If you are going to buy small quantities of dry fiber, whether glass or carbon, there are small specialty houses that supply materials cheaper than buying from large prepreggers like Hexcel with all their overhead costs. Composites Specialists in Laguna Nigel, CA is one. These firms buy up excess materials and resell at prices generally much lower than any major supplier can match. And they will sell smaller quantities, but not like 5 yds of glass, which is very small; more like 25-50 yds at a time.
The large companies buy fibers from manufacturers, weave them and impregnate fabric (prepregging) with resins and freeze it for shipment and storage. These are mostly used by commercial fabricators to make aircraft parts and the resin systems cure at 250-350F intended for autoclave cures at 100 psi. Prepreg is far too expensive for home use and overkill for most experimentals. It provides close control over fiber/resin volume and enables use of more toughened resins that absorb impact energies better than room temp curing resins used at home.
Fibers are coated with a sizing which enhances the bond to resins and it does have a shelf-life around 2 yrs for max performance but for homebuilts, any minor reduction in mechanical properties is probably negligible, so even old fibers will work ok. So bottom line is you can get quantities of woven fabric at reduced prices from small resellers.
I came across Bob H's post during a recent google search. Bob is correct, we are re-sellers, distributors and have a weaving facility and warehouse in Canada. We have 2 warehouses in Southern California. Primarily, we sell dry good reinforcements both FRP and Non-FRP. We sell smaller quantities; which can be less expensive (compared to min buys) and have better lead-times. I share an office with the Principal of Composite Specialists and they are one of the principals I represent. If anyone needs assistance please email me at Greg@G2Technical.com.