Periodic Reporting for period 3 - STELLAR (Development of SmarT Eco-friendly anticontamination technologies for LAminaR wings)
Reporting period: 2022-10-01 to 2023-10-31
The aircraft industry is facing issues with the increase of drag directly impacting the fuel consumption of the fleet. Achieving natural laminar flow requires high surface quality. The accumulation of insect debris on the leading edge of laminar wings has been recognized as one of the most significant operational concerns associated with laminar flow. The main objective of STELLAR is to develop efficient and durable anticontamination coating and cleaning solutions. STELLAR project seeks to gain insight on the understanding of the biochemical transformation of hemolymph during flight phases and the consequent physico-chemical properties of the surface. While it has been confirmed that surface wettability properties and texture play a key role in the adhesion of the insect residues on a surface, STELLAR also highlighted the role of the chemical composition of the coating which can affect the hemolymph coagulation process. The project consortium has gathered cutting edge multidisciplinary knowledge and the needed facilities to provide a deep understanding of the contamination issues. From this approach, new coating and cleaning solutions are developed. Special focus is made on the durability in aircraft environment for the development of anticontamination coatings while the cleaning solution formulation is based on an eco-design approach.
The knowledge acquired and the solutions developed are evaluated through large scale tests : tests in wind tunnel to simulate extreme conditions occurring during flights, short flight tests with SONAIR S200 equipped with cameras and sensors. These tests mainly revealed the easy-to-clean properties of the coating and allow the selection of a promising candidate that will be applied on the slat of a commercial aircraft operating for 6 months at higher altitudes allowing a full validation of the newly developed solution.
The knowledge acquired and the solutions developed are evaluated through large scale tests : tests in wind tunnel to simulate extreme conditions occurring during flights, short flight tests with SONAIR S200 equipped with cameras and sensors. These tests mainly revealed the easy-to-clean properties of the coating and allow the selection of a promising candidate that will be applied on the slat of a commercial aircraft operating for 6 months at higher altitudes allowing a full validation of the newly developed solution.
1. Establishing the link between hemolymph modification (under atmospheric conditions) and interaction with the surface: A comprehensive study on the biochemical modification of hemolymph allowed to determine the main proteins undergoing chemical transformation and the related physico-chemical properties. The laboratory experiments further focused on the evaluation of impact velocity and UV exposure on the biochemical modifciation of hemolymph and the consequent interaction with the surface. The main outcomes from this part of the project is the definition of critical parameters for the design of anticontamination of coating and cleaning solutions; the unexpected and crucial role of chemical composition on coagulation kinetics and the influence of exposure to aircraft environment on the transformation of hemolymph and the consequent increased adhesion on the surface (especially under UV exposure). Part of this work was published ESPCI and CNRS. CIDETEC and UMONS have patented the coating chemical composition.
2. Formulation of smart eco-friendly anticontamination coatings
The coatings are based on several chemistries and include slippery effect and self-healing properties. The formulations were optimized and their durability evaluated. This led to the selection of 3 candidates which were tested following a set of aeronautic requirements (impact and erosion resistance, UV, etc). Several communications (conferences, general publications) were carried out these developments.
3. Development of eco-friendly cleaning solution
SOPURA developed solvent and enzyme-based formulas providing very good detergency effect. The application process was evaluated at laboratory scale and the best solution was tested in real conditions on the test aicraft of SONAIR. Life cycle assessment was carried out on the developed solution and allows to reveal hot spots which might be used for further optimization.
4. Development of a test device for wind tunnel and short flight tests
Fuel tank of the S200 Sonaca Aircraft, selected to be used for testing the 3 coatings, equipped with sensors and cameras by LMSM. The test device was evaluted in wind tunnel, than revised and adapted to satisfy secure flight tests with S200 aircraft.
5. Wind tunnel and short flight tests on selected coatings
The 3 selected coatings were tested in wind tunnel (combined or not with water injection to evaluate self-cleaning under rain) and further tested on the S200 aircraft. Many communication (general press, etc) were carried out during the short flight test campaign.
6. Application of the final selected coating on a slat of a commercial A319/320 aircraft operating for 6 months : the coating was successfully applied on a real slat at SONACA and then installed on the aircraft. Easy to clean properties were verified and maintained during the flying period (with no modification of coating aspect).
A full day workshop has been organized at the end of the project at VKI allowing to present an oveview of the main results obtained in STELLAR and some related projects. Exploitation opportunities are evaluated for the coatings developed, the cleaning solution (for aeronautics sector but also other sectors where similar properties are requested), the testing material and protocols. Collaboration with airlines and aircraft manufacturer for coating evaluation has also been identified as an opportunity for the future.
