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Composite Materials Group
Composites on meso –
macro level
Stepan V. Lomov
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Contents
• Research objectives
• State-of-the-art 2014
• Research perspectives 2015 and beyond
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• Research objectives
• State-of-the-art 2014
• Research perspectives 2015 and beyond
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Hierarchy of structural levels in composite materials: nano
icro
Chowdhury 2007
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Hierarchy of structural levels in composite materials: icro
meso
Mishnaevsky 2009
Goyal 2008
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Hierarchy of structural levels composite materials: meso
Macro MEGA
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Composites on meso - Macro level: Research objective
1. Theoretical understanding, experimental study and formalisation into models
and design tools of the mechanical behaviour of (nano-engineered) fibre
reinforced composites (n)FRC:
• during manufacturing
• in-service performance
2. Optimisation of (n)FRC and development of novel materials with high
mechanical properties, toughness and damage tolerance.
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Composites on meso - Macro level: Subject definition
Structural levels: (nano) – micro – meso – Macro
Materials:
1. Fibre reinforced composites (FRC) in general, including nano-
engineered (nFRC) with the emphasis on:
• Textile composites
• Random fibre reinforced composites
2. Heterogeneous materials in general, with forays towards porous and
biomaterials
Properties:
1. Internal architecture/structure/geometry, hierarchial organisation
2. Mechanical properties and behaviour, including:
• Quasi-static response (elastic properties, non-linearity)
• Fatigue
• Damage initiation, progression, resistance and tolerance
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Composites on meso - Macro level: Materials of special interest
Material type Motivation Typical structure
Woven laminates “Guinea pig” for new developments in
matrices, fibres, nano-reinforcements …
Tri-axial braids Quasi-isotropic
Crash resistant
3D woven: non-
crimp
Best realisation of fibre properties
No delaminations
3D woven: angle
interlock
Net shape
No delaminations
Energy absorption
3D braids Beams
Energy absorption
Non-crimp fabrics
(NCF)
Cheap
Best realisation of fibre properties
Structurally stitched No delaminations
Random fibre
composites
Cheap and formable
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Composites on meso - Macro level: Research philosophy
1. Focus on the material; applications
via partnerships.
2. Behaviour of a composite can be
understood only if research spans
several structural levels.
3. Performance of a composite can be
understood only if manufacturing is
considered as well.
4. Experimental study should lead to a
descriptive, better predictive model.
5. Model development should lead to a
numerical tool.
6. Fundamental studies should
understand about real behaviour and
applications.
7. Applied studies should understand
about fundamental phenomena.
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S.V.Lomov - Singapore - May 2010 11
Integrated design tool for textile composites
x
z
p
h z(x)
Q
Q
d2
d1
Z
A
B
Internal architecture of the reinforcement
Deformation resistance and change of
geometry
Compr. Shear Tension Bending
Permeability
M
R=1/
K
Drapeability and formability
Impregnation
Production
Mechanical properties
and damage
Performance
Structural analysis
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• Research objectives
• State-of-the-art 2014
1. Models of textile composites: – WiseTex
– Method of inclusions
– Integration with PAM-SYSPLY
– meso-FE: homogenisation, embedded elements, micro-CT
– meso-FE: damage
2. Textile reinforcements:
3. Mechanical properties and damage:
4. Materials of special interest:
• Research perspectives 2015 and beyond
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WiseTex: Virtual textiles/composites
