This is the second part of our most recent video series. In this video we demonstrate how to using carbon fibre tooling prepreg to create a prepreg carbon fibre mould. The benefits to making prepreg moulds is that they have a relatively high service temperature (135°C in this case) which is difficult (although not impossible) to achieve with a hand layup process. 

Because the XT135 out of autoclave tooling prepreg uses carbon fibre reinforcement it has an extremely low CTE, lower than can be achieved using metal or glass fibre, this can be quite important when making prepreg carbon fibre components that need to be produced to high accuracy; the reason being carbon's incredibly low CTE - if you use materials with a higher CTE to produce the tools then you 'bake in' the expanded dimensions of the higher CTE mould when you cure carbon prepregs in them at elevated temperatures.

Tooling prepregs also have the advantage of being actually pretty quick and very reliable to work with. Certainly, providing you understand the process and have the right materials there is probably less 'skill' involved in making a good quality prepreg mould compared to hand-layup with more conventional materials (such as Uni-Mould).

Here's the video tutorial demonstrating the layup process for a tooling prepreg (which is quite a bit different to laying up a prepreg component):


If anyone has any questions at all about tooling prepregs or any of the topics raised in this tutorial please post them below, I'd be happy to answer.

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

So when you write that a prepreg carbon fibre mould out of XT135 has a lower CTE than a mould made of metal: does this include steel or just aluminium?

Yes, it depends on the resin content, but it is close to zero.

Impressive. So the main advantage of aluminium or steel moulds is that, due to their higher abrasion resistance, they will endure more production cycles than a prepreg mould?

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

For the geometry of the mould from your above tutorial: how many prepreg demouldings can it withstand when its a) made out of epoxy and b) made out of carbon? I am guessing something with two digits for the epoxy mould and something with three digits for the carbon mould?

There are (usually) no molds solely made of epoxy. The epoxy is all ways reinforced with either glass, or carbon fibres. The advantage of a cte close to 0 only occurs when using carbon. Good moulds, especially infused ones, or prepreg molds, last very, very long. If you are willing to repair some defects from time to time, and don't abuse the mold, several hundred pulls are possible.

just watched the video again, the finish you get is really good, usually I do 45° strips on any tight corners and features but you only done a couple in yor video.

There  must be a very high resin content to get the material to flow into the corners?

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

 XT135 Processing Handbook, where do I find that?