Pressure and temperature induced electrical resistance change in nano-carbon/epoxy composites

In this study, we investigate the changes of electrical resistance of the carbon black (CB) and carbon nanotube (CNT) filled epoxy composites upon compression, swelling and temperature variation. For all samples we observe a decrease of electrical resistance under compression, while an increase of electrical resistance is found upon swelling due to water absorption. With the same volumetric change, the CB/epoxy composites have a more pronounced change of electrical resistance than the CNT/epoxy composites. The influence of temperature variations on the overall electrical resistance is somewhat more complex. At low temperatures, electrical resistance clearly decreases with increasing temperature, mainly owing to the thermal fluctuation induced tunneling conduction mechanism. At high temperatures, electrical resistance decreases much slower and may even increase due to a more prominent thermal expansion effect. The thermal expansion of the epoxy matrix leads to a decrease of tunneling conduction. Without the contribution of the thermal expansion, the sensitivity and linearity of electrical resistance change upon temperature variations is higher.