Polyester fleece or fleecing a carbon fiber ski

[poikenz]

I've heard mention of putting a thin layer of fiberglass or polyester "fleece" between the core and carbon fiber to promote adhesion and prevent sheering and I was hoping someone could shed some more light on what sort of polyester you have been using, where you get it (if needed) and what results you have had.

I'm new to posting here but I am on my 6th set of skis. my current layup is:

ash veneer, Uni glass, biax carbon, ash core, biax carbon, uni glass.

One issue I have is a constant delamination in a single tip of one ski. I hit jumps on ice, so the tip flexes and sheers under the stress. I don't wish to rivet so I was hoping that I could sand and put a piece of polyester in the tip to improve it's chances of not sheering.

Any thoughts on the subject would be greatly appreciated.

[chrismp]

There is indeed some sort of fleece fabric that can be used to improve bonding (we were donated some remnants of this stuff), however I don't have any Information on the manufacturer or the type of material. It is a very thin white non-woven mat, so I guess it could be both fiberglass (most likely c-glass fleece, as most regular glass fleeces are thicker) or polyester. I would prefer fiberglass over polyester in this case as polyester doesn't really form a matrix with epoxy, it just "floats" in there.

Another option might be to use a larger patch of VDS rubber as a bonding agent and shear layer.

[SleepingAwake]

My local supplier has a 30gsm glass veil that works well, but it really shouldn't make much of a difference what exactly you use as long as it has a decent bond with epoxy and will form a resin rich bond line.

[K2skier]

So does the "fleece" create a host for a thicker resin layer? Is that the point? Just wanting to understand why it helps...

[chrismp]

Yes, the point is to keep a certain amount of resin between two layers of different materials where one material might absorb too much resin from the bond line between the two layers.

[TimW]

I build boards with vacuum infusion and use 30gsm c- glass fleece to improve resin flow when needed(e.g for carbon titanal laminates). But for hand lay-up I'd think you are better off properly wetting the carbon and pre- wetting the core. The glass will not necessarily make it stronger.

For your lay-up, why don't you put the UD glass next to the core? Would give you a better torsional to longitudinal stiffness ratio.

[BS Tech]

https://store.acpsales.com/categories/1 ... cing-veils

you can get it in carbon fiber, kevlar, glass and polyester.

We've used it, works really well!

[SleepingAwake]

The point is not just to have a resin rich layer, but to have a smoother transition in the stiffness between different layers to reduce shear stress.
For the same reason it is best practice to have the +/-45° layers inbetween the UD and the core.

[vinman]

Boston materials SuperComp material. The have several weaves with what they call a Z axis fiber, It looks like a fleece like layer but is in reality a cardboard pulp of some kind. Looks interesting. They claim that it improves dampening. I have a sample of it but have not yet used it.

[poikenz]

Thanks for all the replies, I went ahead and just slapped some 11 oz fiberglass in there as no one near me carries anything of lesser weight. Haven't had a chance to test it out yet as I did it right before all the hills closed In March.

[mikic1]

You could also consider a full width VDS or a full width cork rubber material....or it might be a press/mold/layup issue of some sort that can be fixed without extra layers...

[mammuth]

Normally biax carbon to the core should be ok. VDS, kork,... adds weight. You should examine more how it delaminates. There is the possibility that the glass UD is streching/compressing so much more compared to the biax carbon that the carbon starts to buckle and creates the delam issue

[JSquare]

One issue I have is a constant delamination in a single tip of one ski. I hit jumps on ice, so the tip flexes and sheers under the stress. I don't wish to rivet so I was hoping that I could sand and put a piece of polyester in the tip to improve it's chances of not sheering.

Do you have pictures of the failure? Can you clearly tell what layers are delaminating. We had a couple of our first boards delam. The problem went away as we got better and never seen it since (prob 12 or so boards, but more temperature, more pressure, better wetting, more process controls, better VDS placement, more experience).

Where it delams, can you continue to "peel" it apart and clearly see a layer that's not getting good bonding?

Stress can be funny-- it could be that you have a bonding issue. It could also be there's a stress riser (like the above mentioned mismatch of layers) or too much epoxy somewhere that doesn't allow flex

[poikenz]

Thanks for all the replies!
As a follow up, the method of adding in an extra layer in the delaminated area has worked so far. I had a shorter season and took it easier than most due to an injury, but from what I an tell I believe it will hold just fine.

I feel that my issue was with the wet-out of that specific tip given that I have had no issues with any other tip across 2 pairs of skis. With that said, I plan on modifying my layup to better avoid any shearing issue in the future.