Abstract Designing joints requires a clear understanding of the appropriate thickness of the adhesive used. Structural acrylic adhesives have rarely been studied in terms of their thickness effect on the joint performance. To this end, the fracture resistance of a second-generation acrylic (SGA) adhesive was experimentally investigated by conducting a double cantilever beam (DCB) test. Because the SGA adhesive whitened when plastically deformed, the change of the plastic region with the crack growth was visualized. Therefore, the relationship between the fracture energy and the adhesive thickness was explained in terms of the plastically deformed area. With a thinner adhesive layer, the entire layer was whitened, and a linear relationship was obtained. In this region, the fracture energy increased from approximately 2 kJ/m2 with an adhesive thickness of 0.2 mm to approximately 4 kJ/m2 with 0.6 mm thickness. With more increase in the thickness, the fracture energy increased over 8 kJ/m2. Increasing the thickness, however, resulted in partial whitening, yielding a non-linear relationship. Moreover, increasing the loading rate changed fracture behavior. At the opening speed of 2.5 m/s, stick-slip crack propagation was observed in any adhesive thickness, and the critical fracture energy dramatically decreased. In contrast, the arrest fracture energy under unstable crack propagation was independent of the loading rate and the adhesive thickness as approximately 1 kJ/m2.

中文翻译：

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不同加载速率下胶粘剂厚度对结构丙烯酸胶接缝断裂行为影响的实验研究

摘要 设计接缝需要清楚了解所用粘合剂的适当厚度。结构丙烯酸粘合剂很少研究其厚度对接头性能的影响。为此，通过进行双悬臂梁 (DCB) 测试，对第二代丙烯酸 (SGA) 粘合剂的抗断裂性进行了实验研究。由于 SGA 粘合剂在塑性变形时会变白，因此可以看到塑性区域随裂纹扩展的变化。因此，断裂能和胶粘剂厚度之间的关系可以用塑性变形面积来解释。使用较薄的粘合剂层，整个层都变白，并获得线性关系。在这个地区，断裂能从粘合剂厚度为 0.2 mm 时的约 2 kJ/m2 增加到 0.6 mm 厚度时的约 4 kJ/m2。随着厚度的增加，断裂能增加超过 8 kJ/m2。然而，增加厚度会导致部分变白，产生非线性关系。此外，增加加载速率会改变断裂行为。在打开速度为 2.5 m/s 时，在任何粘合剂厚度下都观察到粘滑裂纹扩展，临界断裂能急剧下降。相比之下，不稳定裂纹扩展下的止动断裂能与加载速率和粘合剂厚度无关，约为 1 kJ/m2。然而，增加厚度会导致部分变白，产生非线性关系。此外，增加加载速率会改变断裂行为。在打开速度为 2.5 m/s 时，在任何粘合剂厚度下都观察到粘滑裂纹扩展，临界断裂能急剧下降。相比之下，不稳定裂纹扩展下的止动断裂能与加载速率和粘合剂厚度无关，约为 1 kJ/m2。然而，增加厚度会导致部分变白，产生非线性关系。此外，增加加载速率会改变断裂行为。在打开速度为 2.5 m/s 时，在任何粘合剂厚度下都观察到粘滑裂纹扩展，临界断裂能急剧下降。相比之下，不稳定裂纹扩展下的止动断裂能与加载速率和粘合剂厚度无关，约为 1 kJ/m2。