The modern DMA is a high sensitivity device that measures Storage Modulus (E´) and the Loss Modulus (E´´) of high strength composites, as they are subjected to oscillatory stresses (forces) and resultant strains (displacements). Current instruments provide accurate and reproducible results over a wide range of temperatures. This capability enables the researcher to conduct measurements on rigid composites at low heat-up rates using multi-frequency analysis to give a precise definition of the T_g and associated viscoelastic effects.

Examples

Airframe Composite
A new polymer was strengthened with linear carbon fibers and proposed for an aircraft application. High strength combined with a T_g between 55 and 70°C was desired for best all-around performance.

DMA was employed in a three-point bend mode on a rod-shaped spar. This analysis gave a Young's Modulus (E´) of 58 GPa at 30°C and a T_g = 65.5°C, in accordance with design criteria. High strength was measured even at 230°C and 2140 MPa. Tan d, which is a measure of the energy dissipated to energy stored, showed a peak at 78°C with a value of 0.36. This indicated a high tolerance for mechanical and thermal vibrations in a critical airframe application.

Automotive Composite

DMA of Automotive Composite

A high-strength polymer composite was designed for a heavy-duty automotive application at elevated temperatures.

DMA was employed to test this product using the dual cantilever measurement mode. The analysis, from –20 to 240°C at 1 Hz, showed a high Storage Modulus (E´) with a T_g = 115°C, which was judged desirable for this application. Tan d, which is a measure of the energy dissipated to energy stored, showed excellent elasticity. The DMA also revealed a tendency for surface blistering on the sample. After further heat treatment and curing, the product was selected for the application.