Nowadays, in-service damages such as impacts during overhaul or external influences, such as exposure to severe environments with chemical agents, thermal loadings or ultraviolet light have to be taken into account for the design of the elements. Therefore, knock-down factors have to be determined. This knock—down factors take into account an extensive number of conditions such as loads –both static and cyclic-, temperatures, impact damages or the exposure to aggressive mediums such as engine oils. Due to the costs and complexity of performing full scale tests including factors such as temperature and exposure to a variety of aggressive atmospheres, during the qualification, lot’s of test are necessary in order to certify the integrity of the component material.
The actual state of the art is to determine this knock-down factors independently and not in combination of them, meaning that composite samples are for example immersed during a determined time in a fluid and afterwards tested statically at a given temperature.
The innovative idea to develop during this project was to develop a test set-up permitting to expose on the same time the specimen to not only thermal and cyclic mechanical loading, but also to synthetic engine oils atmospheres in order to be afterwards able to quantify how the global interaction of these parameters is and be able to predict failure of real manufactured parts subjected to “near reality” loading (in terms of loading, temperature and oil exposure) scenarios.
Aircraft components are subject to in-service damage from a variety of threats, including impact, chemicals, high temperatures and ultraviolet light. To calculate the probability of failure (represented by knock-down factor (KDF)), empirical data was collected from numerous experiments. Currently, KDFs are determined individually for each threat rather than in combination, increasing the number of tests and simultaneously cost and time. In addition, such procedures do not adequately represent real in-flight conditions.
EU-funded scientists working on the QUALIFY (Qualification of insulation materials to engine oils) project have developed an innovative test set-up. It enables simultaneous exposure of insulation materials to thermal and cyclic mechanical loading as well as aggressive engine oils and temperature changes. The technology allows quantifying global interactions of parameters to realistically predict failure in manufactured parts. In turn, better understanding of materials and components behaviours will foster development of lighter higher-performance parts for important reductions in fuel consumption and emissions.
Thermoplastic organic polymers have been used in the insulation materials due to their good mechanical properties and chemical and temperature resistance. Engine oils for conditioning of specimens have been taken from those in service for two years and in good condition. The team has also designed the test set-up to enable testing of two specimens simultaneously in different environments. As result of the project, an optimized qualification plan for insulator materials to engine oils in “near reality” conditions has been obtained.
Project results will be widely disseminated to end users within the aircraft industry, including manufacturers, suppliers, industrial bodies and related associations. They are expected to be instrumental in the development of new standards of qualification during manufacturing. The novel testing methodologies will also be included in the portfolio of services offered by one of the world's testing, inspection and certification leaders. Finally, partners will share results with materials and components manufacturers in the plastics and composites industries.
Improved testing procedures will decrease production costs and time-to-market while enhancing product quality. Better design of aircraft components for lower weight and higher performance will help reduce the environmental impact of flight.