I was already on it, and would have had it posted before you, John, but Firefox crashed
I used ultimate tensile strength as other websites have suggested it is the standard for strength-to-weight calculations. I would have thought yield strength is more appropriate, but I can't find that data for Lexan.
GE Lexan (clear, no glass) ---72 MPa -----1.2 g/cm3----- ratio 60
Aluminum 6061-T6 ---------310 MPa -----2.7 g/cm3 ---ratio 114
for comparison:
very strong titanium ------- 320
steels have an incredible range of like 40-250 but as far as I can tell (I'm not sure what are the most common types), structural steel is in the 80-110 range.
Amazingly enough, a high quality piece of wood (European ash, is good, apparently) can have a ratio as high as
320! in the direction of the grain though it is a mere 12 perpendicular to the grain.
I'm trying to find some good data on plywood, but it looks to be approximately equal to PC (but of course it is bidirectional, unlike regular wood.)
carbon fiber ----------------3200
kevlar----------------------2100
I know that what is generally considered the strongest material ever created was carbon nanotube fiber (spun by some of my dad's former co-workers
) but that is using some other measurement of strength (I believe Young's modulus).
Note that the properties of these extremely high tensile strength fibers aren't simply comparable with steel and aluminum. You can't build a robot 20 times lighter out of carbon fiber.