Modeling the indentation size effects of polymers, based on couple stress elasticity and shear transformation plasticity

分类： 力学 >> 固体力学 提交时间： 2022-05-17

Chao peng Fanlin Zeng

摘要： This work attempts to find out the models which can describe the size effects in modulus and hardness of polymers measured by indentation tests. Firstly, the elastic size effects are described by a model, through introducing a model of elastic unloading load with consideration of couple stress elasticity into the Oliver-Pharr indentation approach. The accordingly proposed modulus model and hardness model agree excellently with a large amount of experimental data obtained from literatures. The models show that the elastic size effects of polymers and their experimental observations are mainly determined by the molecular structures. The fitting results verify that the size effects in indentation hardness of polymers with complex molecular structures are significantly elastic. Secondly, it is postulated that the plastic size effects in indentation hardness of polymers are only derived from their glassy components. A shear transformation plasticity theory proposed for glassy polymers is employed to characterize the plastic size effects. A hardness model is accordingly proposed and agrees well with related experimental data.

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