Making Unidirectional Fabric Plies

[mapinto121]

Hello,

I am a research student working on fabricating natural fiber composites using jute. Since unidirectional jute fabric is largely unavailable, I have been tasked with making it using jute yarn. However, I have been having some difficulty in successfully making unidirectional fabric that will stay together. So far I have experimented with tightly wrapping the yarn around a glass plate and painting the yarns with epoxy, but the yarns tend to split apart upon removal from the plate.

Does anyone here have any experience making unidirectional fabric from yarn? And if so do you have any suggestions?

Thank you very much for any advice you can give

 

[berkshire]

This is typical of unidirectional fabrics. In commercial unidirectionals the minimum number of threads that can hold the fabric together are used.
In your case you have none. So the only thing holding your fabric together is the resin.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[RPstress]

There are some UD materials held together by just resin. The resin is often introduced by dipping. It is then B-staged (partially cured) after which it is somewhat handleable (fires can be easily torn apart but do stick to one another a bit) and it has the right tack to be laid up, though it is is usually carefully introduced to some backing matierlal which allows enhanced handling and for rolls to be built up. I'd have thought that doing this by hand is a fairly tall order. Someone involved in making prepreg might have more advice, but you've been hanging now for a week with no further reply. Careful control of tension in the fibre and applcation of heat to B-stage the resin might help. Just wrapping it by hand around a glass plate by hand seems a little uncontrolled. A more elaborate mechanism might be in order. What epoxy resin are you using? This and advice from the resin manufacturer will be vital to any effort to improve its handling by B-staging it. PS: although the rules say 'no student posts' I think this is a practical piece of engineering; and deserves our support. As someone who is interested in natural fibre properties do you have any fibre data you can share?

 

[berkshire]

A little extra information,
In the UK in the 1960s, a company used to make a unidirectional pre preg by filament wrapping fiberglass and resin around a large cylinder, they then B staged the material, sliced through the wrap, and allowed the sheet to fall onto a flat plate for further processing.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[mapinto121]

Thank you all for the suggestions, I was able to successfully make some handlable unidirectional plies by weaving thin nylon filament in the transverse direction and applying epoxy to it (I suppose making the fabric "mainly" unidirectional)

RPstress: I apologize for violating the site rules, thank you for giving your advice still. What kind of information are you interested in on the natural fibers? I would be happy to share what I know.

 

[RPstress]

Mapinto121: We should be able to violate 'rules' if we think it's ok. Generally the people who run Eng-Tips just like to keep out kids looking for easy homework answers and people like recruiters who can be a persistant nuisance, hence their preference for anonymity, only disguised e-mail addresses, etc. People such as yourself should be welcomed. If their no-students policy applied to people trying to learn, it would apply to most of us. I would perhaps describe you as a 'scholar.'

My info on Jute fibres is summarised as:[tt]
...................................................................................................Specific..Specific...U*[sup]1/3[/sup] theoretical
.........Fibre.................................Failure..Density....Fibre Φ.........................strength..stiffness..ballistic resistance
Fibre....type..............UTS (MPa)..E (MPa)..strain...(kg/m^3)..(µm).....Notes...................(m).......(km)
Jutt.....Natural jute......800........30000....0.018....1460.......200.....~0.35–1.5 $/kg..........55900.....2100.......281.7
[/tt]
Any info which conflicts with this is most welcome as is anything else interesting. As you can see I'm biased to the mechanical propereties and I've selected values which are representative rather than ranges, which possibly I should reconsider. Another issue is perhaps susceptability to environment factors should be an issue I should document. Also I've got no feel for how well natural fibres adhere to the matrix; we have a good idea for carbon, glass, Kevlar, UHMPE, etc., but I've got no hints even, for the naturals, not even an interlaminar shear strength which might give a clue. I've also got no data on how well laminates made with them edsist damage and impact. I've put in the U*[sup]1/3[/sup] value but I've got no data at all on how well natural fibres respond to ballistic impacts. Other fibre data which I collect is ratio of tensile properties to compressive (basic fibre compressive is hard to find, though 'elastica loop test' data seems to have some validity). I also collect what information I can find on laminate properties, although many of these are mainly dependent on matrix resin (I document open hole compression where it's available).

 

[Phsledge]

Just thinking..... What about using UV curing resin
Then you will have all the time to adjust your fibers and your resins
Maybe place fibers and resin between 2 glass plates and curing with the UV when you are satisfied
Make yourself a little black room and a red light to work
May need some wax on the glass plates
I never use UV curing resin but it's just an idea