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1. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites
2. Strain measurements during tensile test
3. Stiffening in 3D woven non-crimp carbon/epoxy composites
4. Conclusions
S.V. Lomov CompTest-2011 Lausanne 3
1. Introduction: • The carbon fibre stiffening phenomenon
• Previously observed stiffening effects in carbon fibre textile composites
2. Strain measurements during tensile test
3. Stiffening in 3D woven non-crimp carbon/epoxy composites
4. Conclusions
S.V. Lomov CompTest-2011 Lausanne 4
Inherent stiffening of carbon fibres
First observed:
Curtis, G. J., J. M. Milne and W. N. Reynolds (1968). "Non-Hookean Behaviour of Strong Carbon Fibres." Nature 220(5171): 1024-1025
strain 1%
20% increase E
figure from:
Shioya, M., E. Hayakawa and A. Takaku (1996). "Non-hookean stress-strain response and changes in crystallite orientation of carbon fibres." Journal of Materials Science 31(17): 4521-4532
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Literature on carbon fibre stiffening
1. Curtis, G.J., J.M. Milne and W.N. Reynolds, Non-Hookean behaviour of strong carbon fibres, Nature, 1968, 220(5171): 1024-1025.
2. van Dreumel, W.H.M. and J.L.M. Kamp, Non Hookean behaviour in fibre direction of carbon-fibre composites and the influence of fibre waviness on the tensile properties, Journal of Composite Materials, 1977, 11(Oct): 461-469.
3. Morley, H., A simple strand test for routine fibre strength and modulus evaluation, Composites, 1982, 13(1): 21-23.
4. Beetz, C.P., Jr., Strain-induced stiffening of carbon fibres, Fibre Science and Technology, 1982, 16: 219-229.
5. Beetz, C.P., Jr. and G.W. Budd, Strain modulation measurements of stiffening effects in carbon fibers, Review of Scientific Instruments, 1983, 54(9): 1222-1226.
6. Vangerko, H. and A.J. Barker, The stiffness of unidirectionally reinforced CFRP as a function of strain rate, strain magnitude and temperature, Composites, 1985, 16(1): 19-22.
7. Ishikawa, T., M. Matsushima and Y. Hayashi, Hardening non-linear behaviour in longitudinal tension of unidirectional carbon composites, Journal of Materials Science, 1985, 20: 4075-4083.
8. Hughes, J.D.H., Strength and modulus of current carbon fibres, Carbon, 1986, 24(5): 551-556.
9. Stecenko, T.B. and M.M. Stevanovic, Variation of elastic moduli with strain in carbon/epoxy laminates, Journal of Composite Materials, 1990, 24: 1152-1158.
10. Northolt, M.G., L.H. Veldhuizen and H. Jansen, Tensile deformation of carbon fibers and the relationship with the modulus for shear between the basal planes, Carbon, 1991, 29(8): 1267-1279.
11. Shioya, M and A. Takaku, Rotation and extension of crystallites in carbon fibers by tensile stress, Carbon, 1994, 32(4): 615-619.
12. Shioya, M., E. Hayakawa and A. Takaku, Non-hookean stress-strain response and changes in crystallite orientation of carbon fibres, Journal of Materials Science, 1996, 31(17): 4521-4532.
13. Toyama, N. and J. Takatsubo, An investigation of non-linear elastic behavior of CFRP laminates and strain measurement using Lamb waves, Composites Science and Technology, 2004, 64: 2509–2516
1 1
5
4
1
1960s 1970s 1980s 1990s 2000s
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Cross-ply carbon laminates: stiffening vs damage softening
Toyama, N. and J. Takatsubo (2004). "An investigation of non-linear elastic behavior of CFRP laminates and strain measurement using Lamb waves." Composites Science and Technology 64: 2509–2516.
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Textile composites
Ishikawa, T., M. Matsushima and Y. Hayashi, Hardening non-linear behaviour in longitudinal tension of unidirectional carbon composites, Journal of Materials Science, 1985, 20: 4075-4083
Stiffening effect is noted for 8-harness satin – more pronounced effect for straight fibres
Truong, T. C. . The mechanical performance and damage of multi-axial milti-ply carbon fabric reinforced composites. PhD thesis, Department MTM. Leuven, Katholieke Universiteit Leuven, 2005
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Carbon/PP woven composites
+20%
spectacular increase of stiffness …
… may be caused by decrimping as well …
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Carbon/epoxy twill woven composite
stress, MPa
E, GPa
strain, %
0.4 0.6
60
700.2
0.2 0.4 0.6
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1. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites
2. Strain measurements during tensile test
3. Stiffening in 3D woven non-crimp carbon/epoxy composites
4. Conclusions
S.V. Lomov CompTest-2011 Lausanne 11
Optical extensometry
y = -4.9477x2 + 0.6852x
R2 = 0.9996
y = 0.1848x + 0.0059
R2 = 0.9994
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.000 0.010 0.020 0.030 0.040
eps grips
eps_
X
0
200
400
600
800
1000
0 0.01 0.02 0.03 0.04 0.05 0.06
strain
sig,
MP
a
grips
true: LIMESS
Instron
LIMESS
1. Precise position of zero of LIMESS curves
2. Two regions on the curves
3. Choice of the fitting
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1. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites
2. Strain measurements during tensile test
3. Stiffening in 3D woven non-crimp carbon/epoxy composites
4. Conclusions
S.V. Lomov CompTest-2011 Lausanne 13
The 3D woven non-crimp carbon/epoxy composite
Warp/fill yarnsToho Tenax 12K, 800
texAreal density, g/m2 2499
Z yarns Toho Tenax 1K, 66 tex Ends/picks, per inch in layer 12 / 10
Fiber diameter, µm 7* Fibre Young modulus, GPa 238*