Problem 5 (20 pts): Using the theories we learned from micromechanics of lamina to

estimate the following mechanical properties of a glass-fiber reinforced polymer (GFRP)

lamina with fiber volume fraction of Vr= 50%. The elastic and failure properties of glass

fiber and epoxy matrix are given below:

Glass fiber (isotropic elastic): Ef=70 GPa; vf=0.3; of 1.4 GPa;

Epoxy (isotropic elastic): Em = 2 GPa; Vm = 0.3; om = 60 MPa (tensile strength); tm = 35

MPa (shear strength)

1) The elastic/stiffness properties need to be determined are: E1; E2; V12; G12

2) The strength properties need to be estimated are: Xt; Xc; Y₁; Ye; S

3) estimate the critical fiber volume fraction that has fiber strengthening effect.

4) Estimate the minimum fiber volume fraction that matrix can bridge a localized broken

fiber