Function integration in fiber-reinforced plastics
At Fraunhofer IFAM, functional printing technologies can be used to functionalize various aircraft parts and components. Printed conductors and sensors for temperature, strain or impact measurement as well as heating structures can be incorporated into fiber-reinforced plastics for the aerospace sector.
Functional integrated fiber composites
The demand for fiber-reinforced plastics has grown very strongly in recent years. One of the largest markets in this respect is aviation: more than 50% of aircraft are now made of carbon fiber and glass fiber reinforced plastics (CFRP, GFRP), resulting in the use of around 100 tons of these fiber reinforced materials.
A major driver for this is lightweight construction. The materials have a very high lightweight potential and are therefore significantly lighter than metals. As a result, the weight of an airplane can be significantly reduced, fuel consumption can be cut, and costs can be saved.
In addition, highly individualized production has now become established in aircraft manufacturing. Individual product designs are implemented not only in the aircraft interior, but also in all structures. However, integrating these individual product designs into the process chains of series production is a major challenge. This area of conflict between mass production process chains and simultaneous small batch sizes can be addressed with function integration in fiber composites using digital printing and laser technologies.
Integration of smart systems in aviation
By integrating printed electronics and sensors into the fiber-reinforced plastics, for example, fiber defects and delaminations in highly stressed FRP structures can be detected, thus minimizing the risk of abrupt failure. Cost pressure can also be better countered by possible smaller dimensioning as well as lower safety factors. Maintenance processes can be significantly shortened by contactless readable sensor structures and by functions against icing, e.g. of a sash. The integration of actuator functions is also possible.
In the Fraunhofer project "Go Beyond 4.0", Fraunhofer IFAM was able to demonstrate the integration of temperature, capacitive, and impact sensors as well as UHF antennas and LEDs in fiber-reinforced plastics in a demonstrator using a wing element of a commercial aircraft. Various printing technologies, such as the aerosol jet process, inkjet printing and dispensing processes, were used to integrate the smart systems. The following smart systems were integrated into the lightweight composite materials of a wing leading edge:
Printed conductors integrated in fiber-reinforced polymers
- Properties of printed conductors: more reproducible resistance ±2%, no change in resistance during bending
- No degradation of mechanical properties of components with integrated printed conductors
Printed deformation sensor for impact detection integrated in fiber reinforced polymers
- The deformation sensor/antenna is integrated in a glass fiber reinforced polymer and can be read wirelessly.
Development of printed heating elements integrated in fiber-reinforced polymers
- The heating elements can melt a 2 mm thick, -15 °C cold layer of ice in 6 minutes.
- Heating power of 2.3 W (9 V, 250 mA ~ 0.1 W/cm²)
Technology development for integration of standard LEDs in fiber-reinforced plastic material
- No heat accumulation after 8 hours of operation at 0.03 W (60 % maximum LED power, 3 V, 10 mA)
- No damage to LEDs during component processing
Technology development for integration and polarization of piezo sensors (PZT) in fiber reinforced polymers
- Detection of impact from PZT sensors over a distance of 30 cm (at 0.5 Ns)
- Localization of the impact by travel time differences of the compression pressure waves