Rubber, as a kind of macromolecular material often used in large ships, aviation, aerospace, and other fields, has remarkable viscoelasticity at room temperature. Therefore, it is of great significance to evaluate the viscoelastic properties of polymer composites. In this paper, four kinds of rubber materials are taken as research objects. Based on the principle of ultrasonic detection, the viscoelastic evaluation of the sample materials is carried out through experiments and simulations. On the basis of previous research, the surface reflection method (SRM) and the bottom reflection method (BRM) are compared in depth. First, the spectrum of received signals is analyzed, and the storage elastic modulus, loss elastic modulus, attenuation coefficient and loss tangent value are obtained. Secondly, the results of the BRM and the SRM are compared and analyzed in the frequency domain of -6 dB. The results show that both the SRM and BRM are feasible in the evaluation of the viscoelasticity of the material, and the variation trends observed for the above-mentioned parameters in the effective frequency domain are consistent, especially at the center frequency. Finally, aiming at the mode transformation of the acoustic wave around the ultrasonic sensor, the practical performance of the surface reflection method is optimized by increasing the diameter of the ultrasonic sensor.
Keywords: attenuation coefficient; polymer materials; spectrum analysis; viscoelasticity.