Measuring Linear Thermal Expansion of Solid Materials by TMA

The thermal mechanical analyzer (TMA) with an expansion probe can be used to determine linear thermal expansion (aka CTE) of solid materials. The standard test method ASTM E 831 describes the instrumentation and how the testing is performed and analyzed.  A sample is cut to a small cube or cylinder to fit on the sample stage with the two faces flat and parallel in the direction of interest for CTE measurement, see picture below.  The sample length should be long enough to provide adequate resolution but not too long to cause thermal gradient within the sample.  A small load or force is placed on the sample from the contacting probe to ensure good contact but not inhibit sample expansion during heating.

To measure the through-thickness CTE of a film sample it is sometimes necessary to stack multiple sheets to increase overall sample length/thickness in order to improve resolution of the measurement.

TMA expansion probe with sample

TMA expansion probe with sample