Originally Posted by
peteeng
I think the process is backwards. If you understand vacuum processes I'd do it this way. 1) dry stack the mould and the mould needs to be vacuum tight or you need to put a vacuum bag around the outside of the mould 2) pull the dry stack down to below the local vapour pressure level. Vacuum soak for at least an hour to remove all the water moisture in the stack c) Then have a suitable tubing system that allows epoxy to be drawn into the evacuated mould. Since there is less than 1% air in the mould the resulting "infusion" of epoxy will be very low void. I've done this sort of thing with many materials and even 50ft boats. Infusion requires light moulds as its vacuum not pressure.... There are many infusion grade epoxies around to choose from...
I have done this with 100% alox (65% by volume) and the flexural stiffness was <20GPa. I've done it with sand, aluminium powder, steel fibres, fibreglass, carbon fibre, timber. In fact if you use a long gel time epoxy there is enough room (at least 30-40% void) in a dry stack that if you just pour infusion resin on top it will seep down to the bottom quite quickly. In this way you get no air in the structure due to the mixing as long as the stack is dry. Thats the advantage of the vacuum soak, removing moisture from the stack.
Speaking of strength my testing of fibreglass laminates for vessel survey took a significant step forward once we started vacuum soaking the dry stack vs wetting out the laminate then vacuuming it to spec. Water and epoxy are not friends. Water inhibits the coupling of the epoxy to the substrate. We tripled the strength of the laminate by vacuum soaking.... The amount of water in rocks must be huge unless your in a desert at 40% RH.... or someplace in africa with 17% RH....