First I've got to compliment you guys on a great website, loads of brilliant information, products and support!

I'm about to venture into using composites to create some interesting artwork based loosely around the human torso.  I'm aiming for very low production runs (3 maximum) of carbon fibre / carbon kevlar, etc.  The surface finish / visible pattern from the cloth is the most important thing, strength & weight are much less of an issue.

I'm familiar with using RTV silicone with plaster bandage support shells for creating resin and wax items.

My first question is: Would it be possible to use a flexible RTV mould (with a rigid support shell) for the vacuum infusion process I've seen on the tutorial video?
The plug I will be taking the mould from has some undercuts, so it would be much easier and less time consuming to create a supported skin mould, than a multi-part rigid mould.  I would also hope that this method would reduce the final finishing process as there won't be moulding lines to polish out around the undercuts.

My second question is: Bearing in mind that the final products are going to have small production runs, and 100% accuracy is not critical (98% would be ok), is the vacuum infusion process over-kill?  I already have a vacuum pump, degass chamber etc, so it would be a relatively low setup cost.  But are there better suited products for this kind of project?

Thanks in advance & wish me luck with my learning curve.

Hi John,

Thanks for the kind words; I'm glad you like what we do.

This sounds like an interesting project! In answer to your main question about whether the infusion process would be possible using an RTV silicone mould, the answer would be "yes" however it would make some aspects more difficult, almost all related to the fact that nothing really sticks to silicone. Positioning the reinforcement on the mould surface (particularly a complicated shape like a torso) would be incredibly difficult if you can't stick the reinforcement to the mould surface. Next, positioning the spiral and connectors, which are normally held in place with some sticky tape, would againt be very difficult onto a none-stick silicone mould.

My opinion is that it would be considerably easier, and less work in the long-run, to make a rigid split-mould for the torso. Do you have access to an oven where you could cure the 'torso' at 95'C? - If you do I think I have a suggestion for the manufacturing process. Let me know.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi Matt,

Thanks for your reply. Ah the boon and bane of silicone!

Unfortunately I don't have access to an oven big enough to hold that temperature. I often create a hot-box with polyboard for larger peices to speed up silicone cure times, but they're only good for 50'C or so.

Maybe this is a naive question, but excluding the complicated areas, wouldn't the reinforcement be forced against the mould under vacuum if it has been shaped before hand?

Hi John,

Sorry, I didn't get a chance to reply on Friday. Regarding the reinforcement staying in position, the way I've imagined the 'torso' is that it's a cylinder with some complicated contours. If you're working on it with the cylinder pointing up then you could potentially 'hang' the reinforcement from the top of the moulding but if the whole thing is made of silicone then I really don't know how you're going to stick down the top edge in order to hang it down; and arranging it into the more compound contours would be very difficult indeed. In its dry state, carbon fabric is not possible to 'shape beforehand' really (this is why I was asking about ovens, I thought that pre-preg might be the way forward but it's not an option).

You need the reinforcement to be pretty much in the right place before you pull the bag down otherwise you're likely to end up with a lot of 'voids' where the reinforcment has bridged the corners. My opinion in still that a rigid tool would be the way to go but I'll never stop anyone from trying something that they think might work (you know your piece better than I do).
All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales