Analysis of Environmental and Operational Condition Effects on Guided Ultrasonic Waves in Stiffened CFRP Structures

Abstract : Structural Health Monitoring by Guided Ultrasonic Waves for real world applications relies on compensation of operational and environmental effects. The effects to be taken into account are depending not only on the present factors for a particular application scenario, but as well on the structure to be monitored itself. Especially for stiffened CFRP structures, wave propagation and subsequent temperature effects are of increasing complex nature. The load and temperature condition of aerospace components typically vary along the flight cycle of an aircraft and is subject of a vast number of operational and environmental factors. The extensive research on temperature influence on wave propagation and transduction as the most important influence factor in the last years has broad up two widely spread methods for temperature compensation: Optimum Baseline Selection and Baseline Signal Stretch, which can be applied in a combination as well. In this work the existing compensation concept are challenged regarding its applicability to real world structures and environmental and operational conditions. For that purpose experimental data from two structures are analysed. Firstly, the influence of on wave propagation is analysed in the scope of a lab test by data from a stiffened CFRP panel subject to temperature variation. Secondly, the influence of environmental and operational conditions in the frame of a flight test is analysed.