DISTRIBUTED STRAIN SENSING IN COMPOSITE MATERIALS BY USING A CAPACITIVE SENSOR SHEET WITH CRAKED ELECTRODES.

Distributed strain sensing, i.e., the ability to measure strains at different locations, has become especially important for detecting expected damage locations in structures. To date, monitoring distributed strain with high spatial resolution in composite structures is limited due to several technical limitations. Our solution is based on creating multiple sensing regions within the area of a single capacitive sensor body by considering the sensor as an analogical transmission line, reducing the connections to only two wires and simplifying the electronic interface. The proposed distributed sensor is a stretchable parallel-plate capacitor comprising two cracked electrodes separated by a dielectric layer. The piezoresistivity of the electrodes induces the transmission-line behavior in the entire sensor at radio frequencies. The transmission line behavior allows the sensing signal to be attenuated by high-resistance electrodes along the capacitive sensor's length. Different regions of the capacitive sensor can then be moitored by changing the sensing frequency and creating a virtual sensor length. Our system that allows free movements of deformable systems can be an alternative solution to detect local strain in composite materials without affecting their mechanical properties.