ABSTRACT
The complex shear modulus properties of an electro-rheological fluid, composed of 50 wt.% of starch in 50 wt.% of silicone oil, was determined experimentally by the application of the direct stiffness technique and an ER fluid device consisting of concentric cylinders. The electric field strength, temperature and frequency ranges of the measurements were 0.0 to 2.0 kVmm-1, 0 to 60 °C and 30 to 300 Hz respectively. The results show that the shear modulus of the ER fluid decreased by a factor of up to 20 as the temperature was increased from 0 to 60 °C, whereas the shear loss factor increased from a low value of about 0.05 at 0 °C to a high value of about 1.0 at 60°C. Conversely, as the electric field strength was increased from 0.0 to 2.0 kVmm-1, the shear modulus increased whereas the loss factor decreased. However, both the shear modulus and loss factor increased in value as the excitation frequency was increased. By means of the temperature-frequency superposition principle, master curves of shear modulus and loss factor, which vary with frequency over several decades at a constant reference temperature and for two values of electric field strength, were derived from the measured data.
