Determine maximum stress and modulus of elasticity:
A composite of glass fibres and epoxy has all of fibres laid along the length and is needed to carry a stress of 12 MPa. The limiting stress carried by fibre & epoxy are respectively, σ_{f} = 2400 MPa, and σ_{m }= 80 MPa. The volume ratios and modulii of elasticity are explained below :
V _{f } = 0.7, V_{m} = 0.3, E _{f} = 72 MPa, E_{m} = 3 MPa
Determine maximum stress the composite might carry in the direction of fibres & the modulus of elasticity.
Solution
The stress that composite can carry
σ_{c} = V _{f } σ _{f} + V_{m} σ_{m}
= 0.7 × 2400 + 0.3 × 80
= 1680 + 24 = 1704 MPa
Modulus of elasticity of composite
E = V _{f} E _{f } + V_{m} E_{m}
= 0.7 × 72 + 0.3 × 3
= 50.4 + 0.9 = 51.3 MPa