Advanced Material Characterization: Rheology and DMA using a combined axial-torsional multidrive system

While the use of the upper rotational motor allows one to perform measurements in combined motor transducer (CMT) mode, the use of two rotational motors allows one to work in the separate motor transducer (SMT) mode and the counter movement mode on one device. CMT mode not only allows all tests and options a single drive rheometer can do but advanced powder rheology characterization in the fluidized dynamic state through the use of a classical pressure drop device attached to the rheometer are also possible. A ring shear cell attached to the rheometer in CMT mode allows one to do quasi-static characterization of granular materials at elevated temperatures and humidities.

In the separate motor transducer (SMT) mode the bottom motor acts as the actuator and the top motor acts as the torque transducer. A SMT mode has advantages in sensitivity under certain measurement conditions and allows the use of special tools such as a cone-partitioned-plate (CPP), which enables measurements with edge fracture prone samples, extended frequency sweeps with soft materials such as pressure sensitive adhesives where inertia of the measuring drive can effect results etc., In counter movement mode both motors rotate or oscillate in opposite directions which enables the creation of a stagnation plane in the sheared sample which could be beneficial for investigation of Taylor-Couette instabilities or extending the range of shear rates for high shear rheology applications or for rheo-microscopy, since the structures under investigation are not moving out of the field of view when shear is applied. In addition, combining the upper rotational motor with a linear drive in the bottom permits one to apply force and deflections in the axial direction which has several advantages. For instance, the combination of both linear and rotational measurement makes it possible to determine the complex Young’s modulus |E*| and the complex shear modulus |G*| for a single sample in one continuous measurement which further helps determine the viscoelastic Poisson’s ratio for isotropic materials.

In the case of anisotropic materials modulus information in both longitudinal and transversal directions can be obtained which could be particularly useful to evaluate anisotropy present in the sample. In this talk benefits of having such a modular device configuration for comprehensive material characterization in different modes will be showcased via different application testing examples.