Periodic Reporting for period 2 - GRAPHICING (Application of graphene based materials in aeronautical structures for de-icing, lightning strike protection, fire barrier and water absorption prevention purposes)
Période du rapport: 2022-01-01 au 2023-02-28
In order to improve aircraft efficiency and to decrease fuel consumption and carbon dioxide emissions innovative light weight polymer composite materials with superior mechanical properties for advanced aircraft structures are in development. As an ultimate development goal such new lightweight materials should also enable advanced integration of additional functionalities. Current functional aircraft components are designed separately and integrated afterwards. A future advanced integrative manufacturing approach is leading to fewer but also more complex parts with multiple functions resulting in better energy management, aerodynamic efficiency, improved noise containment and additional weight reduction.
A primary candidate for the development of advanced functional lightweight materials and systems with the capability for more efficient integration in aircraft structures are thermoelectric de-icing systems essential for aircraft safety by avoiding in-flight icing. Present state-of-the-art systems consist of metal or composite structural aircraft components coated with polymers containing a high amount of graphite.
The objective of the GRAPHICING project was the development of multifunctional aeronautical structures (de-icing, lightning strike protection, fire and water barrier) based on graphene related materials – among other properties graphene has unique electrical, thermal and impermeable properties - focused on an effective De-Icing system.
The most important results of this project are, firstly, that four targeted functionalities of de-icing, lightning strike protection, water absorption barrier and flame inhibition can be achieved with the graphene-based materials. Moreover, graphene-oxide can be produced via an electrochemical process in an environmentally friendly, cost-effective and easily up-scalable way. On a laboratory scale, the costs are approx. 500 Euro/kg
The technical feasibility of a multifunctional lightweight and low-cost de-icing system in combination with improved corrosions resistance and reduced water uptake was shown with the help of a leading-edge demonstrator. The mechanical properties of the composites are not deteriorated in this application. And silver-modified graphene oxide makes lightning protection applications possible.
A primary candidate for the development of advanced functional lightweight materials and systems with the capability for more efficient integration in aircraft structures are thermoelectric de-icing systems essential for aircraft safety by avoiding in-flight icing. Present state-of-the-art systems consist of metal or composite structural aircraft components coated with polymers containing a high amount of graphite.
The objective of the GRAPHICING project was the development of multifunctional aeronautical structures (de-icing, lightning strike protection, fire and water barrier) based on graphene related materials – among other properties graphene has unique electrical, thermal and impermeable properties - focused on an effective De-Icing system.
The most important results of this project are, firstly, that four targeted functionalities of de-icing, lightning strike protection, water absorption barrier and flame inhibition can be achieved with the graphene-based materials. Moreover, graphene-oxide can be produced via an electrochemical process in an environmentally friendly, cost-effective and easily up-scalable way. On a laboratory scale, the costs are approx. 500 Euro/kg
The technical feasibility of a multifunctional lightweight and low-cost de-icing system in combination with improved corrosions resistance and reduced water uptake was shown with the help of a leading-edge demonstrator. The mechanical properties of the composites are not deteriorated in this application. And silver-modified graphene oxide makes lightning protection applications possible.
At the start of the project a feasibility study was started to evaluate the current state-of-the-art, requirements for functional parts and possible graphene-based solutions. Via DoE-approaches optimised parameter sets were determined for graphene oxide production, reduction of graphene oxide, or the deposition of Ag-particles on graphene oxide. Due to agglomeration and insufficient dispersion efficiency, an alternative approach via spray-coating was developed. The spray coating process showed good results and reduced graphene oxide layers with sufficient conductivity for de-icing applications were produced and tested in terms of heating functionality. Preliminary fire barrier tests showed no significant influence in flame inhibition properties. In terms of water uptake prevention, the addition of reduced graphene oxide to the epoxy system showed a positive effect reducing the water uptake.
Further non-functional properties like corrosion behaviour and mechanical testing were carried aout during the project. The addition of graphene oxide improves the corrosions protection due to it's barrier effect in the epoxy resin. In a series of mechanical tests, it was shown that the addition of graphene oxide only slightly (< 10%) worsens the mechanical properties.
To demonstrate the project results and the multifunctionality of graphene-based materials, leading edge demonstrators with a size of 400x200x1 mm were produced with a NACA2412 leading-edge geometry at the end of the project.
In terms of dissemination and communication of results a website was established and is updated regularly. Additionally, social media posts on project news were published on the Instagram and Linkedin channels of CEST.
Via six conference participations (3 oral presentations and 3 poster presentations) at scientific conferences, results of the project were presented and discussed with the audience.
Furthermore, 3 open access publications were prepared to communicate scientific results. Two of them are already accepted and published (https://doi.org/10.3390/ma15134639(s’ouvre dans une nouvelle fenêtre) and https://doi.org/10.3390/ma16041743(s’ouvre dans une nouvelle fenêtre)). The third publication has already been accepted and will be published in Q2 2023.
Within the scope of the GRAPHICING project, a PhD student was able to work on his PhD studies in cooperation with the University of Vienna, which should conclude in the defence of the thesis “Development of graphene-based materials for aeronautical applications” mid 2023.
