Low Temperature Effects on Guided Wave Structural Health Monitoring Signals

Kurzfassung

Structural Health Monitoring (SHM) has become a critical technology for maintaining the safety and performance of high-value structures, particularly those exposed to extreme environments such as cryogenic temperatures. Applications such as hydrogen storage tanks and aerospace components experience mechanical and thermal stresses that can degrade material properties, increase brittleness, and compromise structural integrity. In such conditions, traditional inspection methods may be impractical, whereas SHM provides a reliable means for real-time monitoring and early damage detection. Among SHM techniques, guided wave (GW) methods are particularly promising for fiber reinforced polymers, offering long-range coverage and high sensitivity to various defect types. However, GW signals are also sensitive to environmental and operational factors, including temperature, mechanical loads, and surrounding media (e.g., moisture, ice, gas), which can lead to signal variation unrelated to damage. Without proper compensation, these effects may obscure actual damage or result in false positives. This study investigates the influence of cryogenic temperature and surrounding media on GW signal behavior in a unidirectional carbon fiber-reinforced polymer panel instrumented with co bonded DuraAct piezoceramic transducers. The specimen is subjected to controlled thermal cycling from liquid nitrogen temperature to room temperature, while guided waves are recorded across a wide frequency range. Results demonstrate distinct temperature and frequency-dependent behavior in both A0 and S0 wave modes. Amplitude and time-of-flight characteristics reveal strong interactions between temperature, transducer performance, and media boundary effects. These findings underscore the importance of environmental compensation in GW-SHM systems and highlight new opportunities for using wave behavior as a dual indicator of both structural health and environmental state.