Internal geometry: textile unit cell
x
z
p
h z(x)
Q
Q
d2
d1
Z
A
B
WiseTex
LamTex
WeftKnit
woven (2D and 3D) braids
weft-knits NCF laminates
Virtual reality
VRTex
meso-FE
WiseTex -> Ansys
(FETex)
WiseTex -> Abaqus
Composite micromechanics (fast stiffness calculations)
TexComp
Permeability
FlowTex
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WiseTex worldwide
licenses:
industrial (12)
university (37)
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Method of inclusions
G. Huysmans 2000 … G. Perie 2009
1C m s s s
m s m sc c c c
C C C A I A
Eshelby solution
Mori-Tanaka homogenisation
Excellent results for complex textile composites (and random fibre composites)
TexComp
Iso-strain
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Random fibres: Stresses in inclusions
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a11= 0.52; a22 = 0.48
Vf = 0.25
Applied strain = 0.1
Average stress in the inclusion phase
FE MT
S11 1042.5 MPa 1010.4 MPa
S22 -73.1 MPa -54.5 MPa
A. Jain 2013
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Integration WiseTex – SYSPLY
WiseTex
Local deformation
parameters
(thickness, shear…)
Forming:
QUIKFORM
Internal
geometry
Local stiffness [Q]
FE analysis:
SYSPLY
Stress/strain fields
TexComp
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meso-FE: Road map
Geometric modeller
Geometry corrector
Meshing
Assign material properties
Boundary conditions
FE solver, postprocessor
Homogenisation
Damage analysis
N+1 N
N+2
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SACOM,
ABAQUS,
ANSYS…
MeshTex
WiseTex
WiseTex – MeshTex/SACOM – commercial FE packages
State-of-the-art numerical tool for preparation of FE models and FE analysis of textile composites on meso-structural level
Geometric modeller
Geometry corrector
Meshing
Assign material properties
Boundary conditions
FE solver, postprocessor
Homogenisation
Damage analysis
University of Osaka, Prof M. Zako
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Transformation into FE model
WiseTex
Abaqus
Python script
20 D.S. Ivanov, S.A. Tabatabaei 2013
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Embedded elements
Validation on different scales
21 S.A. Tabatabaei 2014
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µCT – voxel FE model
Anisotropy0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Density
130
135
140
145
150
155
160
165
1
10
210
matrix
yarns
segmentation and identification of local fibre directions
22 I. Straumit 2014
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Damage in textile composites: Standard stiffness degradation
scheme Stiffness degradation scheme: generally accepted …
real damage: transverse cracks, propagating along braiding yarns … leads to unphysical direction of
propagation of damage: across the fibres inside the yarns
damage zone
D. Ivanov, L. Gorbatikh 2007
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Advanced damage model …
1) Elementary damaged entity: segment
2) Orientation of the failure plane: Mohr-Hashin-Puck concept
3) Degradation scheme
4) Damage evolution law:
5) Combination: micro/plasticity and damage
Crack plane defines the orientation of degradation
crG
Ydd ~
2
Yarn segment: fibre orientation is constant
Damage energy release rate
)12(
)11(2
12
12
2d
dd
2d
12d
2
2
0
22 )1( dEE )1( 12
0
1212 dGG
)1( 2
0
1212 dvv )1( 2
0
2323 dvv
D. Ivanov, 2009
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… brings good predictions (example: 3-axial braid)
experimental damage initiation
Damage development (shear degradation parameter d12) in MD tensile test
Principal levels of applied strain and stress at failure: 1 - damage initiation; 2 –crack density increase (delamination onset); 3 – ultimate failure;
D. Ivanov, 2009
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• Research objectives
• State-of-the-art 2014
1. Models of textile composites
2. Textile reinforcements – Internal geometry
– Deformability
– Permeability
3. Mechanical properties and damage:
4. Materials of special interest:
• Research perspectives 2015 and beyond
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Internal geometry of textile reinforcements: WiseTex
