Stress adapted design of load application elements for hybrid light-weight shafts manufactured by centrifugal process

• Applicant: Professor Dr.-Ing. Jürgen Fleischer
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing ; Plastics Engineering ; Production Automation and Assembly Technology
• Term: from 2014 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 255536407

Light-weight shafts, pipes and profiles are often constructed as hollow structures made of fiber-reinforced plastic (FRP). For applications with a locally high functional density the use of FRP is not yielding proper results. In transmission technology, for example, connection and fastening elements, such as gear wheels, bears or threads for shaft nuts, need to be made out of metal. In the sense of the multi-material design, hybrid components which consist of a hollow FRP basic structure and localized metal elements are relevant for such requirements. The production of such hybrids is made possible by the centrifugal process.The centrifugal process is a manufacturing process for FRP metal hybrids, in which machined metallic elements are assembled with a dry continuous fiber structure and placed in a closed mold. After the cavity of the mold has been filled with a liquid resin, the tool is rotated at high rotational speeds, so that the fiber structure is infiltrated with the resin due to the centrifugal forces. The rotation is continued until the process of impregnation and curing is completed. Due to short flow paths, this process is offering the potential to realize short cycle times of only a few minutes.In the first funding period of the priority program 1712, a process model for the impregnation in the centrifugal process was developed and experimentally validated as well as process limits. In the second funding period, the focus will be on the transition area from FRP to metal (so-called load introduction area). Due to the intrinsic hybridization - which is seen as a joining process where various materials are connected by primary shaping - the principles of positive fit, adhesion and frictional connection overlap in the load transition area. The influence of the principles for the load transfer on the overall connection is hitherto unknown for rotationally symmetrical components. For this purpose, the connections are to be examined individually, in order to understand the overall behavior. Gained knowledge is going to be used in a simulation model for the optimization of the load transition area, in which the influence of the three principles for the load transfer can be adjusted in a targeted manner and thus a weight reduction can be achieved.In order to ensure the reproducibility of samples, an assembly station is constructed on which the previously manual assembly of the dry endless fiber structure with the metallic elements is being automated. The assembly station can also be used to reproducibly examine the influence of joining and draping effects on the connection strength.Finally, the simulation model for the optimization of the load transition area is to be validated experimentally, whereby the quality of the simulation is iteratively improved by the validation. A guideline can be derived from these results, allowing users to design FRP metal hybrid parts produced by the centrifugal process.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1712: Intrinsic Hybridcomposites for Lightweight Construction Structures - Basics of Manufacturing, Characterisation and Mechanical Design