Preperation of Fibreglass

chris85

Can anyone help with some advice on methods of preperation of long fibre composites. I will be weaving or braiding fibres and I need to find the best way of doing this to keep the density constant.

Any help would be good

Cheers

tak

I will be weaving or braiding fibres

But aren't these long strand/woven/braided/uni-dir, etc reinforcements available off the shelf ? At least in the case of glass for GRP they were anyway. Ask around.
Certainly they can be got in UK.

The best method of manufacture depends on the type of component.
What is the type of component you plan to make ?
What is its form - i.e. lamina, plate, beam, tube, etc ?
What level of loading is to be on the part?
And how is the loading to be applied ?
Are there dimensional limits to the final component ?

Basically sketch both the part and its loading.

JacobM

I know woven fibre cloth is available on the internet. Carbon fibre and fiberglass. The fiberglass is cheaper but only by about 20%. I think the easiest way to go about this is to take a form, say, a broom handle, wrap the stuff around the form in overlapping fashion. I'd do all weave patterns in a line. On each you apply epoxy resin or whatever resin it is you use. It can be had with the cloth materials. The less you can get away with the better (real technical). The broom handle would make a tube. Other forms will be more difficult. But same general idea as long as you can get the form out.

Braiding, as in many fibres in the same direction like hair, is much more difficult and requires fibre spools etc. Their are so many threads it really requires a machine to get a good uniform lock of fibres. could maybe spin them onto a large cylinder and cut them down the side of that cylinder and then you would have locks of a length. Still not something that would be done by hand, the winding, and you'd have to be real good with materials. The braiding works the same way around a form like a plastic cord or something similar and is then laid into a mold. When hardened, the plastic cord can be pulled through. This is probably more sophisticated than it would sound. The real objective is to align the fibres to the forces the form will experience, and they have quantified in proportion to forces or else there is too much waste and the benefits of composite material is lost. The mechanics of this braiding would be similar to that of those girls hair braiders they sell on TV, only around a form or more than one form for more hollow spaces locked together. If you want to get fancy you can add kevlar fibres too but you have to make sure they are good and tight otherwise it's no good for the dangling broken piece. Get that at thread site for $10 or so, smallest single strand, of course.

Wear a resporatory mask and gloves and goggles.

chris85

I will be making components with simple enough geometry. They will be dogbone shaped and symmetrical through each axis. I'll be using vacuum bagging to produce the samples. Just need to prepare the fibres and would be better to prepare them myself although I may buy off the shelf if necessary.

I know they are easily available off the shelf but for this I kinda need to look into attempting to do it myself.

For the weaving the angle will be 90 degrees between fibre in different direction and braiding i may not use but need to see what methods are available.

Loading will be more what i will be looking at. I will be chaging the orientation of fibres and looking at the effect this has on the loading.

tak

Just to clarify things.
Are you making dogbone shaped test-pieces ? For tensile and fatigue testing ?
Flat dogbones made with the woven mat, I assume ?
And you plan to use the braided long strand glass-fibre to make round section test-pieces ?

For weaving I suppose you'd need some sort of loom.
A small one for doing experimental-sized mat would have to be improvised, maybe from a small one got from a fine textile producer.
The braiding machines seem to be there -
http://www.cobrabraids.co.uk/textile.htm
The manufacturers may know of some business in Ireland who has one.

Also :
Loading will be more what i will be looking at. I will be changing the orientation of fibres and looking at the effect this has on the loading.
Surely you mean that you'll be looking at the effect the arrangement of the reinforcing fibres has on the strength of the material.
As a mechanical engineer you will probably have done a module on Mechanics of Composites. Using the analyses provided in that course you could work out a "design estimate" for the final strength of the final part. This won't be the same as the realised test data for strength but it should be a decent guide.

By the way, C85 - if you do any parts made with pre-stressed glassfibre - I'd be interested in the comparitive data between them and the normal GRP.

chris85

I will be estimating the final strength prior to doing the test and will be using this to compare to the actual results got from testing the tensile strength using flat dog bone samples tested using a instron.

I'm just not looking forward to the preparation of the fibre. Will buy off the shelf if I have to but would be better if could be done by myself.