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A new natural reinforcement for polymer composite materials: Long Bamboo
fibres
Aart W. van Vuure, Lina Osorio, Eduardo Trujillo, Carlos Fuentes, Jan Ivens, Ignaas Verpoest
Department of Metallurgy and Materials Engineering,
Katholieke Universiteit Leuven
First; what do we call polymer composite materials?
Fibre: reinforcement
Impregnate
Polymer: matrix
COMPOSITE
Consolidate
Light but weak
Light, stiff & strong
Light but stiff & strong!
• Long fibres give better mechanical properties
• Fibres typically Glass and Carbon
2World Bamboo Congress, April 2012
Natural Fibres (and Bio-polymers): why?
3
Environmental reasons:
• Renewable resources
• Thermally recyclable, optionally biodegradable, CO2
neutral
• Natural fibres: Low energy consumption (low CO2 )
So: low “Carbon footprint”
0
20
40
60
80
100
120
140
lignocellulosicfibres
glass fibre carbon fibre
energy ( MJ/kg)
energy ( MJ/kg)mat
mat
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4
• Cost: often (potentially) low cost (not silk)
• Less abrasive
• Good specific mechanical properties (low density)
• Potential bio-compatibility for e.g. bio-medical applications
• Natural image, design aspects
• Others, like good acoustic & vibration damping, radar transparency, low CTE
Natural Fibres and Bio-polymers: why?
Specific tensile modulus E/rho (MJ/kg) for various fibres
0
20
40
60
80
100
120
140
Flax fibre Bamboofibre
Glass fibre Carbon fibre
Spec
ific
mod
ulus
(MJ/
kg)
Specific FLEXURAL modulus (E(1/3)/rho in N(1/3)m(7/3)/kg) for various fibres
0
0.5
1
1.5
2
2.5
3
3.5
4
Flax fibre Bamboofibre
Glass fibre Carbon fibreSpec
ific
bend
ing
mod
ulus
(N(1
/3)m
(7/3
)/kg)
World Bamboo Congress, April 2012
Good vibrational damping: Flax/Carbon hybrid bicycle frame
ISO2631:WholeBodyVibration
5
Applications of bio-based composites; on the market
Museeuw/Lineo Flax-Carbonhybrid bike(JEC 2007);Prepregtechnology
Decathlon Artengo 820Flax/Carbon Fibre racket(prepreg Lineo)
Mixed NF – PPCar interiors
WoodPolymerComposites(WPC’s)e.g. deckings
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Applications of bio-based composites; prototypes
NPSP front-end train• flax-UP composite• vacuum injection• ~500 kg lighter than steelconstruction!
Toyota 1/X concept car (420 kg!):• Carbon Fibre frame• Roof of kenaf/ramie fibre composite
• heat and sound insulation• lightweight
Motive Kestrel electric vehicle•Launch 2012 in Canada?•Bio-based composite body
Prototype flax/PP (TU Delft)
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Natural Fibres, Quantities
Estimated annual production, in millions of tons:
Wood 1750
Steel 1000
Plastics/polymers 200
Composites (polymer) 5-10 mainly glass fibre composites
Glass fibre 2-4 (at 42% in composites)
Carbon fibre 0.050 (= 50,000 tons)
Synthetic fibres 30
Natural fibres 27 (large part cotton)
Flax fibres ~ 1.0
WPC 1.2
Plant fibre in composites 0.040 in automotive applications Europe
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Natural Fibres
PLANT / Lignocellulosic
FIBRES
Wood Stem/Bast
FlaxJute
HempKenafRamie
Leaf
SisalAbaca
PineappleBananaFique
HenequenPalm
Seed/Fruit
CottonCoconut
Grass
BambooRice
ANIMAL FIBRES (protein)
SoftwoodHardwood
SilkWool
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Main challenges for Bio-based Composites
1)
Fibre
properties:* Understanding structure (morphology) – mechanical property relationships
* Fibre off-axis properties: low transverse and shear properties
** Improve internal interface between elementary fibres
* Moisture sensitivity: Make fibres more hydrophobic? / seal them off (interface)
2) (Fibre) Processing• Extraction, yarn processing, preforming and prepregging
3) Fibre-matrix Interface:• Improving wetting and adhesion (surface energy matching)
4) Environmentally friendly matrices:* Biodegradable or Bio-based
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Bio-based Composites; Natural fibre properties; examples
Silk Composites have excellent falling weight impact performance!