2. Formulation of smart eco-friendly anticontamination coatings
The coatings are based on several chemistries and include slippery effect and self-healing properties. The formulations were optimized and their durability evaluated. This led to the selection of 3 candidates which were tested following a set of aeronautic requirements (impact and erosion resistance, UV, etc). Several communications (conferences, general publications) were carried out these developments.
3. Development of eco-friendly cleaning solution
SOPURA developed solvent and enzyme-based formulas providing very good detergency effect. The application process was evaluated at laboratory scale and the best solution was tested in real conditions on the test aicraft of SONAIR. Life cycle assessment was carried out on the developed solution and allows to reveal hot spots which might be used for further optimization.
4. Development of a test device for wind tunnel and short flight tests
Fuel tank of the S200 Sonaca Aircraft, selected to be used for testing the 3 coatings, equipped with sensors and cameras by LMSM. The test device was evaluted in wind tunnel, than revised and adapted to satisfy secure flight tests with S200 aircraft.
5. Wind tunnel and short flight tests on selected coatings
The 3 selected coatings were tested in wind tunnel (combined or not with water injection to evaluate self-cleaning under rain) and further tested on the S200 aircraft. Many communication (general press, etc) were carried out during the short flight test campaign.
6. Application of the final selected coating on a slat of a commercial A319/320 aircraft operating for 6 months : the coating was successfully applied on a real slat at SONACA and then installed on the aircraft. Easy to clean properties were verified and maintained during the flying period (with no modification of coating aspect).
A full day workshop has been organized at the end of the project at VKI allowing to present an oveview of the main results obtained in STELLAR and some related projects. Exploitation opportunities are evaluated for the coatings developed, the cleaning solution (for aeronautics sector but also other sectors where similar properties are requested), the testing material and protocols. Collaboration with airlines and aircraft manufacturer for coating evaluation has also been identified as an opportunity for the future.
- The developed anticontamination solutions and evaluation protocols are contributing to the preservation of laminar flow. The coatings lead to slight contamination reduction but mainly show excellent easy-to-clean properties (complete removal of residues with a simple water cleaning).
- Formulation of coatings which have direct impact on insect coagulation kinetics which is an unexpected results never reported in the literature
- Formulation of self-healing polyurethane coating : replacement of a fraction of the binder by self-repairable (under RH trigger) was done with success and provide coatings with promising properties.
- Formulation of innovative cleaning solutions showing synergistic effect with anticontamination coating leading to 100% removal of highly sticky insect debris.
- Design of a test device that can be used in wind tunnel and for short flight test
- Test protocols in wind tunnel to evaluate anticontamination and self-cleaning properties of coatings.
- Demonstration of the coating transferability to real conditions: application of the coating on a slat, installation of the slat on a commercial aircraft, flight operations during 4-6 months with demonstration of easy-to-clean properties.
STELLAR project results will impact all the industrial value-chain. The European value chain of part manufacturers involved in NLF – HLFC can benefit of the results of the project. Sonaca as main manufacturer of slats, flaps and spoilers worldwide will be in pole position to exploit the results of those technologies and transfer it to OEMs. The technology, knowledge and testing protocols can be adapted to a larger field of application which will improve European competitiveness and contribute to the overall environmental impact. New coating and cleaning formulations will be available that meet aviation requirements and provide an anti-contamination effect for leading edge applications. This type of coating may have a wider scope of application (including trains, automotive, wind turbine) and the knowledge acquired will be useful in understanding and minimizing contamination in general.
- Formulation of coatings which have direct impact on insect coagulation kinetics which is an unexpected results never reported in the literature
- Formulation of self-healing polyurethane coating : replacement of a fraction of the binder by self-repairable (under RH trigger) was done with success and provide coatings with promising properties.
- Formulation of innovative cleaning solutions showing synergistic effect with anticontamination coating leading to 100% removal of highly sticky insect debris.
- Design of a test device that can be used in wind tunnel and for short flight test
- Test protocols in wind tunnel to evaluate anticontamination and self-cleaning properties of coatings.
- Demonstration of the coating transferability to real conditions: application of the coating on a slat, installation of the slat on a commercial aircraft, flight operations during 4-6 months with demonstration of easy-to-clean properties.
STELLAR project results will impact all the industrial value-chain. The European value chain of part manufacturers involved in NLF – HLFC can benefit of the results of the project. Sonaca as main manufacturer of slats, flaps and spoilers worldwide will be in pole position to exploit the results of those technologies and transfer it to OEMs. The technology, knowledge and testing protocols can be adapted to a larger field of application which will improve European competitiveness and contribute to the overall environmental impact. New coating and cleaning formulations will be available that meet aviation requirements and provide an anti-contamination effect for leading edge applications. This type of coating may have a wider scope of application (including trains, automotive, wind turbine) and the knowledge acquired will be useful in understanding and minimizing contamination in general.