In general, for mechanical properties, one of the components will have a high elastic modulus and low ductility and the other, the matrix, will have a lower elastic modulus and higher ductility. The high elastic modulus material is frequently used in the form of a fine fiber to yield a fiber reinforced composite material. The matrix protects the fibers from damage and permits external load transfer to the fibers. Both continuous and short fibers and whiskers may be employed. Small particles may also be used as the reinforcing phase to give a particle reinforced composite.

The photograph shows a niobium matrix reinforced with niobium carbide whiskers to yield a high temperature composite material. The ceramic whiskers were produced in the metal matrix by the directional solidification of a niobium/carbon eutectic alloy.