Determining the constitutive behavior of nonlinear visco-elastic-plastic PMMA thin films using nanoindentation and finite element simulation

• Published in: Materials & design 2021-01, Vol.197, p.109239, Article 109239
• Main Authors: Li, Hongzhou, Chen, Jialian, Chen, Qinghua, Liu, Ming
• Format: Article
• Language: English
• Subjects: Nanoindentation; Nonlinear visco-elastic-plastic; Poly (methyl methacrylate); Simulation; Strain rate sensitivity
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.109239

Understanding the nonlinear visco-elastic-plastic behavior and properties of PMMA thin films during nanoindentation is helpful for predicting the plastic deformation of thermoplastic polymer products during manufacture and evaluating stress to predict the reliability and failure behavior of their service structures. This article reports a study on the nanoindentation of PMMA thin films via instrumented indentation testing and numerical simulation to determine its constitutive behavior. It is found that both the loading curve and the unloading curve at any depth can be generated from one indentation depth for the indentation tests of PMMA thin films with Berkovich indenter. By coupling experimental investigation and finite element simulation, we investigated the possibility of applying the Oyen-Cook constitutive equation to nonlinear viscous-elastic-plastic PMMA thin films. The results of finite element analysis show that the time-dependent elastic-plastic deformation of the unloading curves becomes more conspicuous when the quadratic viscosity term of the Oyen-Cook constitutive equation is decreased. Finite element simulations using the Oyen-Cook constitutive model reproduce the experimentally-measured indentation load-displacement curves with reasonable accuracy. [Display omitted] •Both loading curve and unloading curve at any depth can be generated from one indentation depth by scaling P ∝ h2•Oyen-Cook constitutive equation is used to explain the nanoindentation behavior of poly (methyl methacrylate) films•Finite element simulations reproduce the experimentally-measured indentation load-displacement curves