Strain-sensitive conductivity of carbon black-filled PVC composites subjected to cyclic loading

This paper reports a study on the strain sensitivity response of polyvinylchloride/carbon black (PVC/CB) composites' electrical conductivity (tensoresistivity) subjected to cyclic tensile loading. This study is part of a research program to develop sensor-enabled geogrids for performance-monitoring of reinforced earth structures. A medium-structure and a high-structure black were used as conductive fillers for a PVC coating which is commonly used for woven geogrids. Five different cyclic loading régimes were used to investigate influences of factors such as the strain amplitude, strain rate and pre-straining on the strain sensitivity performance of the coating composite electrical conductivity. Results showed that the conductive network in the coating specimens filled with the higher-structure CB experienced less damage upon cyclic deformation and showed a greater degree of recoverability in their tensoresistivity response. Also, pre-straining of coating specimens had a positive influence on the recoverability of their strain sensitivity. The degree of pre-straining induced in the specimens was characterized by the ratio of initial peak strain to the subsequent operating peak strain introduced here as the over-elongation ratio (OER). A greater OER value resulted in a more stable and consistent recoverability of tensoresistivity in the filled composite.