Dynamic Mechanical Compliance Testing (DMCT) for depth profiling and viscoelastic properties
Standard load head on the left, DMCT load head on the right
MicroMaterials have developed a new loading head for dynamic compliance testing. This new module allows measurements of depth profiles and viscoelastic properties. In conventional indentation, the load on the indenter is increased continuously to a maximum value before being reduced to produce an unloading Depth vs. Load curve. A single value of contact stiffness can be derived from this curve.
In DMCT, a sinusoidal signal is superimposed on the load ramp such that, in effect, multiple nano unloading steps may be observed during the loading phase. The final unloading curve is not utilized for this measurement. The behavior of the oscillating indenter is described by a forced harmonic motion model. A calibration procedure characterizes the system properties: damping, spring stiffness, and mass of the loading head. These system characteristics, together with measured values of oscillation amplitude for a given oscillatory force or displacement allow the determination of contact stiffness
By monitoring the phase difference between the applied oscillatory force and the resulting indenter displacement, it is also possible to measure the storage and loss moduli of polymers. In the DMCT module, Micro Materials have developed an improved approach using an additional 0-500 mN loading head with software and hardware features enabling a greater control of oscillation parameters which produce more reliable data.
The DMCT module can be used for:
- Depth profiling of the mechanical properties like hardness, elastic modulus, H/E, contact stiffness.
- Viscoelastic property measurements (storage modulus, loss modulus, tan delta) at chosen frequencies and test temperatures.
Important new developments include:
- A novel procedure (patent pending) for optimizing indenter oscillation control at low loads.
- An option for non-constant oscillation amplitude, where the oscillation force varies with load to achieve a fixed oscillation depth and therefore elastic modulus measurements on metallic materials.
- A new head design with the option of variable damping for optimized polymer analysis. The new loading head is again horizontal and maintains a significant advantage for high temperature testing.
Click here for 3 case studies on the various options enabled by the DMCT-module: metallic materials, thin films, and viscoelastic nanocomposites.
