Finite element analyses and simulation of the failure of short-fiber reinforced thermoplastics and aluminium blanks by clinching

最近，在不同的工程应用中，特别是在汽车和航空工业中，新型复合材料的出现正在促进传统金属的替代，其目的是生产高度优化的结构部件，主要是在结构重量，刚度和强度方面。例如，在汽车行业使用短纤维增强塑料（SFRPs）来实现复杂的设计概念，这需要非常高的生产率。在同等的极限强度下，sfrp比金属材料更轻，可以显著减轻新一代汽车的重量，从而提高性能和降低油耗。同时，SFRPs在多轴加载条件下表现出高度复杂的非线性材料行为，这是由于其相应的注塑工艺造成的。当前汽车工业的趋势是新一代汽车结构的概念，其中多材料或混合试样定义正在逐步采用。因此，铝金属板可以与短纤维增强塑料（SFRPs）结合使用，用于生产混合组件。回火夹紧是一种很有前途的机械连接工艺，本项目对其进行了数值和实验研究。考虑到强度和刚度行为，回火夹紧过程中的关键挑战是考虑温度相关变形以及两种材料的高度各向异性材料行为。在SPP 1640项目的第三阶段，在考虑塑性的基础上，对短纤维增强塑料和铝的渐进损伤和破坏进行了表征、建模，并将其整合到不同材料板厚的整体有限元模型中。对铝与短纤维增强塑料在夹紧过程中的渐进损伤和破坏进行了数值模拟和实验研究。因此，数值计算结果与实验研究结果相吻合。随后，对夹持过程进行了参数化，并对夹持接头的渐进损伤和破坏进行了有限元分析。明确了刀具的相关几何参数，确定并验证了刀具的最佳几何形状。这些发展将允许基于仿真的评估和改进所产生的夹持接头的阻力，从而导致可靠和稳健的混合夹持接头制造。

Recently, in different engineering applications, especially in the automotive and aeronautical industries, the advent of new composites is promoting the replacement of the traditionally employed metals with the aim of producing highly optimized structural components, principally in terms of structural weight, stiffness and strength. This is the case for instance for the use of short fiber reinforced plastics (SFRPs) for the realization of intricate design concepts in the automotive sector, where very high production rates are required. At comparable ultimate strength, SFRPs are lighter than metallic materials, allowing a significant weight reduction in the new generation of automobiles which leads to higher performances and lower fuel consumption. Simultaneously, SFRPs shows highly complex nonlinear material behavior under multiaxial loading condition due to their corresponding production process using injection molding procedures.The current trend in automotive industry is the conception of a new generation of automobile construction where multi-material or hybrid specimen definitions are being gradually employed. Accordingly, aluminum metal sheet can be used in combination with short fiber reinforced plastics (SFRPs) for the production of a hybrid component. Tempered clinching is a promising mechanical joining process that is investigated numerically and experimentally in this project. Considering the strength and stiffness behavior, the key challenge in the tempered clinching process is to take into account the temperature-dependent deformations as well as the highly anisotropic material behavior of both materials. In the third phase of the SPP 1640 program, in addition to the consideration of plasticity, the progressive damage and failure of short fiber reinforced plastics and aluminum is characterized, modeled and integrated into an overall finite element model for different material sheet thicknesses. The progressive damage and failure of aluminum and short fiber reinforced plastics by the clinching process are numerically simulated and experimentally investigated. Accordingly, the numerical results are correlated with the experimental investigations results. Subsequently, the clinching process is parameterized and FE analyses of the progressive damage and failure of the resulting clinching joints are carried out. As a result, the relevant geometrical parameters of the tools are clearly identified and the optimum tools geometry are determined and validated. These developments will allow the simulation-based assessment and improvement of the resistance of the resulting clinching joints to be carried out, which leads to a reliable and robust manufacturing of hybrid clinching joints.