CHARACTERISATION OF THE MICROSTRUCTURE AND ......Outline • Synchrotron microfocus X-ray...
Transcript of CHARACTERISATION OF THE MICROSTRUCTURE AND ......Outline • Synchrotron microfocus X-ray...
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Robert J YoungStephen J Eichhorn, James A Bennett, Prasad Potluri
NW Composites Centre, School of Materials, University of Manchester, UK
Richard J DaviesESRF, Grenoble, France
CHARACTERISATION OF THE MICROSTRUCTURE AND DEFORMATION
OF WOVEN COMPOSITES
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Outline• Synchrotron microfocus X-ray diffraction
• Deformation of single aramid fibres
• Cross-ply laminate
- microstructure
- local fibre deformation
• Characterisation of the microstructure of woven composites
- out-of-plane tilt
- in-plane orientation
- local fibre deformation
• Conclusions
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ESRF Synchrotron - Beamline ID13
• High-intensity monochromatic beam - λ = 0.1 nm• 2 μm beam diameter• Single fibre diffraction – 12 μm diameter fibre• Simultaneous deformation/diffraction
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Aramid Single-Fibre Microfocus X-ray Diffraction
CCDCamera
Single Aramid Fibre
Synchrotron x-ray beam
2 μm diameter (λ = 0.1 nm)
Fibreaxis
00l streaks moves closer to central spot under stress → crystal strain
DiffractionPattern
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Crystal Deformation
StressStress on Fibre
StrainCrystal Strain
Calibrationfor
Micromechanicsanalysis
Young RJ, Eichhorn SJ, Shyng Y-T, Riekel C, Davies RJ (2004)
Macromolecules 37:9503
NHNH CO CO
n
0c
0
c cc
σε −=
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5 PPTA fibre stress calibrationApproximate Crystal Modulus = 224 GPaGradient = 2.24 ± 0.03 GPa / % crystal strain
Axi
al fi
bre
stre
ss (
GP
a )
Crystal strain ( % )
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Microfocus Diffraction of Aramid Composites
Kevlar/epoxy
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• Aramid/epoxy 0/90 cross-ply laminate• Beam size – 2 μm• Two crossing diffraction patterns
Diffraction Pattern from a 0/90 Cross-ply Laminate
8 mm
8 mm
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Determination of Fibre Misalignment
0º +5º-5º
Diffraction patterns from an aramid fibre tow at different angles of rotation
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In-Plane Fibre Orientation: Cross-ply
Longitudinal Fibres Transverse Fibres
Misalignment determined from relative rotation of the two diffraction patterns
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Initial Axial Fibre Stress: Cross-ply
Longitudinal Fibres Transverse Fibres
Fibre stress determined from position of 006 peak in diffraction pattern
ResidualCompressive
stresses
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Development of Fibre Stress during Deformation
• Non-uniform stress distribution• Stress concentration around the hole
Longitudinal fibres
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Variation of Local Fibre Stress
0.52%Strain
0.72%Strain
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Stress Concentration at the Hole
• Longitudinal fibres• Scan across the hole• Fits the model for an isotropic material
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Diffraction Pattern from a Woven Aramid
• Satin weave• Beam size – 2 μm• Two crossing diffraction patterns
(Simulated)
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Characterisation of a Woven Aramid Composite
Probing the internal geometry of a woven composite during deformation using an x-ray micro-diffraction imaging techniqueRichard J. Davies, Christian Riekel, James A. Bennett, Stephen J. Eichhorn, and Robert J. YoungApplied Physics Letters, (2007) 91:044102.
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Determination of Out-of-plane Fibre Tilt
0º-15º +15º
CCDCamera
FibreTow
Synchrotron x-ray beam
2 μm diameter (λ = 0.1 nm)
006
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Calibration of Out-of-plane Tilt Angle
-10 -5 0 5 100.0
0.2
0.4
0.6
0.8
1.0
Inte
nsity
Rat
io (0
06bo
ttom/0
06to
p)
Tilt angle (o)
-10 -5 0 5 100
500
1000
1500
2000
2500
3000
3500
4000
Inte
nsity
(arb
)
Tilt angle (o)
006 (bottom) 006 (top)
Measure the relative intensity of the top and bottom 006 Bragg reflections as a function of out-of plane tilt angle
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Mapping Fibre Orientation and AlignmentWoven Aramid Satin Weave with Hole Drilled
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Out-of-plane fibre tilt angle
Vertical tows
Horizontal tows
Woven Aramid Satin Weave with Hole Drilled
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Changes in out-of-plane tilt angle
Tiltincreases
Tiltdecreases
Stress
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In-plane fibre orientation
Horizontal tows
Vertical tows
Fibre orientation affected by hole
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Development of axial fibre stress
Horizontal tows
Vertical tows
Woven Aramid Satin Weave with Hole Drilled
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Development of axial fibre stressStress
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Conclusions
• Microfocus x-ray diffraction allows on the micron level:- the evaluation of local composite geometry- the determination of local fibre stress
• Tremendous scope for further analysis and exploitation:- cross-ply aramid/epoxy- woven aramid/epoxy
Acknowledgements
• EPSRC – funding of the research project• Dr. D. J. Bannister of SP Systems Ltd for supplying the materials
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Development of Fibre Stress during Deformation
Transverse fibres
• Non-uniform stress distribution• Complex stress distribution around the hole
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Development of Axial Fibre Stress
• Only stresses remote from the hole• Initial residual compression in both plies• Transverse fibres go further into compression
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X-ray Diffraction - Reciprocal space
000
002
004
006
kI
Incident Beam
Ewald sphere
c*
Fibreaxis