Soft Elastomeric Capacitive Sensor for Structural Health Monitoring

Propagation of fractures due to high stress loads are a common cause of structural failure. This paper describes a thin soft elastomeric capacitor (SEC) sensor which can be adhered to structures to monitor strain fields and detect sub-millimeter deformations and fractures. Alterations in a mechanical structure change the geometry of the skin-like parallel plate capacitor sensor and the resulting capacitance change is measured as a change in the resonant frequency of a relaxation oscillator circuit. The sensor system comprising of the SEC sensor, the oscillator circuit and a microcontroller demonstrated its capability to detect millimeter scale stretches.