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Numerical Simulation of the Crack Formation in the Quenched Poly( l ‐lactic acid) Spherulites
Author(s) -
Liu Yanping,
Wei Hanghang,
Wang Junli,
Li Qian
Publication year - 2018
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/mats.201700043
Subject(s) - spherulite (polymer physics) , materials science , optical microscope , composite material , stress (linguistics) , quenching (fluorescence) , crystallization , scanning electron microscope , isothermal process , thermal , boundary value problem , mechanics , polymer , optics , thermodynamics , mathematics , physics , mathematical analysis , linguistics , philosophy , fluorescence
The quenching process of poly( l ‐lactic acid) spherulites obtained by isothermal crystallization is simulated by ANSYS software in order to study the mechanism of crack formation. Regular concentric circular or hexagon crack is found by polarizing optical microscope and scanning electron microscope. The rapid temperature variation which brings large thermal stress is considered to be the main reason for the crack, so a spherulite with diameter of 160 µm is modeled by ANSYS to compute the transient change of thermal stress. According to the temperature nephogram, it is found that the spherulites temperature almost reduces to zero during 1 s, also the thermal stress dropped by five orders of magnitude. The stress fluctuation of 35 nodes, which are equally spaced from spherulite center to outer, present regular attenuation of vibration periodically from 10 −6 to 10 −4 s while the peak values are different from each other. Furthermore, the differential result of the peak value shows a bell‐shaped curve while the maximum difference between two adjacent nodes reaches 0.12 MPa. Although insufficient of boundary condition will introduce error of calculation, this research is still an important attempt for simulation technique to solve problem in polymer crystallization.