Ralf Sturm

Methodological development from vehicle concept to modular body structure for the DLR NGC-Urban Modular Vehicle

Three new vehicle concepts in the field of transport are being developed at the German Aerospace Center (DLR) as part of the Next Generation Car META-project: Urban Modular Vehicle, Safe Light Regional Vehicle and Interurban Vehicle. In the submitted contribution, the focus lies on the development and application of a method for determining the vehicle concept and body in white construction for the Urban Modular Vehicle.

Virtual Design Method for Controlled Failure in Foldcore Sandwich Panels

For certification, novel fuselage concepts have to prove equivalent crashworthiness standards compared to the existing metal reference design. Due to the brittle failure behaviour of CFRP this requirement can only be fulfilled by a controlled progressive crash kinematics. Experiments showed that the failure of a twin-walled fuselage panel can be controlled by a local modification of the core through-thickness compression strength. For folded cores the required change in core properties can be integrated by a modification of the fold pattern. However, the complexity of folded cores requires a virtual design methodology for tailoring the fold pattern according to all static and crash relevant requirements. In this context a foldcore micromodel simulation method is presented to identify the structural response of a twin-walled fuselage panels with folded core under crash relevant loading condition. The simulations showed that a high degree of correlation is required before simulation can replace expensive testing. In the presented studies, the necessary correlation quality could only be obtained by including imperfections of the core material in the micromodel simulation approach.

Methodological Approach for Reducing Computational Costs of Vehicle Frontal Crashworthiness Analysis by Using Simplified Structural Modelling

ABSTRACT A challenge in the design and optimisation of the vehicle front structures is the high computational costs required for crash analysis. A methodological approach to simplifying finite element vehicle models and crash barriers is presented in this paper. The methodology uses global deformation characteristics of structures which are obtained from the global crash model. For the simplification of the vehicle crash model, structural regions which sustain only elastic deformations during the frontal crash are replaced by kinematic numerical representations which describe both stiffness and load paths at the interface of the substituted structures. Verification studies of the simplified vehicle model show a very good agreement of the global and local structural response during the frontal crash. Further simplifications were applied to the offset deformable barrier by replacing its detailed crushing behaviour by kinematic descriptions. Through the combined use of both simplified numerical representations, the computational cost of a Euro new car assessment program (NCAP) offset crash analysis can be reduced by around 92%. With the obtained time reduction, structural optimisation studies of the remaining structure can be conducted efficiently for the identification of weight reduction potentials.

Crashworthiness and ditching behaviour of blended-wing-body (BWB) aircraft design

Over the last few decades, the fuel efficiency of aircrafts was mainly improved by the application of refined aerodynamics, new materials, structural optimization and enhanced engine performance. A further potential for a greener aircraft is seen in the unconventional blended-wing-body (BWB) design configuration due to its advanced aerodynamic design and its reduced weight. For the certification of novel aircraft configurations, the airworthiness authorities require proof of at least equivalent safety standards compared to the existing conventional transport aircraft. In this context, the BWB configuration has to demonstrate sufficient crashworthiness for emergency landing on rigid surface and on water. Since structural modifications for improved safety should be applied in the early conceptual design phase of an aircraft, explicit simulations have been performed with the objective to estimate the crash behaviour of the BWB configuration. Based on the simulation results, design principles are derived for improved crashworthiness and ditching behaviour for the BWB aircraft configuration.

Multiscale modeling methods for analysis of failure modes in foldcore sandwich panels

The paper presents an homogenised core model suitable for use in the analysis of fuselage sandwich panels with folded composite cores under combined loading conditions. Within a multiscale numerical design process a failure criterion was derived for describing the macroscopic behaviour of folded cores under combined loading using a detailed foldcore micromodel. The multiscale modelling method was validated by simulation of combined compression/bending failure of foldcore sandwich panels.