S.V.Lomov, 1999 …
x
z
p
h z(x)
Q
Q
d2
d1
Z
A
B
min
,,,
kljWe
jlk
We
jl
We
jlk
We
jlk
We
jlk
kiWa
ik
Wa
ik
Wa
ik
Wa
ik
Wa
ik
p
hF
p
B
p
hF
p
BW
minimum of bending energy + compressibility of yarns
decomposition of the problem + characteristic functions
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Internal geometry of textile reinforcements: Experimental
studies
D. Ivanov, 2007
Nesting, yarn dimensions and distribution of the fibres
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Visualisation and µCT validation
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µCT: examples
30
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Measurements on a µCT image
31
J. Pazmono 2013
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Variability of the yarn paths and dimensions
32
Periodic, systematic variations
Non-periodic, stochastic deviations
Long range
Short range
A. Vanaerschot, B. Cox 2013
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Materials studied 2000 – 2014: internal geometry
Fibres/matrix Reinforcement Publication
carbon/epoxy NCF 0/90, ±45 Comp A 33: 1171 (2002)
NCF tufted with carbon yarn Adv Comp Lett 15: 87 (2006)
Bi- and tri-axial braids Text Res J 72: 706 (2002)
3D woven 3Tex Comp A 41: 1301 (2010)
Hexcel twill 2/2, variability Comp A 44: 122 (2013)
Computers and Struct 122: 55 (2013)
Plain weave Polymer Composites 33: 1335 (2012)
glass/epoxy Plain weave Comp Sci Techn 60: 2083 (2000)
Comp Sci Techn 63: 993 (2002)
3D woven 3Tex Comp Sci Techn 65: 1920 (2005)
Comp B 65: 146 (2014)
glass, steel weft-knitted Text Res J 85: 500 (2014)
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Deformability of textile reinforcements: WiseTex models
S.V.Lomov, 2001 …
Compression
Uni- and Biaxial tension
Shear
(un)bending + compression of yarns
work of compressive force Q on change of thickness db = change of bending energy of yarns dW
d2Wa
d2We
q
d1Wa
d1We
Qij
T T
Q
h
Wa
p
• Friction between the yarns • Lateral compression of the yarns • (Un) bending of the yarns • Torsion of the yarns • Vertical displacement of the yarns T
T Q
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Deformability of textile reinforcements: Experimental studies
Biaxial tensile tester
0
0.004
0.008
0.012
0.016
0 0.5 1 1.5 2Elong [%]
Fo
rce [
kN
/mm
]
1:1 2:1
5:1
1:2
1:5
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 10 20 30 40 50
Shear angle, °
Sh
ear
forc
e,
N/m
m
shear
optical (DIC) registration of the fabric shear
S.V.Lomov, A. Willems 2004 …
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Shear: Benchmarking exercise
plain weave Twintex
picture frame
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Draping, formability and modelling
FE kinematic
K. Vanclooster 2008
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Change of geometry due to shear
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Cross section of warp yarns on sagittal plane
Cross section of weft yarns on transaxial plane
M. Barburski 2014
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Forming studies
39 J. Pazmino 2014
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Deformability and formability
40
in-situ thickness laser measurements on picture frame (KU Leuven)
yarn compressibility tester (KU Leuven)
picture frame test in thermal camera (KU Leuven)
micro-scale forming (KU Leuven)
KU Leuven lab is fully equipped for characterisation of reinforcements for forming simulations
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Identification of a material model
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0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 10 20 30 40 50
Shear angle, °
Sh
ear
forc
e,
N/m
m
baseline fabric
0.25
0.3
0.35
0.4
0.45
0.5
0 0.05 0.1 0.15 0.2 0.25
p, MPa
h1
, m
m
1 ply cycle 1
1 ply cycle 2
1 ply cycle 3
4 plies cycle 1
4 plies cycle 2
4 plies cycle 3
tension
shear
bendin
g
compaction
K. Vanclooster, M. Barburski 2013
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Forming diagram for multi-layered preforms
K. Vanclooster 2009
0° 45°
Formability of multi-layered composites
– Depends on the relative orientation between neighbouring plies
