- #1

blueyellow

## Homework Statement

A composite material is made from a matrix with a tensile modulus of 5 GPa and two different continuous fibres with moduli of 360 GPa (type !) and 450 GPa (type B) respectively.

a) Derive expressions for the transverse modulus and the longitudinal modulus of a 3-component composite.

b) Use the expressions to calculate the volume fraction of type B fibre required to obtain a longitudinal modulus of 200 GPa for a composite material with the above fibres and matrix given that the volume fraction of type A fibres is 0.25.

## Homework Equations

Transverse modulus:

[itex]\epsilon[/itex][itex]_{C}[/itex]=[itex]\epsilon[/itex][itex]_{f}[/itex]=[itex]\epsilon[/itex][itex]_{m}[/itex]

[itex]\frac{\sigma_{C}}{\epsilon_{C}}[/itex]=[itex]\frac{\sigma_{f}}{\epsilon_{f}}[/itex]V[itex]_{f}[/itex]+[itex]\frac{\sigma_{m}}{\epsilon_{m}}[/itex]V[itex]_{m}[/itex]

E[itex]_{C}[/itex]=E[itex]_{f}[/itex]V[itex]_{f}[/itex]+E[itex]_{m}[/itex]V[itex]_{m}[/itex]

etc, etc.

## The Attempt at a Solution

See above. I know what the result should be for a composite with one fibre, but how do I alter the formulae for a composite with two fibres? Do I just replace 'f' with 'f1+f2' or is it more complicated than that? Nowhere in my notes or textbooks or the internet does it tell you.

Please help.