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Rate sensitivity and deformation mechanism of semi‐crystalline polymers during instrumented indentation
Author(s) -
Liu Erqiang,
Wu Jianguo,
Li Huaying,
Liu Haitao,
Zhao Guanghui,
Kong Lingyu,
Lin Jinbao,
Xiao Gesheng,
Jia You
Publication year - 2021
Publication title -
journal of polymer science
Language(s) - English
Resource type - Journals
eISSN - 2642-4169
pISSN - 2642-4150
DOI - 10.1002/pol.20200767
Subject(s) - materials science , indentation , softening , composite material , stiffness , strain rate , hardening (computing) , strain hardening exponent , deformation (meteorology) , deformation mechanism , polymer , microstructure , layer (electronics)
Instrumented indentation tests using both constant loading rate (CLR) and continuous stiffness measurement (CSM) operation modes were performed to investigate the deformation mechanism and their sensitivity to the deformation rate in semi‐crystalline polymers through the quantitative analysis of load‐depth loading and unloading curves. The strain rate was constant during the CSM tests, while the strain rate decreased with the increasing of loading time in CLR tests. The mechanical response mechanism of the semi‐crystalline polymers to these tests was very complicated because of the combined effects of strain‐hardening in the crystal phase and strain‐softening in the amorphous phase. Results show that the loading index m reflects the strain‐hardening or strain‐softening response during indentation. When m > 2, the mechanical response was due to the strain‐hardening, and when m < 2, the response was due to strain‐softening. A method based on the measured contact hardness was proposed to obtain the unloading stiffness, and the other mechanical parameters could then be determined according to the unloading stiffness.