KOBRA
https://kobra.uni-kassel.de:443
Das digitale Repositorium erfasst, speichert, erhält, erschließt und verbreitet digitale Forschungsergebnisse.2024-03-19T02:57:18ZModification of self-reinforced composites (SRCs) via film stacking process
https://kobra.uni-kassel.de:443/handle/123456789/15573
This work presents the mechanical behavior of self-reinforced composites (SRCs) manufactured and modified via film stacking. For modification, interleaved films made of polypropylene (PP), a thermoplastic elastomer and a polyolefin engage were combined in different ways to induce the elastic modifier into the matrix material. The content of modifier was also varied in two ways. First, the films were produced out of a single material and second out of a compound. So, the same content of modifier was implemented in two different ways. It is shown that, in case of this research, only the kind of modifier and the content but not the way of implementation are responsible for the mechanical behavior of SRCs. It is shown that the modification can adjust the tensile strength, tensile stiffness and impact properties in a broad range. It is also shown that different mechanical properties of the composite can be predicted by a regression model that uses the Shore A hardness and the content of modifier.
2022-02-25T00:00:00ZJakob, FabianPollmeier, JoshuaBisevac, SinanHeim, Hans-PeterThis work presents the mechanical behavior of self-reinforced composites (SRCs) manufactured and modified via film stacking. For modification, interleaved films made of polypropylene (PP), a thermoplastic elastomer and a polyolefin engage were combined in different ways to induce the elastic modifier into the matrix material. The content of modifier was also varied in two ways. First, the films were produced out of a single material and second out of a compound. So, the same content of modifier was implemented in two different ways. It is shown that, in case of this research, only the kind of modifier and the content but not the way of implementation are responsible for the mechanical behavior of SRCs. It is shown that the modification can adjust the tensile strength, tensile stiffness and impact properties in a broad range. It is also shown that different mechanical properties of the composite can be predicted by a regression model that uses the Shore A hardness and the content of modifier.Investigation of the adhesive strength in a combined compaction and back-injection process to produce back-injected self-reinforced composites (SRCs)
https://kobra.uni-kassel.de:443/handle/123456789/15572
This publication investigates the adhesion between an injection molded component and a self-reinforced composite (SRC) produced in a combined compaction and back-injection process to produce back-injected self-reinforced composites. To study the influence of the process, the parameters barrel temperature, time of injection, and tool temperature were varied. In addition, samples were taken at different positions along the flow path. In light of the orthotropic material behavior of SRCs, investigations were conducted to see whether different loading cases lead to different mechanical behavior. Shear-off and pull-off tests revealed a different strength as a function of the loading type. In the shear-off tests, a mean strength of 11.37 MPa was recorded over the entire test series, while the measured mean strength in the pull-off tests is considerably lower, 4.04 MPa. The type of failure is determined with the aid of SEM images, and the influence of the microstructure of the thermoplastic fibre materials on the adhesion is set out. It is shown that, as of a sufficiently high level of adhesion, failure occurs within the fibres.
2022-03-08T00:00:00ZJakob, Fabian SimonGothe, MarcelGansiniec, FabianHeim, Hans-PeterThis publication investigates the adhesion between an injection molded component and a self-reinforced composite (SRC) produced in a combined compaction and back-injection process to produce back-injected self-reinforced composites. To study the influence of the process, the parameters barrel temperature, time of injection, and tool temperature were varied. In addition, samples were taken at different positions along the flow path. In light of the orthotropic material behavior of SRCs, investigations were conducted to see whether different loading cases lead to different mechanical behavior. Shear-off and pull-off tests revealed a different strength as a function of the loading type. In the shear-off tests, a mean strength of 11.37 MPa was recorded over the entire test series, while the measured mean strength in the pull-off tests is considerably lower, 4.04 MPa. The type of failure is determined with the aid of SEM images, and the influence of the microstructure of the thermoplastic fibre materials on the adhesion is set out. It is shown that, as of a sufficiently high level of adhesion, failure occurs within the fibres.Climatic Ageing of Components of Polymer Based Electrochromic Devices
https://kobra.uni-kassel.de:443/handle/123456789/15571
Combining a shading function and a polycarbonate window displays an attractive alternative to the currently employed glass roof in vehicles. However, the ageing of such a device must be investigated before any application. Therefore, our investigations focus on the ageing of the components of a polycarbonate based electrochromic device. The optical, electrical, mechanical and electrochemical properties of the ion storage layer as well as the substrate will be assessed after storage in a climate with a high humidity and high temperature level.
