Qualification and optimization of the joint-winding process for processing fiber-reinforced thermoplastics for the production of truss structures

• Applicant: Professor Dr.-Ing. Jürgen Fleischer
• Subject Area: Joining and Separation Technology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397377132

The use of lightweight constructions reduces the energy requirements of moving systems and increases the permissible payload of various applications. One of the most effective forms of lightweight constructions are trusses that are designed according to the main load paths. For applications with high mechanical loads and at the same time a low required mass, the use of fiber-plastic composites (FRP) is a good choice. Since several profiles are joined together within a truss, the joining technology has a decisive influence on the later strength and stiffness of the structure. The existing techniques for joining FRP are only conditionally suitable for the production of a truss. Against this background, the wbk Institute for Production Science has developed the joining-winding process, in which the profiles are joined by multiple wrapping of a robot-guided winding-ring with thermoset towpregs. In a first funded project a basic process model for high process accuracy and reproducibility has already been developed and validated. In order to reduce the costs of the joining process and to increase the freedom of design within the framework, the aim of the research project applied for is to qualify and optimize the joining process with fiber-reinforced thermoplastics.By preliminary work with a heat source integrated in the current winding ring, the general feasibility of winding fiber-reinforced thermoplastics with the robot-guided winding ring could be demonstrated. In this project the interactions during the winding process of fiber reinforced thermoplastics are to be investigated and suitable production parameters are to be derived by means of a statistical test plan. In addition, the existing simulation model for the winding kinematics from the funded project will be extended for the new technology.Parallel to this, a numerical model for the stiffness and strength calculation will be developed. This is followed by the development of a methodology for the mechanical optimization of the joint connection under consideration of manufacturing restrictions. By using a genetic algorithm, the mechanical strength of the joint is to be further increased. Finally, the simulation model and the methodology for mechanical optimization are to be validated by mechanical tests on a test rig set up for this purpose. In addition, the test specimens will be examined by computer tomographic measurements for the type of damage present and with regard to the location of failure. From the results, the potential of joining winding with fiber-reinforced thermoplastics can be determined conclusively.

• DFG Programme: Research Grants