Thermo-structural Qualification of a Composite Control Surface

Control surfaces of launch vehicles are made of high-temperature composite materials, in order to operate at elevated temperatures effectively. The design of a composite control surface was validated by carrying out a thermo-structural functional test on the prototype, simulating the flight conditions. The hardware experienced simultaneous aerodynamic loads (applied as localized resultant loads) and thermal environment (applied using short-wave infrared heating system) during the qualification test. Test was executed using an open-loop load control for the structural loads and an open-loop heat flux control (five different profiles) for the thermal environment. The main outcome of the test was the functionality check of the tip control of the control surface, which was demonstrated successfully in high-temperature environment. In order to achieve this, a scheme was designed to de-link the load on the tip of the control surface, before the functionality check. Additionally, the temperature experienced by the shaft of the tip control was measured and verified to be within the acceptable limits of the material. Estimation of natural frequency of the entire structure before and after the qualification test ensured structural integrity of the hardware.