Dual-FBG arrays hybrid measurement technology for mechanical strain, temperature, and thermal strain on composite materials

Abstract

This paper proposes a hybrid measurement method using dual-FBG arrays to monitor the mechanical strain, temperature, and thermal strain during spacecraft re-entry. This method effectively separates temperature and mechanical effects and enables the simultaneous measurement of three physical parameters. Four service temperatures applied by the spacecraft were simulated to illustrate the application prospects of the method, with the highest test temperature being 160 °C. Under the thermal non-steady state, the average absolute error of the temperature measurement between the dual-FBG and the thermocouple did not exceed 2.799 °C. Meanwhile, the dual FBG-based thermal strain calculation was compared with the thermally measured strain with a relative error of no more than 6.520%. A finite element model at different temperatures was developed to calculate mechanical responses and is compared with the results obtained by FBG. The results show significant agreement between the measurement and the simulation, with a maximum error of 3.61%. These results provide a reliable reference for measuring the thermal response of the spacecraft.