Abstract Stress concentrations at the overlap ends are one of the main reasons for strength reduction in adhesive joints. The bi-adhesive technique was introduced as an efficient solution to reduce the stress concentrations at the overlap ends. Although several works have dealt with the numerical analysis of edge effects in bi-adhesive joints, none of them have experimentally analyzed the strain distribution along the bi-adhesive bondline. Moreover, the interaction of some geometrical parameters on the performance of bi-adhesive joints has not been studied yet. The aim of the current research is to present a comprehensive experimental analysis of bi-adhesive single lap joints using the digital image correlation (DIC) technique. Therefore, two different adhesives (one stiff and one flexible) were selected. Different parameters such as adhesive thickness, substrate thickness and length ratio (length of flexible adhesive at one overlap end to the total overlap length) were considered. Furthermore, the interaction of these parameters were experimentally analyzed using the DIC method. A numerical analysis was also conducted to analyze the effect of length ratio on the strain distribution along the bondline. Based on the results, the failure initiates at the interface between the stiff and flexible adhesives and kinks through the brittle adhesive. DIC results illustrate that the effect of length ratio on the adhesive peel strain increases by increasing the adhesive thickness and decreases by increasing the adherend stiffness.

中文翻译：

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使用DIC技术的双胶单搭接接头综合实验研究

摘要 搭接端应力集中是胶接接头强度降低的主要原因之一。引入了双粘合剂技术作为减少重叠端应力集中的有效解决方案。尽管有几项工作处理了双胶接头边缘效应的数值分析，但没有一项工作对沿双胶粘合层的应变分布进行了实验分析。此外，尚未研究一些几何参数对双粘接头性能的相互作用。当前研究的目的是使用数字图像相关 (DIC) 技术对双胶单搭接接头进行全面的实验分析。因此，选择了两种不同的粘合剂（一种是硬的，一种是柔性的）。考虑了不同的参数，例如粘合剂厚度、基材厚度和长度比（一个重叠端的柔性粘合剂的长度与总重叠长度）。此外，使用 DIC 方法对这些参数的相互作用进行了实验分析。还进行了数值分析以分析长度比对沿粘合线的应变分布的影响。根据结果​​，失效开始于刚性和柔性粘合剂之间的界面，并通过脆性粘合剂扭结。DIC 结果表明，长度比对粘合剂剥离应变的影响随着粘合剂厚度的增加而增加，随着被粘物刚度的增加而降低。考虑基材厚度和长度比（一个重叠端的柔性粘合剂长度与总重叠长度）。此外，使用 DIC 方法对这些参数的相互作用进行了实验分析。还进行了数值分析以分析长度比对沿粘合线的应变分布的影响。根据结果​​，失效开始于刚性和柔性粘合剂之间的界面，并通过脆性粘合剂扭结。DIC 结果表明，长度比对粘合剂剥离应变的影响随着粘合剂厚度的增加而增加，随着被粘物刚度的增加而降低。考虑基材厚度和长度比（一个重叠端的柔性粘合剂长度与总重叠长度）。此外，使用 DIC 方法对这些参数的相互作用进行了实验分析。还进行了数值分析以分析长度比对沿粘合线的应变分布的影响。根据结果​​，失效开始于刚性和柔性粘合剂之间的界面，并通过脆性粘合剂扭结。DIC 结果表明，长度比对粘合剂剥离应变的影响随着粘合剂厚度的增加而增加，随着被粘物刚度的增加而降低。还进行了数值分析以分析长度比对沿粘合线的应变分布的影响。根据结果​​，失效开始于刚性和柔性粘合剂之间的界面，并通过脆性粘合剂扭结。DIC 结果表明，长度比对粘合剂剥离应变的影响随着粘合剂厚度的增加而增加，随着被粘物刚度的增加而降低。还进行了数值分析以分析长度比对沿粘合线的应变分布的影响。根据结果​​，失效开始于刚性和柔性粘合剂之间的界面，并通过脆性粘合剂扭结。DIC 结果表明，长度比对粘合剂剥离应变的影响随着粘合剂厚度的增加而增加，随着被粘物刚度的增加而降低。