Study On Fabrication And Properties Of2-2Piezoelectric Composites

2-2piezoelectric composites combine high piezoelectric properties of piezoelectric ceramic and flexibility of polymer.2-2piezoelectric composites have a larger electromechanical coupling coefficient, broad-band, lower acoustic impedance and weak lateral coupling. They have been extensively applied in the ultrasonic and underwater fields.In this article, the improved dice-fill was used to prepare2-2piezoelectric composite materials. We discussed the influence of the heat-treating and coupling agent on the properties of piezoelectric composites. The effects of both the size and type of polymer as well the size of piezoelectric vibrators on the vibration mode of composites were studied, Theoretical analysis about the vibrators of composites was by ANSYS. Conclusions are as follows:1. Temperature stability of the resonant frequency of piezoelectric vibrators was able to be improved by the treatment of50-80℃. Coupling agent can improve the bonding strength of the polymer phase and piezoelectric phase. Tensile strength of composites dealed with ND-42was up to1.66MPa.2. The size of the piezoelectric vibrator has an important influence on its vibration. Vibration of piezoelectric vibrator has nothing to do with the width, if T》 d1, L》d1. When the ratio L/T is great than11, thickness vibration was not couple with dimensional vibration, but the loss is much. when the ratio L/T is little than2. When the dimensions of piezoelectric vibrator is T=3.8mm, d1=1.4mm, L=9mm, piezoelectric vibrator that have a single thickness extension vibration mode and low-loss be got. ANSYS finite element modal analysis is consistent with the measured results.3. The resonant frequency of the piezoelectric composites have a direct relationship to binding force that it suffered. The greater the binding, the higher the resonant frequency. There were three kinds of vibration in piezoelectric composites that have a low width of polymer. They were natural vibration, deformity vibration and lateral coupling vibration. They were all related to width of polymer. Limit of deformity vibration is0.1mm, limit of lateral coupling vibration is0.4mm for PU. Both deformity vibration in piezoelectric vibrators and restraint of polymer played a important role in bandwidth. As reducing the deformity vibration, increase the restrain the bandwidth will be larger.4.The elastic modulus of the polymer have a big impact on the vibration char-acteristics of composite materials. The material of high elastic modulus can make a coupling vibration between the piezoelectric vibrator easily, while the low elasti c modulus material can prevent this vibration. The cycle-coupled vibration was very weak when the polymer was polyurethane adhesive with polymer width d2=0.3mm and piezoelectric phase width d1=0.7mm, the composite acoustic impedance was17Mrayls, the electromechanical coupling coefficient was0.58and the bandwidth was10.5kHz.