🚀 go-pugleaf

>>What is the difference in composition and mechanical properties
>>between carbon and graphite fibre?
>>Why carbon fibre materials are generally considered better than
>>fiberglass?
>>What is carbon foam (used in construction of bow limbs)
>>Where to get carbon composites in small quantities?
>
>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))

>Carbon fiber, in general, has a higher stiffness than glass fibers
>which would allow you to use less fibers for the same stiff bow. The
>only problem is that the strength is not necessarily as good as the
>fiberglass. 

Much higher stiffness!  35Msi compared to 5-10Msi.

>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.

Becareful about your starting point for design iteration.

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


-- 
Christopher M. Pastore 	    |Life would be so pleasant
NC State University         |If we all could be
Textile Materials Science   |Helpless, homeless creatures
cpastore@nelson.tx.ncsu.edu |Marching to the sea.