contestada

A continuous and aligned fiber reinforced composite having a cross-sectional area of 1130 mm^2 (1.75 in.^2) is subjected to an external tensile load. If the stresses sustained by the fiber and matrix phases are 156 MPa (22,600 psi) and 2.75 MPa (400 psi), respectively; the force sustained by the fiber phase is 74,000 N (16,600 lbf); and the total longitudinal strain is 1.25 10^ -3, determine: (a)the force sustained by the matrix phase, (b)the modulus of elasticity of the compos- ite material in the longitudinal direction, and (c) the moduli of elasticity for fiber and matrix phases.

Respuesta :

Answer:

a) [tex]F_m=1803.013\ N[/tex]

b) [tex]E=53665.84\ MPa[/tex]

c) [tex]E_f=124800\ MPa[/tex]

   [tex]E_m=2200\ MPa[/tex]

Explanation:

Given:

  • cross-sectional area of reinforced composite, [tex]A=1130\ mm^2[/tex]
  • stress sustained by the fiber phase, [tex]\sigma_f=156\ MPa[/tex]
  • force sustained by the fiber phase, [tex]F_f=74000\ N[/tex]
  • Total strain on the composite, [tex]\epsilon=1.25\times 10^{-3}[/tex]
  • stress sustained in the matrix phase, [tex]\sigma_m=2.75\ MPa[/tex]

Now, the area of fiber phase:

[tex]A_f=\frac{F_f}{\sigma_f}[/tex]

[tex]A_f=\frac{74000}{156}[/tex]

[tex]A_f=474.359\ mm^2[/tex]

∴Area of matrix phase:

[tex]A_m=A-A_f[/tex]

[tex]A_m=1130-474.359[/tex]

[tex]A_m=655.641\ mm^2[/tex]

(a)

Now the force sustained by the matrix phase:

[tex]F_m=\sigma_m\times A_m[/tex]

[tex]F_m=2.75\times 655.641[/tex]

[tex]F_m=1803.013\ N[/tex]

(b)

Total stress on the composite:

[tex]\sigma=\frac{(F_f+F_m)}{A}[/tex]

[tex]\sigma=\frac{(74000+1803.013)}{1130}[/tex]

[tex]\sigma=67.082\ MPa[/tex]

Now,Modulus of elasticity of the composite:

[tex]E=\frac{\sigma}{\epsilon}[/tex]

[tex]E=\frac{67.082}{1.25\times 10^{-3}}[/tex]

[tex]E=53665.84\ MPa[/tex]

(c)

Since, strain will be same in this case throughout the material.

Now the modulus of elasticity of fiber phase:

[tex]E_f=\frac{\sigma_f}{\epsilon}[/tex]

[tex]E_f=\frac{156}{1.25\times 10^{-3}}[/tex]

[tex]E_f=124800\ MPa[/tex]

Now the modulus of elasticity of matrix phase:

[tex]E_m=\frac{\sigma_m}{\epsilon}[/tex]

[tex]E_m=\frac{2.75}{1.25\times 10^{-3}}[/tex]

[tex]E_m=2200\ MPa[/tex]