Patent: WO 2007-110758 (with Hermès)
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MatricesClassification of matrices:
* Thermoplastic (TP) and thermoset resins (TS)
• Research on renewable matrices is relatively recent, especially for bio-thermosets
Examples of polymers Natural polymers:(renewable)
BIO-BASED
polymers (renewable feedstock, synthesized!):
“Synthetic” petroleum based polymers
Biodegradable Lignin PLAPHA, PHBStarch
PBSPCLPVA
Non-biodegradable Cashew nut shell resin (CSNL)
Furan resinVegetable oil -PUR (polyol)AESOEthanol based PESome nylons (PA-11)
Most well-known polymers:* PP, PE, nylons, etc.* Epoxy, UP
12World Bamboo Congress, April 2012
Bio-based Composites; Developing environmentally friendly matrices
Development of renewable gluten based bio-polymers:
• Improvement of toughness & rheology
• Patent on thiol-based modifiers (WO 2004/029135)
• So far 50% improvement in strength and strain to failure (approaching epoxy)
Gluten
ResinBio-based
Polymer or CompositeMaterial
Controlled-releaseNitrogenFertilizer
Wheat
agriculture
Starch
industrialprocessing
recycling
chemical or(bio)catalyticmodification
polymerprocessing
Compost
composting
Thiol-terminated star-branched modifiers:Crosslinking + phase separation?
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Fibre processing research; Effect of twist on FLAX UD-composite stiffness (CELC)
-
35 % !!
Back-calculatedfibre stiffness(matrix=epoxy)
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Bio-based Composites; Fibre
processing
80‐100%
~50% !
Research in cooperation with CELC
Combined effect of twist and crimp on composite modulus
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Bio-based Composites; Paper honeycomb panels
Applications of ‘Torhex’ cardboard honeycombs; sandwich panels with NF composite skins
www.econcore.com
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Large Projects at SLC - BioComposites
•Cornet Nature Wins (with Centexbel and ITA Aachen)
Thermoplastic bio‐composites, flax/hemp + PLA
•
Mixed yarns & textiles / non‐wovens
•
Consolidation and thermoforming
•TIS Change2Bio (with VKC and Centexbel)“Renewable polymers – important element to develop the bio‐economy”
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Bamboo Fibre Composites
Culm with vascular bundles Technical
fibre(s)
• Bamboo fibres have excellent
mechanical properties
• Specific properties comparable to glass fibre
• Bamboo can grow to 20 m in 6 months
• Can fix 50-60 tons of C/ha.year
• Challenge is to extract technical fibres
Elementary fibres
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Bamboo Fibre processing
150
250
350
450
550
650
750
850
0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0
Extraction method
Stre
ngth
(MPa
)
Mechanical(rolling mill machine)
Chemical extraction(in some cases
mechanical process is required)
Steam explosion
Mechanical process(in some cases chemical process is required)
KULeuven process
Loop test
Bamboo Fibre
Extraction
19
Bamboo Fibre properties
Single fibre tensile tests;
Corrected for system compliance
* E(extrapolated) ~ 44 GPa
New developments: * use of Digital Image Correlation (camera extensometer)
* Fibre bundle tests (dry + impregnated)
* Study of off-axis properties
E-modulus as f(1/test length), Single bamboo fibre testing
05
1015202530354045
0.00 0.05 0.10 0.15 0.20 0.251/test length (1/mm)
E-m
odul
us (G
Pa)
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Bamboo Fibre morphology (Lina Osorio)
4
3
Bamboo wallLiese, W., 1998Vascular bundleFibre
bundle
Bamboo culm Cross section
Elementary fibres
Vascular bundles have higher concentration towards the outside of the culm
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Bamboo Fibre morphology
Most elementary fibres seem to havea simple 2 layer structure
Next: Measurement of off-axis properties (tests on composites)
Primary layer with 90° orientation;from fracture surface
Secondary layer with 0° orientation;After etching away primary layer
5 μm5 μm5 μm
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Continuous UD prepreg
Discontinuous UD prepreg
Discontinuity of the fibre
Length of internodes
(± 25 cm)
Node
Internode
Bamboo fibre process development(Eduardo Trujillo)
Problem statement
UD prepreg with discontinuous fibres; continuous process?
