FBG-based strain monitoring and temperature compensation for composite tank

Abstract

The composite tank has become the trend and focus for the power system of the new generation aerospace vehicles. However, the evaluation methods and monitoring technologies for composite tanks under cryogenic experiments are still challenging problems. In this paper, fiber Bragg grating (FBG) is used to measure the strain and temperature of the stiffened composite tank under room and cryogenic temperature pressurization experiments. Temperature compensation based on the thermal stratification phenomenon is proposed to increase the reliability and accuracy of strain monitoring in cryogenic environment. A non-linear fitting based calibration method of temperature sensitivity coefficient addresses the non-linear relationship between the FBG wavelength and temperature change from liquid nitrogen temperature to room temperature. The results show that the average absolute error of the nonlinear calibration method in the cryogenic test is less than 50 με. It is also illustrated that the structural features of the sensor location can be qualitatively determined according to the strain changes of different sensors. The comparison of strain increments in the cyclic pressurization illustrated that the different performance degradation phenomena of different regions could be observed. These results provide strong support for the high stability and reliability of FBG-based composite tank strain monitoring.