Signal instability due to temperature fluctuations, sensor degradation, and debonding introduces additional amplitude loss in the detected signals during acousto-ultrasonic detection, which may be falsely attributed to defects in a structure. First, we determined that the amplitudes of both high-frequency and low-frequency Lamb waves decrease after propagation through a damaged area. Then, we found that the amplitude ratio of such waves not only exhibits a downward trend but is also immune to fluctuations in the input signals. A qualitative numerical expression was proposed to explain this phenomenon, and preliminary experiments were conducted to demonstrate that the amplitude ratio is an effective parameter for mitigating instability in signal detection. Particularly, the number of impacts on a composite laminate was evaluated with respect to changes in the input signal amplitude. Notably, this method can be further simplified by designing a dual-frequency input signal. After conclusively validating the performance of the novel method in a composite subjected to temperature fluctuations, we conclude that the proposed acousto-ultrasonic detection method is robust in mitigating signal instability, and that it yields reliable information for damage evaluation.

由于温度波动，传感器退化和脱胶而导致的信号不稳定性会在声波-超声波检测过程中在检测到的信号中引入额外的幅度损失，这可能会错误地归因于结构中的缺陷。首先，我们确定高频和低频兰姆波的振幅在传播通过受损区域后均减小。然后，我们发现这种波的振幅比不仅呈现下降趋势，而且不受输入信号波动的影响。提出了定性的数值表达式来解释这种现象，并进行了初步实验，证明了振幅比是缓解信号检测不稳定性的有效参数。特别，相对于输入信号幅度的变化，评估了对复合层压板的冲击次数。值得注意的是，该方法可以通过设计双频输入信号来进一步简化。在最终验证了该新方法在温度波动的复合材料中的性能后，我们得出结论：所提出的声-超声波检测方法在缓解信号不稳定性方面具有鲁棒性，并且可以为损伤评估提供可靠的信息。