Simultaneous noncontact strain and temperature measurement is needed together with continuous recording of the sample weight. Displacements are monitored at several points by non-contacting optical sensors. Relative motion of the top of the spring to the sample top gives the sample weight change via the spring constant. Relative motion of the sample bottom to top gives the expansion coefficients. Laser speckle sensors have been used but a simpler method involves the integrated luminance of a laser spot moving across a sample feature such or a silver paint spot.
Temperature is measured with an infrared thermometer or thermocouples on a witness sample.
A second method employs an athermalized quartz reference frame design. A PZT stack makes electrical contact to the sample supported by the spring and further PZT displacement pushes the sample against another contact for length measurement. Applications are discussed and typical results are given for fiber reinforced polymer matrix composite materials. Data on CME, CTE, diffusivities and boundary layer effects are presented to show the systems' capabilities. However, actuating and then sensing the load and deformation are difficult and pose major problems in testing micro-specimens mechanically.