Localized creep analysis of polyurea elastomer from full-field measurements
Localized creep analysis of polyurea elastomer from full-field measurements
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DOI：
10.1007/s11043-022-09572-x
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发表时间：
2022-10
影响因子：
2.5
通讯作者：
N. Huynh;B. Koohbor;G. Youssef
中科院分区：
文献类型：
--
作者：
N. Huynh;B. Koohbor;G. Youssef
聚脲是一种弹性体聚合物，具有分离的链段微观结构和对加载时间和温度敏感的上级机械性能。在导致本报告的研究中，主要目标是阐明不同节段结构对随时间变化的蠕变变形和材料性能（如泊松比和蠕变模量）的贡献。该方法包括记录高分辨率的数字图像和解决全场应变分量的蠕变加载聚脲使用数字图像相关（DIC）分析。由此产生的法向轴向和侧向应变例示了不可压缩弹性体聚合物的典型蠕变响应，表示主要和次要蠕变区域。尽管在单轴加载条件下，可检测到的剪切应变的存在表明蠕变激活剪切软化行为的发生。解析的应变等值线图，独特的DIC应变分析，显示值得注意的应变定位（区分为条纹的应变等值线图）在选定的区域内观察到的区域的兴趣。本地化的菌株被分离和组织的功能经过加载时间。高应变区域归因于聚脲的软段，其机械性能比硬段差。提取的时间历史的条纹揭示了三个不同的分子松弛过程：一个内的主要蠕变归因于复杂的贡献的硬/软段的微观结构和两个过程内的二次蠕变独立地与硬和软域，分别。这项研究的结果是重要的，有效的和通用的聚脲为基础的冲击缓解结构的发展。
Polyurea is an elastomeric polymer with segregated segmental microstructure and superior mechanical properties that are sensitive to loading time and temperature. In the research leading to this report, the primary goal was to elucidate the contributions of different segmental structures to the time-dependent creep deformation and material properties, such as Poisson’s ratio and the creep modulus. The approach consisted of recording high-resolution digital images and resolving the full-field strain components of creep-loaded polyurea using digital image correlation (DIC) analysis. The resulting normal axial and lateral strains exemplified a typical creep response of incompressible elastomeric polymers, denoting the primary and secondary creep regions. Despite the uniaxial loading conditions, the presence of detectable shear strains demonstrated the occurrence of creep-activated shear softening behavior. The resolved strain contour maps, unique to DIC strain analysis, revealed noteworthy strain localization (demarked as striations on the strain contour plots) in selected regions within the observed regions of interest. The localized strains were separated and organized as functions of elapsed loading time. The high-strain regions were attributed to the soft segments of polyurea with inferior mechanical properties to their hard counterparts. The extracted time history of striations revealed three distinct molecular relaxation processes: one within primary creep attributed to the convoluted contributions of the hard/soft segmental microstructure and two processes within secondary creep associated independently with the hard and soft domains, respectively. The outcomes of this research are important for the development of effective and versatile polyurea-based impact-mitigating structures.