UD bamboo fibre-polypropylene tape
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Technical fibre ~100 – 200 μm
Elementary fibre ~10 μmWith micro/nano fibrils:
Microstructure Surface
Chemical composition
Topography
Wetting
vapour
liquid
Micro balanc
e
F (μN)
R
Fibre
and matrix
Molecular kinetic theory
Equilibrium contact angle
SEC theories
Owens/Wendt
Dsv
Psvsv
Acid/base
cos1, iiL =)θ+(γ
)(2 ,,, SiLSiL
LWS
LWiL
Adhesion Improvement
Approaches:1. Make a good match
with untreated fibre:
Polyvinylidene fluoride (PVDF)
2. Treat the surface to get a good match:
Chitosan layer, Silanes
Interface Characterization
Streaming Potential
Micromechanical test: Pull-out tests
Flexural test: Transverse
3 point bending test
X-ray photoelectronspectroscopy (XPS)
AFM
Profilometer
Primary wall: 90°
orientation
Secondary wall: 0°
orientation
Understanding and improving the fibre-matrix interface;a combined physical-chemical-mechanical approach(Carlos Fuentes)
Bamboo fibre surface analysis
0
10
20
30
40
50
60
70
80
0.0 0.2 0.4 0.6 0.8 1.0
C1/C (%)
O/C
O/C vs C1/C
Non‐autoclave treated bamboo
Autoclave treated bamboo
Theoretical Cellulose
Theoretical milled wood Lignin
Protobind 1000 Granit Lignin
Cellulose
Lignin
Measured Lignin
XPS results; courtesy C. DuPont, UCL
Extracted bamboo fibre surface seems to be covered with lignin
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Interface studies; Bamboo fibre composites
Bamboo fibre UD composites
R2 = 0.6963
0
5
10
15
20
25
40 45 50 55 60 65 70 75 80
Work of physical adhesion (mJ/m2)
Tran
sver
se 3
PB
str
engt
h (M
Pa)
Matrix: PP and PVDF (+ some treatments)
Results of Surface Energy Component matching; Effect of Physical Adhesion in thermoplastic composites
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Addition of chemical adhesion
Transverse 3 point bending strength for UD Bamboo-epoxy
15
20
25
30
35
40
45
0 1 2 3 4 5 6Alkali treatment (%) (20 min)
T3PB
(MPa
)
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Work of Adhesion versus Interface strength for coir composites
Chemical bonding dominant Physical adhesion
U = Untreated
T = Alkali treated
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Bio-based Composites; Fibre properties
Flax fibre property improvement* Fibre Treatment to Reduce Direct and Indirect Moisture Uptake
* Fibre Treatment to Improve internal fibre strength
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Bamboo Fibre Composite performance
COMPOSITE longitudinal flexural tests
Efficiency factor = measured property / theoretical property based on fibre properties
.... ..
Force
..
Efficiency factors in longitudinal flexural test
0
10
20
30
40
50
60
70
80
90
100
Efficiency factor strength Efficiency factor modulus
Effic
ienc
y fa
ctor
(%)
PPPVDFepoxy
+ Transverse 3 PB strength values
15 MPa
15 MPa23 MPa
33 MPa23 MPa
33 MPa
30
World Bamboo Congress, April 2012
Moisture resistance Bamboo fibres Moisture uptake of bamboo fibre at 23oC (from dry
condition)
02468
1012141618
0 20 40 60 80 100
Environmental relative humidity (%)
Moi
stur
e up
take
(wt%
)
Fibre moisture uptake,
Absorption isotherm
Moisture uptake is intermediate to literature data for (solid) lignin and cellulose
Diffusion coefficient [m2/sec]
Bamboo 1.04 x 10-10
Flax 1.25 x 10-8
31
Moisture effects on Bamboo fibres
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Thermal degradation Bamboo fibre composites
Single fibres: Degradation starts around 170°C in normal atmosphere
Flexural strength and failure strain for UD bamboo fibre/thermoplastic composites at different processing
temperatures
020406080
100120140160180200220
0 0.5 1 1.5 2 2.5 3
Strain at maximum strength (%)
Stre
ngth
(MPa
)
PP/BF 175°C
PP/BF 185°C
MAPP/BF 170°C
MAPP/BF 180°c
.... ..
Force
..
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Concluding (Bamboo Fibre Composites)
• A promising fibre extraction process was developed for Bamboo Fibres• Next processing development is cleaning, stretching, aligning and prepregging• Most elementary fibres have predominantly 0 degree nanofibril orientation, combined
with an outer wrap of 90 degrees• Extracted bamboo fibre seems covered by lignin• Surface energy component matching allows improving physical adhesion; so far good
results with PVDF• There is a clear correlation between interface strength and UD longitudinal strength• Efficiency factors for epoxy reach 95% for modulus and 80% for strength• Moisture uptake is as expected intermediate to solid cellulose and lignin• Fibre strength and modulus are hardly affected by moisture; strain to failure is
affected (plasticisation)
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Thanks for your attention!
JEC 2012 Tradeshow in Paris: KU Leuven - SLC booth
35World Bamboo Congress, April 2012
CompositesWeek@Leuven16-20 September 2013
The Composite Materials Groupof the Department of Metallurgy and Materials Engineering (MTM) of the
Katholieke
Universiteit
Leuven
(Belgium)cordially invites you to the
Three one-day symposia
on : •nano-engineered composites,
•designing with composites •bio-based composites
+the TEXCOMP 11
conference on textile composites
www.mtm.kuleuven.be/Onderzoek/Composites/Composietenwww.texcomp10.com