Michael Krahl

Linkage Solutions for the Manufacture of Complex, Thermoplastic Lightweight Structures

The manufacturing of novel, high-performance fibre composite components based on hybrid yarns necessitates the development of new process solutions. In the particular case of manufacturing open core sandwich panels, tools are required which facilitate automated manufacturing. Such automation can be achieved using specially adapted wedge kinematics, which in turn require handling systems that ensure a correct position of these tools. One mainpart of such handling system is a comb system, which is successfully approved by the manufacturing of planar sandwich panels. Single-bend sandwich panels requires the development of new solutions, which facilitate the oriantation of the consolidation tools with a minimum of drive effort. Thereby the focus is on the design of a comb system based an a scissor mechanism.

Manufacturing and Process-based Property Analysis of Textile-Reinforced Thermoplastic Spacer Composites

Novel woven spacer fabrics based on hybrid yarns are suitable for an efficient fabrication of three-dimensional composite structures in high volume production. In this paper, an innovative manufacturing process with short cycle times and high automatisation is introduced for textile-reinforced thermoplastic spacer structures suited for bending load cases. The different process steps hybrid yarn fabrication, weaving technology for three-dimensional textile preforms and consolidation with unique kinematics and hot pressing technology are described in detail. The bending properties of the manufactured spacer structures are evaluated by means of experiments as well as finite element simulations. Numerical parametric studies are performed in order to validate the influence of manufacturing tolerances on the bending stiffness of the spacer structures.

Thermoplast-Sandwichstrukturen aus recycelten C-Fasern

Recycling im Fokus Die hohen Anforderungen, die seitens der Industrie an Massereduzierung und Kosteneffizienz von neu zu entwickelnden Bauteilen – etwa für Mobilitätsanwendungen – gestellt werden, haben in jüngster Vergangenheit zum Erfolg von hybriden Leichtbaustrukturen geführt. Besonders hervorzuheben sind dabei neue Kombinationsverfahren, bei denen f lächige Halbzeuge aus Metall oder textilverstärkten Kunststoffen umgeformt und mittels Spritzgießtechnik funktionalisiert werden. Die Synthese unterschiedlicher Werkstoffe mit ihren charakteristischen Eigenschaftsprofilen ermöglicht zwar einerseits eine optimale Anpassung der Bauteileigenschaften an die auftretenden Belastungen, führt aber andererseits zu neuen Herausforderungen hinsichtlich Recycling, da eine stoff liche Verwertung in der Regel auch eine stoff liche Trennung voraussetzt. CFK-Recycling

Optical thermal model for LED heating in thermoset-automated fiber placement

Abstract Control of material temperature distribution and governing phenomena during automated fiber placement is an important factor. Numerical modeling of the radiative heat transfer for a newly presented LED-based heating unit is developed and analyzed in theory. An optical model allows taking into account the radiative energy output of every individual LED. By adjusting the electrical input to the multiple LED arrays on the heating unit, the irradiance distribution on the substrate’s surface can be controlled. To investigate the capability to adjust the surface temperature distribution resulting from this feature, thermal models for two and three dimensions are developed and employed for the calculated irradiance distributions. The resulting temperature distributions show that temperature gradients can be avoided or created, depending on the input to the heating unit. The results from the two models are compared and a method to select an appropriate model in general is proposed.

Influence of Laser Surface Treatment for Process-Integrated Joining of Textile Reinforced Thermoplastic Composites to Metal Sheets

Laser-structured metal surfaces in combination with thermoplastic compression mould processes allow intrinsic hybrid structures with high-strength connections. Suitable process parameters are still to be identified to provide optimised assembly parameters. Therefore, laser structures with different configurations are applied to steel sheets and compressed with textile reinforced thermoplastic composites to manufacture hybrid structures. Laser processing parameters, such as pulse duration or energy as well as laser scanning strategies and therefore structure dimensions are analysed.After manufacturing, specimens are extracted and characterized in single-lap shear tests comparing different configurations to identify boundary conditions for the laser structuring with optimal bonding characteristics.

Analyses of Boundary Conditions for Process Integration of Sensor Elements in Complex Fibre-Reinforced Thermoplastic Spacer Structures

The application of hybrid yarns and their further processing to textile preforms enforce adapted manufacturing processes. Furthermore, a consolidation of cross-section varying parts requires an adapted mold and core system for a reproducible production process. Similarly, the application of hybrid yarns facilitates low consolidation pressures and thus favors the integration of electronic components in fibre-reinforced thermoplastic parts. In this paper, the analyses of the boundary conditions for a process integration of sensor elements in complex fibre-reinforced spacer structures are presented.