Adhesive bonding is a predominant bonding technique in the aeronautical and automotive industries. Cohesive zone models, used together with the finite element method, are a viable tool to predict the strength of adhesive joints. The main objective of this study is to evaluate experimentally and numerically (by cohesive zone model) the mechanical performance of carbon-fiber reinforced polymer stepped-lap bonded joints submitted to tensile loads, for different overlap lengths (LO) and adhesives. The failure mode analysis showed a predominant failure type for all adhesives and good correspondence with the numerical predictions. Normalized peel (σy) and shear (τxy) stresses in the adhesive highly increased with LO, which then reflected on different maximum load (Pm) evolution with LO, depending on the adhesive's ductility. The damage variable SDEG (stiffness degradation) was also evaluated and emphasized on the smaller damage zone at Pm for the brittle adhesive. A significant geometry and material effect were found on Pm of the stepped-lap joints, with benefit for large LO. In this regard, cohesive zone model revealed to be a suitable tool in determining the behavior of different joints. Comparison with joints with aluminum showed that, provided that no carbon-fiber reinforced polymer delamination occurs, stepped-lap joints between carbon-fiber reinforced polymer adherends give better results due to the higher composite stiffness.

中文翻译：

---

胶粘复合阶梯搭接接头的材料及粘接效果

粘合剂粘合是航空和汽车行业的主要粘合技术。内聚区模型与有限元方法一起使用，是预测粘合接头强度的可行工具。本研究的主要目的是通过实验和数值（通过内聚区模型）评估碳纤维增强聚合物阶梯搭接接合接头在拉伸载荷下的机械性能，对于不同的搭接长度 (LO) 和粘合剂。失效模式分析显示所有粘合剂的主要失效类型与数值预测良好对应。粘合剂中的标准化剥离 (σy) 和剪切 (τxy) 应力随 LO 高度增加，然后反映在随 LO 变化的不同最大载荷 (Pm) 上，具体取决于粘合剂的延展性。还评估了损伤变量 SDEG（刚度退化），并强调了脆性粘合剂 Pm 处较小的损伤区域。在阶梯搭接接头的 Pm 上发现了显着的几何形状和材料效应，这对大 LO 有利。在这方面，内聚区模型被证明是确定不同接头行为的合适工具。与铝接头的比较表明，如果没有发生碳纤维增强聚合物分层，碳纤维增强聚合物被粘物之间的阶梯搭接接头由于更高的复合刚度而得到更好的结果。在这方面，内聚区模型被证明是确定不同接头行为的合适工具。与铝接头的比较表明，如果没有发生碳纤维增强聚合物分层，碳纤维增强聚合物被粘物之间的阶梯搭接接头由于更高的复合刚度而得到更好的结果。在这方面，内聚区模型被证明是确定不同接头行为的合适工具。与铝接头的比较表明，如果没有发生碳纤维增强聚合物分层，碳纤维增强聚合物被粘物之间的阶梯搭接接头由于更高的复合刚度而得到更好的结果。