Structure-Integrated Thin-Film Supercapacitor as a Sensor.

Today, aircraft composite structures are generally over-dimensioned to avoid catastrophic failure by unseen damages. This leads to a higher system weight and therefore an unwanted increase in greenhouse gas emissions. To reduce this parasitic mass, load monitoring can play an important role in damage detection. Additionally, the weight and volume of future aircraft structures can also be reduced by energy storing and load carrying structures: so-called power composites. In this study a novel method of combining both approaches for maximum weight reduction is shown. This is achieved by using power composites as load monitoring sensors and energy suppliers. Therefore, supercapacitors are integrated into fiber reinforced polymers and are then used to investigate the mechanical load influence. By using four-point bending experiments and in situ electrochemical impedance spectroscopy, a strong relation between the mechanical load and the electrochemical system is found and analyzed using a model. For the first time, it is possible to detect small strain values down to 0.2% with a power composite. This strain is considerably lower than the conventional system load. The developed model and the impedance data indicate the possibility of using the composite as an energy storage as well as a strain sensor.