Dynamic mechanical analysis

Dynamic Mechanical Analysis (DMA) or Dynamic Mechanical Thermal Analysis (DMTA)

DMA is a technique used to study and characterise materials. It is most especially useful for observing the viscoelastic nature of polymers. An oscillating force is applied to a sample of material, the resulting displacement of the sample is measured. From this the sample stiffness can be measured, and the sample modulus can be calculated. By measuring the time lag in the displacement compared to the applied force it is possible to determine the damping properties of the material. Viscoelastic materials such as polymers typically exist in two distinct states. They exhibit the properties of a glass (high modulus) at low temperatures and those of a rubber (low modulus) at higher temperatures. By scanning the temperature during a DMA experiment the change of state can be observed and the 'glass transition' temperature (Tg) can be determined.

See also: http://www.triton-technology.co.uk/dmatheory.htm