Piezoresistance of conductor filled insulator composites

Several series of electrically conducting composites composed of a conducting filler randomly dispersed into an insulating polymer matrix were prepared. The fillers were the tin–lead alloy powder, copper powder, aluminium powder and carbon black, and the matrices were polyethylene, polystyrene and epoxy resin. The piezoresistance effects of these composites have been investigated under uniaxial presses. It was observed that the piezoresistance depends on the applied stress, filler particle diameter, filler volume fraction, matrix compressive modulus and potential barrier height. Piezoresistance increases with increase of applied stress, filler particle diameter and potential barrier height, but decreases with increases of filler volume fraction and matrix compressive modulus. A model based on the change in interparticle separation under applied stress, is developed. By analysing this model, the piezoresistance of composites is studied and the effects of influencing factors are theoretically predicted quantitatively, showing good agreement with the experimental data.