Natural rubber (NR) exhibits strain-induced crystallization (SIC), enhancing tearing strength and crack resistance. However, the reinforcement mechanism along with nonuniform strain around a crack tip remains unclear. We reveal the nonuniform stress field around a crack tip using the DIC-based deformation field data and a hyperelasticity approach. A hyperelastic strain energy density function (W) is derived to be able to replicate stress-strain data across various deformations, encompassing equal and unequal biaxial, uniaxial, and pure shear stretching. These data cover the full range and magnitude of deformations around the crack tip. SIC significantly impacts the singular behaviors of strain and stress near the crack tip, causing a pronounced stress increase and strain decrease within the SIC zone that extends up to approximately 100 μm away from the crack tip. This results in a distinct crossover in singularity power-law index between the SIC zone and the fully amorphous zone. With increasing crack opening, the stress upturn intensifies, and the crossover shifts away from the crack tip due to SIC zone enlargement and local crystallinity increase. These findings deepen our understanding of the physics of SIC near crack tips and its reinforcement mechanism in strain-induced crystallizable soft solid materials.

中文翻译：

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应变诱导结晶弹性体中的裂纹尖端应力增强


天然橡胶 （NR） 表现出应变诱导结晶 （SIC），增强了撕裂强度和抗裂性。然而，加固机制以及裂纹尖端周围的非均匀应变仍不清楚。我们使用基于 DIC 的变形场数据和超弹性方法揭示了裂纹尖端周围的非均匀应力场。推导了超弹性应变能密度函数 （W），以便能够复制各种变形的应力-应变数据，包括相等和不相等的双轴、单轴和纯剪切拉伸。这些数据涵盖了裂纹尖端周围变形的整个范围和大小。SIC 显著影响裂纹尖端附近应变和应力的奇异行为，导致 SIC 区域内应力明显增加和应变减少，该区域从裂纹尖端延伸至约 100 μm。这导致 SIC 区和完全非晶区之间的奇异性幂律指数出现明显的交叉。随着裂纹张开度的增加，应力上翻加剧，由于 SIC 区扩大和局部结晶度增加，分叉从裂纹尖端移开。这些发现加深了我们对裂纹尖端附近 SIC 的物理特性及其在应变诱导可结晶软固体材料中的加固机制的理解。