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提出低频多模式超声兰姆波定征方法来估计超薄层状单向纤维增强复合材料的密度、厚度、弹性常数等参数。这里“超薄”的概念是指材料厚度 h远小于材料中的声波波长 λ,导致在时域上材料前后界面的各次回波信号相互混迭。分析了沿平行和垂直于纤维两个方向上 ,在超薄层状单向纤维增强复合材料中传播的低频兰姆波色散特性 ,提出在最小二乘意义下以材料色散曲线为基础的反向算法对材料参数进行了估计。文中分析了影响估计准确性的各种因素 ,研究了该方法对材料参数的灵敏度及其在误差传递中的意义。结合超声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 2 MHz的宽带纵波换能器 ,实验结果证实 ,该方法能够准确估计 h<0 .0 5 λ的单向玻璃纤维增强双酚 A型聚砜 (PSF)复合材料的材料参数
A low-frequency multi-mode ultrasonic Lamb wave method is proposed to estimate the density, thickness and elastic constants of ultra-thin layered unidirectional fiber-reinforced composites. The concept of “thinness” here means that the thickness h of the material is much smaller than the wavelength λ of the acoustic wave in the material, resulting in the overlapping of the echo signals of the front and back interface of the material in the time domain. The dispersion characteristics of low frequency Lamb wave propagating in ultrathin layered unidirectional fiber reinforced composites parallel to and perpendicular to the fiber are analyzed. The inverse of the dispersion based on the material dispersion curve is proposed in the least squares sense The algorithm estimates the material parameters. In this paper, various factors affecting the accuracy of estimation are analyzed, and the sensitivity of the method to material parameters and its significance in error transfer are studied. The results show that this method can accurately estimate the value of h <0. 05 λ with the method of ultrasonic wave leakage Lamb wave analysis in frequency domain and using ultrasonic coupling agent coupling method and a pair of wide-band longitudinal wave transducer with center frequency of 2 MHz. Material Parameters for Unidirectional Glass Fiber Reinforced Bisphenol A Polysulfone (PSF) Composites