– Depends on friction between the plies (PP-interlayer thickness)
measurement of interply friction for thermoplastics and FE modelling
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Materials studied 2000 – 2010: Deformability
Fibres Reinforcement Publication
carbon NCF 0/90, ±45, 0/45/-45/90 Comp A 34: 359 (2003)
Comp A 36: 1188 (2005)
Twill weave with and without grafted
carbon nanotubes
Comp Sci Tech 71: 315; 1746 (2011)
Carbon 49: 2079; 4458 (2011)
Comp A 64: 167 (2014)
glass Plain weave J Reinf Plast Comp 19: 1329 (2000)
Comp Sci Techn 66: 919 (2006)
Text Res J 76: 243 (2006)
3D woven Comp Sci Techn 73: 9 (2012)
Comp A 61: 76 (2014)
Comp B 65: 146 (2014)
Twintex Plain weave
Twill
Comp Sci Techn 65: 1920 (2005)
Comp Sci Techn 68: 807 (2008)
Comp A 39: 1037 (2008)
steel Knitted Key Eng Mat 42: 16 (2012)
Key Eng Mat 43: 554 (2013)
alumina (Al2O3) Plain weave with grafted carbon
nanotubes
Comp Sci Techn 90: 57 (2014)
flax Quasi-UD weave Key Eng Mat 611: 257 (2014)
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44
Permeability of textile preforms: Simulations
pΚ
gradv
p = 0
<u>
<u>
p = p
A
A´
B. Verleye 2008
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1st International Permeability benchmark
Balanced Carbon twill 2x2 (G986) Unbalanced Glass twill 2x2 (G1113)
45
2007 – 2010
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2nd International Permeability Benchmark
46
2011 – 2013
Ecole Polytechnique Montreal
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47
Materials studied 2000 – 2014: Permeability
Fibres Reinforcement Publication
carbon NCF 0/90, +45/-45 SAMPE Europe 2003
Twill 2/2 Comp A 42: 1157 (2011)
Comp A 61: 172 (2014)
glass Plain weave Comp A 35: 1407 (2004)
Comp A 42: 1157 (2011)
NCF 0/90 Adv Comp Lett 18: 121 (2009)
n/a Stereolithographic reference medium Comp A 40: 244 (2009)
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48
• Research objectives
• State-of-the-art 2014
1. Models of textile composites:
2. Textile reinforcements:
3. Mechanical properties and damage: – Damage monitoring during test and post-mortem
investigation
– Fatigue
4. Materials of special interest:
• Research perspectives 2015 and beyond
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49
Motivation: early damage initiation in textile composites
stress
AE
strain, % No stiffness reduction up to failure
Early damage initiation
Design strain at 0.3 ... 0.4%
Ratio Ultimate strain / Design strain of 4...5
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50
AE and DIC monitoring of damage
S.V. Lomov 2008
objective characterisation of te progressive damage
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51
Experimental road map
Textile preparation (shear...), measurements
Impregnation(RTM...)
X-Ray of the unloaded samples
Tension test with AE, strain-mapping
Identification of 1, 2, 3
Tensile tests till 1, 2, 3
C-scan
X-Ray
Cutting according to the crack pattern
Analysis of the cracks on micrographs
Tension diagrams
AE diagrams
Strain maps
Dynamics of damage extent
Damage periodicity
Cracks placement and orientation
Crack length distribution
Damage initiation threshold
Cutting the samples in characteristic directions
Thermal/cure damage characterisation
Architecture of the textile
Fine structure of damage
SEM at the selected positions Micro-characterisation of damage modes
Study of the reinforcement geometry
S.V. Lomov 2008
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52
Damage development: glass/epoxy
at failure (2.7%)
S.V. Lomov 2010
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53
Damage development:
carbon/epoxy
A: Sporadic cracks on yarn boundaries
B: Well-developed system of transversal cracks and cracks on boundaries of the yarns; sporadic transversal matrix cracks
U: Massive transversal cracks; local debondings on the boundaries of the yarns and matrix cracks parallel to the sample surface
M. Karahan, A. Bogdanovich 2013
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AE cluster analysis
54
A, dB
frequency parameter, kHz
1. “Ternary” clusters pattern is the same for 2D and 3D woven composites, glass and carbon
