Sandwich Lightweight Design in Automotive Usage

Kurzfassung

In times of climate change and the associated global warming, measures and concepts to save resources and to decrease emissions are significant factors in the effort to limit the en-vironmental 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 sandwich 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 estab-lished 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 ena-bles developing a novel compact vehicle. Multifunctional structures are playing a major role in the implementation of this powertrain concept. A very light body in white structure (≈ 80kg) with a high level of damage tolerance in case of accidents has been developed. This is achieved by adapting materials and using architecture of high damage tolerance 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. 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 complete the car body structure. In combi-nation with unconventional shape architecture an overall concept of a weight optimized, mul-tifunctional 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 case (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. To explain the behaviour of sandwich structures in crash scenarios, basic tests on generic foam elements are necessary. Tensile strength, compressive strength and shear strength tests were performed. The influence of failure velocity was discussed and various FEM-models were established. Different trigger modes were tested to find the most efficient mechanism for absorbing crash energy. Additional experiments with sandwich structures with varying geometrical shapes were carried out. 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 con-tribution for future development of body in white structures. Additionally, it is now possible to generate concepts using sandwich structures, thanks to the overall understanding of material behaviour of foam in different load cases.