低频多模式超声兰姆波超薄层状横观各向同性复合材料定征方法:理论与实验

Low frequency ultrasonic multi-mode Lamb wave method for characterizing the ultra-thin transversely isotropic laminate composite:theory and experiment

研究使用低频多模式超声兰姆波估计超薄层状横观各向同性复合材料的弹性常数、密度和厚度等参数的方法。这里“超薄”的概念是指材料厚度远小于材料中的声波波长，导致在时域上材料前后界面的各次回波信号相互混迭。文章分析了沿平行和垂直于纤维两种方向上，在超薄层状横观各向同性复合材料中传播的低频兰姆波的色散特性，提出在最小二乘意义下以材料多模式兰姆波色散曲线为基础的反向算法对材料进行了参数估计．文中分析了影响估计准确性的各种因素，研究了方法对材料各参数的灵敏度及其在误差传递中的意义，建立了评判反演材料参数准确度的理论依据。结合超声泄漏兰姆波频域分析方法并使用超声耦合剂耦合方式和一对中心频率为 ２ＭＨｚ的宽带纵波换能器，实验结果证实该方法能够准确估计的单向玻璃纤维增强聚醚砜（ＰＥＳ）的材料参数．

A low-frequency multi-mode ultrasonic Lamb wave method suitable for characterizing elastic stiffness tensors, thickness and density of the ultra-thin transversely isotropic laminate composite is presented. The 'ultra-thin' there means that the thickness of the plate is only a fraction of the ultrasound wavelength. The dispersion properties of the low frequency Lamb wave propagating along and parallel to the fiber direction are derived, which is the basis of the multi-mode Lamb wave characterization method. In conjunction with the method of least square, the secant algorithm is used to estimate the parameters of the ultra-thin fiber-reinforced composite layer. The reasons for evaluation error of the parameters and the sensitivity of the method to different parameters are analyzed. Using the ultrasound coupler and a pair of broadband longitudinal wave transducers with 2 MHz center frequency, we can successfully estimate the parameters of the ultra-thin grass fiber reinforced PES composite layer with by employing the leaky guided wave frequency-domain analysis method.