聚合物玻璃变形过程中的结构弛豫时间
The structural relaxation time of a polymer glass during deformation
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中文总结 AI 辅助
通过应变率切换实验测定轻度交联PMMA玻璃变形时的结构弛豫时间，发现其约等于链段关联时间，Chen-Schweizer模型可定性预测相关响应，实验与材料时间假设一致。
中文摘要 AI 辅助
为了测定聚合物玻璃变形过程中的结构弛豫时间，在稳态塑性流动区开展了应变率切换实验。实验采用轻度交联的聚甲基丙烯酸甲酯（PMMA）玻璃，同时利用光学探针重新取向法定量表征玻璃中的链段运动。应变率切换后，观察到非单调的应力响应，与前人研究结果一致；而链段运动的关联时间则单调演化至新的稳态，为变形过程中的结构弛豫时间提供了明确测量值，该值约等于链段关联时间。Chen-Schweizer模型定性预测了链段关联时间的变化及观测到的非单调应力响应。此外，本实验与聚合物变形建模中所用的材料时间假设合理一致，该方法通过将线性响应模型与随时间变化的链段关联时间相结合，描述聚合物玻璃对大变形的响应。
英文摘要
In order to determine the structural relaxation time of a polymer glass during deformation, a strain rate switching experiment is performed in the steady-state plastic flow regime. A lightly cross-linked poly (methyl methacrylate) (PMMA) glass was utilized, and simultaneously the segmental motion in the glass was quantified using an optical probe reorientation method. After the strain rate switch, a non-monotonic stress response is observed, consistent with previous work. The correlation time for segmental motion, in contrast, monotonically evolves towards a new steady-state, providing an unambiguous measurement of the structural relaxation time during deformation, which is found to be approximately equal to the segmental correlation time. The Chen-Schweizer model qualitatively predicts the changes in the segmental correlation time and the observed non-monotonic stress response. In addition, our experiments are reasonably consistent with the material time assumption used in polymer deformation modeling; in this approach, the response of a polymer glass to a large deformation is described by combining a linear-response model with a time-dependent segmental correlation time.
