Dissertations / Theses on the topic 'Einflussgrösse'

The knowledge economy, learning and innovation have moved to the foreground both in regional and industrial policies in the past decade. Concrete policies were shaped in the past by the linear innovation model (focus on R&D and technology diffusion), and more recently, by "best practice models" of interactive innovation derived from high tech- and well performing regions. These were often applied in a similar way across many types of regions. In this paper an attempt was made to show that there is no "ideal model" for innovation policy. Empirical investigations demonstrate that preconditions for innovation, innovation activities and processes, as well networks differ strongly between central, peripheral and old industrial regions. The RIS approach allows to take such differences into account by analysing the strengths and weaknesses of the various subsystems, clusters and the interdependencies within the respective region and beyond. In the present paper we are going to analyse different types of regional innovation systems with respect to their preconditions for innovation, networking and innovation barriers. Based on this classification different policy options and strategies are developed and discussed. Besides high performing regional innovation systems with well developed and dynamic clusters we will deal with situations which are characterised by low levels of clustering, a weak endowment with relevant institutions, fragmentation and "lock in". We argue that policy approaches will differ - amongst other dimensions - with respect to the weight given to the stimulation of incremental/radical innovations, the orientation on endogenous/exogenous companies and knowledge sources, and the fostering of internal/external networking. (author's abstract)
Series: SRE - Discussion Papers

The need of using the underground space was limited in the human history, but in the last century and due to the increase of world population, the use of the underground space has become essential. Underground metro stations, deep garages, tunnels and basements, etc... are examples of using the underground space inside the cities. The use of underground space is conducted through deep excavation or tunneling. Several techniques are used to conduct the deep excavation and one of the most popular and well known techniques used for deep excavation is the diaphragm walling technique which is widely used specially inside the cities to safe space because it requires a very small space to conduct a deep reinforced concreted wall under the ground. However, the construction of such walls causes deformation of the surrounding ground and it could also affect the nearby existing structures. In some recorded cases the slurry trench failed and causes a great deformation which effect the nearby structures. However, Minor damages and cracks were observed in buildings near stable slurry trenches, because the soil deformation was high. The existing structures inside the cities have been constructed on shallow or deep foundations and this research was oriented to study the effect of diaphragm wall installation on the existing adjacent piled foundation. Very limited studies were made to investigate such an effect. At Cambridge university centrifuge model tests were conducted to investigate the effect of slurry reduction on single piles. Field observation was conducted in several projects and showed the settlement and deformation of buildings located on deep foundation during the diaphragm wall trenching. Numerical analysis was conducted using FLAC 3D to simulate the laboratory and the available field works. FLAC 3D is a commercial software and it depend in its analysis on finite difference method. The purpose of the simulation was to verify the used numerical analysis method. The results from the numerical analysis were in a good agreement with the available field data results, and they were also in good agreement with the laboratory test results regarding soil settlement but it was not in such good agreement when they were compared regarding the pile. Generally, from the verification the numerical analysis method is considered to be reliable. A parametric study was performed using the verified numerical analysis method. The flexible nature of the numerical analysis allows to simulate different cases and to study a variety of parameters. The output of the parametric study was the pile deflection, the bending moment and the shaft friction. The study was divided into three main parts while each part contains several parameter combinations. The first part studied the effect of the single and double panel(s) on the single pile group that has different piles numbers and formations. The second and third parts studied the effect of multiple panels on connected pile groups and piled raft foundation, respectively. Generally, the studied parameters can be divided into three main groups. The first is related to the trench which includes the panel dimension, the number of panels and the slurry level inside the panel. The effect of slurry pressure reduction at some levels inside the trench was also studied. The second group concerned the soil type and ground water level. The third group is related to the deep foundation which includes pile characteristics, location, and formation within the group. The results from the parametric study showed that the pile behavior was greatly affected by panel length, groundwater level, slurry level inside the trench and steadiness of the slurry pressure. The piles were also affected by the different stages of construction related to the pile location from the constructed panel. The piles within the group act together so they behave different from each other according to their position. The effect of the pile on the trench stability is presented through a simple analytical approach which is based on the wedge analysis. The analytical approach provided equations that calculate the factor of safety in two and three dimensions. The pile location was governing the equation that calculate the factor of safety because the pile could be fully inside the failure wedge or intersect with the failure surface. A comparative study was conducted to find out the effect of the different pile location and other parameters on the safety factor. Generally, this comparative study showed that the pile located within the failure wedge reduces the factor of safety, while the pile that intersects the failure surface could increase it. The pile row near a trench that contains piles inside the failure wedge and others intersects the failure surface act together to balance the failure wedge. The factor of safety results of some cases from the analytical approach were also compared with those calculated from the numerical analysis. In general, the factor of safety from the numerical analysis was higher than that calculated from the proposed analytical approach. This research helped to understand the trenching effect on the ground surface and on the nearby piled foundations. It provided charts that could help to predict the soil deformation and earth pressure coefficient which could be used in the design. It showed through the parametric study the precautions that should be taken into consideration during trenching process near piled foundation. This research provided a design method for the slurry trench panel near piled foundation.

