Temperature and strain rate dependences on hardening and softening behaviours in semi-crystalline polymers: Application to PEEK
Temperature and strain rate dependences on hardening and softening behaviours in semi-crystalline polymers: Application to PEEK
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DOI：
10.1016/j.ijsolstr.2019.08.021
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发表时间：
2020-01-01
影响因子：
3.6
通讯作者：
Garcia-Gonzalez, D.
中科院分区：
文献类型：
--
作者：
Barba, D.;Arias, A.;Garcia-Gonzalez, D.
半结晶聚合物通常呈现出复杂的非线性行为，其结合了与不同变形机制相关的热粘弹性和热粘塑性贡献。在初始变形阶段，该过程的影响，而在最终变形阶段，该过程主要是由非晶分子链的流动性和取向的结晶相的断裂和重新取向。此外，结晶相和非晶相的再取向水平强烈地受诸如温度和应变速率的变量的影响。这项工作集中在聚醚醚酮（PEEK）在其不同的热行为区域内的力学行为的作用，这些机制：初始玻璃化区，玻璃化转变和最终橡胶区。为此，PEEK样品在20至240摄氏度的温度和0.0001至0.1 s（-1）的应变速率（涵盖等温和绝热条件）下在单轴拉伸下经受大变形。此外，本构模型提出了补充解释的实验观察，通过熵应变硬化由于热粘弹性效应的影响，以及热粘塑性行为定义的微晶变形和断裂的材料屈服的聚合物链的重新取向。这些结果提供了新的见解低于和高于玻璃化转变，这是显着相关的生物医学假体的热成型工艺的半结晶聚合物的变形机制。(C)2019爱思唯尔有限公司版权所有。
Semi-crystalline polymers often present a complex non-linear behaviour that combines thermo-viscoelastic and thermo-viscoplastic contributions associated to different deformation mechanisms. During the initial deformation stages, the process is influenced by the rupture and reorientation of crystalline phases while, during the final deformation stages, the process is mainly governed by the mobility and orientation of the amorphous molecular chains. Moreover, the level of reorientation of crystalline and amorphous phases is strongly affected by variables such as temperature and strain rate. This work focusses on the role of such mechanisms in the mechanical behaviour of polyether-ether-ketone (PEEK) within its different thermal-behaviour regions: initial glassy region, glass transition and final rubbery region. To this end, samples of PEEK are subjected to large deformations under uniaxial tension at temperatures from 20 to 240 degrees C, and strain rates from 0.0001 to 0.1 s(-1) (covering both isothermal and adiabatic conditions). In addition, a constitutive model is proposed to complementarily explain the experimental observations by means of entropic strain hardening due to reorientation of polymer chains influenced by thermoviscoelastic effects, as well as thermo-viscoplastic behaviours defining the material yielding by means of crystallites deformation and breaking. These results provide new insights into the deformation mechanisms of semi-crystalline polymers below and above glass transition, which are significantly relevant for thermoforming processes of biomedical prosthesis. (C) 2019 Elsevier Ltd. All rights reserved.