Piezoresistive effect in epoxy-graphite composites

In this work, we investigate the piezoresistive response of epoxy-graphite composites. A resistive thick-film Wheatstone bridge is deposited by screen-printing onto a beam, a weight is then applied on the tip of the beam and the resulting electrical signal response is recorded, allowing the calculation of the gauge factor. The characterization was made at room temperature, 65°C and 100°C for different matrixes (epoxies with different glass transition temperatures, Tg), substrates (alumina and aluminum) and particles sizes (4 !m and 15 !m). The creep of the signal in time and temperature was also observed. The present work shows also the tremendous effect of Tg on piezoresistive behavior: the high Tg epoxy demonstrating better stability in time and temperature than the other one.