"jim beam" <[email hidden]> wrote in message
news:[email hidden]...
Quoted message said:to continue the peter cole's recent pollution on the subject of
confusing plastic deformation with elastic deformation:apparently, carbon fibers are inferior to 6061 aluminum because they
only elongate 1.5% before failure vs 6061 which he alleged elongates 25%
before failure.first up, he needs to stop exaggerating. 6061 is typically more like
16% in t4 temper - the common bike application. [various online sources]second, and much more important, let's clarify between elastic/plastic
elongation. for a bike application, we are not interested in the
material yielding - yielding = failure. let us therefore keep apples to
apples and concern ourselves with the elastic part of the stress/strain
graph.for /elastic/ deformation, how do carbon and aluminum compare? well,
since aluminum doesn't typically have strain at yield cited, we can't
just look it up, so let's do a little math.young's modulus is only concerned with the elastic region of this graph,
and the formula for that is:E = stress / strain.
E and yield stress are commonly cited, hence we can calculate strain at
yield:strain = stress / E
for a 6061 with E = 69GPa, and 275MPa yield, that gives an elastic
deformation limit of 0.275/69 x 100% = 0.04%.how does that compare again?
I recommend that you "lurk before you leap"; get a sense of the audience and
the regular posters before you post.