Abstract
The acoustic properties of (0-3) composite materials for acoustic matching layer of MHz-range air-coupled ultrasonic transducer are studied experimentally. The composite materials are formed from a mixture of silicone rubber and hollow thermoplastic microspheres. The acoustic properties of the composite materials are measured and compared with Reuss model, which is theoretical model for elastic properties of composite materials. The measured values of velocity and characteristic acoustic impedance of the composite materials agreed well with the theoretical estimation up to 10% weight fractions of hollow thermoplastic microspheres. The optimal value of characteristic acoustic impedance for acoustic matching layer of air-coupled ultrasonic transducer was calculated using transmission line model. The acoustic matching layer having the optimal value was obtained from the composite material, for which the weight percentage of hollow thermoplastic microspheres is 5%. Transmission of air-coupled ultrasonic wave of 1 MHz using piezoceramic transducer with the acoustic matching layer is demonstrated, and the sensitivity of transmission was improved by 10 dB using the optimal composite material.
