Elastomer rubbers as deflection elements in pressure sensors: investigation of properties using a custom designed programmable elastomer test rig

Elastomers are of interest for use as deformation elements in pressure and force sensors. In this paper, a custom designed programmable elastomer test rig (PETR) developed in order to allow the routine mechanical evaluation (compression mode) of small elastomer structures (0.3-30 mm thick) is described and characterized. The mechanical properties of two polyurethane and two silicone rubbers were investigated using the PETR. Silastic silicone (Dow Coming 9161) was found to display relatively low hysteresis and good elasticity. More in-depth investigation of this material revealed that the elastic modulus and the hysteresis were independent of the amount of catalyst used in its preparation over the range 2-6% (w/w). The Zener model was found to provide a good representation of the actual stress-strain behaviour of test specimens subjected to load-unload tests at strain rates in the range 1.25-60% min(-1) (load rates 4-200 N min(-1)) and dynamic tests at frequencies in the range 0.001-0.1 Hz. The combined hysteresis and creep for a 1 h test period was not greater than 4%, with the creep contribution being up to 2.3% and occurring in a manner predicted by the Zener model. Specimen form-factor strongly influenced both the elastic modulus and the hysteresis. Increasing the form-factor from 0.5 to 2.6 increased the elastic modulus from about 3.0 to 7.6 MPa while also increasing the hysteresis from 2.4% to 25.2%.