Metal Matrix Composites (MMCs) can offer increased specific strength and stiffness, increased toughness, and an ability to operate at high temperatures. However, the mechanical properties of MMCs can be greatly influenced by residual stresses that result during fabrication from the differences in coefficients of thermal expansion of the constituents [1]. There are a number of non-destructive techniques for measuring residual stresses in these types of composites. The two most widely used techniques are x-ray and neutron diffraction. The x-ray diffraction technique is limited in that it has small penetration depths and beam sizes which are generally much greater than the reinforcement diameter. Although the neutron diffraction technique can provide through-thickness measurements, the availability of the specialized test equipment is a limitation, due to the necessity for using a neutron source [2]. An alternative technique for measuring residual stresses is using ultrasound.