Remote strain measurement by multi-walled carbon nanotube-dispersed resin

A new remote strain measurement method has been developed by applying the highly sensitive change of electronic conductivity of CNTs. Multi-walled CNTs were dispersed in various kinds of resins to form a thin film which can be attached rounded surfaces. The length of the CNTs was about a few μm. One of the base materials of resin employed was polycarbonate and the volumetric concentration of CNT dispersed was about 11.5%. The thickness of the film was about 500 μm. An uni-axial strain was applied to the CNT-dispersed resin by applying a 4 point bending method, and the change of the electric resistance was measured. The range of the applied strain was from -0.025% to 0.025%. The electric resistance changed almost linearly with the applied strain. The ratio of the resistance change under the tensile strain was about 40%/1000-μstrain and that under the compressive strain was about 15%/1000-μstrain. The micro wave of 99.5 GHz was irradiated to the CNT-dispersed polycarbonate film through the metallic prove 1 mm in diameter. The change of the intensity of the beam reflected from the film was measured by changing the amplitude of the uni-axial in-plane strain applied to the film. The intensity of the reflected beam increased almost linearly with the increase of the applied tensile strain and the change rate of the intensity was about 0.5%/1000-μstrain. This result clearly indicated that the surface dynamic strain can be detected by micro wave nondestructively and remotely.