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Recycling of high performance thermoplastic
composites with high voltage fragmentation
Alex Bian, Maxime Roux, Clemens Dransfeld
University of Applied Sciences Northwestern Switzerland, Institute of Polymer Engineering
IEA IA-IEV Task 17 Workshop. October 09, 2014
209.10.2014A. Bian IEA IA-HEV Task 17 Workshop
www.bmw.com
www.flightaware.com
www.ffffound.com
www.team.aero
• How to process and recycle a complex aerospace part
made of high performance carbon fiber reinforced
thermoplastic?
3
Steel door hinge
Airbus Helicopter
EC135 Germany
09.10.2014A. Bian IEA IA-HEV Task 17 Workshop
Source: www.helis.com
• Carbon fiber (CF) reinforced thermoplastic composite
Materials and processing
4
Chopped (Discontinuous) tapes
55 Vol% Carbon fibers (20mm)
Temperature: 360°C
Pressure: 75 Bars
Thermoplastic
composite hinge
Weight saving: 83%
• Compression molding
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
5A. Bian IEA IA-HEV Task 17 Workshop
Efficiency
Motivation
09.10.2014
Thermoplastic
Composite
Recycled
Fragments
Cradle-to-Cradle
How to recycle CFRP materials from aerospace industry?
Pyrolysis
• Recovery of the carbon fibers by removing the matrix through thermal processes
6
• Reuse of matrix - generate fuels, oils• Energy intensive
• Some polymers very expensive (e.g.
PEEK)
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
+500 – 700°C
N2
How to recycle CFRP materials from aerospace industry?
Mechanical Shredding
• Grinding of carbon fiber composite to smaller fragments
7
• Direct reprocessing of fragments
possible
• Significant loss of mechanical properties
• Composites with high CF content wear
out shredding blades very quickly
http://www.itsgreen.com.au
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
High Voltage Fragmentation (HVF)
8
Source: Selfrag AG
Process parameters
• Voltage between 50 - 200 kV
• Pulse rise time below 5 µs
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
• Breakdown voltage versus pulse rise time: Water acts as isolating medium
High Voltage Fragmentation (HVF)
9A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Technology: High Voltage Fragmentation
• Explanation HV fragmentation
Creation of the discharge: Plasma channel + shockwave
10
Source: Selfrag AG
• Discharge pressure along the plasma channel: 10 GPa
• Plasma temperature: up to 10,000 °C
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Technology: High Voltage Fragmentation
• Current applications
11
Source: Selfrag AG, Tyvek
• Main Advantages
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
• No tool wear
• No dust
• Selective fragmentation
Recovery: Fragmentation of the CFRP hinge
12
HV Fragmentation
Sieving
Initial
hinge
200 pulses
(2 cycles)
300 pulses
(3 cycles)
600 pulses
(6 cycles)
Powder
<1mm
Fragments with
targeted size
Large Fragments
>4mm
Recycled
fragments
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
13
Recycled CFRP door hinge
Successful processing of door hinges with 100% of recycled fragments.
Compression molding
Recycled CF
thermoplasic
fragments
2 cm
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Analysis of the recycled fragments
Recycled chips:
Polymer partly removed from
the surface of the fragments,
(estimated 3wt% loss)
14
Recycled chips Chopped tape
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Mechanical testing: Recycled versus original
• Maximal load:
• 17% reduction compared to chopped tapes (20mm)
15
Loading conditions
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Observations: Fracture analysis
• Chopped tapes:
Fibers still covered with polymer:
Cohesive failure
16
• Recycled chips:
Fibers partially covered with
polymer: Cohesive failure
Polymer is removed from the
surface of the fragments:
Adhesive failure
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Discussion: High voltage fragmentation process in a CFRP
17
I: Loss of fibers II: Cleaned fibers
with no polymer on
surface
First impact on a CFRP plate during HVF Random impact on a door-hinge during HVF
III: Bundles of fibers lifted
up still embedded in polymer
a b
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
• I: Fiber sublimation
• II: Polymer pyrolysis
• III: Mechanical delamination
• IV: Pressure waves
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Mechanisms of fragmentation induced by HV pulses in composites
(Ogasawara 2010; modified)
IFiber
sublimation
IIPolymer
Pyrolysis
IIIFiber/polymer
delaminated
in mode 1
IIIMechanical
delamination
IVCracks in the
polymer
matrix
IVPressure
waves
IShorter
fibers
Pyrolysis
gas
Force induced
by internal
pressure
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
IINaked fibers
Conclusions
Successful fragmentation of CF thermoplastic composite with high content of carbon
fibers
Production of a complex part with 100% of recycled materials
Promising results:
• Slight reduction of the mechanical properties (shorter fragments, less polymers at the
surface of the fragments)
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Acknowledgements
• IKT Research Group, FHNW, Switzerland
• Clean Sky JTI, Eco-Design ITD
• Airbus Helicopters
• Selfrag AG, Switzerland.
20A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
Thank you for your attention. Questions?
21
Point of Contact:
Alex Bian
Institut of Polymer Engineering
Klosterzelgstrasse 2
5210 Windisch
Switzerland
Tel: +41 56 202 8264
alex.bian@fhnw.ch
www.fhnw.ch/technik/ikt/
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
13.10.2014Institut für Kunststofftechnik / Institut für nanotechnische Kunststoffanwendungen 22
Technology: Electrodynamic fragmentation
• Propagation in the material
• Interfaces with different dielectrical properties
• Inclusion with high dielectrical constant (metallic or
CF) attract the discharge track
• Heterogeneity
• Residual stresses.
• Separation of the material:
• A compression wave is transformed into a tensile
and shear wave by reflection and refraction at an
inclusion and separate it from the matrix.
23
Source: Selfrag AG
A. Bian IEA IA-HEV Task 17 Workshop 09.10.2014
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