Dynamic mechanical analysis (DMA)

The most common method for thermal characterisation of polymeric matrix composites is the dynamic mechanical analysis (DMA) method. There are several types of DMA, including torsion pendulum analysis (TPA) and forced oscillation measurements where the oscillation may be in tension, torsion or shear. All these DMA techniques produce curves of dynamic storage and loss modulus and loss tangent (tan ) as a function of temperature. Tan is proportional to the ratio of the loss modulus (E" or G") to the storage modulus (E' or G'). The parameters give the amount of energy dissipated during each loading cycle. At the glass transition, these parameters go through a peak value. Similarly to other methods of measuring , the interpretation of the curves is aided by software and the value of may be determined as the temperature at the onset or the midpoint of the transition based on the storage modulus curve at the maximum in tan .

For DMA testing of composites ASTM D 4065 is often used although this was developed for plastics. The methods describes both forced and resonance techniques.