Hand layup in silicone mould?

Talk Composites - The Forum for Advanced Composites

Back

Hand layup in silicone mould?

Author	Message
trillian	t trillian posted 4 Years Ago HOT Topic Details
t Group: Forum Members Posts: 4, Visits: 32	Just trying to find out if there's any reason why you cannot do a hand layup in a silicone mould (in this case epoxy / carbon fibre). All I tend to see in searches are silicone moulds being used to cast solid resins or plasters. Silicone would be the perfect material to make a mould from the object I want to duplicate (although, there are no complex curves or fine details) and ideally I would use the mould to make both a plaster 'buck' for vac forming and also do a carbon fibre hand layup. Edited 4 Years Ago by trillian
	Reply Like 4
Hanaldo	Hanaldo posted 4 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	The issue with silicone is its extremely low surface energy, so you will find the resin will bead up a lot and pool in the low areas, and the carbon won't stay where you put it. You can't use vacuum to hold things in place either so it all tends to result in very poor quality components. Can work for some things though, depending on the shape. Sometimes a second silicone matched mould can work to hold the carbon in place. In general though, it is not a cheap material and it doesn't work well, hence why it isn't common practise.
	Reply Like 3
trillian	t trillian posted 4 Years Ago HOT Post Details
t Group: Forum Members Posts: 4, Visits: 32	+x Hanaldo - 7/7/2020 1:50:00 AM The issue with silicone is its extremely low surface energy, so you will find the resin will bead up a lot and pool in the low areas, and the carbon won't stay where you put it. You can't use vacuum to hold things in place either so it all tends to result in very poor quality components. Can work for some things though, depending on the shape. Sometimes a second silicone matched mould can work to hold the carbon in place. In general though, it is not a cheap material and it doesn't work well, hence why it isn't common practise. Thanks Hanaldo, since I posted this I was told by one supplier that it can be done :-o The part I am duplicating is a very simple shape with gentle curves, almost like a small boat hull. One idea I have had is laying up one resin layer and stick on the cloth onto the original form, ala a skinning approach, and then apply a clear coat and press the silicone mould over that. I have one part so far that I made entirely by skinning it onto the original and removing it, which worked quite well except for all the sanding needed to smooth the outer surface.
	Reply Like 3
Chris Rogers	C Chris Rogers posted 4 Years Ago HOT Post Details
C Group: Forum Members Posts: 120, Visits: 933	I agree that it may be problematic but there are so many different hardness and types of silicone that you could probably make it work. Do you need the silicone to mold in undercuts? If not then an epoxy tooling dough might be worth a look. I have hand laid up into silicone before but with polyester and mat over gelcoat - it was messy but worked well to mold complex textures that you couldn't tool any other way. The mat and polyester conforms easily - and of course cosmetics weren't an issue - so you may have a harder time with carbon/epoxy that you want to clear!
	Reply Like 3
trillian	t trillian posted 4 Years Ago HOT Post Details
t Group: Forum Members Posts: 4, Visits: 32	+x Chris Rogers - 7/7/2020 2:45:57 AM I agree that it may be problematic but there are so many different hardness and types of silicone that you could probably make it work. Do you need the silicone to mold in undercuts? If not then an epoxy tooling dough might be worth a look. I have hand laid up into silicone before but with polyester and mat over gelcoat - it was messy but worked well to mold complex textures that you couldn't tool any other way. The mat and polyester conforms easily - and of course cosmetics weren't an issue - so you may have a harder time with carbon/epoxy that you want to clear! Thanks Chris. I think what I will do is go ahead and make a silicone mould and then cast something sturdy to work from because I want to preserve the original as it's a one-off item. I can cast in some material, maybe something like Alumilite, using the silicone mould, that I can use to make an epoxy mould from or experiment with vac forming. This is the object I am casting, it's a custom made rc helicopter canopy, made in carbon fibre - I suspect using a vac infusion process. So I want to keep it in pristine condition and make a couple copies in other materials as well as one in carbon fibre. (the one with the green stickers is the original and the other one is my first foray into carbon skinning. Edited 4 Years Ago by trillian
	Reply Like 3