Re: more cfrp bleating

Peter Cole wrote:
jim beam wrote:
Peter Cole wrote:
jim beam wrote:
<snip usual wriggle and squirm>

Whatever.


the "brittle" argument is bull*** if you don't understand the failure mode - cfrp does not shatter like glass.

No, it shatters like CFRP, which is different than fiberglass or Kevlar-epoxy composites and certainly very different than aluminum.

it doesn't shatter. we've just seen a thread on that where a fork was ripped through the head tube. it's evident from the fracture that failure was gradual and energetic. but you wouldn't admit that since you don't understand that lack of ductility doesn't mean lack of toughness. unless there's some defect, cfrp fails just like wood - piece by piece, and with significant energy absorption.

Brittle failure is a well known characteristic of CF composites.

what? that it shatters like glass??? bull***.


That said, it is possible to design energy absorbent *structures* with CF composites. Such structures usually rely on the tearing of fibers from the composite rather than simple fiber tensile failure. I posted an example of this in the Audi design for a tubular crash structure. The example of the steerer tube tearing through the head tube is similar,

which contradicts your earlier statement. which one do you want peter? you can't have it both ways.



but not representative of a more typical failure (in bicycles) of a tubular beam failing in bending.

bull***. you have no experience with this material and have never tried to make any cfrp bike componentry fail or you'd never be able to make that statement. not without /knowing/ yourself to be a bullshitter at any rate.



In the case of CF composites, lack of ductility does mean lack of toughness -- by definition.

finally, the truth starts to dawn...


You continue to confuse force and energy.

er, no. you're the one with the fundamental concept problem.



what? peter cole bull*** on something he doesn't know about? surely that would never happen!

Whatever.


You forget, it was the Boeing guy (and anyone else you care to consult) who used the term.

er, you mean the guy using emotive language designed to stir up controversy. "brittle" to most lay persons means that something shatters like glass. this is /not/ the case with this material.

"Brittle" is a term commonly used to describe CF-epoxy composites by experts in the field.

er, "brittle" is a term used by self-proclaimed "engineers" that don't know what they're talking about but want to stir up fear by implying cfrp shatters like glass.


> Lack of "toughness" is another.

and that is bull***. cfrp can be /extremely/ tough. see above for misapplication of "fear".



and apparently succeeding if the ridiculous bleating on r.b.t is a gauge.

Nothing in common, actually. The Boeing engineer's primary charge is that the testing protocols are insufficient for the new technology.

the "new" 30 year old technology that's been used in mil aps that whole time. and it's especially ironic given that planes were made of wood, that natural composite.
http://en.wikipedia.org/wiki/Hughes_H-4_Hercules
http://www.warbirdalley.com/mossie.htm

what? ignore facts? peter cole would never do that!

What "facts"? The problem is safety, specifically crashworthiness.

ah, the peter cole ethereal undefined crap. just like "impact".

so how much "crashworthiness" does a plane need peter? nose in at 700kts? would that be reasonable?

Boeing tested a fuselage section per existing FAA requirements and claimed that those tests validated their computer models. The Boeing employee claims that the tests, which were designed to certify metallic fuselages, are not sufficient. I think he has a case.

based on what? emotive fear-mongering non-comprehension of the materials? from the guy that thinks cfrp shatters like glass??? from the guy that doesn't understand the distinction between elasticity and plasticity??? yeah, that's a /real/ sound basis for judgment!





undefined emotive sensationalism is so much crap. especially from a guy that calls himself an "engineer".


The Boeing engineer argues that the new material in a fuselage application requires more testing to qualify it. His opinion is that the design would fail such tests.

but boeing have tested to industry standards. what more do you want? undefined "impact" testing?

The Boeing engineer said he wanted a fully loaded, full fuselage section at 30 fps. He would also like to see fire resistance added to the test.

why does cfrp have to withstand /more/ than metal???

and the fire resistance is bull*** - the plane is /full/ of toxic combustibles, not least of which is fuel. if you can't exit the plane in 90 seconds, you're pork crackling. cfrp won't make any damned difference to that.




still, as part of the old saying goes, "you can fool some people all of the time", and thus it is proved.

Nothing is "proved". You don't even have the facts straight.

typical peter cole. cherry pick the points you want to argue and ignore the others that make them a crock.

You didn't (as usual) address the points I raised.

er, inability to read or understand basic science on your part is /not/ failure to address on mine.




I address every point you raise.

no you don't!!! what about the long and successful history of composites in a/c over the decades. since the dawn of flight in fact. you just routinely ignore anything inconvenient, then proceed as if nothing is wrong.

Yeah, OK, wood was used first. I am aware of that, I've toured the spruce goose, my dad was flown into London on a mosquito during the war. I've worked on various boat hulls, wood plank, molded plywood, glassed plywood, and plain glass. I'm very aware of the relative qualities.

The specific topic is crashworthiness of composite fuselages. This is a new application.

it's not "new". and it's not inferior - your implication.



that's bull***.

Whatever.


You should return the courtesy -- but I suppose that's an oxymoron.

yeah, and the day you don't bull*** is the one i'm waiting for too.

Whatever.

you're a bullshitter.
Whatever.

but you are.

Whatever.

get with the program. learn about this stuff /before/ you run about like chicken little. buy a carbon fork [nashbar, $99, bike swap, much less] and try to destroy it. go to an r/c model plane store and buy some cfrp forms and mess about with them. break them. and please please please /try/ to get the basic science right - you have no basis for criticism if your fundamentals are wrong.
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