Reflection of plane waves at medium-composite interfaces and input acoustic impedance of laminated piezoceramic polymer composites

Plane wave propagation at the composite-medium interface is analyzed for the piezoceramic polymer composites with laminated periodic structure. It is found that the input acoustic impedance of the composite depends on the elastic properties of the medium at the interface and in general is a complex number and dispersive. It is also found that the reflected wave from the medium-composite interface suffers a more than 180° phase change, which implies that the thickness of the conventional antireflection "quarter wave matching layer" at the interface should be less than a quarter wave length.