2. Frequency boundary is the same for 2D and 3D, but different for glass and carbon.
3. Amplitude boundary is the same for 2D and 3D woven composites, glass and carbon
4. The A and F cluster boundaries are consistent with literature and with the hypothesis:
• FH = fibre breakage
• ALFL = inter-fibre matrix cracks
• AHFL = delaminations
ALFL
AHFL
FH
L. Li 2014
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55
Materials studied 2005 – 2010: Progressive damage
Fibres/matrix Reinforcement Publication
Experimental methodology in general Comp Sci Tech 68: 2340 (2008)
carbon/epoxy NCF 0/90, ±45, 0/-45/90/45 Comp A 36: 1207 (2005)
NCF ±45, sheared Comp A 39: 1380 (2008)
NCF 0/90, ±45, toughened resin Comp A 40: 251 (2009)
NCF tufted with carbon yarn Comp Sci Tech 69: 2701 (2009)
3-axial braid Comp Sci Tech 69: 1373 (2009)
Uniaxial braid Comp Sci Tech 68: 2340 (2008)
Uniaxial weave tufted with carbon Plast Rubb Comp 38: 98 (2009)
Woven twill 2/2 with carbon nanotubes Carbon 49: 4650 (2011)
Comp A 42: 1835 (2011)
3D woven 3Tex Mech Mater 62: 14 (2013)
Text Res J 84: 1373 (2014)
3D braided 3Tex ECCM-14 (2010)
carbon/PPS 5H satin Comp Sci Techn 71: 1171;1217 (2011)
glass/epoxy Plain weave Comp A 40: 1134 (2009)
Comp A 40: 1144 (2009) 3D woven 3Tex
Plain weave Compos Struct 116: 286 (2014)
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56
Tension-tension fatigue: S-N curve and progressive damage
0
50
100
150
200
250
300
350
400
450
500
1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07
I
II
III
stress, MPa
number of cycles
time
stre
ss
max
min K. Vallons, 2007 …
in collaboration with V. Carvelli, Milano
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57
Damage development:
carbon/epoxy
10,000
100,000
1,000,000
M. Karahan 2013
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58
Fatigue limit vs damage initiation threshold
_min: first AE event
_1: damage initiation
_2: initiation of high energy damage events
_ULT: failure
NCF carbon/epoxy, stitched
NCF carbon/epoxy
NCF carbon/epoxy, unstitched
plain weave glass/epoxy
3D glass/epoxy
carbon/epoxy braid
3D carbon/epoxy
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59
Materials studied 2007 – 2010: Fatigue
Fibres/matrix Reinforcement Publication
carbon/epoxy NCF 0/90 Comp A 38: 1603 (2007)
NCF 0/90, ±45, toughened resin Comp A 40: 251 (2009)
Comp A 42: 16 (2011)
NCF 0/90 Comp Sci Tech 70: 2216 (2010)
NCF tufted with carbon yarn
Woven twill 2/2 ICCM-17 (2009)
3D woven 3Tex Comp Sci Techn 71: 1961 (2011)
3D braided 3Tex J Compos Mat 47: 3188 (2013)
carbon/PPS 5H satin Comp Sci Techn 74: 20 (2013)
glass/epoxy Plain weave Comp Sci Tech 70: 2216 (2010)
3D woven 3Tex
Quasi-UD NCF Mech & Industry 14: 175 (2013)
Comp A 56: 272 (2014)
short glass,
steel fibre /
termoplasts
straight glass fibres
wavy steel fibres
ECCM-16
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60
• Research objectives
• State-of-the-art 2014
1. Models of textile composites
2. Textile reinforcements
3. Mechanical properties and damage
4. Materials of special interest: – 3D non-crimp woven composites
– 3D angle interlock composites
– Non-crimp fabrics
– Structurally stitched composites
– Random fibre reinforced composites
– Steel fibre textiles
• Research perspectives 2015 and beyond
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61
3D woven non-crimp composites: Glass/epoxy
in collaboration with A. Bogdanovich,
3Tex and V. Carvelli, Milano
comparative study: plain weave laminate vs 3D woven composite
3D 2D
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62
3D woven non-crimp composites: Carbon/epoxy
in collaboration with A. Bogdanovich, 3Tex,
M. Karahan, Bursa and V. Carvelli, Milano
detailed study of internal geometry
non-Hookean tensile behaviour
0
100
200
300
400
500
600
700
800
900
1000
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
strain, %
str
ess,
MP
a
0
10
20
30
40
50
60
70
80
90
100
E,
GP
astress, fill
E, fill
damage progression and fatigue
AE
S-N
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63
3D woven non-crimp composites: FE modelling
63
• correct modelling of degradation
of stiffness
• reasonable evaluation of damage
initiation threshold
