Of course, these materials are not generally usable as fibers
alone, and typically they are impregnated by a matrix material
that acts to transfer loads to the fibers, and also to protect the
fibers from abrasion and environmental attack. The matrix
dilutes the properties to some degree, but even so very high
specific (weight-adjusted) properties are available from these
materials. Metal and glass are available as matrix materials, but
these are currently very expensive and largely restricted to R&D
laboratories. Polymers are much more commonly used, with
unsaturated styrene-hardened polyesters having the majority of
low-to-medium performance applications and epoxy or more
sophisticated thermosets having the higher end of the market.