MMCs can have much higher strength-to-weight ratios,[2] stiffness, and ductility than traditional materials, so they are often used in demanding applications.
MMCs typically have lower thermal and electrical conductivity and poor resistance to radiation[citation needed], limiting their use in the very harshest environments.
For example, carbon fibers are commonly used in aluminium matrix to synthesize composites showing low density and high strength.
In structural applications, the matrix is usually a lighter metal such as aluminum, magnesium, or titanium, and provides a complete support for the reinforcement.
Because the fibers are embedded into the matrix in a certain direction, the result is an anisotropic structure in which the alignment of the material affects its strength.
Later on, when they are cooled down to the ambient temperature, residual stresses (RS) are generated in the composite due to the mismatch between the coefficients of the metal matrix and fiber.
In some cases, thermal RS are high enough to initiate plastic deformation within the matrix during the manufacturing process.
Ultimately, the increase in elastic modulus is significant because the metals get the benefit of the higher specific stiffness of ceramics while retaining some ductility.
[14] For example the Cu/Al2O3 system has a high thermal expansion mismatch causing localized stresses encouraging crack propagation in the form of delamination.
Therefore, pinning them causes a large increase in the energy and stress required for plastic deformation (see Precipitation hardening).
Today these applications are found most often in aircraft components, space systems and high-end or "boutique" sports equipment.