What is the worlds strongest fiber?

Answer 1

The strongest synthetic fiber is carbon nanotubes.

The strongest organic fiber is spider silk. Both are stronger than silk, but I don't know if the nanotubes or spider silk is stronger.

Zylon®, the world's strongest fiber, contradicts almost everything we know about fibers and fabrics. Zylon is made by mixing a polymer called PBO (para-phenylene benzobisoxazole), while forcing it through a spinning machine.

Answer 2

Carbon nanotubes currently claim almost 22 million pounds per square inch on the high end. (150 GigaPascals) These are, by weight more costly than gold. They are difficult, and very expensive to make in any quantity.

http://depts.washington.edu/polylab/cn.html

Alot of times you will see articles comparing strengths to steel; The strongest steel used as a cord, or cable (tensile strength) is Maraging steel with about 250,000 psi Tensile strength. There are other steels with higher tensile strengths such as some Tool steels, (Carpenter Micromelt A11 ~750,000 psi, Tensile) however these are more prone to fracture when stressed in tension, so they are not used for cables. (Suspension bridges / suspension rooves.)

There are two Tensile strengths (tension / stretching) for all materials, Ultimate, and Yield.

For some brittle materials the two are equal, for all the rest the Ultimate is higher than the Yield.

All materials will stretch when pulled on. Elastic stretching is before the yield strength is hit.

Materials will deform permanently (plastically, as opposed to elastically) if they see stress above their yield strength.

Materials break when they see stress above their Ultimate strength (for tension they snap.)

Values below are Ultimate:

Kevlar / Twaron / Nomex (Aramids)

Density ~1.5 grams / cubic centimeter

500,000 - 600,000 psi Tensile strength.

Carbon fiber (non-nanotube)

Density ~1.8 grams / cubic centimeter

500,000-800,000 psi Tensile strength

Dyneema / Spectra (Ultra High Molecular Weight polyethylene, UHMWPE)

Density < 1 gram / cubic centimeter (floats on water)

500,000+ psi Tensile strength

Is lighter than carbon fiber / Kevlar

UHMWPE generally stretches many times it's length before it fails, think of plastic grocery bags, as the monomer (Ethylene) is the same.

More info on carbon nanotubes:

http://news.bbc.co.uk/2/hi/science/nature/7038686.stm

http://news.bbc.co.uk/2/hi/science/nature/7038702.stm