Abstract In this work we propose to model the mechanical and fracture response of semi-crystalline low-density polyethylene (LDPE) films exposed to accelerated ultraviolet (UV) ageing using a physically based visco-hyperelastic–viscoplastic approach. UV irradiation induces an alteration of the chemical and structural properties of the semi-crystalline polymer, which affects significantly its mechanical behavior. In this work, pristine and oxidized low-density polyethylene films are characterized by conventional physico-chemical and mechanical techniques (FTIR spectroscopy, DSC, HT-GPC, and uniaxial tensile testing). Polyethylene exhibits an oxidation-induced strengthening for a low range of UV radiation doses and a cavitation-induced softening for higher UV radiation doses. A competing multi-scale phenomena induced by UV radiation are incorporated into the constitutive model to capture the macroscopically observed mechanical and fracture behavior. Namely, the model will incorporate at the nano scale, chain scissions and cross-linking and at the meso and macro scales, oxidation-induced cracking, chemi-crystallization, and mechanical damage. The model used the high-temperature gel permeation chromatography-measured molecular weight as degradation indicator. The model was able to capture accurately the evolution of the macroscopically observed mechanical and fracture behavior over a wide range of UV irradiation doses.

中文翻译：

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模拟光降解半结晶低密度聚乙烯薄膜的粘-超弹-粘塑性行为

摘要 在这项工作中，我们建议使用基于物理的粘-超弹-粘塑性方法模拟暴露于加速紫外线 (UV) 老化的半结晶低密度聚乙烯 (LDPE) 薄膜的机械和断裂响应。紫外线照射会导致半结晶聚合物的化学和结构特性发生改变，这会显着影响其机械性能。在这项工作中，原始和氧化的低密度聚乙烯薄膜通过传统的物理化学和机械技术（FTIR 光谱、DSC、HT-GPC 和单轴拉伸测试）进行表征。聚乙烯在低范围的紫外线辐射剂量下表现出氧化诱导的强化，而在较高的紫外线辐射剂量下表现出空化诱导的软化。由紫外线辐射引起的竞争性多尺度现象被纳入本构模型，以捕捉宏观观察到的机械和断裂行为。也就是说，该模型将在纳米尺度、断链和交联以及在中观和宏观尺度上结合氧化诱导开裂、化学结晶和机械损伤。该模型使用高温凝胶渗透色谱法测量的分子量作为降解指示剂。该模型能够准确捕捉宏观观察到的机械和断裂行为在广泛的紫外线照射剂量范围内的演变。断链和交联以及细观和宏观尺度、氧化诱导开裂、化学结晶和机械损伤。该模型使用高温凝胶渗透色谱法测量的分子量作为降解指示剂。该模型能够准确捕捉宏观观察到的机械和断裂行为在广泛的紫外线照射剂量范围内的演变。断链和交联以及细观和宏观尺度、氧化诱导开裂、化学结晶和机械损伤。该模型使用高温凝胶渗透色谱法测量的分子量作为降解指示剂。该模型能够准确捕捉宏观观察到的机械和断裂行为在广泛的紫外线照射剂量范围内的演变。