Piezoresistive properties of polydimethylsiloxane (PDMS) filled with copper particles in volume fraction above the electrical percolation threshold (25.3-50.7 vol%) were investigated. Piezoresistive behavior of the PDMS-copper composites under compressive pressure showed not only a change in resistance by approximately six orders of magnitude (similar to 1.5 MPa), but also a change in the critical pressure due to variations in the hardness of the composites. Resistivity relaxation was observed near the critical pressure and was explained through a stress relaxation and percolation mechanism. The mean tunneling distance was calculated by using a theoretical equation for percolation under compression. When the gauge factors of the composites were plotted versus strain, a universal curve was obtained regardless of the copper contents. Finally, the PDMS-copper composite demonstrated good repeatability, showing only small differences in the relative resistance after five successive tests. (C) 2013 Elsevier Ltd. All rights reserved.