Additionally two student internships were executed to train young female researchers on graphene-based materials. Within the consortium, 3 workshops were organized to exchange know-how.
Further non-functional properties like corrosion behaviour and mechanical testing were carried aout during the project. The addition of graphene oxide improves the corrosions protection due to it's barrier effect in the epoxy resin. In a series of mechanical tests, it was shown that the addition of graphene oxide only slightly (< 10%) worsens the mechanical properties.
To demonstrate the project results and the multifunctionality of graphene-based materials, leading edge demonstrators with a size of 400x200x1 mm were produced with a NACA2412 leading-edge geometry at the end of the project.
In terms of dissemination and communication of results a website was established and is updated regularly. Additionally, social media posts on project news were published on the Instagram and Linkedin channels of CEST.
Via six conference participations (3 oral presentations and 3 poster presentations) at scientific conferences, results of the project were presented and discussed with the audience.
Furthermore, 3 open access publications were prepared to communicate scientific results. Two of them are already accepted and published (https://doi.org/10.3390/ma15134639(s’ouvre dans une nouvelle fenêtre) and https://doi.org/10.3390/ma16041743(s’ouvre dans une nouvelle fenêtre)). The third publication has already been accepted and will be published in Q2 2023.
Within the scope of the GRAPHICING project, a PhD student was able to work on his PhD studies in cooperation with the University of Vienna, which should conclude in the defence of the thesis “Development of graphene-based materials for aeronautical applications” mid 2023.
Additionally two student internships were executed to train young female researchers on graphene-based materials. Within the consortium, 3 workshops were organized to exchange know-how.
In the de-icing process, the effectiveness of graphene-based materials was proven via the spray-coating process. 20 to 30 µm thick layers schow an electrical resistances of 100 to 2000 ohm/sq. 5 to 2000 ohm/sq are required for de-icing window. The electrical resistance can be adjusted on the one hand by the amount of powder applied (see Fig. 1) and on the other hand by the "degree of reduction" of the graphene-oxide base material. To ensure the heating functionality of the conductive layer, various heating tests on unsealed and sealed samples were carried out. By applying different potentials on the samples, a heating process could be observed. The heating capability was monitored by an infrared-camera to confirm uniformity of the heating process. Figure 2 shows a glass fiber based de-icing sample during the heating test with a layer of 3.17 mg/cm² rGO and with an electrical resistance of approx. 100 ohm/sq. The material costs for the low-cost de-icing layer are down to 16€/m².
In the case of water-uptake, it was shown that the addition of graphene-based materials (15 w%) reduces the water absorption to 1 w% for aluminum substrates.
Ligthning-strike protection was demonstrated with small scale flat panels. A sheets resistance of approx. 50 mOhm/sq. was achieved with silver modified rGO.
All functionalities were demonstrated on small scale flat panels.
The combination of De-Icing, Water Uptake Prevention and Corrosion Protection in an rGO-based system was demonstrated with a mulfifunctional leading-edge demonstrator (TRL 4) with 4 different heating zones based on requirements according to thermal simulations (see Fig. 3).
The addition of 5 w% rGO to the laminate structure shows no deterioration of the mechanical properties.
Production costs of graphene-based materials:
With the current production process (graphene-oxide production, graphene-oxide reduction and modification) of graphene-based materials, the production costs are currently around EUR 500/kg for a production capacity of 10 kg/month on a laboratory scale.
Green chemistry:
No toxic chemicals are used in the entire production process of graphene-based materials. Graphene-oxide production requires caustic soda, sulphuric acid and electrical energy. A subsequent reduction process uses ascorbic acid, also known as vitamin C. During the spray coating process on a laboratory scale, care is taken to use non-toxic solvents that are as environmentally friendly as possible.
In the case of water-uptake, it was shown that the addition of graphene-based materials (15 w%) reduces the water absorption to 1 w% for aluminum substrates.
Ligthning-strike protection was demonstrated with small scale flat panels. A sheets resistance of approx. 50 mOhm/sq. was achieved with silver modified rGO.
All functionalities were demonstrated on small scale flat panels.
The combination of De-Icing, Water Uptake Prevention and Corrosion Protection in an rGO-based system was demonstrated with a mulfifunctional leading-edge demonstrator (TRL 4) with 4 different heating zones based on requirements according to thermal simulations (see Fig. 3).
The addition of 5 w% rGO to the laminate structure shows no deterioration of the mechanical properties.
Production costs of graphene-based materials:
With the current production process (graphene-oxide production, graphene-oxide reduction and modification) of graphene-based materials, the production costs are currently around EUR 500/kg for a production capacity of 10 kg/month on a laboratory scale.
Green chemistry:
No toxic chemicals are used in the entire production process of graphene-based materials. Graphene-oxide production requires caustic soda, sulphuric acid and electrical energy. A subsequent reduction process uses ascorbic acid, also known as vitamin C. During the spray coating process on a laboratory scale, care is taken to use non-toxic solvents that are as environmentally friendly as possible.