Materials

These figures are culled from around the web. I've seen significant variations from test to test.

Prices also vary widely from source to source and are provided only for comparison.

Material	Density (lbs/in^3)	Tensile Strength	Yield Strength	Izod Impact	Cost / Lbs	Notes
Titanium 6AL-4V	.174	145kpsi	132kpsi	.	$25	Very tough, springy and dent resistant. Difficult to cut. Titanium Joe
Aluminum 7075-T6	.102	82kpsi	73kpsi	.	$12	Comes surprisingly close to Ti's strength / weight. Cheaper and easier to work with than Ti. Online Metals
Aluminum 2024-T3	.102	70kpsi	50kpsi	.	$10	Like 7075-T6, but more ductile. More prone to dent, less prone to break. Online Metals
Aluminum 6061-T6	.102	45kpsi	39kpsi	.	$5	Not as strong as other alloys, but cheaper and more available. Online Metals
Lexan / Polycarbonate	.043	9.8kpsi	9kpsi	15ft-lb/in	$6	Very tough plastic. Can crack under high pressure (like when bolted). Loctite will cause it to become brittle and shatter. McMaster Carr
UHMW	.034	6.8kpsi	3.4kpsi	"No Break"	$4	Even "tougher" than lexan with less tensile strength. Very light. Will not break / crack. Popular for use in frames. McMaster Carr
Garolite - (FR4, FR5, G9, G10, G11)	.065	40-50kpsi	.	6.5-9ft-lb/in	$10	High performance fiberglass composite. Properties similar to carbon fiber at much lower cost. Not as stiff and somewhat heavier. Does not conduct electricity. The listed "alloys" have similar properties. McMaster Carr
Carbon Fiber	.05	120kpsi (varies)	.	.	$100	Carbon fiber is a high performance composite material. It is extremely stiff, strong and quite expensive. Many varieties with varying properties. Robotcombat.com Dragon Plate