Enhancements of the DLR tool Pandora for automated detailed preliminary design and crash analyses

Kurzfassung

The DLR Institute of Structures and Design (BT) in Stuttgart has been developing the tool PANDORA (Parametric Numerical Design and Optimization Routines for Aircraft) [1] in Python since 2016, initially designed for aircraft fuselage preliminary sizing and mass estimation in process chains and parameter studies using the Finite Element Method (FEM). The development of new propulsion concepts with hydrogen or battery systems with different structural loading compared to traditional kerosene systems can only be partially represented in the preliminary design using conventional methods. In addition to quasi-static flight and ground load cases, dynamic crash load cases have also to be considered to ensure equivalent safety standards of new concepts. In first versions of PANDORA, the modeling was focused on GFEM (global FEM) models for static analyses. The GFEM base model uses a regular surface grid with simple reinforcements like frames and stringers as beam elements. This approach is fast to analyze multiple different concepts but limited to a specific range of parameters and predefined structural layouts. In a further development step, local model refinements using mesh-based approaches such as element splitting and extrusion of previously defined cross sections were implemented to allow for the first generation of DFEM (detailed FEM) models for transient crash and ditching analyzes [3]. To overcome limitations of the mesh based DFEM generation and to increase the range of fully automated and parametrized models in the preliminary design phase to be analyzed, PANDORA has recently been extended with an interface to Open Cascade (OCC) to offer versatile geometry usage. This enables geometry-based modeling and subsequent meshing (e.g. with GMSH) to analyze a wide range of concepts with more details resulting in PANDORA as a general environment for any kind of modeling. This approach is described in the first part of this paper. Specific aircraft parameters are defined in the xml based CPACS format (Common Parametric Aircraft Configuration Schema) [2] which allows interdisciplinary exchange of aircraft configurations. Based on these specific parameters PANDORA automatically creates a detailed geometry-based parametric description of the configuration which can be modified or extended and finally be used to build the FE model. This approach is exemplarily used to model double shell LH2 tanks incl. their connection to the fuselage primary structure and filling with SPH particles for subsequent sloshing analyzes (proposed paper [3]). In the second part of the paper the analysis of static flight and ground loadcases in combination with tank integration concepts is presented.