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Inherent carbon fibre stiffening as seen in textile reinforced composites

Inherent carbon fibre stiffening as seen in textile reinforced composites Stepan V. Lomov 1 , Alexander E. Bogdanovich 2 , Ichiro Taketa 1,3 , Jian Xu 1 , Ignaas Verpoest 1 1 Depertment MTM, Katholieke Universiteit Leuven, Belgium 2 3Tex Inc, Cary, NC, USA 3 Toray Industries, Japan.

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Inherent carbon fibre stiffening as seen in textile reinforced composites

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  1. Inherent carbon fibre stiffening as seen in textile reinforced composites Stepan V. Lomov1, Alexander E. Bogdanovich2, Ichiro Taketa1,3, Jian Xu1, Ignaas Verpoest1 1Depertment MTM, Katholieke Universiteit Leuven, Belgium 23Tex Inc, Cary, NC, USA 3Toray Industries, Japan S.V. Lomov CompTest-2011 Lausanne

  2. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites Strain measurements during tensile test Stiffening in 3D woven non-crimp carbon/epoxy composites Conclusions Contents S.V. Lomov CompTest-2011 Lausanne

  3. Introduction: The carbon fibre stiffening phenomenon Previously observed stiffening effects in carbon fibre textile composites Strain measurements during tensile test Stiffening in 3D woven non-crimp carbon/epoxy composites Conclusions S.V. Lomov CompTest-2011 Lausanne

  4. 20% increase E strain 1% 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." Nature220(5171): 1024-1025 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 Science31(17): 4521-4532 S.V. Lomov CompTest-2011 Lausanne

  5. Literature on carbon fibre stiffening • Curtis, G.J., J.M. Milne and W.N. Reynolds, Non-Hookean behaviour of strong carbon fibres, Nature, 1968, 220(5171): 1024-1025. • 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. • Morley, H., A simple strand test for routine fibre strength and modulus evaluation, Composites, 1982, 13(1): 21-23. • Beetz, C.P., Jr., Strain-induced stiffening of carbon fibres, Fibre Science and Technology, 1982, 16: 219-229. • 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. • 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. • 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. • Hughes, J.D.H., Strength and modulus of current carbon fibres, Carbon, 1986, 24(5): 551-556. • 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. • 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. • Shioya, M and A. Takaku, Rotation and extension of crystallites in carbon fibers by tensile stress, Carbon, 1994, 32(4): 615-619. • 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. • 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 S.V. Lomov CompTest-2011 Lausanne

  6. 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 Technology64: 2509–2516. S.V. Lomov CompTest-2011 Lausanne

  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 Textile composites 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 S.V. Lomov CompTest-2011 Lausanne

  8. Carbon/PP woven composites +20% spectacular increase of stiffness … … may be caused by decrimping as well … S.V. Lomov CompTest-2011 Lausanne

  9. Carbon/epoxy twill woven composite stress, MPa E, GPa 0.4 0.6 0.2 70 60 strain, % 0.2 0.4 0.6 S.V. Lomov CompTest-2011 Lausanne

  10. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites Strain measurements during tensile test Stiffening in 3D woven non-crimp carbon/epoxy composites Conclusions S.V. Lomov CompTest-2011 Lausanne

  11. Optical extensometry LIMESS • Precise position of zero of LIMESS curves • Two regions on the curves • Choice of the fitting Instron S.V. Lomov CompTest-2011 Lausanne

  12. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites Strain measurements during tensile test Stiffening in 3D woven non-crimp carbon/epoxy composites Conclusions S.V. Lomov CompTest-2011 Lausanne

  13. The 3D woven non-crimp carbon/epoxy composite * datasheet of Toho Tenax S.V. Lomov CompTest-2011 Lausanne

  14. Expected values of Young’s modulus * datasheet of Toho Tenax S.V. Lomov CompTest-2011 Lausanne

  15. expected: Change of Young’s modulus fill expected warp S.V. Lomov CompTest-2011 Lausanne

  16. Change of Young modulus and damage stress, MPa E*10, GPa AE 20% increase of E strain AE S.V. Lomov CompTest-2011 Lausanne

  17. Impregnated carbon yarns: 6K and 12K stress – strain: mixed data for 3K and 12 K 6K fabric, warp and fill 12K Young’s modulus, normalised VF = 70% S.V. Lomov CompTest-2011 Lausanne

  18. Stiffening and fatigue: S-N curve warp fill S.V. Lomov CompTest-2011 Lausanne

  19. Post-fatigue tensile test: Fatigue @ 450 MPa, 1,000,000 cycles stress warp E fill static @450 MPa static @450 MPa initial static strain strain quasi-static evolution of Young’s modulus S.V. Lomov CompTest-2011 Lausanne

  20. Introduction: The carbon fibre stiffening phenomenon and previously observed stiffening effects in carbon fibre textile composites Strain measurements during tensile test Stiffening in 3D woven non-crimp carbon/epoxy composites Conclusions S.V. Lomov CompTest-2011 Lausanne

  21. Conclusions: Evolution of Young’s modulus of carbon/epoxy textile composites • Quasi-static tension: • inherent stiffening of carbon fibres • softening of the composite due to damage • Fatigue and post-fatigue: • change of Young modulus in the first cycles: possible high modulus • softening due to damage S.V. Lomov CompTest-2011 Lausanne

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