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Freiburg, Germany

The Fraunhofer Institute for High-Speed Dynamics , commonly known as the Ernst Mach Institute and also by the abbreviation Fraunhofer EMI, is a facility of the Fraunhofer Society in Germany. The Institute is based in Freiburg im Breisgau. Its activities are applied research and development in the fields of materials science and high-speed measurement techniques. The Institute also has offices in Efringen-Kirchen and Kandern.The name "Ernst Mach Institute" is named for the physicist Ernst Mach , who first used high-speed photography to visualize ballistic and gas-dynamic processes. Wikipedia.

May M.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut | Hesebeck O.,Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research
Engineering Failure Analysis | Year: 2015

Experimental studies on adhesively bonded metallic joints are presented. The T-joints were mounted in a servo-hydraulic machine and loaded in three different directions (rear, front and side) and at three different loading velocities (0.5. mm/s, 50. mm/s and 5000. mm/s). The variation in loading direction allowed triggering of different failure mechanisms: metal plasticity, peel failure of the adhesive, shear failure of the adhesive and combined failure. Some scatter was seen in the joint performance which can be attributed to two major manufacturing parameters. The use of glass spheres for defining the bond line thickness has a positive effect on joint performance. Interestingly, T-joints manufactured from two different batches of adhesive showed large differences in behaviour although the manufacturing parameters were the exactly same. © 2014 Elsevier Ltd. Source

May M.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut
Composites Part A: Applied Science and Manufacturing | Year: 2016

Composite materials are often subjected to mechanical impact causing delamination. For quasi-static loading, measuring the mode I fracture toughness has been standardized. However, for high-rate loading, additional challenges arise. Consequently, no standard test has yet been defined for measuring the mode I fracture toughness under high rates of loading. This article therefore reviews candidate tests for measuring the high-rate mode I fracture toughness. Strength and weaknesses of different specimen designs and test setups are shown. Different approaches to measuring crack growth and loads are presented. The different approaches are compared and recommendations are provided for measuring the mode I fracture toughness of composites under high rates of loading. © 2015 Elsevier Ltd. Source

Krell A.,Fraunhofer Institute for Ceramic Technologies and Systems | Strassburger E.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut
Materials Science and Engineering A | Year: 2014

Laboratory-made Al2O3 and spinel ceramics were investigated so as to enable ballistic tests with a variation of individual influences while keeping other factors constant. The study was aimed at answering the question about influences of different microstructures and of basic mechanical properties and included also a systematic investigation of the effects of backing materials. Contradictive findings of the past are explained by the observation that the ballistic impact stability of ceramics and single crystals with different backings (steel, aluminum, glass) is governed by a strict hierarchy of few major influences: (1) Top priority is the mode of ceramic fragmentation governed by microstructural features and by the dynamic stiffness of the ceramic/backing target; these influences also affect the relative importance of dwell and penetration. (2a) On a lower rank, Young's modulus of the ceramic is responsible for projectile damage during dwell but the importance of this influence depends on the priority of ceramic fragmentation. (2b) On penetration, the abrasive benefit of a high ceramic hardness depends on the size of the ceramic debris, i.e. on priority (1). In contrast, all average strength data are weakly correlated with the ballistic efficiency. © 2014 Elsevier B.V. Source

May M.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut
Composite Structures | Year: 2015

This paper compares four cohesive zone models for modeling delamination caused by impact on composite materials. The four cohesive zone models differ by the way rate-dependent material properties, such as strength and fracture toughness, are treated. The influence of the cohesive zone model formulation on the prediction of delamination size is evaluated using the numerical example of a dynamic punch test. It is demonstrated that the use of strain-rate dependent material models significantly influences the numerical result. It is also shown that both, the rate-dependent strength and the rate-dependent fracture toughness, must be considered. © 2015 Elsevier Ltd. Source

Ganzenmuller G.C.,Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut | Patey G.N.,University of British Columbia
Physical Review Letters | Year: 2010

We report a computer simulation study of an electroneutral mixture of oppositely charged oblate ellipsoids of revolution with aspect ratio A=1/3. In contrast with hard or soft repulsive ellipsoids, which are purely nematic, this system exhibits a smectic-A phase in which charges of equal sign are counterintuitively packed in layers perpendicular to the nematic director. © 2010 The American Physical Society. Source

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