Talk Composites - The Forum for Advanced Composites

Using a silicone foot mould for vacuum resin infusion

By zappafile123 - 7/11/2021 5:16:44 AM


I'm making cycling shoes with resin infusion and have a slightly irritating issue in that it's almost impossible not to delaminate the toe box area of the sole when removing the concrete mould post cure. To address this issue, I'm thinking of the following process:

a) make a concrete foot mould as I always do --> turn it into a sole mould by adding extra concrete to form a toe box and a cleat platform
b) casting this concrete mould with alginate to make a flexible silicone mould
c) using this mould to lay up the sole for resin infusion 

Will a silicone mould work or will it simply deform under vacuum pressure of the bag? If this wont work, ya'll have any other ideas?

Ideally I would skip the first step altogether (because the enormous mess working with concrete makes does my head in), but I don't think its possible to mould silicone like concrete... but if you have a suggestion!?


By Hanaldo - 7/11/2021 11:30:50 AM

Yeh you can't use a flexible mould in a vacuum process, it just won't come out the right shape. If you need vacuum, you need a rigid mould. 

The only way I can see carbon shoes being made nicely is using pre-preg with a rigid outer mould and a silicone intensifier inside. Ideally you would use the expansion of the silicone as the consolidation method, however I think to get the intensifier out again afterwards you would need to do it as a glove mould that you can collapse inwards on itself and still use vacuum as the consolidation. Then the silicone is just there to leave a smooth inner surface. Little bit trickier than I've made it sound there, it often doesn't work that easily.

Shoes certainly are not an easy thing to make, there is an art there for sure.