Prediction of viscoelastic and plastic properties of polymers

Indentation methodologies are gaining popularity as they provide means of local property estimation, utilize small-er sample sizes, and do not destroy specimens. Classically, indentation has been used to measure hardness and Young’s modulus [1], but researchers have also proposed ways of predicting stress–strain curves [2], yield strength [3], and fracture toughness [3]. Different indentation techniques are being used by researchers for differ-ent types of investigations. Nanoindentation is an indentation at very small scales to obtain local properties via sin-gle indent. Reference Point Indentation (RPI) is a technique wherein multiple indents are carried out at the same location and the material response with repeated loading is monitored. Researchers have shown that increase in indentation depth during loading cycles can be used to predict material’s resistance to fracture [4]. Osteopro-be is a hand held indentation device which has been designed for in-situ bone quality measurements in clinical setting. In this study, we investigate the viscoelastic and plastic properties of polymers like PMMA using different microindentation techniques. Nine different polymers have been selected, which are commonly used for rapid prototyping applications. Some of the polymers exhibit very rubber like behavior, whereas others are stiffer and brittle. Indentation experiments are conducted on the nine polymers using the RPI equipment as well as the Os-teoprobe. Similarities and differences in material behavior and predicted properties between these methods are o