Does anybody have any figures or the coefficient of expansion of this material. I understand that it is also affected by humidity. If so, can this effect be reduced by applying a protective varnish or similar?

Unfortunately we do not have any data for the coefficient of thermal expansion of the rods.  The manufacturer does not have the data available.

The CTE would vary depending on direction of the fibres, general construction, resin type, humidity, fibre/resin ratio and a number of other variables.  As such it would be hard to give you any estimated "general" figures as their validity for this rod is likely to be doubtful.

I suspect the only way to get accurate figures would be to conduct some tests on the actual rod to measure the figures for yourself.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Carbon fibre reinforced polymers tend to have extremely small thermal expansion .. the CF itself is one of the materials with the lowest thermal expansion ..

A pultruded CF tube or rod will have almost zero thermal expansion within the temperature range where the binding resin is still stable.

In some cases the thermal expansion of the resin may actually lead to a small negative expansion coefficient for the rod/tube.

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