Flexible Graphite for Sensing Stress/Displacement

Flexible graphite sandwiched by copper, after stabilization by two cycles of compressive stress, is a piezoresistive compressive stress/displacement sensor for stresses (perpendicular to the sandwich plane) up to 4 MPa and displacements up to 25% of the flexible graphite thickness. The stress sensitivity (fractional change in resistance per unit stress) is up to 5.4 MPa-' and displacement sensitivity (fractional change in resistance per unit strain in graphite) is up to 6.2. The sensitivities decrease with increasing stress/displacement. The electrical resistance decreases reversibly upon compression, due mainly to reversible decrease in the contact resistivity between graphite and copper. Stabilization removes most irreversibility.