• qualitative representation of
intensity of damage
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Resolution of yarn interpenetrations 1
2
3
p01
p11
p02 p12
s1
s2
p01
p11 s1 s2
p01=p11
P02=p12
s1
s2
p01=p11
6 2 3 4 5 7
1 6
2 3 4 5 7
1
64 E. Bedogni 2013
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65
3D angle interlock composites
G. Perie, 2010
WiseTex model: excellent predictions of the stiffness
1 m
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66
3D textiles 1995 – 2014
Material Properties Publication
General 3D weave Coding of the weave Technische Text 38: 20 (1995)
Modelling Text Res J 81: 26 (2011)
3D woven, carbon/epoxy Stiffness Comp Sci Tech 60: 2083 (2000)
3Tex, glass/epoxy Internal geometry Comp Sci Tech 65: 1920 (2005)
Stiffness, strength Comp A 40: 1134 (2009)
Damage Comp A 40: 1144 (2009)
Fatigue Comp Sci Techn 70: 2068 (2010)
3Tex, carbon/epoxy Internal geometry Comp A 41: 1301 (2010)
Stiffness, strength, damage Mech Mater 62: 14 (2013)
Text Res J 84: 1373 (2014)
Fatigue Comp Sci Techn 71: 1961 (2011)
3D angle interlock,
carbon/epoxy
Internal geometry
Stiffness
ICCM-17 (2009)
Text Res J 81: 1 (2011)
3D braided Damage J Compos Mat 47: 3188 (2013)
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67
NCF: Internal geometry
S.V. Lomov, 2002; R. Loendersloot, 2005
Distortions of fibrous plies due to stitching
change of geometry in a sheared fabric
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68
NCF: Deformability and permeability
Biaxial -45/+45 MD/CD
0
0.004
0.008
0.012
0.016
0.02
0 0.5 1 1.5 2Elong [%]
Fo
rce [
kN
/mm
]
forming
shear (picture frame) and biaxial tension
permeability
S.V. Lomov, 2002, 2005
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69
NCF: Mechanical properties, damage and fatigue
Truong, 2005, 2008; Mikhaluk 2008; Vallons 2008, 2009, 2010
MD
Damage initiation and development is linked to the stitching sites
S-N fatigue curves and development of cracks during fatigue
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70
Structurally stitched reinforcements
Koissin 2006, 2009
internal geometry and WiseTex model
correlation between damage
and stitching
sites
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71
A book @ Woodhead Publishers, 2011
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72
NCF and structurally stitched 2000 – 2010
Material Properties Publication
Carbon/epoxy NCF Internal geometry Comp A 33: 1171 (2002)
Comp A 37: 103 (2006)
Deformability Comp A 34: 359 (2003)
Comp A 36: 1188 (2005)
Permeability SAMPE-Europe 2003
Mechanical properties, damage Comp A 36: 1207 (2005)
Comp A 39: 1380 (2008)
Fatigue Comp A 38: 1633 (2007)
Comp A 40: 261 (2009)
Comp A 42: 16 (2011)
Impact and post-impact Comp A 41: 1019 (2010)
FE modelling Eng Fract Mech 75: 2751 (2008)
Comp A 39: 1380 (2008)
Glass/epoxy NCF Machanical properties and fatigue Mech & Ind 14: 175 (2013)
Comp A 56: 172 (2014)
Structurally stitched Internal geometry Adv Comp Lett 15: 87 (2006)
Mechanical properties, damage, FE
damage
Plast Rubb Comp 38: 98 (2008)
Comp Sci Tech 69: 2701 (2009)
Fatigue Comp Sci Tech 70: 2216 (2010)
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73
Random fibre reinforced composites
Jao Jules 2005
5% 4 3 1 2
Successful use of inclusions method for prediction of stiffness and onset of debonding
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Short wavy steel fiber composites
• Short steel fiber composites are novel
material combining outstanding properties
of stiffness and ductility.
• Typically used for improved shielding
properties of polymers.
• Processing of injection molded short steel
fiber composites leads to significant fiber
waviness.
VF 0.5%
VF 2%
Very dense and wavy
structures at low
volume fractions
Y. Abdin 2014
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Geometrical modelling of short
wavy steel fiber composites
Model:l
Micro-CT characterization for determination of geometrical
parameters
Wavy fiber modelled with 2 parameter harmonic
functions
Y. Abdin 2014
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Validation: RVE of SSFRC
• Application of the inclusion model on RVE of wavy steel fibers, comparison
with FE.
