Material with best tensile strength to weight ratio?

[BasketDaN]

Could anybody tell me what material will give the best tensile strength to weight ratio? I figure it's between steel cable and the nylon type stuff used in some dog leashes, but I'm not sure which.

 

[FredGarvin]

Spider silk comes immediately to mind.

http://en.wikipedia.org/wiki/Spider_silk

 

[hitssquad]

http://en.wikipedia.org/wiki/Carbon_nanotube

--
Ray Baughman's group from the NanoTech Institute at University of Texas at Dallas produced the current toughest material known in mid-2003 by spinning fibers of single wall carbon nanotubes with polyvinyl alcohol. Beating the previous contender, spider silk, by a factor of four, the fibers require 600J/g to break. In comparison, the bullet-resistant fiber Kevlar is 27-33J/g.
--

 

[rdt2]

Yes, but that's toughness/weight rather than strength/weight.

The highest strength/weight ratio is usually found in whiskers in which there's no room for defects (so it might still be a nanotube) but it sounds like BasketDan has a larger-scale application in mind.

 

[1123581321]

carbon nanotube?

 

[PerennialII]

carbon nanotube?

It seems we haven't really had an in-depth discussion about the topic, but good ones nonetheless :

https://www.physicsforums.com/showthread.php?t=66407
https://www.physicsforums.com/showthread.php?t=53874
https://www.physicsforums.com/showthread.php?t=9472

 

[NSX]

I think Titanium has high strength:weight, since I remember reading an article about the NSX and it's Ti connecting rods.

 

[Astronuc]

Some information to consider -

Fibers
http://www.machinedesign.com/BDE/materials/bdemat3/bdemat3_6.html

Kevlar (Aramid)

PBO (Zylon) - PBO consists of rigid rod chain molecules of poly (p-phenylene-2, 6-benzobisoxazole)

Highest strength-to-weight ratio of any fiber
Highest resistance to heat of among high modulus fibers (decomposes at 1200° F)
Negligible creep
Poor abrasion resistance
Should be protected against degradation from light sources

HexWeb® Honeycombs
http://www.hexcelcomposites.com/Markets/Products/Honeycomb/Selector_HC.htm

Titanium and Ti alloys
http://www.key-to-metals.com/Article20.htm

World's First Carbon Nanofiber Bridge Debuts
http://www.netcomposites.com/news.asp?1699

 

[Gokul43201]

In general, you want to go the composites way for strength to weight. Among metals, Ti and Ti alloys are pretty high. Among composites, (especially in the low strength regime) most FRPs have a very high s/w.

Is this a question about a specific bit of trivia, or a general design related question ?

 

[PerennialII]

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/strength-density/NS6Chart.html

Ashby's "classics" work pretty well in general terms.

 

[Chronos]

Aromatic polyamide fibers [e.g., Kevlar] have the highest tensile strength to weight ratio of any commercially available material.

 

[bmyers]

M5 Fiber

I know I'm a little late on this reply, but I just read your question today. I am at a loss as to why no one has mentioned the M5 Fiber. So, I did a little googling and found some fascinating info at:

http://www.m5fiber.com/magellan/m5_fiber.htm"

Currently, this IS the strongest, most versatile synthetic fiber that I am aware of. If anyone knows of another, please let me know, as I am always looking for new materials to experiment with.


"So long, and thanks for all the fish!"

---- Bill Myers ----

 

[Facial]

Kevlar and basalt fiber are two contenders on the practical scale; carbon nanotubes are the strongest on the laboratory/R&D world.

But while there are many fibers that exist with high tensile strength, I still think man has not found any composite, polymer, ceramic, or metal that can come close to the versatility of steel.

Currently, this IS the strongest, most versatile synthetic fiber that I am aware of. If anyone knows of another, please let me know, as I am always looking for new materials to experiment with.

I find this interesting. Are there any specs on the mechanical properties of this polymer?

 

[Astronuc]

I find this interesting. Are there any specs on the mechanical properties of this polymer?

The Magellan site has a page with the mechanical properties.
http://www.m5fiber.com/magellan/m5_technical_info.htm

It maybe sufficiently new that it is not yet in other databases.

Interestingly M5 (pyridobisimidazole-2,6-diyl (2,5-dihydroxy-p-phenylene) is structurally similar to Zylon (p-phenylene-2, 6-benzobisoxazole). In M5, the oxygen in the benzobisoxazole ring is replaced by NH, hence the pyridobisimidazole, and the phenylene ring has OH attached at 2,5, hence 2,5-dihydroxy-p-phenylene.

The patent 5,674,969 in the first in a series of four which discuss this and related polymers.
5,674,969

1. A rigid rod polymer in which at least 50% of the recurring groups correspond to the formula: $STR4$

2. The rigid rod polymer according to claim 1, wherein at least 50% of the recurring groups are composed of pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene), and in the remaining groups (a) the 2,5-dihydroxy-p-phenylene is replaced by an arylene which may be substituted or not, (b) the pyridobisimidazole is replaced by at least one of benzobisimidazole, benzobisthiazole, benzobisoxazole, pyridobisthiazole, and pyridobisoxazole, or (c) both.

The three other patents are: 5,939,553, 5,945,537, and 6,040,478.
Ref: Magellan Systems International.

