Multi-layered composite structures are becoming widely used in industry. The quantitative evaluation of the quality of bonded interfaces is critical. With the introduction of composite materials as a substitute for metal, the potential for reducing the overall weight of structure is being realized. The composite structure must be designed layer by layer in order to meet the same functional specifications that were met by the previous metal design. The resulting laminate is a sophisticated product with a complex structure and anisotropic material properties. Because of its complexity and anisotropy it is very difficult to inspect. Conventional inspection methods cannot be used and new methods must be developed.