Structural health monitoring (SHM) can be described as 'the nervous system' of a component. Sensors and evaluation electronics register external impacts on the structure and detect any damage.
Damage from foreign objects 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 plastic (FRP) sandwich structures, this damage is rarely visible on the outside. Operational safety is therefore ensured by extensive inspections and the corresponding design of the components.
According to Fraunhofer LBF, new SHM systems could allow costs, weight and maintenance of composite aircraft structures to be reduced. Self-diagnosis reduces downtimes and the reduction in weight cuts fuel consumption. Continuous monitoring of the aircraft fuselage, even in difficult to access areas, would reduce inspection demands. Electrical and optical strain gauges, as well as piezoelectric fibre modules and accelerometers, can be used to record measurements.
To integrate sensor technologies into the production of aircraft structures, the Fraunhofer LBF works closely with sensor technology companies and composite materials manufacturers.
The structural part of the aircraft wing which will be shown at COMPOSITES EUROPE (Stuttgart, 27-29 October), was constructed by the Fraunhofer LBF in conjunction with the Darmstadt University of Applied Sciences, with 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 into the wing during its manufacture. The loading on the upper and lower side of the wing is measured at 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.
