Carbon nanotube (CNT) yarns are micron-size fibers that contain thousands of intertwined carbon nanotubes in their cross sections and exhibit piezoresistance and thermoresistance characteristics that can be tapped for sensing purposes including strain measurement, damage detection and temperature sensing in polymeric and composite materials. The sensing ability of these CNT yarns is thus determined by their coupled mechanical-electrical (piezoresistive) and thermal-electrical (thermoresistive) responses. The former had been studied in the case of the unconstrained carbon nanotube yarns revealing a piezoresistive response that is strongly dependent on the strain rate. In this study, the CNT yarns were embedded in polymeric beams and subjected to 4-point bending. Depending on the position of the CNT yarns within the beam, the piezoresistive response of the constrained CNT yarns was determined under either tension or compression. It is revealed that the effect of the lateral constraint of the CNT yarn on its piezoresistive response is very significant. The thermoresistive response of the CNT yarns embedded in polymeric beams was also determined by subjecting them to heating-cooling cycles. It was observed that their electrical resistance decreased with increasing temperature.
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