It would appear that Magellan's M5 will replace Kevlar and Zylon in certain (perhaps most) applications - although cost will play a role.

 

[russ_watters]

Could anybody tell me what material will give the best tensile strength to weight ratio? I figure it's between steel cable and the nylon type stuff used in some dog leashes, but I'm not sure which.

Steel is actually pretty mediocre in that department. My guess is that Nylon's is several times that of steel (I tried to google it, but all I got was this thread! ) . There are lots of relatively mundane elements and alloys - even basic aluminum - that have much, much better strength to weight ratios than steel. And then there's the more exotic, like some of the things others mentioned. But as asked - what is the purpose of the question? Application makes a big difference.

 

[Astronuc]

Russ brought up a very important (crucial) point - Application - or particularly - Environment.

Environment certainly include temperature, but could also involve chemical (corrosion or chemical reaction) and radiation.

High temperatures, might require refractory alloys, because organics would thermally decompose. Carbides of refractory metals would be required for even higher temperatures.

High radiation environments can destroy organic fibers.

 

[BioMajorette]

Equation needed, please

Would one of you be so kind as to tell me the formula (simplest possible, please) for determining the lowest number of fibers of a particular tensile strength, bundled together into the lowest number of cables, that would be required to lift an object of, let's say, 1200 lbs.? (Physics isn't my forte, so please keep it simple for me. Thanks!)

Also, would the equation change over time? What I mean is, would the fibers of the cables weaken enough to change the equation between lifting the object 10 feet versus 50 feet in the air? Let's assume that no other outside forces (wind, for instance) are involved. Thanks.

 

[BioMajorette]

Oops. I should have said "minimum of four cables" rather than "lowest number of cables." Sorry.

 

[mtworkowski@o]

Could anybody tell me what material will give the best tensile strength to weight ratio? I figure it's between steel cable and the nylon type stuff used in some dog leashes, but I'm not sure which.

Don't ignore your basic wood. That's right. Wood comes in many forms. It's really hard to beat, light, strong, underrated. It's a secret weapon. Tell me what you thindk is better than wood. I could use a laugh. I should ask what your application is. Oh. that's it. Oh, that changes everything. The answer would be...WOOD!

 

[BioMajorette]

Thanks for your help.

I appreciate your reply to my question. I apologize for not providing the application initially.
I am a theater owner, and I need to hoist a heavy (800 lbs.) set piece with the least visible cables possible. I was hoping some sort of wire or fiberoptics cable might work . . . I could attach a lot of cables . . . I was wondering if there is a basic formula to calculate how many fibers of a particular strength it would take to do the job. Thanks!

 

[Mapes]

Here are a few equations you might apply:

$$\mathrm{wire\,area}=\frac{\mathrm{load}\times \mathrm{safety\,factor}}{\mathrm{material\,strength}\times \mathrm{number\,of\,cables}}$$


$$\mathrm{number\,of\,cables}=\frac{\mathrm{load}\times \mathrm{safety\,factor}}{\mathrm{material\,strength}\times \mathrm{wire\,area}}$$

$$\mathrm{wire\,diameter}=\sqrt{\frac{4}{\pi}\frac{\mathrm{load}\times \mathrm{safety\,factor}}{\mathrm{material\,strength}\times \mathrm{number\,of\,cables}}$$

Make sure to match up your units correctly.

Steel is an ideal material if you consider cost, availability, and strength. I calculate that four 1/8-inch steel rods (or slightly larger cables) would support your load with a factor of safety of five. Would this be suitably low profile?

 

[BioMajorette]

Looks great! Thanks!

I think this might do the trick! Thanks very much. Liz

 

[blimkie.k]

there are these weeds that grow in the field behind my house there amazing. they seem similar to balsa wood but harder and stiffer. i don't know what the name of the weed is but id like to know they grow out of the ground up to about 5 feet. diameter ranches from milimitres to almost 2 inches. Almost like bamboo but not nearly as strong but twice as light. They woulnt be usefuly for structural objects but if they were grown comercially they could be used for making lightweight furniture or something like that haha. extremely light yet strong and organic

 

[mtworkowski@o]

blimkie.k
That's a good observation. Perhaps you could bring one down to the extension service in your area. Or a horticulturist. Interesting...

 

[toughsteel]

Steel wins every time. Good steel cable is double the strength of a kevlar wire Same size of course. However it really only matters how small you can get the filaments in the cable to be.

If you take braided fishing line and made a 1/2inch rope you would get around 6000 pounds safely on it. While a mono-filament of that size might only take 500.

Material itself is important but the way the cable is constructed is much more important when it comes to overall strength. If someone took the time to make steel fibers 0.007 of an inch then braid them into a 1/2 cable they would have an incredibly strong wire that would be extremely difficult to break with anything short of bolt cutters.

Thats just my though on the subject

 

[ThomasEdison]

I would use Aircraft Cable.
Its very strong for its size.
Thats what electricians use to hoist heavy lights when the supports have to look discreete.
Its fairly standard; tried and true.

I've used Aircraft Cable plenty of times to hoist large heavy lights within its approved support strength.

Aircraft cable, which is steel woven cable, is so common that it even can come in different colored nylon outercoatings for weather resistance or looks.