A composite formed of a polymer matrix phase having a reinforcement phase including
polymeric microfibers. The microfibers are preferably formed of a highly oriented
polymer, having a high modulus value and a large surface area. The large surface
area can serve to tightly bind the microfibers to the polymer matrix phase. The
microfibers can be provided as a fully- or partially-microfibrillated film, as
a non-woven web of entangled microfibers, or as a pulp having free fibers. The
microfibers can be embedded in, or impregnated with, a polymer or polymer precursor.
Some composite articles are formed from thermoset resins cured about a highly oriented
polypropylene microfiber reinforcement phase, providing a strong, tough, moisture
resistant article. One composite includes a matrix and reinforcement formed of
the same material type and having substantially equal refractive indices, allowing
the composite to be optically clear.