Re: Cables stronger than steel
Posted by Uncle Al on Aug 14, 2003 at 11:06
(68.5.243.16)Re: Cables stronger than steel (Amaranth Rose)
Kevlar (liquid crystal spun poly-para- terephthalamide) is about 5X as strong as steel wt/wt. Spectra/Dyneema (gel-spun oriented ultra high molecular weight polyethylene) is about 3X as strong as Kevlar wt/wt. Being slightly boyant in water, it is fantastic for long lines (miles, especially vertically) because it doesn't have to support its own cumulative net weight.
The trick with spider silks (especially dragline) is not only specific tensile strength, it is failure mode. Spider silk is oriented very long linear protein molecules that periodically massively zig-zag upon themselves and are secured by hydrogen bonding. When spider silk is elongated to failure, tremendous amounts of energy are absorbed as the zig-zags are stretched out. Spider silk does not abruptly fail. It forgivingly stretches, absorbing and distributing the insult.
Spider silk, or a genetically engineered improvement, is thus potentially really hot stuff for body armor and otehr extreme engineering applications where very rare impulse loading can lead to general failure.
Note that Kevlar is degraded by moisture (sweat) and fractures. Kevlar body armor on a hot day or that has stopped one round is substantially degraded. Spectra is much more apropriate to the task.
--
Uncle Al
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)