2013-09-09T00:00:00ZHeim, Hans-PeterDesjean, AlineCombining a shading function and a polycarbonate window displays an attractive alternative to the currently employed glass roof in vehicles. However, the ageing of such a device must be investigated before any application. Therefore, our investigations focus on the ageing of the components of a polycarbonate based electrochromic device. The optical, electrical, mechanical and electrochemical properties of the ion storage layer as well as the substrate will be assessed after storage in a climate with a high humidity and high temperature level.Bend Straightening of a Carbonitrided Gear Shaft – Consequences on Residual Stresses and Retained Austenite near the Surface
https://kobra.uni-kassel.de:443/handle/123456789/15570
Carbonitriding of shafts in drive technology is strongly connected with distortion. Bend straightening is an important process step in order to eliminate distortion without removing the hardened surface layer. As shown in several investigations, even for simple part geometries, bending induced stresses and plastic deformations have a strong impact not only on the residual stress state but also on the microstructure after straightening. As gear shafts become increasingly filigree and complex in their geometry, the components state after straightening is only understood in rare cases. Due to indispensable, function based notches as well as changes in the cross section, these effects will occur especially in areas of small cross sections or notches in conjunction with high bending stresses. It is the objective of this work, to characterize these critical areas with respect to the distribution of residual stresses and retained austenite along the circumference as well as in the in-depth direction. Therefore, the measured distributions of residual stresses, integral width values and retained austenite near the surface will be presented and discussed. For this purpose a carbonitrided gear shaft taken out of a large production volume was investigated before and after a commonly used straightening operation.; In der Antriebstechnik stellt das Biegerichten nach der Einsatzhärtung von Wellen einen wichtigen Prozessschritt dar, um den oftmals unvermeidlichen Verzug zu beseitigen und gleichzeitig die harte Randschicht des Bauteils zu erhalten. Wie bereits in einigen Untersuchungen dargestellt wurde, beeinflussen die beim Richten vorliegenden Spannungen und die daraus resultierenden plastischen Deformationen sowohl den Eigenspannungszustand als auch die Mikrostruktur schon bei geometrisch simplen Bauteilen. Für die zunehmend filigranen und in ihrer Geometrie komplexen Wellen ist der Zustand nach dem Richten jedoch nur in seltenen Fällen bekannt und nachvollziehbar. Bei einer Welle, die konstruktiv notwendige Querschnittsänderungen oder auch Kerben aufweist, werden die genannten Effekte dort auftreten, wo Bereiche mit geringem Querschnitt und solche mit hohen Lastspannungen durch den Richtprozess zusammenfallen. Ziel dieser Arbeit ist es, diese kritischen Bereiche im Hinblick auf die Verteilung von Eigenspannungen und Restaustenit, sowohl entlang des Umfangs als auch in Tiefenrichtung, detailliert zu charakterisieren, um ein besseres Verständnis für den Zustand gerichteter Wellen zu gewinnen. Dazu werden die ermittelten randnahen Eigenspannungsverläufe und die Verteilungen der Integralbreiten sowie der Restaustenitgehalte am Beispiel einer in großer Stückzahl hergestellten Getriebewelle vor und nach einem praxisüblichen Richtprozess vorgestellt und diskutiert.
2017-06-20T00:00:00ZSchott, ChristopherZinn, WolfgangScholtes, BertholdNiendorf, ThomasCarbonitriding of shafts in drive technology is strongly connected with distortion. Bend straightening is an important process step in order to eliminate distortion without removing the hardened surface layer. As shown in several investigations, even for simple part geometries, bending induced stresses and plastic deformations have a strong impact not only on the residual stress state but also on the microstructure after straightening. As gear shafts become increasingly filigree and complex in their geometry, the components state after straightening is only understood in rare cases. Due to indispensable, function based notches as well as changes in the cross section, these effects will occur especially in areas of small cross sections or notches in conjunction with high bending stresses. It is the objective of this work, to characterize these critical areas with respect to the distribution of residual stresses and retained austenite along the circumference as well as in the in-depth direction. Therefore, the measured distributions of residual stresses, integral width values and retained austenite near the surface will be presented and discussed. For this purpose a carbonitrided gear shaft taken out of a large production volume was investigated before and after a commonly used straightening operation.
In der Antriebstechnik stellt das Biegerichten nach der Einsatzhärtung von Wellen einen wichtigen Prozessschritt dar, um den oftmals unvermeidlichen Verzug zu beseitigen und gleichzeitig die harte Randschicht des Bauteils zu erhalten. Wie bereits in einigen Untersuchungen dargestellt wurde, beeinflussen die beim Richten vorliegenden Spannungen und die daraus resultierenden plastischen Deformationen sowohl den Eigenspannungszustand als auch die Mikrostruktur schon bei geometrisch simplen Bauteilen. Für die zunehmend filigranen und in ihrer Geometrie komplexen Wellen ist der Zustand nach dem Richten jedoch nur in seltenen Fällen bekannt und nachvollziehbar. Bei einer Welle, die konstruktiv notwendige Querschnittsänderungen oder auch Kerben aufweist, werden die genannten Effekte dort auftreten, wo Bereiche mit geringem Querschnitt und solche mit hohen Lastspannungen durch den Richtprozess zusammenfallen. Ziel dieser Arbeit ist es, diese kritischen Bereiche im Hinblick auf die Verteilung von Eigenspannungen und Restaustenit, sowohl entlang des Umfangs als auch in Tiefenrichtung, detailliert zu charakterisieren, um ein besseres Verständnis für den Zustand gerichteter Wellen zu gewinnen. Dazu werden die ermittelten randnahen Eigenspannungsverläufe und die Verteilungen der Integralbreiten sowie der Restaustenitgehalte am Beispiel einer in großer Stückzahl hergestellten Getriebewelle vor und nach einem praxisüblichen Richtprozess vorgestellt und diskutiert.