• “Real” fibers extracted from micro-CT data.
• Homogeneous fiber cross-sections.
FE model
= 2273365 elements Model shows very good predictions compared to FE.
Y. Abdin 2014
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Flow chart of proposed algorithm
77
0 Read Input SN data – stress level and
corresponding number of cycles
Calculate Initial Young’s modulus E0 – MT
formulation
Calculate the modulus and damage
parameter at stress level, S1 read from SN
curve
For second RVE: loading increments is
modelled and the modulus and damage
parameter is calculated
σ
ԑ
E0
Dfirstcycle = 1-E1/E0
Stress at which damage parameter
Dfirstcycle is reached, S2 is the stress to
failure for initially choosen cycles
S1
N
SN-ref
S2
ԑ
E02
E12
Dfirstcycle = 1- E1RVE / E0
RVE
1
1
2
2
3 3
4 4
5 5
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Fiber Matrix debonding in RFRC
78
1. Debonded inclusions are replaced by fictitious “EqBI”
2. FE based validations confirm that the average stresses in inclusions for different debonded lengths are accurate
3. Also one is able to track correctly the stresses in the interface by combination of the Mori-Tanaka formulation and Cox Model
1
2
3
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Experimental validation
79
Good results for scaling irrespective of the input SN-curve
Two points are usually enough for scaling linear SN-curves
Only one SN-curve was enough to predict the fatigue properties for other points
A. Jain 2014
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80
Short fibre composites 2000 – 2014
Material Properties Publication
Genearl Modelling Comp Sci Techn 87: 86 (2013)
Glass / thermoplast Mechanical ICCM-15 (2005)
Micromechanics, damage TexComp-11, 2013
Fatigue ECCM-16, 2014
Steel / thermoplast Geometry Comp A 67: 171 (2014)
Micromechanics ECCM-16, 2014
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81
• Research objectives
• State-of-the-art 2014
• Research perspectives 2015 and beyond
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Short fibres
82
2013 – 2014 2014 – 2015
Finalise the fatigue scaling Toolset: fatigue scaling
Experimental validation Toolset: fatigue micro-analiser
Include in LMS macro-model Validation fatigue micro-analiser
Start fatigue micro-analyser
Start experimental program on steel and
glass fibres
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Internal geometry
83
2013 – 2014 2014 – 2015
Finish variability models Start variability for natural fibres
Finish µCT-Abaqus (voxels) Release VoxTex
WiseTex – Abaqus Finish µCT for flax
Release CIVATex Release FETex 2.0
Deformation and geometry Geometry Dry Tape Laying
µCT = “standard” tool
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Deformability
2013 – 2014 2014 – 2015
In-depth high T° steel Compressibility of nano-veils
Finalise forming modelling Validation of meso-FE
Formability flax
Thickness laser on biaxial tester
84
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Permeability
2013 – 2014 2014 – 2015
Participation in the International
benchmark
Release VoxTex with FlowTex link
Benchmark FlowTex vs ANSYS Submit C2 project on permeability
µCT – voxels – FlowTex
85
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Damage and meso-FE
2013 – 2014 2014 – 2015
In-situ microscopy Embedded elements
Self-reinforced materials Damage in meso-FE
Hybrid textiles XFEM for textile composites
Embedded elements AE analysis
Damage in meso-FE Telene matrix
AE analysis Inclusion model for damage
Telene matrix Damage Dry Tape Laying
Micro-macro damage
Damage Dry Tape Laying: Stepan, Nghi Effect of defects
86
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Fatigue
2013 – 2014 2014 – 2015
Models for short fibres Toolset: fatigue short fibres scaling
Experimental data short fibres Toolset: fatigue short fibres micro-analiser
Experimenatal data glass/CNT Micro-macro fatigue
Effect of defects
87
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Software
88
2013 – 2014 2014 – 2015
New licenses and collaborations release FETex 2.0
Software µCT – Abaqus release VoxTex
start collaboration MeshTex