOS 200: Fibre Orientation in Nonwovens

Situation

Strength of the nonwoven web is directly

connected to the fibre orientation

Fiber orientation along and across the

machine direction is crucial indicator for

strength, tenacity and working capacity

of the nonwoven

Demand for non-destructive and fast

control of the MD-CD ratio Approach

High-speed CCD camera and intense

LED light combined with real-time

image analysis

Continuous online feedback about

the present fibre orientation

Constant quality level with minimum

waste loss


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Features

Fully automatic tensile tests on up to 48 yarn

ends / packages

Linear-density range from 1 to 5000 tex

Patented force-reduction cams

Integrated twister for better force-distribution

between the filaments

Reliable and objective

No user influence on results

Sealed version and dust suction for save

operation with carbon fibres

STATIMAT 4U: Automatic Tensile Testing

Situation

Textechno is manufacturing automatic

tensile tester for more than 50 years

STATIMAT 4U latest evolutionary stage

for high-tenacity materials


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Summary

Textechno’s testing solutions for carbon fibres

Textechno offers in house

testing services

FAVIMAT+

mechanical

properties

DRAPETEST

drapability of

fabrics

NOS 200

fibre orientation

in nonwovens

STATIMAT 4U

automatic tensile testing

DIAMSCOPE

diameter- and

length distribution

FIMATEST

fibre-to-matrix

adhesion

fibre – yarn – fabric – composite

Methods apply to both CF and rCF


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Textechno: 100% Made in Germany

Testing Solution for the CF Industry - Fraunhofer IGCV...Precise determination of modulus and...

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