what is the best strength to weight ratio?

[SleeplessNights5150]

Hey all, My first post here. I am designing some roll cages for dune buggys and my research has come to a halt. I am trying to advance the technology of the industry. I wanted to gather opinions as to what the best combination you can think of for best strength to wieght ratio. (example: Aluminum wrapped in Carbon Fiber) Production cost is no object as these will be fully custom and prototype rigs. So what metal and fiber re-enforcement has the best (lightest) ratio in your opinion? Thanks in advance.

 

[Carburize]

I think if you model your approach on current aerospace and Formula 1 technology you will find that carbon fibre is considered the optimum material when strength to weight is the only criteria.

 

[TVP]

SN5150,

Are you sure that strength-to-weight is the only parameter of interest? What about stiffness? For spaceframe structures that are extremely stiff (fully constrained truss-type frames), strength-to-weight becomes the limiting parameter, as long as buckling has been adequately addressed. Metals with the highest strength-to-weight ratio are maraging steels and several metastable Beta titanium alloys. These metals will also have appreciable ductility, fracture toughness, and yielding behavior under dynamic events like rollovers, crashes, etc. Composite structures based on toughened epoxies reinforced with carbon fibers, aramid fibers, or S glass fibers (S is structural glass vs. the normal Electical glass) will all have high strength to weight ratios, but will not show similar fracture toughness, ductility, or yield behavior. Aerospace and high performance racing applications still use honeycomb sandwich construction (skins of fiber-reinforced epoxy laminated over a honeycomb core of aluminum or nomex) for crash structures, which can be difficult to integrate into an open frame architecture-- they are distinctly closed, monocoque structures. Anyway, you should be able to get some preliminary information on strength and density from Matweb, or perform a keyword search on Eng-tips for maraging steel to find additional information in this area.

 

[SleeplessNights5150]

wow, thanks guys...

TVP - Is there a resource for purchasing a small quantity of Titanium Alloy to build a prototype with? Im having some trouble finding a good source without a large minimum order. And it's not exactly something youd find in scrap

A friend mentioned
Chromium Molybdenum
Though I dont know much about using it in fabrication. I've only ever worked with steel.


Thanks for the quick response.. you set me in the right direction. This site is great!

 

[metman]

Chrome-Moly in the vernacular actually means Chrome-Moly Steel which you apparently have some experience.

AISI 4130 is Cr-Mo Steel and has a reasonable stength to weight ratio but hardly cutting edge. It has the advantage of being easily welded without having to pre/post heat.

 

[SleeplessNights5150]

Well, I do have limited knowledge. I'm just an apprentice welder right now but I have some goals for this so thanks for helping me out.

 

[TVP]

Timet, Sandvik, and Plymouth Tube all produce titanium alloy tubing, but you will need to find out directly what kind of minimum quantity they require. Use the following links for more info:

Timet

http://www.timet.com

Sandvik

http://www.titanium.org/business2.cfm?BusinessID=55

Plymouth Tube

http://www.titanium.org/business2.cfm?BusinessID=43

There are some more companies listed in the International Titanium Association Buyers Guide that provide tubing. Use the following link to search:

http://www.titanium.org/business.cfm

 

[btrueblood]

You can also buy short (6' lengths) of Ti tubing from

http://www.mcmaster.com

(look under metal tubing) up to 2" dia.

 

[SleeplessNights5150]

ah great!
great sites... just what I needed.
TVP and btrueblood - Thanks alot.