Gas sensing properties of conductive polymer nanocomposites

Nanocomposites consisted of carbon nanotubes (CNT) dispersed in various polymer matrices were prepared for the investigation of their sensing properties. The results from morphology study and electrical/dielectric characterization showed good dispersion of the filler with low percolation threshold. The response to water and ethanol vapour, at different concentration, was also studied showing better response for the more hydrophilic polymers and those with glass transition temperature below room temperature. © 2011 Published by Elsevier Ltd

Strain and damage sensing in carbon fiber polymer-matrix composite by electrical resistance measurement

The measurement of electrical resistance appears to be a valuable non-destructive technique that can be used to monitor the damage in carbon fiber reinforced polymers. In this work composites of poly-ether-ether-ketone (PEEK) with unidirectional carbon fibers at a content of 38wt% were tested. The samples were subjected to tensile loading in parallel to the fiber direction and the longitudinal strain was measured very accurately, with a laser-extensometer which permits a non-contact measurement of the longitudinal deformation distribution of the sample. Simultaneously with the mechanical tests, electrical resistance of the specimen was monitored with the use of gold sputtered electrodes on its surface. Different electrode configurations were used in order to measure longitudinal, through thickness or oblique resistance. In all cases, a fixed current was applied and the resulting voltage drop was continuously monitored. The resistivity increased monotonically with strain in all configurations where voltage drop is measured in the direction of current application. Furthermore, resistance changed irreversibly during tensile cyclic loading at various stress levels. © 2012 Taylor & Francis Group, London

Electrical resistance measurement for in situ health monitoring of carbon nanotube/polymer composites

In this work multiwall carbon nanotubes (MWCNTs) dispersed in a polymer matrix have been used for damage sensing of the resulting nanocomposite under tensile and cyclic loading. This was achieved by measuring the electrical resistance change in conductive polypropylene/CNT nanocomposites with 4% and 8% wt MWCNT content well above the percolation threshold. The samples were subjected to tensile loading and the longitudinal strain was measured together with the longitudinal electrical resistance. For the electrical resistance measurements a four-probe method was used by applying a fixed current through the two outer electrical contacts and measuring the voltage between the two inner electrodes. By lowering CNT content (being above the percolation threshold) the relative change of resistance ΔR/R o as a result of applying the same stress has been found to increase but there is a trade-off with the electrical noise of the measurements. The increase of electrical resistance with strain could be explained as a result of destruction of percolating paths forming the conducting network. The results showed that CNT dispersed in a polymer matrix forming a conductive network have a potential to be used as a sensitive network to monitor or predict the damage in polymer/carbon nanotube nanocomposites. © 2012 Taylor & Francis Group, London