mould for prepreg

Hello, I will build a mould for prepreg carbon rudder stock. I will use 140TG hexion epoxy as resine and will use glass UD, My question is should I use carbon instead of glass because the product will be carbon or still can I use glass as mould material and it will not affect seriously.. what do you advise??

 

Use a carbon mould.The thermal expansion coefficient differs for carbon and glass and the movement may cause you problems.Unfortunately this is the more expensive answer.

 

Have you looked at CNC your mold from billet aluminium stock... easy and precise...

 

So I am switching to carbon then, yes I checked alu milled mould but its much more expensive, length is more than 2 meters so it requires bigger machine and cnc shops are full these days and they are asking expensive prices..

 

We used only cold molded fiberglass tooling for our high temperature, vacuum bagged, oven cured aerospace parts. The secret is in the high temperature rated tooling resin we used. For dimensional accuracy, the molds are allowed to expand and contract on the metal tooling frame by having "free floating joints" so that it can expand in the X, Y, and Z axis.

Reserve the carbon fiber tooling to autoclave.

 

surely machined "hard" aluminuim moulds will have enormous thermal expansion differences compared to the carbon parts being made ?