Modeling and Simulation of Nanoindentation into Polymer Thin Films by Finite Element Method
Keywords:
UHMWPE, PMMA, Loading/unloading characteristic, Nanoindentation, FEM,Abstract
Nanoindentation technique is being widely used to measure the hardness and elastic modulus of thin film coatings. It is being used extensively to measure the nanomechanical properties of hard thin films. However, the determination of the surface mechanical properties of polymeric materials with such techniques is relatively new. In this paper, an attempt has been made to simulate the nanoindentation process into polymer thin films by Finite Element Modeling (FEM) Technique. FEM has been done to extract both elastic and visco elastic properties of polymeric thin films. The experimental values of elastic moduli available from the literature for bulk Polymethyl Methacrylate (PMMA) and ultra-high molecular weight polyethylene (UHMWPE) are used to simulate the nanoindentaion into their thin films. In linear elasticity case, the load-displacement data obtained by simulation is used to calculate the Young’s modulus and hardness of the thin films and it is found that the thin films are superior in surface hardness than to bulk materials. The Stress and Strain calculation with plastic deformation of the thin film was simulated by FEM. The model is extended to measure time-dependent behavior (Visco elastic) of polymeric films. In Visco elastic case, the load-displacement data is obtained as a function of time and is compared with that of the analytical results. A good correlation is found between the simulated results and analytical results. The obtained load-displacement data is used to calculate visco elastic properties of polymer thin films i.e., the relaxed shear modulus and Creep compliance. The thin films properties are measured with no substrate influence, and considering the indentation experiments made with in the thumb rule of 10% of the film thickness.
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