Experimental and Mechanistic Studies on the Tensile Sensitivity of a PDMS/MWCNT Nanocomposite and Its Application in Concrete Crack Monitoring

A polydimethylsilosane/multiwalled carbon nanotube (PDMS/MWCNT) nanocomposite, as a tensile-strain-sensing material, was manufactured using a simple solution casting method. The percolation threshold, the relationship between the temperature and resistance, the tensile sensitivity, and the mechanism of the tensile sensitivity of the PDMS/MWCNT nanocomposite were studied, along with its application in concrete crack monitoring. The results show that the PDMS/MWCNT nanocomposite demonstrated a significant percolation phenomenon. The resistance change ratio of the PDMS/MWCNT nanocomposite changed linearly with the environmental temperature, gradually decreasing with an increasing environmental temperature. The PDMS/MWCNT nanocomposite had a higher tensile sensitivity, and the sensing factor was 6.65 when the volume fraction of carbon nanotubes was 1.26 <i>v</i>/<i>v</i>% near the percolation threshold, and the sensing factor of the PDMS/MWCNT nanocomposite decreased with an increase in the volume fraction of carbon nanotubes. The relationship between the relative electrical conductivity of the PDMS/MWCNT nanocomposite and the tensile strain can be expressed as ln(<i>σ</i>/<i>σ</i>₀) = <i>Aε</i>. In addition, the quantitative relationship between the electrical conductivity of the PDMS/MWCNT nanocomposite and the volume fraction of carbon nanotubes was obtained based on the tunneling effect theory and the effective medium model. PDMS/MWCNT nanocomposites can be used as a sensing material to monitor the propagation of concrete cracks under the impact of a free-falling ball.