Effects of experimental variables on PMMA nano-indentation measurements

This work aims to investigate the effects of experimental variables on nano-indentation measurements on PMMA. A wide range of conditions, including different load levels, loading rates, holding times and unloading rates were employed to examine the sensitivity of nano-indentation measurements to the selected experimental variables. The test results indicate that the elastic modulus and hardness of PMMA are approximately load-level invariant. However, they are sensitive to the loading rate, holding time and unloading rate. Both elastic modulus and hardness increase with increasing loading rate, while increasing holding time leads to decreasing elastic modulus and hardness. Moreover, the unloading rate has almost no obvious effect on the hardness of PMMA, while the opposite is true for elastic modulus.