Ken Mintz Composite Information pg.2 ==

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	A Short Description of Fiber Types and Properties  
  
	Well here goes!  The first installment of "Composite Corner".  This one is a short description of the types
	and properties of the fibers used in composite construction today.	
  
	In terms of weight the glass fibers are the heaviest weighing in at 2.59 grams/ cubic centimeter for E-glass
	and 2.46 g/cc for S-glass. The next lightest are the carbon fibers: Carbon at 1.66 g/cc and Graphite at
	1.8 g/cc.  Next are the Aramid 	(Kevlar) fibers at usually 1.44 g/cc for the most common types used.
	Next is the relatively new fiber called Spectra at 0.97 g/cc.

	After these the fiber types get more exotic, ie. harder to make and much more expensive.  I don't know
	of any homebuilts that use boron fibers or carbon-carbon yet.  Possibly those competing for the low earth
	orbit prize will use them. Most of us composite builders are stuck (so to speak) with fiberglass due to its
	relative cheapness (like most of us).  Carbon-graphite is becoming cheaper and more available.

	Next for consideration is the relative tensile strength of these fibers. ( I'll come up with some tables for this
	information as soon as I can figure out how to scan them out of my notes and sources).  Graphite is actually
	listed as having the weakest tensile strength at about half that of S-glass. Next is Spectra.  After Spectra are
	the  Aramids (Kevlar) which have about the same tensile strength range as that of the glass fibers.
	The weakest of the glass fibers is E-glass.  It is about 25% weaker than S-glass, the next strongest fiber
	material.  E-glass is not generally used in key structural areas like spars for this reason.  Carbon fibers are
	next stongest at about 50% stonger than S-glass though the range varies.  As you can see glass does have
	another advantage other than cost.

	Another factor concerning composite fibers is stiffness.  Here I'll be even more brief.  The Aramids have a
	very wide range of stiffness being the least stiff of the materials listed here on one end of the range to being
	twice as stiff as S-glass on the other end.  S-glass is about 17% stiffer than E-glass.  Carbon is about three
	to five times stiffer than S-glass and Graphite is the stiffest of all the materials listed at about 11 times stiffer
	than S-glass, five times stiffer than Spectra and almost three times stiffer than Boron.  Stiffness is a
	consideration in that it affects how well the fiber will conform to the shape it is being formed into.  The more
	stiff it is the harder it is to get it to bend into complex shapes.  This characteristic of fibers is called "drape",
	a term borrowed from the textile industry.

	S-glass is the most common composite fiber used in homebuilt construction to date I believe and that is
	why it has been used most often as the base comparison here.  It is plentiful and, as I noted earlier,
	cheap in comparison with the other fibers.

	Well, it's time to go to the corn roast.  More on this subject next time..

	Ken Mintz
	Technical Counselor
	Phone: (702) 567-1938
	Email Ken

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