Sara Palacios García, financial technician at SOFITEC: "With the impetus of CDTI Innovation, PROTECT-AIR develops lighter and more sustainable materials to protect aircraft from the impact of lightning"
The use of composite materials in the construction of aircraft makes it possible to reduce their weight, but replacing metallic materials also means dispensing with some essential properties to protect the structure. Among them is the electrical conductivity, necessary to prevent the impact of a ray from causing damage. The Sevillian company SOFITEC addresses this challenge through PROTECT-AIR, a project that develops new composites with integrated conductive function and also studies how to recover them at the end of their useful life. The initiative is supported by the CDTI Innovation through the Science and Innovation Missions line
SOFITEC was born in 1999 with the mission of accompanying the customer throughout the life cycle of an aeronautical part, from the first phases of design and development to its manufacture, assembly and delivery. This comprehensive vision has allowed the company to consolidate itself as a TIER 1 supplier of Airbus and TIER 2 supplier of Boeing and participate in reference aeronautical programs such as the A320, the A350 or the C295, in addition to collaborating with international manufacturers and integrators.
Throughout these years, the Sevillian company has made a determined commitment to innovation, developing its own engineering and manufacturing capabilities to meet the needs of the sector. "Since our inception, R&D&I has been one of the growth engines of SOFITEC, allowing us to develop new industrial capacities, generate our own technology and respond to the challenges of an aeronautical industry in constant evolution," explains Sara Palacios García, the company's financial technique.
Protect without adding weight
Composites make it possible to lighten aircraft, however, unlike metals, they do not allow the passage of electricity naturally, a property necessary to protect the structure against electrical phenomena. "The more we advance in the use of composite materials to reduce the weight of aircraft, the more difficult it is to maintain a property that metals inherently provided: electrical conductivity," explains the technique.
Members of the PROTECT-AIR project consortium
The usual solution is to place a metal mesh on the surface to conduct the current in case of a lightning strike. This alternative adds weight, requires additional operations to integrate it into the structure and hinders the recovery of the component at the end of its useful life.
PROTECT-AIR starts from a different idea, since, instead of adding an external metallic element, it seeks to integrate the conductive function into the compound itself. To this end, the consortium has developed a solution in which the matrix incorporates graphene by means of an ultra-thin sheet of carbon nanotubes.
This approach combines lightness and mechanical performance with the necessary driving ability to preserve the structure. It also eliminates the adhesive used to fix the metal mesh and reduces the risks of galvanic corrosion associated with the combination of metals and compounds.
In addition, it provides advantages in the production process, since this composite can be processed by high-cadence compression molding, integrating in a single operation the manufacture of the piece, its machining and the electrical protection function.
From research to aeronautical application
One of the main challenges of PROTECT-AIR is to check that the compound maintains its characteristics when moving from the laboratory to a real component and that its manufacture allows to obtain reproducible results. As Sara Palacios explains, at this point the amount of conductive particles incorporated into the resin is key, since an insufficient concentration can prevent reaching the required electrical properties, while an excess can hinder processing.
To validate it, the consortium has carried out a series of lightning impact tests that allow us to study how the material responds to small variations in the process. As a result, an "All-in-one" technology demonstrator has been validated: an in-flight refueling POD fairing maintenance cover, installed on the wing of certain Airbus A330 MRTT. It is a piece that integrates the different solutions developed and combines physical tests with numerical models to analyze their behavior.
The results obtained have been promising, although they have also allowed to detect aspects that still need to be optimized, especially to achieve a behavior comparable to that of aluminum under certain conditions. "The next step is to parameterize the process variables and establish a sufficiently robust manufacturing window that allows the technology to scale to ensure that the performance achieved in the laboratory is maintained in an industrial production," he says.
Thinking also about the end of life
The research also addresses the challenge of the future use of these composites when the piece ceases to be useful for the aircraft. "PROTECT-AIR studies the recyclability of the new material and opens up new possibilities to move towards a more circular aeronautics, in which the materials can have a second life and the generation of waste is reduced," explains the representative of SOFITEC.
To achieve this, the project has studied two ways. The first uses solvolysis, a chemical process that allows the nanotube sheet to be recovered in a practically intact state. The second uses a simpler and cheaper mechanical alternative to obtain a recycled compound that can be used in other industrial applications.
The objective is that the improvement of the performance during the useful life of the piece does not generate a new difficulty when it reaches the end of its journey. The recovery and reuse of these resources is related to SDG 12, Responsible Production and Consumption, and SDG 13, Climate Action, by proposing alternatives to reduce waste and prolong its use.
A consortium that covers the entire chain
This type of development requires combining knowledge ranging from the formulation to the manufacture and validation of the parts. Therefore, PROTECT-AIR brings together companies and specialized centers with SOFITEC at the head of the initiative, as responsible for bringing the solutions to a real aeronautical application.
The following companies are part of the project: CT Engineers, which contributes with its experience in design, engineering and simulation, Menzolit, which works in the development and manufacture of SMC (Sheet Moulding Compound) type compounds, Avanare contributing its specialization in chemistry, nanotechnology and advanced materials to develop the conductive systems and Ensatec, which participates in the experimental validation. The AIMPLAS, IMDEA and INTA agencies complete the consortium with their expertise in characterization and validation and in the study of issues such as lightning strike response, electromagnetic shielding and recycling and recovery alternatives.
This combination allows to connect the development of this innovation until its integration into an aircraft. "The main value of the consortium therefore lies in the fact that this multidisciplinarity allows us to cover the entire chain of technological development," he says.
The impulse of the CDTI Innovation
The support of the CDTI Innovation through the Science and Innovation Missions line has allowed SOFITEC to face a project with a high technological risk and work in coordination with companies and specialized centers.
Team of SOFITEC in its facilities in Seville
For Sara Palacios, this help has also led the company to explore different solutions and expand its expertise in this area. "The Science and Innovation Missions line has allowed us to advance in technologies that go beyond our usual industrial activity, expand our internal R+D+I capabilities and work together with entities specialized in advanced materials, nanotechnology, engineering and validation," he highlights.
Towards the aeronautics of the future
The next stage is to raise the maturity level of the solutions, optimize their manufacture and transfer the results to future aeronautical programs. For SOFITEC, the project also opens the door to new applications capable of reducing weight without compromising the performance required by the sector and incorporating circularity criteria from the design.
The evolution towards lighter and more efficient aircraft will also depend on manufacturing processes capable of responding to these new requirements. The work developed in PROTECT-AIR provides a basis for further research into components with integrated and alternative functions to recover their composites at the end of their useful life. "Innovation in materials and processes will be a key element in moving towards the decarbonization and aviation objectives of the 2050 horizon," he concludes.
CDTI Innovation
The Center for Technological Development and Innovation, CDTI E.P.E. It is the innovation agency of the Ministry of Science, Innovation and Universities, whose objective is the promotion of technological innovation in the business environment. The mission of the CDTI is to ensure that the Spanish business fabric generates and transforms scientific and technical knowledge into globally competitive, sustainable and inclusive growth.
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