The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required. In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem. Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process. With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process. With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.

Um den Einfluss einer Distalbissbehandlung sowie einer kombiniert kieferorthopädisch-chirurgischen Behandlung auf die Kaufähigkeit näher zu untersuchen, wurde bei 103 Probanden mit einer Kaueffektivitätsprüfung das Zerkleinerungsvermögen von Erdnüssen getestet. Hierzu wurden eine erwachsene Kontrollgruppe mit Regelbiss, eine Gruppe nach erfolgreicher Behandlung des Distalbisses mit bleibendem Gebiss, eine Probandengruppe mindestens sechs Monate nach erfolgreicher kieferorthopädisch-kieferchirurgischer Operation, Probanden im Wechselgebiss/Ruhephase mit Regelbiss und Probanden im Wechselgebiss/Ruhephase mit Distalbiss untersucht. Ausserdem wurde die Bedeutung verschiedener Einflussfaktoren wie Alter, Geschlecht, okkludierende Seitenzähne, okklusale Kontaktpunkte sowie Okklusionsfläche geprüft. Es konnte kein signifikanter Einfluss von Alter und Geschlecht auf die Kaueffektivität gefunden werden. Die Anzahl okkludierender Seitenzähne sowie die Okklusionsfläche hingegen stellten wichtige Einflussfaktoren für die Kaueffektivität dar. Der Vergleich von Probanden im Wechselgebiss mit Regelbiss und Probanden im gleichen Alter mit Distalbiss zeigte, dass dieser nicht zu einer geringeren Kaueffektivität führte. Die Kaueffektivität nach einer Distalbissbehandlung war relativ gut, erreichte aber nicht das Niveau von Probanden ohne Behandlung mit neutraler Okklusion. Nach einer kieferorthopädisch-kieferchirurgischen Behandlung blieb der Kaueffekt weiterhin niedriger als bei nicht operierten Probanden mit Regelbiss
Orthodontic treatment as well as orthognathic surgery to correct an Angle Class II deformity is often thought to improve masticatory performance.The chewing ability was measured using the Masticatory Performance Index. This Index measures chewing performance based on the percentage of a bolus that is reduced below a given paticle size. The groups tested were firstly an adult group with Angle Kl.I, secondly a group after a successful orthodontical treatment of an Angle Kl. II, thirdly a group 6 months after successful surgery and two children groups (10 years of age), one with neutral occlusion and the other one with Angle Kl.II. Furthermore different influencing variables like age, gender, number of teeth in occlusion, contact points and occlusal contact area are examined. Age and sex showed no direct significant influence on mastication. Number of teeth in occlusion and occlusal contact area had a great influence on masticatory efficiency. The comparison of masticatory efficiency between the two groups of children with distal occlusion and neutral occlusion showed no significant difference. Masticatory efficiency of the group after orthodontic treatment was relatively good, but didn`t reach the level of control subjects. Chewing efficiency was significantly different between surgery and control group

The need of using the underground space was limited in the human history, but in the last century and due to the increase of world population, the use of the underground space has become essential. Underground metro stations, deep garages, tunnels and basements, etc... are examples of using the underground space inside the cities. The use of underground space is conducted through deep excavation or tunneling. Several techniques are used to conduct the deep excavation and one of the most popular and well known techniques used for deep excavation is the diaphragm walling technique which is widely used specially inside the cities to safe space because it requires a very small space to conduct a deep reinforced concreted wall under the ground. However, the construction of such walls causes deformation of the surrounding ground and it could also affect the nearby existing structures. In some recorded cases the slurry trench failed and causes a great deformation which effect the nearby structures. However, