2012 composites in construction
TRANSCRIPT
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Composites in construction
Jan Wastiels
20 April 2012
Content
intro composite materials
(G)FRC and applications
ECC and applications
TRC and applications vubonite
tensile modelling
processing
vubonite applications
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Composite materials
strong and stiff fibres are embedded in a matrix
fibres are oriented following structural needs
with polymer matrix: high fibre fractions Vfarepossible
result: lightweight and strong materials
aerospace > aviation > transport > building
building applications ?
Comparison steel - flame retardant
polyester composite
E E/ f f/
Steel 205 26 250 32
Pol 2,5 1,7 50 35
Polc 16,5 11 270 175
E: stiffness modulus (GPa)
E/: specific stiffness
f: strength (MPa)
f/: specific strength
Pol: flame retardant polyester
Polc: polyester composite with 20wt% UD glass fibres
Conclusion:
the composite improves much when specific properties are considered:
absolute stiffness of the composite is poor, but specific stiffness is acceptable
absolute strength of the composite is OK, but specific strength is very good
BUT: drawbacks of polymer matrix: use of solvents, VOCs, bad fire resistance, high cost
price, hazardous waste
building applications ???
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CIF5 Newcastle July
10 20085
An absolute fire resistant matrix for composites:
vubonite
Polyester - glass composite0 sec 15 sec
30 sec 40 sec
CIF5 Newcastle July
10 20086
An absolute fire resistant matrix for composites:
vubonite
M1 Polyester - glass composite
65 sec60 sec
20 sec 40 sec
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CIF5 Newcastle July
10 20087
An absolute fire resistant matrix for composites:
vubonite
M1 Polyester - glass composite
65 sec60 sec
20 sec 40 sec
Cement matrix?
Polyester Cement C/P
E (GPa) 2.5 25 x 10
fc (MPa) 40 40 =
ft (MPa) 50 5 /10
mu()
20 0.2 /100
matrix fails in tension long before fibres!
composite stress at matrix cracking is very low!
behaviour in cracked stage is normal
E : stiffness modulus
fc : compressive strength
ft : tensile strength
mu : matrix tensile failure
strain
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Minimum amount of fibres
Vf crit = (mu / fu ).Vm
mu = 5 MPa
fu = 2 GPa
Vm 1 (> 0.95)
Vf crit = 0.25 %
Glass fibre reinforced cement (GRC)
Traditional production technology: short fibres
Typical 2 to 4%
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Fibre length effect Short fibres: critical length lc lc = (fu . r)/fu
fu 1 MPa
r = 7 m (fibre) lc = 14 mm
r = 0.1 mm (bundle) 200 mm
in practice always l < lc
pullout occurs
efficiency l = 0.03 to 0.5
Fibre orientation effect
efficiency of oriented fibres is lower than 1
different values for uncracked and crackedmatrix
dependent on distribution of fibres (2D-3D)
strongly dependent for cracked matrix onbending stiffness of fibres
values between 1/6 and 3/
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Combined efficiency
for 2D distribution: = 3/8 . 3/10 . l/lc
for individual fibres: = 0.11,
thus Vf crit = 0.25%/0.11 = 2.3%
for fibre bundles: < 0.01,
thus Vf crit = 25%
since Vf< 5%, pseudo plastic behaviour intension is hardly obtainable
Consequences of production technique
no tensile strength increase
limited ductility
hardly crack opening
control by fibres
no load bearing
applications
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Use of GRC: various
Engineered Cement Composites (ECC)
Vf= 2 % of short,
random PVA fibres
self compacting
cement Ductile and very
flexible, due to
tuned interaction
cement-fibres
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ECC: behaviour in bending high ductility compared to conventional GRC
however limited post-cracking stiffness
ECC: behaviour in tension
enormous ductility (3 to 7 %) and limited crack width
but nearly no strain hardening (post-cracking stiffness)
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Applications of ECC
mainly surface repair of retaining walls, bridgedecks and dams
Structural application needs
compressive strength: is provided by the matrix
ductility: can be solved (ECC)
tensile strength significantly higher than the cement itself:cu = fu Vf
significant post-cracking stiffness: Ec = EfVf enough fibres: Vf> Vf crit = (mu / fu).Vm controlled efficiency of fibres
strict crack width control (see later)
many strong, stiff and aligned fibres!
cost price: glass fibres
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Fibre Reinforced Cement TRCFRC - ECC
Short fibres
Distribution & orientation not
controlled
Low fibre content
Concrete processing:- Casting
- Pressure forming (plates)
- Shotcrete
Textile Reinforced Cement
24
TRCFRC - ECC
Short fibres Prefabricated textiles
Distribution & orientation not
controlled
Low fibre content
Concrete processing:- Casting
- Pressure forming (plates)
- Shotcrete
Carefully controlled orientation
and distribution
High fibre content possible
Composite processing:- Hand lay-up
- Pultrusion
- Calendaring
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TRC opportunities
25
- Lightweight constructions
- Freeform constructions
- High fibre volume fraction
- Flexible reinforcement
-Compressive AND tensile stresses
structural material
durability is very important issue
- Limited concrete cover
1. Felix Candela, Mexico,1958
2. Heinz Isler, UK
Applications of TRC: sandwich elements
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Applications of TRC: thin walled elements
Applications of TRC: diamond-shaped grid
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Applications of TRC: pedestrian bridge
Which cement?
Traditional:production technique leads to limited VfE-glass must be replaced by AR-glass ($) for
durability reasons
Hydration products cause embrittlement withtime, even with AR-glass
heavy coating is needed, so bad interaction cement-fibre
and low efficiency
Vubonite does not present these drawbacks
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CIF5 Newcastle July
10 200831
An absolute fire resistant matrix for composites:
vubonite
Why (or what is) vubonite ?
Powder component: based on the calciumsilicatemineral Wollastonite (CaSiO3)
CIF5 Newcastle July
10 200832
An absolute fire resistant matrix for composites:
vubonite
Why (or what is) vubonite ?
Powder component: based on the calciumsilicatemineral Wollastonite (CaSiO3)
Liquid component: proprietary metal ion modified
phosphoric acid
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CIF5 Newcastle July
10 200833
An absolute fire resistant matrix for composites:
vubonite
Why (or what is) vubonite ?
Powder component: based on the calciumsilicatemineral Wollastonite (CaSiO3)
Liquid component: proprietary metal ion modifiedphosphoric acid
Acid-base setting reaction after mixing
CIF5 Newcastle July
10 200834
An absolute fire resistant matrix for composites:
vubonite
Why (or what is) vubonite ?
Powder component: based on the calciumsilicatemineral Wollastonite (CaSiO3)
Liquid component: proprietary metal ion modified
phosphoric acid Acid-base setting reaction after mixing
Fresh mixture is acidic (pH=1), but neutral (pH=7)after hardening: compatible with glass fibres
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CIF5 Newcastle July
10 200835
An absolute fire resistant matrix for composites:
vubonite
Why (or what is) vubonite ?
Powder component: based on the calciumsilicatemineral Wollastonite (CaSiO3)
Liquid component: proprietary metal ion modifiedphosphoric acid
Acid-base hardening reaction after mixing
Fresh mixture is acidic (pH=1), but neutral (pH=7)after hardening: compatible with glass fibres
Vubonite is always used in combination with fibresand/or fillers: it is a matrixor binderfor (fibre)composites, similar to organic resins like polyester
Tensile experimental data
0
20
40
60
80
100
120
0 0,4 0,8 1,2 1,6
strain(%)
stress(MPa)
0
10
20
30
40
0,0 0,4 0,8 1,2 1,6 2,0
strain (%)
stress(MPa)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
5,5
0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 9,0 10,0 11,0 12,0
Elongation in mm/m
Force in kN
E-modulus of the matrix
first crack in the matrix
starting point of the crack pattern
last crack in the matrix
E-modulus of the reinforcement
breaking point
Random E-glass 10% (vubonite)
UD E-glass 10% (vubonite)
UD AR-glass 2% (OPC)
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0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1
strain (%)
stress (MPa)
Stress-strain behaviour
static loading
matrixfibre
matrix
fibre
matrix-fibreinterface
Stress-strain behaviour
static loading
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ACK theory (Aveston, Cooper, Kelly)
Three stages in tensile behaviour:
uncracked
multiple cracking
crack opening
Aligned UD
reinforcement
ACK Stage 1
Fibres and matrix linear elastic
Perfect adhesion fibres-matrix
Law of mixtures: Ec = EmVm + EfVf
The end of stage 1 is reached when c = mu(and m = mu) : the first crack appears at a
composite stress
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ACK Stage 2
At crack location: all load taken up by fibresVfmust be larger than Vf crit to avoid failure:
Deterministic material properties: not onlyone crack appears at mc , but all possible
cracksmultiple cracking stage
ACK Stage 2
Local high shear stress at interfacedebonding of fibre and matrix over length 0
diameter 2r
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ACK Stage 2 Constant frictional shear stress 0 at debonded
interface stress transfer from fibres to matrix
starting at crack after debonding length 0 the
matrix stress again reaches mu
In the debonded length no new crack can appear
ACK Stage 2
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ACK Stage 2
In the end, the crack spacing x is everywherebetween 0 and 20
mean crack spacing: x = 1.3370 the deformation increases due to the multiple
cracking:
with
ACK Stage 3
Fibres and matrix debonded over the wholelength everywhere frictional slip
stress in matrix remains unchanged during
loading all the extra load is taken up bythe fibres
stiffness : EfVf (adapted law of mixtures)
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0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1strain (%)
stress(MPa)
experimental
theory ACK
ACK-Theory versus experiment
mu1
mu2
mu3
EfVf
Stress-strain behaviour
static loading
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Weibull distribution function for matrix tensile strength (Curtin 1998)
c
c
1
exp1:
=
0
m
R
cXxngcrackspaci
+=
xEc
cc
0
1
1
=
104
1
cff
ccE
x
VE
Stochastic Cracking Model
0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1strain (%)
stress(MP
a)
experimentaltheory stochastic crackingtheory ACK
Stochastic cracking model vs. experiment
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Example: glass fibre chopped mat 2%
0
5
10
15
20
25
30
0 0,5 1 1,5 2strain (%)
stress(MPa)
Vf= 2%
0
1
2
3
4
5
6
0 5 10 15 20 25
Vf (%)
X(mm)
ductility: no
strength: 7 MPa
post-cracking stiffness: 0.5 GPa
Example: glass fibre chopped mat 5%
0
5
10
15
20
25
30
0 0,5 1 1,5 2strain (%)
stress(MPa)
Vf= 5%
0
1
2
3
45
6
0 5 10 15 20 25
Vf (%)
X(mm)
ductility: yes
strength: 16 MPa
post-cracking stiffness: 1.2 GPa
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Example: glass fibre chopped mat 10%
0
5
10
15
20
25
30
0 0,5 1 1,5 2strain (%)
stress(MPa)
Vf= 10%
0
1
2
3
4
5
6
0 5 10 15 20 25
Vf (%)
X(mm)
ductility: yes
strength: 33 MPa
post-cracking stiffness: 2.4 GPa
Example: glass fibre chopped mat 20%
0
5
10
15
20
25
30
0 0,5 1 1,5 2strain (%)
stress(MPa)
Vf= 20%
0
1
2
3
45
6
0 5 10 15 20 25
Vf (%)
X(mm)
Conclusion: Vf has an important effect on the stress-strain curve
ductility: yes
strength: 67 MPa
post-cracking stiffness: 4.8 GPa
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Low Vf leads to large crack spacing and crack opening. For V f higher than 5%,crack spacing is dense, and average crack width is limited for all stress levels
vubonite composite: crack width and spacing
0
10
20
30
40
50
60
70
0 10 20 30stress (MPa)
