The fracture toughness of inelastic materials consists of an intrinsic component associated with the crack tip fracture process and a dissipative component due to bulk dissipation. Experimental characterization of the intrinsic component of fracture toughness is important for understanding the fracture mechanism and predictive modeling of the fracture behavior. Here we present an experimental study on the intrinsic toughness of a soft viscoelastic adhesive. We first obtained full-field and full-history data of the displacement and deformation fields in pure shear fracture tests using a particle tracking method. By combining these data with a nonlinear constitutive model, we extracted the intrinsic toughness through an energy balance analysis. A two-stage crack propagation behavior was observed in our fracture experiments: under monotonic loading the crack first underwent a slow propagation stage and then suddenly entered a fast propagation stage. We found that the intrinsic toughness was highly scattered for the slow propagation stage, but remained consistent for the fast propagation stage. Further examination of the fracture surface and the onset of fast propagation revealed that transition from the slow to the fast propagation stage was governed by the applied stretch and was likely due to a change in the crack tip fracture process.

中文翻译：

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软粘弹性粘合剂的固有断裂韧性


非弹性材料的断裂韧性由与裂纹尖端断裂过程相关的固有成分和由于体耗散引起的耗散成分组成。断裂韧性本质成分的实验表征对于理解断裂机制和断裂行为的预测建模非常重要。在这里，我们对软粘弹性粘合剂的固有韧性进行了实验研究。我们首先使用粒子跟踪方法获得了纯剪切断裂试验中位移和变形场的全场和全历史数据。通过将这些数据与非线性本构模型相结合，我们通过能量平衡分析提取了内在韧性。在我们的断裂实验中观察到两阶段裂纹扩展行为：在单调载荷下，裂纹首先经历缓慢扩展阶段，然后突然进入快速扩展阶段。我们发现，在慢速传播阶段，内在韧性高度分散，但在快速传播阶段保持一致。对断裂表面和快速扩展开始的进一步检查表明，从慢速到快速扩展阶段的转变是由所施加的拉伸控制的，并且可能是由于裂纹尖端断裂过程的变化所致。