Ultrasonic measurement and simulation optimisation method for stress in carbon fibre reinforced polymer laminates based on critically refracted longitudinal waves

The excitation and detection of critically refracted longitudinal (LCR) waves in carbon fibre composite materials are investigated. By utilising the principles of equivalent stiffness and linear elastic ultrasonics, the variations in LCR waves under uniaxial stress are experimentally explored. For materials that exhibit orthotropic anisotropy or are approximately transversely isotropic, models and methods for ultrasonic LCR wave stress detection are established. To determine the stress coefficients of laminated plates, calibration experiments using ultrasonic LCR waves under uniaxial prestress are conducted, and the accuracy of this approach is experimentally validated. Additionally, the mechanical parameters of the composite laminate are determined by employing an inverse algorithm with elastic constants. By substituting actual experimental parameters for material parameters in the finite element model, more precise stress‒sonic coupling simulation results are obtained. An optimisation method for equivalent acoustic-elastic constants based on parameter inversion algorithms is established to increase the accuracy of predicting stress-induced sound velocity changes in simulation models.