Using thermoplastic polymers is one essential strategy in order to achieve particularly short cycle times in the production of fiber-reinforced plastic composites. Besides high production rates by melting or solidifying thermoplastic are recyclable at the same time. These economical properties combined with appropriate processing methods result in in a very cost-efficient process.

The work presents a structural optimization and the appropriate novel manufacturing process, in which various continuous fiber-reinforced inserts are overmolded and/or extrusion coated within an injection molding process. Here, the short-fiber-reinforced injection molding process allows high geometric freedom while maintaining high surface quality. UD inserts can provide excellent mechanical properties along the main load paths.

The digital development and design includes the determination of highly loaded areas by topology optimization and finite element (FE) simulations. A comprehensive virtual design of hybrid thermoplastic FRP structural components is pursued by methodically developing a simulation chain to link different design tools (CAD, FE, topology optimization, process simulation)

The structural optimization results in a part design according to the design space and load conditions - followed by the tool design. Tool design, on the other hand, has to consider manufacturing conditions, such as time dependent resin viscosity, shear force, thermal expansion or injection pressure to guarantee a functional manufacturing setup. In this case, an injection molding simulation with Moldex 3D was carried out via finite element analysis and topology optimization for the tool. 

The novel manufacturing process combines tape laying combined respectively 3D-printing with the injection molding process. A split winding mold allows a loop deposition by a six-axis robot. The wall thickness of the loop is 7.2 mm. A hot gas nozzle melts the tape and then a cooling roller consolidates it. The tape laying process uses hot gas nozzle which enables high material output with excellent geometric accuracy. One disadvantage of tape laying is the reduced geometric freedom in path deposition. For example, undercuts are difficult to implement. Therefore, the alternative process 3D-printing with continuous fiber reinforced filaments is presented to implement undercuts on the demonstrator part. For the comparability of the inserts it is necessary to use the same material. Therefore, a small production system for 3D-printing UD filament was built and validated. In the future, various tape materials can be formed in order to be able to use it in the UD 3D-printer.

In addition, results from overmolding tests at sample level will be presented - such as shear strength and fracture surface analysis.