Damage and load sensing is rapidly advancing as driven by vast applications in aerospace and mechanical structures. Recently significant amount of efforts have been reported to develop new piezo-resistive strain sensor made from polymers with carbon nanoparticles, such as carbon nanotubes, carbon nanofibers, and graphene. These nanoparticles with advanced mechanical, electrical, and thermal properties are recognized as potential materials which can enhance mechanical performance and provide beneficial functionalities in polymers and composites. However, most previous research focused on the improvement of material properties for sensing applications. Limited work balanced the sensor design and material innovation for real time strain sensing. In this paper nanocomposite membranes are proposed to accurately measure local strain, especially for the strain sensing and health monitoring in composites. The micro-scale morphology and structures are first experimentally characterized. Both the fabrication process and the nanoparticle concentration are investigated to obtain the optimal sensing capabilities. The sensing function is achieved by correlating the piezoresistance variations to the stress or strain applied on the sensing area. Due to the conductive network formed and the tunneling resistance change in neighboring nanoparticles, the electrical resistance measured will show a clear correlation with the load conditions. The characterized membrane structures have the potential to be further applied to continuously monitor impact loads, especially focusing on low velocity barely visible damage in composites.

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