Structural design of the newly developed lightweight carbon chassis for the Krone Big X
In order to reduce CO2 emissions in the commercial vehicle and agricultural sectors, new ways to reduce the weight of the machines, which usually weigh several tons, are being sought. One approach is structural lightweight construction using innovative material concepts, such as fiber composites materials. The Institute for Manufacturing Technology and Machine Tools (IFW) at Leibniz University Hannover informed that it has developed a carbon chassis for the Krone Big X in the AgriLight project together with its project partners. With the innovative design, the chassis weight of the forage harvester can be reduced by 50% while at the same time increasing torsional rigidity.
In order to be able to work larger fields more efficiently, the performance of agricultural harvesting machines has increased significantly in recent decades. Due to the higher performance of the machines, their weight has also increased, which pushes manufacturers to the limits of road traffic law and confronts users with greater soil compaction and higher fuel consumption.
This problem was addressed by the IFW together with the project partners Krone GmbH & Co. KG, M&D Composites Technology GmbH and the Institute for Polymer Materials and Plastics Technology (PuK) at Clausthal University of Technology in the AgriLight research project. By fundamentally rethinking the chassis of the Krone Big X and converting it into an innovative fiber composites construction, its weight was significantly reduced.
Particular challenges arose from the different material properties of fiber composites and metallic materials, the associated complexity in the design of thick-walled fiber composite structures and the integration of the new, fiber-friendly design into the existing vehicle structure. The new design options of the CFRP monocoque construction were used to create additional advantages for the customer. These include, for example, larger, integrated tanks and simplified cleaning of the machine thanks to closed surfaces. For the design, the IFW and PuK jointly examined a number of different resin systems in order to find the optimal matrix for the application and the manufacturing process using vacuum infusion without autoclaves. Ansys Composite PrePost was used to carry out the finite element simulation. Shell models of the entire CFRP structure as well as detailed analyzes using volume models were created. Based on a load spectrum newly developed by Krone, design adjustments and optimizations were made to the laminate structure.
In addition to the design and dimensioning of the frame structure, the IFW has also researched new approaches for introducing high loads into the frame structure of commercial vehicles in a fiber-composite manner. With the help of the innovative hybrid insert concept, which is ideal for the proposed vacuum infusion process, significantly higher loads can be introduced into the fiber composite structures – together with classic connecting elements such as screws and bolts – without the preload forces having to be borne by the laminate. The result of the development process is an innovative carbon chassis that has a weight reduction of 50% compared to the steel frame while offering greater frame rigidity.
In the next step, a prototype of the chassis will be manufactured at M&D Composites Technology. For this purpose, tool making is carried out first, followed by the production of the individual shell components of the monocoque. This prototype is then subjected to a dynamic structural test at our partner Krone, during which the developed load spectrum is tested on the X-Poster. The results of the design and the underlying finite element models are validated. The main goal of this research is to ensure that both the carbon fiber-based chassis and the hybrid inserts used in high-wear areas do not show any deterioration over the life of a vehicle. To record the loads and deformations of the chassis, the IFW implements a measurement concept that includes Rayleigh and DMS sensors as well as optical 3D measurements. Through the development process, the IFW was able to use its expertise in development and further strengthen and expand the design of large fiber composite structures as well as the conception of application-related force introductions.