Sandwich lightweight connection of the NGT wagon structure

In order to achieve the conceptually required maximum weight saving, DLR favours a hybrid lightweight design for the supporting body structure of the NGT HST high-speed train. The middle sections of the wagons consist of load-bearing, simply curved sandwich panels with web-reinforced foam cores and CFRP face sheet layers. Due to its high specific stiffness and strength, the sandwich design offers an optimal ratio of payload to structural weight. However, sandwich elements are sensitive to the introduction of local loads. Therefore, mostly complex, large-area load introduction elements are used, which, however, can cause a high proportion to the total weight of the sandwich structure. Therefore, the goal is to minimize the weight of the connections between the sandwich elements. 

Two-part, through-the-thickness inserts, potted to the core, are used to introduce the structural loads into the side sandwich panels of the wagon. This type of insert offers an optimum ratio of transferable load to mass (maximum connection quality), enables simple tolerance compensation, quick installation and ensures an aerodynamically smooth outer surface. The minimum diameters of the inserts were calculated with the help of an analytical-mechanical pre-design tool, developed by the DLR. The locally prevailing maximum loads, the behaviour of the rigid foam core and the relevant material properties were taken into account. 


The demonstrator shows a section of the middle carriage designed by the composite design department including weight-optimized inserts in the sandwich elements of the side sandwich panel.