Convective Nonlinearity in Non-Newtonian Fluids

In the limit of infinite yield time for stresses, the hydrodynamic equations for viscoelastic, Non-Newtonian liquids such as polymer melts must reduce to that for solids. This piece of information suffices to uniquely determine the nonlinear convective derivative, an ongoing point of contention in the rheology literature.Comment: 4 page

Tailored Fibre Placement Technology – Optimisation and computation of CFRP structures

Recent Developments of the Tailored Fibre Placement Technology have shown strong potentials of reducing structural weight by optimised mechanical utilisation of roving cross sections. The Presentation gives a brief overview on Tailored Fibre Placement (TFP) technology. Projects on TFP at DLR and the developed numerical optimisation methods are presented and explained. Application of TFP to a structural component is shown together with selected results

Buckling and postbuckling analysis of shells under quasi-static and dynamic loads

Thin-walled fuselage structures, partly subjected to compression and shear (torsion), are endangered by buckling. Present design procedures rest upon nonconservative conditions as to dynamic loading, e.g. landing impact, and on too conservative assumptions, if buckling due to quasi-static loading is considered. With dynamic loading like landing impact a distinction should be made between relatively short and long, quasistatic loading durations, and loadings the durations of which are in the order of the longest lateral period (lowest eigenfrequency) of the structure. A particular problem is to be expected under the later loadings where the interaction of loading dynamics with the dynamics of the buckling process may lead to substantially reduced dynamic buckling loads, as compared with the buckling loads predicted by quasi-static loading. This load reduction actually is not considered in the design process. In order to overcome that problem, a fast and reliable simulation procedure has to be developed. With buckling due to quasi-static loading, experiments have shown that the potential exists for further weight savings with stiffened composite structures by allowing postbuckling of the skin to occur during operation. Proper design enables the structures to act far within the postbuckling regime without any damage. This demand requires the development of an appropriate fast and reliable simulation procedure

New design tools for lightweight aerospace structures

This paper presents two new design tools for lightweight aerospace structures. The first tool is the Tailored Fibre Placement (TFP) design tool TACO. It is used to optimize the fibre orientations of structures made of Carbon Fibre Reinforcement Plastics (CFRP). The optimization concept is explained and results are given for a horizontal tail plane connection beam of an aircraft. The second tool, iBuck, is a fast, semi-analytical local buckling and post-buckling tool for stiffened panels that are loaded in-plane. The panels are assumed to be representative for an aircraft fuselage and are stiffened in axial and circumferential direction. Results are presented for axially loaded panels and compared to FE-results