Large area capacitive sensors for impact damage measurement

Abstract

Impacts in fiber reinforced polymer matrix composites can severely inhibit their functionality and lead to failure of the composite prematurely. This research focuses on determining the efficacy of a novel capacitive sensor, termed as the soft elastomeric capacitor or SEC, for the purpose of monitoring the magnitude of out-of-plane deformations in composites. This work aims to forward 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 inherits the strains of the material it is bonded to. The structure of the sensor, manufactured to function as a parallel plate capacitor, responds to impacts by transducing strains into a measurable change in capacitance. In this work, the large area capacitive sensors are deployed on randomly oriented fiberglass-reinforced plate with a polyester resin matrix. The material is impacted at various energy levels until the material reached its yielding point. The behavior of the sensor in impacts below the proof resilience shows little to no change in capacitance of the sensor. As the impacts surpassed this yielding point, the sensor responds linearly with induced change in area. The results performed within 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.