🚀 go-pugleaf

>>The way we knew it at Hercules was that carbon fibers only had to go 
>>through one 'low temp' furnace while the graphite fibers had to go
>>through both the 'high and low temp' furnaces. The majority of the 

>The difference is in the purity of the carbon content.  There is a
>higher concentration of "real" graphite in the graphite fibers.  Fibers
>are now being made from pitch bases and have high carbon contents, as
>can be seen by the densities (2.1 g/cc for pitch based, versus 1.8 for
>polyarcylonitrile (PAN))

Very true! The higher temp furnace burned off the 'extras' leaving
a higher elemental carbon content. Based on what Agarwal says, 
carbon fibers are at 80-95% carbon while graphite fibers come in 
at +99%. Its a heck of an effort to get that extra couple of percent
but when you want stiffness, its worth it.

>>If I was to design a bow, I would determine what a user wants from
>>the device (a certain shape, an energy distribution, etc...). Then
>>I'd sit down with a flat plate analysis program (a fairly close
>>analogy to the bow) and get the curvatures or stresses that you want
>>for your ideal bow. Materials, thicknesses, and ply orientations can
>>be chosen at this point... Kinda vague?  I know, but I really don't 
>>know what makes a bow good?!

>This approach is acceptable, but not ideal.  If you start with plate
>analysis, you are assuming homogeneous isotropic material.  Consequently
>you will probably end up with a relatively isotropic lay-up.  The actual
>design process (currently) is going to iterative, and not necessarily
>coming up with a true optimum, just a local one.

Assuming a lack of expertise on the analyzer's part, this would give 
them a result that would get them in the ballpark. There are a number
of programs on the market that will walk you thru the numbers/concepts like
MicMac and PC-LAM... You are correct as to the iterative nature of
the problem; it is like designing a ski to yield a constant
radius of curvature under all loads. 

>Becareful about your starting point for design iteration.

>Also, strongly consider braiding processes for tubular like structures
>(such as the bow.)

Braiding would be especially good for a proto bow with a small
factor of safety (or a new and doubtful design). It could keep splinters
from your hands if it blows.

I still have some questions though as to what the 'carbon foam' 
actually is, Rhoacell(sp?) with GR/EP face sheets perhaps? Finite 
element analysis would be good way of finishing the bow design (if available).

Good Luck!



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Chris Stepanian			| "Its my wife, and its my life"
Dept of Ocean Engineering	|
Texas A&M University		|     Lou Reed/Velvet Undergound
CJS1722@ZEUS.TAMU.EDU		|
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