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Hopmann C.,Institutsleiter | Michaeli W.,Ehem Institutsleiter | Bastian R.,Institute For Kunststoffverarbeitung
Gummi, Fasern, Kunststoffe | Year: 2012

The gap impregnation process was developed at the IKV, Institute of Plastics Processing, for manufacturing high performance composite parts from fibre-reinforced plastics (FRPs) in only a few minutes. The process offers a high potential for the automated serial production of high-grade plane structural composite parts and the reduction of the process cycle times. The isothermal process control allows to achieve a high energy efficiency. Meanwhile this process technology also permits to manufacture successfully not only plane but also curved parts with transitions in thickness and components with integrated cut-outs in less than 5 min. The results obtained will now be transferred to more complex structures and the production of a carbon fibre engine hood in integral construction. Source

Klein J.,Institute For Kunststoffverarbeitung | Hopmann C.,Institute For Kunststoffverarbeitung
Experimental Mechanics | Year: 2016

Stress respectively force oscillation in mechanical testing is a phenomenon that can be monitored independent of material, stress state and test setup. This study looks at the phenomenon of force oscillation in tensile impact testing on viscoelastic materials and its dependency on longitudinal stress wave propagation. In addition to the extensive research on stress wave propagation and the force oscillation phenomenon, published within the last decades, the Society of Automotive Engineering (SAE) also gives valuable recommendations regarding tensile impact testing on polymer materials. Existing limitations to tensile impact testing reported earlier can be overcome using the approach outlined in this paper. Furthermore, we give an analysis to stress wave propagation in tensile impact testing and its correlation to force oscillations: We find that (1) longitudinal stress wave propagation in tensile specimens cannot be considered to be the origin of the force oscillation phenomenon - even more so it can be neglected, (2) specimens in tensile impact testing are exposed to a nearly oscillation free loading which is presented for haul-off velocities of up to 10 m/s and (3) it is not possible to achieve force equilibrium in the load train conducting tensile impact tests. In addition, we present an approach to measure a nearly oscillation free force signal in tensile impact testing on polymer materials up to 10 m/s. For this purpose a modification of a standard dumbbell specimen is introduced. Measurements presented in this paper are conducted using state of the art 3D high-speed deformation measurement technology based on Digital Image Correlation (DIC). © 2016 Society for Experimental Mechanics Source

Michaeli W.,Institute For Kunststoffverarbeitung | Hopmann Ch.,Institute For Kunststoffverarbeitung | Opendwinkle K.,Institute For Kunststoffverarbeitung
KGK Kautschuk Gummi Kunststoffe | Year: 2011

Special injection molding processes are increasingly important in rubber processing. Foam injection molding of elastomers with physical blowing agents offers technological advantages and a wide range of adjustable mechanical part properties as well as economic incentives. Based on selected tests the basic suitability of physical blowing agents is discussed and the used system technology for direct loading of is presented. By adapting the process conditions and mold characteristics part properties can be achieved that are comparable with those that are produced with the established technique of chemical foaming. Source

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