Hi,
This thread title confuses me a little bit. I'm not sure if you want to make prepregs parts in an existing mold or if you want to build a mold out of prepregs.
Say you want to make prepregs parts in your existing mold: then you need your mold AND release agent to survive to the temperature on which you want to set your prepregs cure. Some prepregs will cure as low as 80°C (EC carry them). If you have for example a mold made of UniMold system, then you need to post cure your mold in an oven, following post cure cycles given by EC, you can find it at Pg 4
in this document.
Now say you want to make a mold made of prepregs. I know people do it, so there's no reason you cant if you can at least access an oven, which is the thing you cant do without for prepregs. Better cure the mold in an autoclave tho. Some will say they use heat blankets and its fine, really, but you need insulation, and be sure about your monitoring. In some cases you want to be precise for temperature, ramp up and down, cycles themselves etc. Typical ramp up for example, in most cases, should be like 1-3°C per minute, and usually cool down is about twice that amount. So, it really depends which goals you set.
Cure/postcure cycles are usually found in the technical documents of the products you did buy. Then you know which ramp up, time intervals, temperature cycles and ramp down.
No, you dont need aluminium or any metal mold to go in an autoclave. Its all about the resin you use to make your mold. Metal molds have way bigger heat inertia compared to composite molds, which is not so good. Thermal expansion is totally different than your composite parts too. Plus you need a cnc mill (or router) to make them (for complex shapes that is). And they're heavier to move around... You can achieve high temp resistant, non porous, dimensionally stable, and highly polished molds with composites, prepregs or not.
Hope it helps.
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