Scientists from Novosibirsk State Technical University (NETI) have proposed monitoring the integrity of composite honeycomb structures using the thermal method of non-destructive testing.
According to scientists, during the operation of modern aircraft, defects with damage to cellular structures (dents, water or ice in the cellular filler, peeling of the skin) have become more common. NSTU-NETI conducted a study on the possibility of using the thermal method of non-destructive testing (NDT) to search for peeling of the skin.
"During the life cycle, the problem arises of identifying, controlling, and repairing various defects on the surfaces of the aircraft. These defects are often found on the control surfaces of modern aircraft (elevator, rudder, ailerons, wing mechanization elements) and significantly affect airworthiness and flight safety. Therefore, it is necessary to apply the most effective methods for detecting and evaluating defects — in terms of quality, labor costs, and economic component. The task of our research was to explore the possibility of using the thermal method of non—destructive testing to detect peeling skin from cellular filler in composite cellular structures," said Ilya Zverkov, Professor of the Department of Aircraft and Helicopter Engineering at NSTU-NETI.
Nikita Klochkov, a graduate student at NSTU-NETI, and Denis Gavrilov, a graduate student at NSU, used software to simulate the thermal control of a composite honeycomb panel (PCB) in order to test the effectiveness and expediency of using thermal NDTM to search for and evaluate peeling, and then conducted an experiment. Because of the thermal effect, more intense heating of the skin was indicated in the area of its detachment, while the temperature was lower in the area without damage. The thermoprophylogram of the longitudinal axis of the PCB obtained as a result of modeling showed the difference in the obtained temperature of the whole and defective regions. The distribution of the temperature difference field on the sample surface at the beginning of the heating cycle and the end of the cooling cycle was also considered. Because of processing the experimental results, a pronounced area was obtained where peeling of the skin occured.
"At the moment, we are manufacturing an experimental setup that will provide a repeatable heating-cooling cycle over the entire surface of the sample under study. By varying the heating time and cooling intensity, we will find out at what parameters it is possible to quickly detect the peeling area of the skin," Ilya Zverkov added.
The scientist also noted that the thermal imaging method is promising because it has a high diagnostic speed and sufficient accuracy to detect defects.