Find out the modulus of elasticity:
A unidirectional FRP is produced with fibre volume ratio of 60%. The density of fibre is 1480 kg/m^{3} and that of matrix is 1200 kg/m^{3}. Calculate the weight percentages of matrix and fibre and the density of the composite. Also find out the modulus of elasticity of composite if E_{f} = 70 MPa, E_{m} = 3 GPa.
Solution
Supposed that composite has a volume of 1 m^{3}, so that
V _{f} = 0.6 m^{3} and V_{m} = 0.4 m^{3}
Mass of fibre = 1480 × 0.6 = 888 kg
And mass of matrix = 1200 × 0.4 = 480 kg
Mass of composite = 888 + 480 = 1368 kg
Density of composite = 1368 kg/1 m^{3} = 1368 kg/m^{3}
Weight % of fibre = (888 /1368) × 100 = 64.9%
Weight % of matrix = 100 - 64.9 = 35.1
Modulus of elasticity of composite
E = V _{f }E _{f} + V_{m} E_{m}
= 0.4 × 3 + 0.6 × 70
E = 43.2 MPa