ANALYSIS OF LAMB WAVE DISPERSION CHARACTERISTICS OF THERMOELASTIC ANISOTROPIC LAMINATES BASED ON THE POLYNOMIAL METHOD

A theoretical model of the dispersion characteristics of ultrasonic guided waves in anisotropic laminates with temperature field is developed based on Legendre's polynomial method and Green-Nagdhi thermoelasticity theory to reveal the propagation process of ultrasonic guided waves in multilayered composites under temperature field environment. At the same time, the acoustic frequency domain simulation model of multilayer isotropic and anisotropic laminates in a temperature field environment is constructed to extract the dispersion curves of ultrasonic guided waves of the laminates at specific temperatures. The validity of the proposed theoretical method is verified by comparing the simulation data with the theoretical calculations. After that, the dispersion curves of the ultrasonic guided waves of anisotropic laminates are analyzed by taking laminates composed of unidirectional fiber materials with different layup directions as an example, and the distribution characteristics of the displacement and stress wave structure of the A0 modes at a specific frequency are analyzed in detail concerning the fiber angle of the intermediate ply at the same temperature condition. In addition, the mechanism of the influence of temperature field changes on the dispersion characteristics of ultrasonic guided waves in carbon fiber composite laminates is focused on, the shift laws of the ultrasonic guided wave fundamental modes are pointed out, and the values of the fundamental mode phase velocities at different frequencies and temperatures are listed in detail. In the end, the phase velocity temperature sensitivity change curves of multilayer anisotropic laminates are extracted by utilizing the phase velocity difference values at different temperature conditions, and the phase velocity temperature sensitivity of symmetric and antisymmetric modes at different frequencies is explored, which provides a theoretical basis for ultrasonic nondestructive testing and evaluation of the mechanical properties of multilayer composites.