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• # Thermal Expansion of Carp Brand Tufnol

Discussion in 'Calculations' started by Rob73, Mar 24, 2012.

1. ### Rob73New Member

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Mar 2012
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Hi everyone,

This is my first ever post on here so firstly hello everyone.

I am currently designing a product that I wish manufacture from Carp Brand Tufnol. I am trying to work out the Thermal expansion in areas so that I can dimension my design properly to allow for growth and contraction.

The only published data I can find for the Coefficient of Thermal Expansion is 1.9x10-6/K in plane of laminae.
What exactly does this mean? I understand that tufnol like most composites is Anisotropic so it will expand and contract different amounts in different directions. So does "through plane of Laminae" mean that it only applies in the X-Y plane of a sheet of Tufnol? If so what is the Thermal Expansion value in the Z plane?

Or am I completely wrong?

Any help would be greatly appreciated. Thanks in advance.

2.
3. ### ErichWell-Known Member

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Feb 2012
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253
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They are giving you the expansion coefficient in the plane of the fabric reinforcement. They do not give you the value normal to the plane of reinforcement. It is time to place a call the manufacturer to solicit that info.
I can say the the unknown expansion will be MUCH larger than the value they proudly publish. In that direction the properties are mostly driven by just the resin.
If I could not get any better answers I would use the value of expansion of plain unreinforced resin, what ever it actually is.

4. ### VirguleActive Member

Joined:
Nov 2011
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The linear coefficient of thermal expansion is described as follows :

alpha = delta length / ( initial length * delta temperature)

This is given as a mean coefficient for a temperature domain in which the expansion is linear. This coefficient changes for some materials depending in what plane of the geometry the length is measured. Usually, the coefficient is a very small number since the change in length is far lesser than the initial length.

Let's say you're looking at a sheet of laminae. Let's call the length of the sheet the X axis, it's width the Y axis and it's thickness the Z axis. If you are given the coefficient in the plane of laminae, it should be the coefficient in the plane where the cross section of your sheet is (usually YZ plane), so it should represent the expansion of the sheet's length (X). That coefficient will be the same in the XZ plane (expansion of the sheet's width (Y) ) only if the resin and reinforcement fibers are laid in a similar manner relative to X and Y axises. For instance, fibers laid in perpendicular fashion (along the length AND width) offer similar properties in both these axises. Finally, the expansion of the sheet's thickness will be different from the other two as Erich said. Since no fibers are laid in the Z direction, the expansion will be that of the resin, having no other reinforcement. However, the thickness being much smaller that the length or width, the change in the sheet's thickness is usually very small (having a small value for initial length, in formula).

Last edited: Mar 26, 2012