Design methodology for highly loaded composite bolted joints with local metal hybridization at low temperature

Kurzfassung

Bolted joints are broadly utilized in composite structures due to their ease of assembly, disassembly, and repair. However, they also possess certain drawbacks including reduced load transfer efficiency resulting from high stress concentrations near holes. By local metal hybridization of the joining area in highly loaded structures these drawbacks can be overcome. The concept of local metal hybridization involves the substitution of specific layers of the composite with metal layers in the joining area, resulting in an overall higher bearing efficiency. The reinforcement effect through hybridization has been proven for steel and titanium hybridized composite laminates under room temperature conditions. In CFRP-steel hybrid laminates, high inter- and intralaminar thermal residual stresses are present, which influence the material behavior especially at lower temperatures. The aim of this thesis is to investigate whether the reinforcement effect of steel hybridization is also present at low temperatures. Furthermore, the thesis aims to determine whether the design process for bolted joints with local metal hybridization requires consideration of thermal residual stresses. The results of this work confirm that the reinforcement effect by hybridization is also present at low temperatures, specifically for CFRP-steel hybrid laminates. In addition, the work contributes to the development of numerical and analytical design tools for the purpose of preliminary and detailed design of hybridized bolted joints, thereby contributing to a broader application of local metal hybridization in composite structures.