Einbringung und Gestaltung von Lasteinleitungsstrukturen für im RTM-Verfahren hergestellte FVK-Sandwichbauteile

Beschreibung

In der Automobilindustrie stellt Leichtbau eine Schlüsseltechnologie dar. Durch ein geringes Fahrzeuggewicht kann Energie eingespart, die Fahrdynamik verbessert, bei Verbrennerfahrzeugen der CO2-Ausstoß reduziert und bei Elektrofahrzeugen die Masse der Batterie ausgeglichen werden. FVK-Sandwichstrukturen bieten ein hohes Gewichteinsparungspotential. Hiermit ist es möglich, das Gewicht von Karosseriebauteilen stark zu reduzieren. In der Luft- und Raumfahrt sind FVK-Sandwichstrukturen bereits weit verbreitet. Um lokale Lasten aufnehmen zu können, werden sogenannte Inserts verwendet, welche die Kräfte großflächig in die Struktur einleiten. Die dort angewendeten Einbringungs- und Auslegungsverfahren sind für kleine Stückzahlen optimiert. Für eine automobile Großserienfertigung von FVK-Sandwichbauteilen eignet sich der „Resin Transfer Moulding“-Prozess (RTM-Prozess). Hierfür ist aktuell kein geeignetes Insert-Konzept bekannt. Im Rahmen der Arbeit wird daher ein Insert-Konzept erarbeitet, welches kostengünstig und schnell in RTM-Bauteile eingebracht werden kann und gleichzeitig eine hohe mechanische Belastbarkeit bei geringem Gewicht ermöglicht.
Lightweight engineering represents a key technology in the automotive industry. The low weight of the vehicle allows to save energy, improve vehicle dynamics, reduce CO₂ emissions of combustion vehicles and compensate the battery weight of electric cars. FRP sandwich structures offer a considerable weight-saving potential. The weight of car body parts can be substantially reduced with these structures. They are already widely used in the aerospace industry. In order to pick up local loads, so called inserts are used for large-area load application to the structure. The used insertion and layout methods in that sector are designed for smaller quantities. A suitable process for large-scale production of FRP sandwich components in the automotive sector is the RTM (resin transfer moulding) process. However, a suitable insertion concept has not yet been developed for this process. Therefore, this research work aims at elaborating an insertion concept which can be cost-efficiently and quickly introduced to the RTM components while at the same time demonstrating high mechanical strength at a low weight. First, the insert introduction is examined. A general insertion method shall be developed allowing the most important insert types to be integrated. To this end, the insert is considered a black box that can be designed as needed at a later point in time. In the search for a suitable insertion process, the whole RTM process chain consisting of foaming, preforming, RTM and post-processing is analysed. It turns out that the insert integration during the foaming process constitutes the most effective solution. Process steps are then modified or added to allow the placing of inserts. The new process steps subsequently serve as the basis for deriving subfunctions, for which in turn multiple technical solutions are elaborated. The results are then summarised in a morphological box and overall concepts for integrating these inserts are respectively deduced. The next step involves the assessment of the concepts by means of a benefit analysis. The winning concept uses a plastic mandrel that positions and seals the insert throughout the entire process chain. After that, the insert design is considered. The black box of the insert is now arranged in a sensible way. Different load application concepts are developed, and test specimens are then manufactured with the previously defined insertion method. This way, the basic feasibility of the insertion method can be demonstrated. The test specimens are then quasistatically tested for the most critical load case, a vertical tensile load. Thereupon, a parametric simulation model is derived from the experimental results. This model in turn aims at determining the mechanical load capacity for various insert geometries. The geometry of the insert is varied based on a systematic variation and by means of an evolutionary algorithm. The objective is to increase the mechanical load capacity. For the geometry with the highest increase, test specimens are again manufactured and experimentally tested. The experiments show that the mechanical load capacity can be significantly increased by a new geometry.

Autor*in

Jan Schwennen

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Elektromobilität Evolutionäre Algorithmen FVK Leichtbau Produktionstechnik RTM Sandwich

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