Maybe twice as much as aluminium, I am not sure about type of resin:
Aluminium 22.2 . 10-6 m/mK
Epoxy, castings resins & compounds, unfilled 55 . 10-6 m/mK
Is 'unfilled resin' the right number to use? I thought carbon composite is much better than that - because of the fiber, optical tables made of it have a COE typically 1/10th that of steel for instance, so I thought the number is lower than Al, not higher.
The hugely dominant effect is flexure in flight, have you seen the wings on takeoff?