Due to environmental concerns, modern transportation solutions demand drastic reductions of fuel consumption and emissions, which can only be achieved with advanced structures using high-performance lightweight materials. For joining these dissimilar materials, adhesive bonding appears as an optimal solution, since mechanical fastening adds weight to the structure, and welding technology is not easily applicable to reinforced plastics and composites. However, one of the major drawbacks associated with bonded joints is the presence of stress concentrations at the overlap ends, especially in single lap joints. In order to reduce these stress concentrations, several techniques have been developed. One of these is the functionally graded adhesive, in which the adhesive properties gradually vary along the overlap length, leading to a more uniform stresses distribution and improving the joint strength. However, the manufacture of an adhesive layer with properties which gradually vary is complex in practice and so is the creation of numerical models that represent these configurations. In the present work, a numerical model for different-graded distribution of adhesive properties along the overlap was developed, using programmed step functions on finite element analysis background in order to discretize and simplify the continuous properties distribution gradient. Cohesive zone modelling was introduced in the numerical model, enabling it to effectively predict graded joint strength. The model was validated with experimental results of functionally graded joints available in the literature. The numerical model developed presents itself as a powerful tool to predict joint strength for functionally graded joints, without imposing large computational demands.

中文翻译：

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剪切载荷作用下多材料梯度接头的数值模拟

由于环境问题，现代交通解决方案需要大幅减少燃料消耗和排放，而这只能通过使用高性能轻质材料的先进结构来实现。对于连接这些不同的材料，粘合剂似乎是一种最佳解决方案，因为机械紧固会增加结构的重量，而且焊接技术不易应用于增强塑料和复合材料。然而，与粘合接头相关的主要缺点之一是在重叠端存在应力集中，尤其是在单搭接接头中。为了减少这些应力集中，已经开发了几种技术。其中之一是功能梯度粘合剂，其中粘合剂性能沿重叠长度逐渐变化，导致更均匀的应力分布并提高接头强度。然而，具有逐渐变化的特性的粘合剂层的制造在实践中是复杂的，并且代表这些配置的数值模型的创建也是如此。在目前的工作中，为了离散化和简化连续的性能分布梯度，开发了沿重叠的不同等级粘合剂性能分布的数值模型，在有限元分析背景下使用程序化的阶跃函数。数值模型中引入了内聚区建模，使其能够有效地预测分级接头强度。该模型通过文献中可用的功能分级关节的实验结果进行了验证。