The transparent counter-rotating shear cell was designed and developed in CEMEF. This apparatus consists of two glass plates rotating in opposite directions. The principle of the counter-rotating geometry is represented in Figure 1. Each plate is driven by an independent motor. The advantage of this geometry is that the relative velocities of the two plates can be adjusted so that the velocity of a given particle can be set to zero in the reference framework of the laboratory. This allows to observe the behaviour of a particle suspended in a matrix under shear either for a certain period of time at a given shear or while increasing the shear rate and thus the applied shear stress. Observations during shear are performed via an optical microscope. The device is equipped with powerful motors in order to be able to shear high viscosity fluids like elastomers. A heating system permits the control of the temperature up to 180°C. It consists of a metallic heating plate (see Figure 2) against which the lower plate stands and an oven equipped with resistances. The heating of the sample is performed by conduction through the direct contact between the lower plate and the heating plate. The upper oven heats the shear cell by radiation. Its aim is to keep a constant temperature of the air around the sample and thus to avoid temperature gradients. The upper part of the oven is constituted by two separate parts. This allows to mount the upper oven when the sample is introduced between the two glass plates.
counter-rotating cell : general vue - 56.1 ko