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Schneider S.,Bundeswehr Research Institute for Materials
International Journal of Modern Physics B | Year: 2012

In this work, a new method to determine the wall shear stress was developed step by step. To determine the wall shear stress, methods of the suspension rheology are being used for the first time to characterize ER fluids. This work focuses on investigations of the flow behavior of electrorheological suspensions in flow channels with different geometries at different electrical field strengths. Careful interpretation of the results with respect to different gap geometries has shown that the measured flow curves should undergo a combination of corrections. As a result it can be shown that wall slip effects can be measured under application like conditions on a hydraulic test bench. © 2012 World Scientific Publishing Company.

Heimbs S.,Airbus | Nogueira A.C.,Airbus | Hombergsmeier E.,Airbus | May M.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut | Wolfrum J.,Bundeswehr Research Institute for Materials
Composite Structures | Year: 2014

An experimental and numerical study of the failure behaviour of composite T-joints under quasi-static and high-rate dynamic loading is presented, focusing on the investigation of a novel reinforcement technique in the through-thickness direction using metallic arrow-pins to increase failure resistance and damage tolerance. Specimen manufacturing and testing are described in detail. The test campaigns covering 0° T-pull and 30° T-bending tests were conducted under quasi-static and high-rate dynamic conditions in order to assess potential loading rate effects. The novel concept with the arrow-pin reinforcement showed significantly increased post-damage load levels and energy absorption capability with the pins being pulled out of the laminate under large global deformations. In addition to the experimental test campaign, numerical simulations with the explicit finite element code LS-Dyna were conducted on local, global and macro-modelling level. The models were validated against the test results and applied to ballistic impact simulations of an exemplary composite fuel tank structure under hydrodynamic ram loading, where the novel joint design led to significantly higher damage resistance. © 2013 Elsevier Ltd.

Eibl S.,Bundeswehr Research Institute for Materials
Fire and Materials | Year: 2012

The influence of the orientation of carbon fibres on the reaction-to-fire characteristics of a layered composite has been investigated in detail. 8552/IM7 prepregs were laid up to give unidirectional and quasi-isotropic laminates. Specimen thickness (0.25 to 8.0 mm) and heat flux (15 to 80 kW/m 2) were varied for irradiation. Fundamental reaction-to-fire properties of this composite are interpreted on the basis of the matrix components: epoxy resin and polyethersulfone. Cone calorimetry and temperature distributions through the laminate showed that the velocity and degree of combustion are dominated by fibre orientation for a given resin. In general, a quasi-isotropic fibre orientation leads to faster ignition, because of preferred delaminations, but retards combustion processes more effectively than a unidirectional lay-up. Migration velocities of the pyrolysis zone were measured. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.

Yu T.H.,California Institute of Technology | Yu T.H.,California State University, Long Beach | Hofmann T.,University of Nevada, Las Vegas | Hofmann T.,Bundeswehr Research Institute for Materials | And 6 more authors.
Journal of Physical Chemistry C | Year: 2013

To facilitate a less empirical approach to developing improved catalysts, it is important to correlate catalytic performance to surrogate properties that can be measured or predicted accurately and quickly, allowing experimental synthesis and testing of catalysts to focus on the most promising cases. Particularly hopeful is correlating catalysis performance to the electronic density of states (DOS). Indeed, there has been success in using just the center of the d-electron density, which in some cases correlates linearly with oxygen atom chemisorption energy, leading to a volcano plot for catalytic performance versus "d-band center". To test such concepts we calculated the barriers and binding energies for the various reactions and intermediates involved in the oxygen reduction reaction (ORR) for all 12 transition metals in groups 8-11 (Fe-Cu columns). Our results show that the oxygen binding energy can serve as a useful parameter in describing the catalytic activity for pure metals, but it does not necessarily correlate with the d-band center. In addition, we find that the d-band center depends substantially on the calculation method or the experimental setup, making it a much less reliable indicator for ORR activity than the oxygen binding energy. We further examine several surfaces of the same pure metals to evaluate how the d-band center and oxygen binding energy depend on the surface. © 2013 American Chemical Society.

Eich G.,Bundeswehr Research Institute for Materials
Journal of Failure Analysis and Prevention | Year: 2012

Incorrect material selection does not always lead to corrosion. In addition to an inferior selection of materials, unsuitable operating conditions and poor design also contributed to the presented failure. A combination of erosion and corrosion caused a leak in an oil cooler of a Navy ship. Because there was no welding seam between the deflectors and tube plate on the carbon steel cooler, cooling water could stream between them, and the flow rate became excessive. This caused erosion on the tube plate. In addition, the repeated change of the cooling liquid after servicing caused a uniform corrosion attack. © ASM International 2012.

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