crackwidth(m) Vf = 2%
Vf = 5%
Vf = 10%
Vf = 20%
0
10
20
30
40
50
0 10 20 30
stress (MPa)
x(mm)
Vf = 20%
Vf = 10%
Vf = 5%
Vf = 2%
1
m
m
no load 15% 30% max load
1mm
T
Textile fibre structures for
vubonite
Biaxial
Multiaxial Knitted
Leno-woven
Spacer with
varyingdistances
Spacer
Circular
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Composite processing
Cement composite processing
30 to 50% particles: non-Newtonian viscous
fluid with non-zero yield stress separation
and filtering
58
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CIF5 Newcastle July
10 200859
An absolute fire resistant matrix for composites:
vubonite
Processing: hand lay-up
1 4
2 3
CIF5 Newcastle July
10 200860
An absolute fire resistant matrix for composites:
vubonite
Processing: vacuum bagging
1 3
2
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CIF5 Newcastle July
10 200861
An absolute fire resistant matrix for composites:
vubonite
Processing: pultrusion
CIF5 Newcastle July
10 200862
An absolute fire resistant matrix for composites:
vubonite
Processing: pultrusion
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CIF5 Newcastle July
10 200863
An absolute fire resistant matrix for composites:
vubonite
Processing: spray-up
Self compacting impregnator
Translation of the hand lay-up processing intoa mechanised and automatic process: well
controlled wetting and impregnation with
precise fibre volume
64
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Self compacting impregnator
Translation of the hand lay-up processing intoa mechanised and automatic process: well
controlled wetting and impregnation with
precise fibre volume
65
Self compacting impregnator
Feeding of textile fibre
structure (2 to 4 textiles)
66
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Self compacting impregnator
Continuously refreshed
matrix material
67
Self compacting impregnator
Grooves for controlled wetting
and impregnation of fibres
68
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Self compacting impregnator
Adjustable calendar pressure for
controlled impregnation
(pneumatic muscles up to 12 kN)
69
Self compacting impregnator
Adjustable pressure for
compaction (self weight 600N,
eventually increased to 3kN)
70
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Self compacting impregnator
Continuous process 300m/hour
through movable support
(thickness buildup)
71
1 min 5 min400C
14 min
After 120 min
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CIF5 Newcastle July
10 200873
An absolute fire resistant matrix for composites:
vubonite
Applications
Intelli Fire Wall , used to separate high power transformers in case of calamity.
Each wall is composed of 24 lightweight panels and can be erected in very short time.
The walls are designed to withstand the forces of an explosion and the heat of a
transformer fire
CIF5 Newcastle July
10 200874
An absolute fire resistant matrix for composites:
vubonite
Applications
Fire protective cable duct to be used in large buildings, industry, tunnels, etc.
This shape has been designed for pultrusion
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CIF5 Newcastle July
10 200875
An absolute fire resistant matrix for composites:
vubonite
Applications
Thin composite mould for the thermoforming
of curved glass panels (size approx. 50 cm)
CIF5 Newcastle July
10 200876
An absolute fire resistant matrix for composites:
vubonite
Applications
Protection of electricity and data transmissionpoles against bush fires in California
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CIF5 Newcastle July
10 200877
An absolute fire resistant matrix for composites:
vubonite
Applications
Fire resistant piping
CIF5 Newcastle July
10 200878
An absolute fire resistant matrix for composites:
vubonite
Applications
Thermal insulation forConstant volumecombustion chamber(UGent)
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CIF5 Newcastle July
10 200879
An absolute fire resistant matrix for composites:
vubonite
Applications
Prototype bridge with sandwich panels
CIF5 Newcastle July
10 200880
An absolute fire resistant matrix for composites:
vubonite
Applications
Sculptures
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CIF5 Newcastle July
10 200881
An absolute fire resistant matrix for composites:
vubonite
Applications
Decoration of the main desk in the health center
of luxury hotels in Slovenia and Italy. Ivan Kisovec
CIF5 Newcastle July
10 200882
An absolute fire resistant matrix for composites:
vubonite
Applications
Rubensplein Knokke Franz West
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Uplifting the roof of the operahouse Unter der Linden Berlin:
vubonite screen transparent to sound