Development of a single subfloor plate for a light cargo vehicle in sandwich construction

The Institute for Vehicle Concepts of the German Aerospace Center is developing new concepts for very light vehicles. One of these concepts is a light freight vehicle for urban logistics. The complete chassis is designed as a sandwich structure. Challenges in using these sandwich structures are the introduction of loads and joining technology. Additionally, the structure should be easy and efficient to produce. This leads to the question, if it is possible to use a single sandwich subfloor plate as the load-bearing structure of this vehicle. As a solution, the implementation of through-the-thickness inserts, which are mounted in the production process of the sandwich structure are proposed. Validation with simulations will be presented and the production process of such structures will be illustrated

Dynamic bending behaviour of magnesium alloy rectangular thin-walled beams filled with polyurethane foam

This study investigates the load-deflection curve characteristics and deformation/fracture modes and energy absorption capacity for polyurethane foam-filled magnesium alloy AZ31B rectangular thin-walled beams under dynamic three-point bending loads, and compares these characteristics with those for mild steel DC04 beams. Different foam-filled AZ31B beams with a variation of foam density (0.05 g/cm3, 0.20 g/cm3 and 0.30 g/cm3) were fabricated through several manufacturing processes: cold bending, tungsten inert gas welding, cathodic dip painting and polyurethane foam injection. It was found that 0.20 g/cm3 and 0.30 g/cm3 foams stabilised the cross sections of the thin-walled AZ31B beams and no inward folds occurred during the bending process, which resulted in significantly higher load carrying capacity than the empty beam. A nonlinear non-monotonic relationship between the specific energy absorption and the foam density was found for the foam-filled AZ31B beams. The AZ31B beam filled with 0.20 g/cm3 foam reached the highest specific energy absorption; moreover, it absorbed nearly 33% more energy and reached nearly 2.9 times higher specific energy absorption than the foam-filled DC04 beam filled with the same foam, although the former one was nearly 54% lighter. This outperformance is associated to the high work hardening rate of AZ31B in compression, where more material is involved in plastic deformation. However, the foam-filled AZ31B beams tend to fracture at the compression and tension walls, because the foam exhibits brittle fracture behaviour in tension and AZ31B exhibits low ductility in compression and plane-strain conditions, which limits their energy absorption at a larger deflection

Development of a lightweight car body, using sandwich-design

developed, with a body in white structure of only 90 kg and a high level of damage tolerance, in case of accidents. The structural concept is a consequent implementation of hybrid materials, resulting in a lightweight structure made of few parts with relatively simple shape. This is achieved by adapting materials and using a sandwich architecture for structural components. Especially structural foams and honey comb for cores in combination with metallic sheets are qualified. Hereby a high lightweight design potential is achieved and an overall concept of a weight optimized, multifunctional and highly integrated body in white structure is generated and analysed by using FEM- crashsimulation. As a feasibility study of the design, a full size body in white demonstrator was built. Also, tests of several components are performed, in order to validate the simulation results. Future developments will result in the assembly of a roadworthy prototype with a fuel-cell drive-train, as well as crash testing of the entire body in white

Metal-hybrid structures for an improved crash behaviour of car body structures

Zur Zeit verwendete Karosserien in Stahl-Schalen-Bauweise bestehen vorwiegend aus durch Punktschweißen gefügten Blechschalen. Solche Strukturen können im Crashfall, bei einer konzentrierten Lasteinleitung wie dem Pfahlcrash, zu hohen Intrusionen führen, auch da die Blechschalen konzeptbedingt zum Beulen und Falten neigen. Mit dem Ziel, das Crashverhalten von Karosserien bei gleichzeitiger Gewichtsreduzierung zu verbessern, wurden die Vorteile von Trägerstrukturen in Metall-Hybrid-Bauweise untersucht. Der Schwerpunkt lag dabei auf der Verbesserung der gewichtsspezifischen Crashperformance, insbesondere bei einer nahezu punktuellen Last, wie sie beispielsweise beim Pfahlcrash auftritt. Durch die Verwendung möglichst leichter Kernstrukturen im Inneren metallischer Trägerstrukturen wurde das Kollabieren der Metallschalen erfolgreich verhindert. Somit entstehen Strukturen, die im Crashfall nicht lokal versagen, sondern sich als Ganzes verformen, und damit in größeren Bereichen Energie absorbieren. Dies führt zu einer besseren Materialausnutzung und damit zu einer Erhöhung der gewichtspezifischen Energieabsorption. Eine wichtige Rolle für die Funktion der Energieabsorption spielt die Wahl geeigneter Kernstrukturen und -werkstoffe, da diese nicht nur eine möglichst hohe Druckfestigkeit bei möglichst geringem Gewicht aufweisen müssen. Sie müssen vielmehr auch während der Verformung der Struktur ihre Stützwirkung innerhalb des Profils beibehalten. Als Werkstoffe für die Profilschalen kommen vor allem Metalle mit hoher gewichtsspezifischer Festigkeit und Dehnbarkeit wie z.B. Edelstähle, neu entwickelte Manganstähle, aber auch Aluminium-Legierungen mit hoher Dehnbarkeit in Frage. Im Vortrag werden Versuchsergebnisse zu Verformungsverhalten und Energieabsorption von mit geeigneten Kernen verstärkten Trägerstrukturen präsentiert. An generischen Bauteilen konnte eine Steigerung der gewichtsspezifischen Energieabsorption auf das dreifache einer hohlen Struktur erzielt werden. Außerdem werden weiterführende konzeptionelle Ansätze für die Berechnung und Integration solcher Strukturen in Karosserien vorgestellt

Extreme sandwich-lightweight design with high degree of functional integration

In times of climate change and the associated global warming, measures and concepts to save re-sources and to decrease emissions are significant factors in the effort to limit the environmental impact of global technological improvement. With the development of lightweight vehicle concepts, research institutes as well as the automobile industry can contribute an important part to the future manufacture of ecological and technologically advanced cars. At the Institute of Vehicle Concepts, German Aerospace Center (DLR) a car body structure in sand-wich architecture is developed. This structural concept is a consequent implementation of hybrid materials resulting in a lightweight structure made of few parts with relatively simple shape. The packaging and the weight distribution of this newly vehicle architecture has been established in close collaboration between the department of Lightweight and Hybrid Design Methods and some experts from the department of Alternative Powertrains of the Institute of Vehicle Concepts. A hybrid battery fuel cell powertrain added to the car body concept enables developing a novel compact vehi-cle. Multifunctional structures are playing a major role in the implementation of this powertrain con-cept. A very light body in white structure with a high level of damage tolerance in case of accidents has been developed. This is achieved by adapting materials and using an architecture of high damage tolerance for structural components. Especially structural foams and honey comb for cores in combi-nation with metallic sheets are qualified. Hereby a high lightweight design potential is achieved. The basic scientific approaches like the novel hybrid material structure architecture, inventive concepts for passenger compartment, innovative frontends or the special crosswise seat beam construction com-plete the car body structure. In combination with unconventional shape architecture an overall concept of a weight optimized, multifunctional and highly integrated body in white structure is generated. The car body structure is analysed by using FEM-tools. This FEM crash calculation is realized in two different crash scenarios: a frontal load cases (100% overlap) and the pole test (rigid standard pole). Furthermore two static analyses (bending and torsion) are made. Conceptual ideas and innovations will be shown in terms of demonstrating hardware. The objective is a widespread statement concerning the potential, the lightweight construction quality and the practicability of an overall sandwich car body structure to provide a contribution for future development of body in white structures