This paper presents the development of polymer-nanofiller systems as strain sensor materials and the development of novel sensor fabrication and characterization techniques. The developed sensor has shown to overcome the limitations of conventional strain sensors — having the capability to measure macroscale strains in any desired direction over a finite surface area, which may be subjected to combined loading modes, including tension, compression, flexure, and shear. They have sufficient flexibility and toughness to accommodate most curved surfaces and corners in components and structures. The methodologies use high aspect ratio multi-walled carbon nanotubes (MWNTs) in order to take advantage of their capability to form efficient conductive network. The results will lead to tailoring of sensor performance, particularly sensitivity factor, by controlling conductive network and optimizing sensor design and fabrication. To date, sensitivity factor of almost 20 at 1 wt.% of MWNTs in poly(methyl methacrylate) (PMMA) has been achieved. The developed sensor can be used in various military and commercial applications, including macroscale strain sensing over a wide surface area (e.g. aircraft skin), high sensitivity strain sensing on stiff components, and crack detection at critical stress concentrated regions for health monitoring.
Patterning of graphene for highly sensitive strain sensing on various curved surfaces
