I used analytical methods to find that the Young's moduli in wrap (0°) and fill (90°) direction of a carbon-fiber/epoxy twill are Ex=Ey=57 GPa.
This, however, means that, when rotating the twill by 45°, the Young's moduli will only be Ex=Ey =11Gpa, which is quite low. Are there any sources where the angular dependence of Young's modulus in carbon/epoxy 2x2 twills is discussed?
A woven cloth is a great example of an orthotropic rather than isotropic material. The 45 degree modulus is driven by the shear modulus of the material which is significantly affected by resin stiffness. I am not surprised by the 11GPa value. It is possible to use Digimat to do detailed analysis of the behaviour based on the meso-mechanical geometry and constituent properties.
Have a good holiday,
Andrew
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