Water jet cuttng carbon fiber fabric

[thehitchhiker]

Hello!

I've just received information that there may be a requirement to cut some carbon fiber fabric on the water jet machine in our lab. The party that wants the cutting done, requires an option that's quicker than using shears to cut it.
That's pretty much all the information I have at the moment and we have never cut the material before. So I know that carbon fiber can be cut on the water jet, but I'm not sure about how to clamp it down and how to keep it from moving around during the cut. I'm also unsure about whether or not abrasive will be needed. I'm guessing it won't be. Finally, will the CF fabric be affected by the water when it is submerged? I've heard something about the fibers swelling up and fraying.

 

[CWatters]

I've only ever hand cut plain carbon fibre cloth but in the absence of a better reply...

I don't think carbon fibre will absorb water and swell up but the cloth would need to be dried well before being impregnated with resin. Perhaps they want you to cut "Prepreg" rather than plain woven cloth? Prepreg already has resin in it that is later heat activated.

Plain cloth can fray easily when it's handled - particularly on cuts that are parallel to the weave or at corners/points. I think it could be difficult to get cut pieces out of the water without it falling apart/fraying? I think Prepreg would be much less prone to this.

 

[thehitchhiker]

I don't think carbon fibre will absorb water and swell up but the cloth would need to be dried well before being impregnated with resin. Perhaps they want you to cut "Prepreg" rather than plain woven cloth? Prepreg already has resin in it that is later heat activated.

Plain cloth can fray easily when it's handled - particularly on cuts that are parallel to the weave or at corners/points. I think it could be difficult to get cut pieces out of the water without it falling apart/fraying? I think Prepreg would be much less prone to this.

Thank you for your reply CWatters, it's the most helpful I've received from anywhere till now. I haven't worked with carbon fiber so far. I'm very unsure what it's going to be like and I have very little information about it at the moment. But I'm very excited to see how this goes about.

I was told that it will be just the plain woven fiber, but I'm yet to see what it will be like when it arrives. Our main concern at the moment is how to hold it down.
Do you think there would be any other issues if the water jet is used to cut the carbon fiber with resin?

 

[Nidum]

The easiest way to hold down Carbon Fibre cloth for cutting is to pre make a shape in metal which replicates the required shape but which has clearance along the lines of cut just sufficient to clear the water jet .

Plate and cloth are then just weighted down .

If cutting table has widely spaced bars then pre make another plate to support cloth from underneath .

Carbon Fibre cloth does not respond well to punching through to initiate cuts and particularly to make small holes . Best where possible to punch through in scrap areas and then arrange easy run into the profiling cut .

Water is not a problem as such but there is a niggle problem in that gobs of water caught in the weave near the cutting edge can 'burst' and displace the edge fibres . Common solution is to use a vigorous air jet to disperse any residual water in cutting zone .

Some professional companies don't like cutting Carbon Fibre cloth with water jet and will always use laser cutting when possible .

 

[Nidum]

Another way of supporting the cloth for cutting which is used sometimes for low value one off jobs is to put the cloth between top and bottom layers of something like MDF board and just cut through the lot .