# Finding Thermal Coefficient

1. May 5, 2014

### ravenscroft

I need a question answered. If given the density of 2 materials in a composite, the fibres & the matrix, but not the over all density of the composite, how can one go about finding the thermal expansion coefficient, alpha of the composite? I have Youngs modulus, density of each individual material, & α's of each material. I can use Turners Formula when i have have the volume fraction, but can I get those (the volume fractions) without the overall density of the composite?
Thanks for any help or insight.

2. May 7, 2014

### Staff: Mentor

You obviously can't do it if you don't know the volume fraction, and, as you said, you can't get that unless you know the density of the composite. By any chance, do you have some idea of the layout of the materials in the cross section, or the proportions of the materials that were combined to make the composite (i.e., the mass fractions of the materials)? If you know the mass fractions, then you know the composite density and the volume fractions.

Chet

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