Direct and Indirect Measurement of Complex Poisson's Ratio - Direct Measurement in Tension

Here, the axial and transverse strains were measured locally with strain gauges (K-CXY3-0015-3-350-O, HBK, Darmstadt, Germany) on cylindric polymethyl methacrylate (PMMA, EH-Design, Wörrstadt, Germany) samples with a diameter of d = 5 mm. Frequency measurements were performed with a rheometer (MCR 702, linear motor, Anton-Paar, Graz, Austria) in the range of 1 Hz to 100 Hz with an axial strain of 0.01 % at constant temperatures in the range of 15 °C to 105 °C. 500 periods were measured per frequency and recorded using a measuring amplifier (Universal Amplifier MX1615B, HBK, Darmstadt, Germany).

Transversal and axial strain is then measured on the PMMA sample with strain gauges in tension mode. The material response in the time domain is transformed to the frequency domain using the Fast Fourier Transform. This gives the axial and transverse amplitude as well as the axial and transverse phase shift.