In-situ SEM micropillar compression and nanoindentation testing of SU-8 polymer up to 1000 s−1 strain rate
Rahul Cherukuri, Aloshious Lambai, Lassi Sukki, Jari Väliaho, Pasi Kallio, Essi Sarlin, Rajaprakash Ramachandramoorthy, Mikko Kanerva, Gaurav Mohanty
Abstract
In situ micropillar compression and nanoindentation were performed on photolithographically fabricated SU-8 polymer inside a scanning electron microscope (SEM), covering seven orders of strain rates from 10-3 to 103 s−1. The extracted mechanical properties – modulus, hardness, yield strength, strain rate sensitivity (SRS) exponent – were systematically compared from both microscale tests and showed excellent agreement. No change in deformation mechanism was observed at high strain rates. We report a novel experimental protocol for high strain rate nanoindentation, comprising of input profile smoothing, that minimizes resonance amplitude during unloading and allows reliable extraction of modulus and hardness using standard Oliver-Pharr analysis. To the best of our knowledge, this is the first report of mechanical properties of SU-8 beyond 1 s−1 strain rate using nanoindentation based tests.