Garolite

Garolite G-9, G-10 and G-11 are high performance fiberglass composites.

While less glamorous, its properties are very similar to carbon fiber in many ways.

Many circuit boards are made of G-10 Garolite. If you have an old PC motherboard or expansion card lying around, try breaking it in two pieces. You'll find it's amazingly tough. G-10 is also frequently referred to as FR4.

I've seen various technical data reported, but my own experiments indicate all of the mentioned grades have very similar physical performance. G-9 has a melamine binder as opposed to phenolic, and may have higher impact resistance.

Other grades of Garolite are available, but most of them are actually paper or cloth-based composites, that lack the mentioned grade's tensile strength and impact resistance.

Unlike carbon fiber, Garolite is not conductive, and hence won't interfere with radio reception.

Garolite costs approximately 10% of what carbon fiber does.

Garolite is slightly heavier than carbon fiber.

Garolite is quite stiff, but measurably less stiff than carbon fiber is.

Garolite has poorer tensile than carbon fiber, but this may not be as important as impact resistance.

Impact resistance data for carbon fiber is hard to come by, however my own informal tests indicate that Garolite and carbon fiber are similar in this regard.

Like a lot of robot builders, I like to keep a stockpile of material available for when I feel, "moved" to put something together. Garolite's reasonable pricing makes it far more practical to do this with than carbon fiber.

McMaster Carr is the best place to purchase Garolite I've found so far.

Like carbon fiber, it's not healthy to breathe Garolite dust. Use a dust mask rated for fiberglass work and proper eye protection when cutting it.

Uncolored Garolite is generally green, and has a pattern not quite as cool looking as carbon fiber does. However, some thicknesses of Garolite are available in various sporting colors - including the ever-popular black.

Both materials are less prone to bend out of the way than Lexan, and hence may ultimately be subject to more catastrophic failure under heavy impact. Composites have little sense of humor when damaged. They hold up extremely well, until they don't.