Hi Forum..!

I need to process by hand layup Aramid Fabrics (Kevlar) with epoxy resin. How much resin the Kevlar will need to be wetted?

Kevlar Propiertes
360 g/m2
1500 Denier
0/90°

Epoxy
Laminating epoxy, low viscosity

Thanks!

For hand layup you generally aim for a 50/50 fiber/resin fraction. So if your fabric (doesn't matter if its fibreglass or carbon or Kevlar etc) is a 360gsm, then you will need 360g of resin for every square meter of fabric. Plus a little bit of wastage factor for resin in the bottom of your cup, in your brushes, etc.

Are you using woven glass or chopped strand? Chopped strand is much thirstier and does need twice its weight in resin. Woven glass it should certainly only need it's own weight in resin and it should be easy to achieve a 50/50 ratio. In fact a skilled hand laminator should be able to achieve an even lower resin content, but I've never managed to balance that with a decent cosmetic finish.

Are you sure about a consistent rule for every fibre material? Different cloth types aside, glass is almost twice as dense as aramid, wich means you would use almost twice as much resin for the same volume of fibres.
Speaking volumetric this would lead to:
Glass 29% fibre content:
Carbon 36%
Kevlar  42%

The smaller the workpiece, the more you should take into account, that some resin will stay in your mixing pot and in the brush.

I have never noticed any difference in resin consumption between different types of fibre, only different types of cloth, ie. mat, woven, rovings, etc.

I always just use the equal weight of resin for the weight of material that I have, regardless of fibre type. 

I almost never work with carbon in hand lamination process, and hardly use Kevlar at all. Honestly the only things I make using wet layup techniques are bigger moulds. But for resin infusion I can definitely say that similar weighted carbon takes up way more resin compared to glass. But the difference between similar weighted glass mat and woven glass is much greater. Glass vleece behaves like a sponge.

With the resin in prepreg being around 40% of the carbon weight, a 1:1 wet lay carbon/resin ratio adds a fair bit of weight to the part. Vacuum bagging using perforated peel ply and at least 2 layers of breather cloth will reduce the amount of excess resin, resulting in a stronger and lighter part. Too much resin is almost as bad as not enough :-)

I progressed from wet lay to prepreg, bypassing infusion so I have no experience of this process.

If you See trying to achieve prepreg resin content with hand laminating techniques you will almost certainly get a very ugly part. For carbon mixing up resin equal to the weight of cloth seems to be at the right spot. But even my glass fibre reinforced tools contain less resin than fibres (Speaking of the weight, and excluding the tooling gelcoat). So I would say for woven glass fibre cloth, the ratio should be smaller than 1:1 (reducing resin). For kevlar it should be the other way around.