Friday, November 23, 2012

Carbon fiber bridge from 2005 SAMPE competition

While at UCSB, I built a bridge from carbon fiber and aluminum with the help of three other students. We took first place in the SAMPE lightweight bridge-building competition held at Long Beach in 2005. The bridge spanned 24", weighed 2.62 lbs, and supported 8905 lbs at mid-span before failure. It was built from pre-made carbon fiber tubes for compression loads, which we joined together with aluminum end brackets. We added unidirectional carbon fiber ribbons to handle tension loads. The fibers were pre-impregnated with epoxy resin, and kept in a freezer until they were laid in place and cured at high temperature and pressure.




17 comments:

Steven Huang said...

Wow, 9 tons over 24"... that's pretty amazing. Weighs only 3 pounds too, damn great job.

Unknown said...

A ton is 2,000 lbs...

Anonymous said...

It's actually only 4.5 tons, but still impressive!

Anonymous said...

"Only" 4.5 tons.

Anonymous said...

Uh no, a ton is 2,000 lbs. A tonne is 1,000 kg (=2204.6 lbs).

Anonymous said...

"Uh no, a ton is 2,000 lbs. A tonne is 1,000 kg (=2204.6 lbs)."

even if this were the case, he said ton, not tonne, and people usually refer to it as a "metric ton" rather than a tonne. And even if he had meant to say 9 tonnes, he was still wrong.

Anonymous said...

The author made reference to tonne nor ton ... go away!

Anonymous said...

I think he meant 9 metric assloads.

Anonymous said...

For the rest of the world this would be...

"The bridge spanned 61cm, weighed 1.19kg, and supported 4039kg at mid-span before failure."

Anonymous said...

You guys are all idiots. He was obviously referring to tongues. An adult male giraffe's tongue weighs precisely 989.444 lbs.

Martin Marincic said...

Curious, why measure the span in inches, the load in pounds yet the bridge in grams? Why not just use metric for the entire system?

I realize you personally are not in charge, but if the competition is to show creativity, logic and insight, then perhaps some logic in it's rules and measurements would give a good example to follow. Surely the whomever in charge cannot find a good reason for not making this logical change.

Ben Krasnow said...

Of all the interesting things that we could be talking about (carbon fiber engineering, high-temp/pressure curing, machining, contact stress, bridge design, etc), it seems a shame that all of the comments except one concern units. However, since you all asked...The benchtop scale measured in grams, and the load-application device measured in pounds. Since this was a competition, it was easier for the judges to just directly copy the number from the scale/device directly to the scoreboard without any conversion. There would be less chance for error, and everyone in the crowd could see that the number was copied correctly. The mixed-system P/W value is pretty silly, and many students at the competition commented on how creating such a value on school coursework would result in a beat-down and a low grade from the professor. Nonetheless, the lbs/g number creates a nice value ranging from 0 to 10, which was handy.

CrankyMatt said...

What kind of kit was team STAN using?
(apparently one that went to 11)

Ben Krasnow said...

CrankyMatt, Stan worked (works?) at Scaled Composites, where he helped build SpaceShipOne, winner of the Space X Prize in 2004. Stan often entered the contest, but did not compete with the students. He just tried to outdo himself every year. Needless to say, he knows an awful lot about making lightweight composite structures.

matteo said...

Very impressive, Ben!
What was the failure mode, and do you have a photo of what it looked like at 8,906 lbs? (which seems to come in around 123.9 centumpondus, btw)

Ben Krasnow said...

matteo, the bridge failed when the vertical straps that carry the load up to the frame delaminated. This was frustrating since that portion of the bridge shouldn't require much engineering (the straps are just simple tension members that wrap around the frame. I seem to remember having trouble manufacturing those pieces since the whole bridge didn't fit into the autoclave, and so the straps may have been cured at room temp or "by hand" with heat guns. With proper vacuum-bagging and autoclave, I really doubt there would have been a failure in the straps. Sorry, I don't have any photos.

matteo said...

thanks ben- impressive even so!

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