dietz@SLB-DOLL.CSNET (Paul Dietz) (12/17/85)
I need to know the density and tensile strength of Kevlar fiber. Does anyone out there know what these are? Paul Dietz
FONER%MIT-OZ@MIT-MC.ARPA ("Leonard N. Foner") (12/20/85)
This is from memory, but I'm pretty sure it's right. Ordinary kevlar fiber, used as rope, has a strength roughly five times as strong as an equal mass of steel (I don't know which kind of steel, but this gives you the ballpark). Its specific gravity is fairly close to one (making it ideal for building underwater structures, where it's pretty close to neutrally bouyant). Thus (since steel's density is around five or so---clearly dependent on just what sort of steel we're talking about), an equal volume of kevlar is about as strong as an equal volume of steel, but that volume will weigh a fifth as much. Note that this makes it still weaker than spiderwebs (which are more than seven times as strong as steel for their weight), and that various glassy fibers are also extremely strong. However, kevlar can be made in large quantities, cheaply. It will cut itself, though, so using it around pulleys etc is a bad idea. As a skyhook it should do okay, but it's not strong enough to be used for an Earth-based hook. (I don't remember where I read the calculations talking about skyhooks, but I do remember computing that kevlar wouldn't cut it. On the other hand, the requirements in materials strength for Earth-based skyhooks are nowhere near the theoretical limits on material strength, which are based on things like the strength of a single crystal.) <LNF>
space@ucbvax.UUCP (01/02/86)
call Fiberite, (507) 454-3611. Jon Weispfenning there, at x206 should be good help. Rick