Silicon as reinforcement?

[RPstress]

Just eyeballing the basic properties, silicon looks like a candidate for a high preformance reinforcement. (Strength maybe 7000 MPa, E about 150 GPa, density 2330 kg/m³.) However, I can't find any reference to its use as such (and no references to any sort of fibres of silicon).

Anyone aware of use as reinforcement (maybe in a non-fibrous form)? And anyone have any idea why it's not used as such?

 

[berkshire]

RP
Silicon is used as an extender or filler in a non fibrous form usually as fumed silica i.e. Cabosil or Aerosil.
added as a powder to stiffen and increase the compressive strength of a resin.
Somehow I feel this is not what you are after.
B.E.

 

[blakmax]

I have seen some silicon carbide fibres years ago. I am not sure if pure silicon as fibres would be a risk of causing silicosis during production or if they need to be repaired.

 

[RPstress]

I'd missed the forms used as a filler. But yes, I was more curious about uses that take advantage of its mechanical properties. Also hadn't thought about the poss H&S aspects. Not sure about its molten properties but it melts at a similar temp to glass so presumably could be processed similarly. Vast quantities of course are produced for silicon chips.

 

[CoryPad]

Silicosis is from silicon dioxide, not silicon.

The quantities of high purity silicon produced for integrated circuits is quite small compared with the amount of metallurgical grade silicon used for aluminum casting alloys. That type of material would be the starting point for any theoretical development of a reinforcement product.

I don't see much of a market for this fiber due to the other options available in glass, aramids, UHMWPE, SiC, and carbon.

 

[Compositepro]

Silicon fibers would be about as useful as aluminum fibers. What is the point of the added cost and complexity when you get better properties from solid material. There is a steel wire composite which has a small market. The wire-drawing process can create steel with unusually high tensile strength. But in the cross fiber direction the properties are close to zero.

 

[geneiusxie]

Huh. I've been interested in iron whiskers for a long time. Where'd you find info on steel wire composites?
And if you're talking about the low shear strength of the fibers, remember that carbon fiber laminates have as much shear strength as plastic.

 

[berkshire]

The tire industry used to use a lot of steel wire woven preforms for belts, but I think that has now been overtaken by the Kevlar.
B.E.

 

[Compositepro]

Metals are isotropic materials. They have the same properties in all directions. Why make them into fibers and get only 65% fiber volume in a ply? In a 0/90 laminate only half the plys run in one direction. The 90 degree properties are a small fraction of the zero degree properties.

Hardwire uses steel tire cord to make steel composites. Steel wire is still the most common tire reinforcement.

Bekeart (?) makes stainless steel fibers with filaments similar in diameter to carbon fibers.

 

[cloa]

Metals are isotropic materials if they are polycrystalline with random orientation with normal heat treatment that is the form. Fibers can be monocrystalline.

 

[RPstress]

Thanks everybody. Been off sick for a while hence no previous thank yous.

http://www.hardwirellc.com/solutions/reinforcments.html

draw out wire and get impressive properties. Specific strength still not that high, though.

My thought for silicon as a reinforcing fibre was that you could get much higher modulus with otherwise similar aspects to glass (E about 2x glass, density and virgin strength very similar, strength about 10x Al, maybe, and similar economics?). None of the terrible compression strength of organics like Kevlar/Dyneema. The higher modulus would give much improved ballistic properties over glass in theory. A bit like basalt, which there seems to be a market for even though its E is only 25 to 30% more than E-glass (

http://www.basfiber.com/).