ENG762S2 Calculate the resultant elastic modulus of the composite assuming the length efficiency factor is 0.8.

Part 1

(a) Carbon fibres are considered as a material for composite part in a wind turbine structure.

a) Calculate the theoretical strength of the carbon fibres by assuming a carbon-carbon bond length of 0.15 nm, a material surface free energy of 50 mJ/m2 and an elastic modulus of 1 TPa.

b) Sketch a Lennard-Jones curve for the carbon-carbon bonds in the carbon fibre and show a comparable Lennard-Jones curve for copper fibres where the strength and elastic modulus of the copper is lower than for carbon. Clearly indicate the differences between the two materials.

c) Sketch a diagram to show carbon fibre production. Your diagram should clearly indicate the three temperature treatments required in the production and name each of these temperature treatments.

(b) The composite uses the carbon fibres with 50% in a 45? and 50% in a -45? orientation to improve fatigue resistance. An epoxy with an elastic modulus of 1 GPa and a low-grade carbon fibre with an elastic modulus of 200 GPa are used in the composite.

(i) State the Krenchel equation that can be used to predict the elastic modulus of the composite.

(ii) Calculate the orientation factor for the composite.

(iii) Calculate the resultant elastic modulus of the composite assuming the length efficiency factor is 0.8.

(iv) Suggest how the resultant composite elastic modulus would vary compared to your answer in (iii) for fibre orientation approaching Voigt and Reuss conditions.