Our recent studies departed from the conventional description of polymer fracture behavior while maintaining consistency with the principles of material mechanics including linear elastic fracture mechanics (LEFM). In traditional fracture mechanics of brittle materials, crack resistance is quantified in terms of toughness G_c, which represents the critical energy release per unit fracture surface area. This perspective suggests that high G_c involved high energy dissipation. A new perspective has surfaced, proposing a fundamental yet underexplored, seemingly universal fracture mechanism and explaining the origin of high G_c within an alternative framework. According to this view, for unfilled plastics and elastomers, fracture initiates when local tensile stress surpasses the polymer’s fracture strength σ_F(inh), and high toughness is a consequence of high fracture strength. Remarkably, for polymers in both plastic and elastomeric states, their inherent strength σ_F(inh) appears to be of a comparable magnitude to the nominal tensile strength σ_b. Spatial–temporal resolved polarized optical microscopic (str-POM) measurements have started to provide insight into the fracture mechanism and unveil a concealed length scale (P) representing the size of a stress saturation zone at the crack tip. The two-parameter theoretical framework shows (a) toughness of brittle plastics increases quadratically with its strength σ_F(inh) and linearly with P and (b) elastomers exhibit significantly greater toughness and higher tensile strength at lower temperatures due to the increased stability of covalent bonds given the lower thermal energy and plausible frictional effect on bond vibration frequency. Embracing this emerging paradigm where we recognize polymer strength to be time-dependent, we anticipate new advancements in polymer design and a clearer understanding of the fracture behavior of polymeric materials.

中文翻译：

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聚合物在塑性和弹性状态下的断裂行为

我们最近的研究偏离了聚合物断裂行为的传统描述，同时保持了与包括线弹性断裂力学（LEFM）在内的材料力学原理的一致性。在传统的脆性材料断裂力学中，抗裂性用韧性G _c来量化，它代表单位断裂表面积的临界能量释放。这个观点表明高G _c涉及高能量耗散。一种新的观点已经出现，提出了一种基本但尚未充分探索、看似普遍的断裂机制，并在替代框架内解释了高G _c的起源。根据这一观点，对于未填充的塑料和弹性体，当局部拉伸应力超过聚合物的断裂强度σ _F(inh)时，断裂就会开始，而高韧性是高断裂强度的结果。值得注意的是，对于塑性和弹性状态的聚合物，其固有强度 σ _F(inh)似乎与标称拉伸强度 σ _b相当。时空分辨偏振光学显微 ( str -POM) 测量已开始深入了解断裂机制，并揭示了代表裂纹尖端应力饱和区大小的隐藏长度尺度 ( P )。双参数理论框架表明，(a) 脆性塑料的韧性随其强度 σ _F(inh)呈二次方增加，并与P呈线性增加；(b) 弹性体在较低温度下表现出明显更大的韧性和更高的拉伸强度，因为弹性体的稳定性增加共价键具有较低的热能和对键振动频率的合理摩擦效应。拥抱这一新兴范例，我们认识到聚合物强度随时间变化，我们预计聚合物设计将取得新进展，并对聚合物材料的断裂行为有更清晰的了解。