Is it possible to produce a continuous and oriented aramid fiber–epoxy matrix composite having longitudinalandtransverse moduli of elasticity of 35 GPa (5×106psi) and 5.17 GPa (7.5×105psi), respectively? Why or why not?Assume that the elastic modulus of the epoxy is 3.4 GPa (4.93×105psi).Also, the value ofEfor aramid fibers is 131GPa.

Respuesta :

Answer:

Not possible

Explanation:

[tex]E_{cl}[/tex] = longitudinal modulus of elasticity = 35 Gpa

[tex]E_{ct}[/tex] = transverse modulus of elasticity = 5.17 Gpa

[tex]E_m[/tex] = Epoxy modulus of elasticity = 3.4 Gpa

[tex]V_{\rho l}[/tex] = Volume fraction of fibre (longitudinal)

[tex]V_{\rho t}[/tex] = Volume fraction of fibre (transvers)

[tex]E_f[/tex] = Modulus of elasticity of aramid fibers = 131 Gpa

Longitudinal modulus of elasticity is given by

[tex]E_{cl}=E_m(1-V_{\rho l})+E_fV_{\rho l}\\\Rightarrow 35=3.4(1-V_{\rho l})+131V_{\rho l}\\\Rightarrow 35=3.4-3.4V_{\rho l}+131V_{\rho l}\\\Rightarrow V_{\rho l}=\frac{35-3.4}{131-3.4}\\\Rightarrow V_{\rho l}=0.24764[/tex]

Transverse modulus of elasticity is given by

[tex]E_{ct}=\frac{E_mE_f}{(1-V_{\rho t})E_f+V_{\rho t}E_m}\\\Rightarrow 5.17=\frac{3.4\times 131}{(1-V_{\rho t})131+V_{\rho t}3.4}\\\Rightarrow \frac{3.4\times 131}{5.17}-131=-127.6V_{\rho t}\\\Rightarrow V_{\rho t}=\frac{\frac{3.4\times 131}{5.17}-131}{-127.6}\\\Rightarrow V_{\rho t}=0.35148[/tex]

[tex]V_{\rho l}\neq V_{\rho t}[/tex]

Hence, it is not possible to produce a continuous and oriented aramid fiber.