Validation of large area capacitive sensors for impact damage assessment

Abstract

Impacts in fiber-reinforced polymer matrix composites can severely inhibit their functionality and prematurely lead to the composite’s failure. This research focuses on determining the efficacy of a novel capacitive sensor, termed as the soft elastomeric capacitor (SEC), to monitor the magnitude of out-of-plane deformations in composites. This work forwards the development of a sensing skin that can be used as an in situ monitoring tool for composites. The capacitive sensor can be made to arbitrary sizes and geometries. The sensor is composed of an elastomer composite that measures strains experienced by the material it is bonded to. The structure of the sensor, fabricated to function as a parallel plate capacitor, responds to impacts by transducing strains into a measurable change in capacitance. In this work, the SECs are deployed on randomly oriented fiberglass-reinforced plates with a polyester resin matrix. The material is impacted at various energy levels until the monitored composite material reaches its yielding point. The behavior of the sensor in impact detection applications below the proof resilience shows little to no change in the capacitance of the sensor. As the impacts surpass this yielding point, the sensor responds linearly with induced change in the area. The sensor performed within the expectations of the proposed model and demonstrated the efficacy of the proposed large-area sensor as a damage quantification tool in the structural health monitoring of composites.