Si/SiC-Ceramic low process shrinkage - high temperature material for the Laser Sinter process

Actual RP-systemsare very limited in producing adequate ceramic prototypes. In the presented process, the SiC..green part manufacturing bythe laser sintering process in combination with special postprocessing allows the fast production of SUSiC prototypes. A mixture of SiC powder and a reactive polymer binder system is used in the Laser Sinter process. In the following postprocessing the porous green part has to be .infiltrated with a precursor resin, carbonised and finally infiltrated withimolten silicon.•Incontrast to cold isostatic moulding or slip casting the shrinkage is very low (2-4 0/0).• Experiments with suitable materials/and process conditions were successful. This paper will show the state of and the possible further investigation into process.Mechanical Engineerin

Systematic Approach for Finite Element Analysis of Thermoplastic Impregnated 3D Filament Winding Structures—Advancements and Validation

This work aims to enhance and validate a systematic approach for the structural finite element (FE) analysis of thermoplastic impregnated 3D filament winding structures (fiber skeletons). The idealized modeling of geometrically complex fiber skeletons used in previous publications is refined by considering additional characteristic dimensions and investigating their mechanical influence. Moreover, the modeling approach is transferred from the meso- to the macro-level in order to reduce modeling and computational effort. The properties of meso- and macro-level FE models are compared using the example of simple loop specimens. Based on the results, respective application fields are defined. In the next step, the same modeling approach is applied to a more complex, three-dimensional specimen—the inclined loop. For its macro-level FE model, additional material characterization and modeling, as well as enhancements in the modeling of the geometry, are proposed. Together with previously determined effective composite properties of fiber skeletons, these results are validated in experimental tensile tests on inclined loop specimens

Si/SiC-Ceramic Prototypes via LS2I-Process (Liquid Silicon Infiltration of Laser Sintered C-SiC Parts)

The liquid silicon infiltration of laser sinteredC-~iC parts (LS2 I) is solidfreeform fabrication technique which allows the production of complexshapedSi/SiC prototypes. A mixture of SiC powder and reactive polymer binder isused in the las~r sinteringprocessto generate a porous green part. In the\postprocessing, the porous green part structure has to be infiltrated with a.precursor·resin, carbonised and finally·.infiltrated•. with molten silicon. The infiltrated silicon reacts with the residualcarbontobuild~~SiC.Results generated by the use of reduced primary particle sizes as well asaltemative infiltration materials and the use of other·RPtechniquesfor the green partfabrication will be discussed in this paper.Mechanical Engineerin

TheoPrax - Wie die Praxis Schulen und Hochschulen durchlüftet

Wirtschaft und Hochschulen beklagen, dass sich zu wenige Abiturienten an den Universitäten für ingenieur- und naturwissenschaftliche Fächer einschreiben. Die Absolventenzahlen in allen Ingenieurdisziplinen und in den Naturwissenschaften gingen seit Anfang der 90er-Jahre drastisch zurück und stiegen in den vergangenen Jahren nur geringfügig

Temperature Dependent Optical Properties of Polymers as a Basis for Laser Process Modeling

The knowledge of laser absorption is essential to describe the behavior of polymers in different laser processes, i.e. SLS, LOM, etc. By means of transmission IR-spectroscopy a method for measuring temperature dependent penetration depths (absorption length) of polymers, especially at a wavelength of 10.6Jlm (C02-Laser), is developed. Results for the laser sintering materials polystyrene (PS), nylon 11 (PA 11), nylon copolymer (CoPA) and polyethylene terephtalate (PET) are presented. It is detected that the absorption length of polymers will increase or decrease significantly dependent on temperature. This paper will point out simplified methods based on the one dimensional heat transfer equation with volume heat source to set the processing parameters i. e. for the SLS process. The calculations correspond with the measured data.Mechanical Engineerin