ABSTRACT

In this paper, local damping behaviour of S₀ ultrasonic Lamb mode is investigated to determine the reason of amplitude reduction of signals come from a rich resin defect in a composite plate. A four-layer woven glass fibre-epoxy (WGF/epoxy) composite plate, containing a predefined rich resin area as the damage, has been manufactured and inspected with S₀ Lamb mode via through transmission and pulse-echo method. Results have shown that there is a considerable amplitude reduction in the transmitted wave while a negligible damage reflected wave has been captured in the related receiver. An experimental based method has been employed in order to extract Rayleigh damping coefficients for the healthy composite plate, followed by a novel methodology to evaluate the damping coefficients at the defected area. Having calculated Rayleigh damping coefficients for both damaged and undamaged areas of the composite plate, several finite element simulations have been carried out, in order to quantify the wave amplitude reduction due to attenuation at the damage. The Amplitude Reduction Ratio (%ARR), obtained from numerical simulation matches closely with experimental ARR, represents that the proposed method for Rayleigh damping coefficients evaluation at the rich resin area can be used for further rich resin defect investigations.

摘要

本文研究了S ₀超声波兰姆模式的局部阻尼行为，以确定信号幅度减小的原因是复合板中的富树脂缺陷。一个四层编织玻璃纤维-环氧树脂（WGF/环氧树脂）复合板，包含一个预定义的富树脂区域作为损坏，已经制造并用 S ₀检查Lamb 模式通过直通传输和脉冲回波方法。结果表明，传输波的振幅有相当大的降低，而相关接收器中捕获的反射波损坏可忽略不计。为了提取健康复合板的瑞利阻尼系数，采用了一种基于实验的方法，然后采用了一种新的方法来评估缺陷区域的阻尼系数。计算复合板损坏和未损坏区域的瑞利阻尼系数后，进行了多次有限元模拟，以量化由于损坏处的衰减引起的波幅减小。从数值模拟中获得的幅度减小比 (%ARR) 与实验 ARR 密切匹配，