Abstract This study quantifies the effect of mixed mode loading and bond line thickness on adhesive joint strength for automotive structural applications. This research is motivated by the need to address the complex loading that occurs during automotive crash events, as well as the variation in bond line thickness that may occur due to gap variability when joining mass-produced structural components. A newly developed specimen geometry for Mode II and Mixed Mode loading is presented, while a recently published test methodology was used to characterize the Mode I response. Three nominal bond line thicknesses (0.18, 0.30 and 0.64 mm), were investigated for a toughened structural adhesive and steel adherends. The traction-separation response, required for cohesive zone modeling (CZM) of adhesive joints, was determined for each combination of bond line thickness and mode of loading. Mode I loading resulted in higher peak traction and lower critical energy release rates compared to Mode II loading, with the Mixed Mode responses typically falling between Mode I and II, in relation to the loading angle tested. Increasing bond line thickness resulted in a reduction in initial stiffness and peak traction, as well as an increase in critical energy release rate for all modes of loading. Two existing CZM mixed mode failure criteria were assessed and demonstrated a good fit to the tested mixed mode responses, despite the limited ability of the CZM implementation to predict the end of the plateau region of the traction-separation response. The experimental approach described in this study was shown to provide repeatable results that could be directly used to fully define an adhesive CZM, ready for use in finite element modeling without the need for inverse modeling.

中文翻译：

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使用新型测试试样几何形状量化混合模式载荷和粘合线厚度对胶粘剂接头强度的影响

摘要 本研究量化了混合模式载荷和粘合线厚度对汽车结构应用中粘合接头强度的影响。这项研究的动机是需要解决汽车碰撞事件期间发生的复杂载荷，以及在连接批量生产的结构部件时可能由于间隙可变性而发生的粘合层厚度变化。介绍了一种新开发的用于模式 II 和混合模式加载的试样几何形状，同时使用最近发布的测试方法来表征模式 I 响应。研究了增韧结构粘合剂和钢被粘物的三种标称粘合线厚度（0.18、0.30 和 0.64 毫米）。粘合接头的内聚区建模 (CZM) 所需的牵引-分离响应，确定粘合线厚度和加载模式的每种组合。与模式 II 加载相比，模式 I 加载导致更高的峰值牵引力和更低的临界能量释放率，混合模式响应通常介于模式 I 和 II 之间，与测试的加载角度有关。增加粘合线厚度导致初始刚度和峰值牵引力降低，以及所有加载模式的临界能量释放率增加。尽管 CZM 实施预测牵引分离响应的平台区域结束的能力有限，但评估了两个现有的 CZM 混合模式故障标准，并证明了与测试的混合模式响应的良好拟合。