Design of low frequency ultrasonic transducers by 1-3 tubular piezocomposite

Transverse piezoelectric (TP) mode 1-3 tubular piezocomposites have been developed recently for low frequency ultrasonic transducer applications. The new piezocomposite made of piezoceramic tubes embedded in a polymer matrix has many unique features, such as increasing the tunability of acoustic impedance, enhancing the effective piezoelectric responses and improving the electrical impedance matching with the driving circuit. This paper theoretically described the surface displacement profile of 1-3 tubular piezocomposites under uniaxial stress. The effective piezoelectric coefficients of 1-3 tubular piezocomposites have been derived in terms of the tube volume fraction, tube size and the elastic constants of the matrix polymer. The theoretical analysis and experimental results indicate that the elastic parameters of the polymer matrix have significant effects on the performance of 1-3 tubular piezocomposites. By optimizing the structure of the composite and elastic properties of the polymer matrix, the 1-3 tubular piezocomposite has a exceptionally large effective piezoelectric coefficient, d₃₃, and less undesirable resonance modes. A low electrical impedance and large effective piezoelectric coefficients suggest that the TP mode 1-3 tubular piezocomposites are superior to conventional 1-3 rod piezocomposites in low frequency ultrasonic transducer applications