Surface Wrinkling Based Method of Measuring Thin Film’s Mechanical Properties

摘要

The main goal of this project is to develop a wrinkle-based method to measure mechanical properties of thin interfacial polymeric films. Instead of working on a mechanically equilibrium system, this study is focusing on the case where mechanical equilibrium is hard to reach due to the very high viscosity of the bulk phases.udThis thesis describes an air/viscous polymer system with a few-micron scale thick polymer film placed at the interface. We have developed a method to generate dynamic wrinkle patterns on the film via compressing the high viscous substrate. Two experiment parameters are controlled: the substrate thickness H and the compressing strain rateε ̇. This thesis developed an accurate method to measure H while avoiding the interference from the edge effect of the fluid. The compressing strain rate is calculated upon a Matlab program.udWe report the value of wrinkle number under different compressing strain rate and different substrate thickness. Critical strains under different compression strain rate and substrate thickness has been obtained via analyzing the strain for the onset wrinkle.udWe normalize the wrinkle number as well as the compressing strain rate in order to compare them with previous works. With dimensional analysis, a power law relation has been demonstrated between normalized wrinkle number and normalized strain rate.ud