Because of their lightweight construction, fibre-reinforced composites offer particular advantages in the aviation sector. However, their more complex damage behaviour relative to metallic materials means that this lightness cannot always be fully exploited.
In aviation, for example, the impact of foreign objects on reinforced composite structures represents a particular danger, limiting their potential uses and frequently causing greater safety factors that need to be counteracted with a certain amount of over-dimensioning. However, sensors in specific parts, such as the wings, can identify at an early stage structural damage that would otherwise not be externally visible, and reduce inspection demands.
The operating safety of the structure is ensured by the design and by manual inspections held at regular intervals. In the future, it will be possible to reduce costs and weight thanks to supplementary, automatic monitoring with structure-integrated sensors.
SHM - A component's nervous system
The basic idea: Structural Health Monitoring acts like the nervous system for a component. Sensors and evaluation electronics register external impacts and detect any damage.
In particular, foreign objects damage such as hail or bird strikes present a considerable danger to aircraft. Aircraft can also be chipped by grit from the runway or damaged by tools dropped during maintenance work. With fibre-reinforced sandwich structures, such damage is very rarely visible on the outside. As yet, the operating safety is therefore ensured by extensive inspections and the corresponding design of the components.
New SHM systems allow costs, weight and maintenance to be reduced, thus enabling lightweight structures to fully exploit their potential. Self-diagnosis reduces downtimes and the reduction in weight cuts fuel consumption. Continuous monitoring of the aircraft fuselage, even in areas difficult to access, reduces inspection demands. Electrical and optical strain gauges as well as piezoelectric fibre modules and accelerometers are used to record measurements.
In integrating various sensor technologies in the production of aircraft structures, the Fraunhofer LBF works closely in an interdisciplinary manner with sensor technology companies and composite materials manufacturers. The structural part of the aircraft wing shown in Stuttgart was constructed by the Fraunhofer LBF in conjunction with the Darmstadt University of Applied Sciences, with additional support from Evonik Röhm, Saertex and Hexion.
Sensors inside the aircraft wing measure the structural loads. In addition to eight piezoelectric modules from the Fraunhofer LBF, 18 electrical and 16 optical load transducers from HBM combined with sensor film from Fujifilm Prescale were integrated in the wing during its manufacture. The loading on the upper and lower side of the wing is measured with a rate of up to 200 Hz. As soon as the data exceeds a predefined loading limit, an alarm signal is activated. Software from HBM saves and analyses all the data from the electrical and optical measurements.Clean Sky JTI: Environmentally friendly technology for the aviation industry
Anke Zeidler-Finsel | Fraunhofer Gesellschaft
Further reports about: > CLEAN > Clean Sky > Clean Sky Joint Technology Initiative > Fibre-reinforced Composites > HBM > LBF > SHM > automatic monitoring > composite materials manufacturers > environmental impact > fuel consumption > health services > information technology > lightweight construction > metallic materials > nervous system > structure-integrated sensors
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