The Moscow Aviation Institute (MAI) has created a methodology for calculating fatigue strength of composite materials for Superjet 100

Photo by © Moscow Aviation Institute Press Service

Import substitution in the aviation industry requires not only the development of new materials, but also the improvement of their research methods. In particular, to accelerate the process of creating new aircraft it is important to minimise the time and costs of in-situ testing. Specialists of the laboratory No. 2 Composite Materials of NIO-101 MAI have developed a comprehensive methodology for calculating the fatigue strength of Superjet 100 airframe units made of polymer composite materials (PCM), which will speed up the process of substantiating their durability.

‘The methodology is based on a foreign mathematical model of composite material behaviour, widely recognised in world practice. The initial model was validated by Ghent University specialists on experimental data from the Japanese corporation Honda Ltd. In MAI it was adapted for application to composite units of Superjet 100, an aircraft with a different level of responsibility and a larger size,’ MAI told.

Adaptation required the development of a number of digital solutions. MAI specialists created a programme for processing experimental data and author’s loading programmes for testing special PCM specimens on a servo-hydraulic machine, which were patented. The developed methodology makes it possible to assess the durability not only of the original PCM structures, but also of their repairs, including those using adhesive and bolted joints. At present in Russia there is no similar methodology, both computational and experimental, to assess the durability of repairs of composite units.

‘To substantiate the fatigue strength of Superjet 100 PCM units, life tests are carried out, during which the structures are subjected to cyclic loads similar to those experienced by the aircraft during flight. The number of load cycles must exceed the actual load up to a ratio of 1:4. In order to assess in advance how well the structure will meet such stringent requirements, for example in case of composite replacement in the structure or after adhesive repair, the calculation method developed by the IARI is needed. That’s why the works on fatigue strength calculation methods become of critical importance,’ the head of the laboratory Egor Nazarov noted.

At the moment MAI specialists have developed models for calculation of elementary samples of imported PCM materials and validated them based on test results. The developed calculation methods of structural-like samples, both zones of the structure itself and zones with performed repairs, are waiting for the end of field tests for their validation. Computational models of aircraft units are under development and after completion will be handed over to the customer for independent validation.

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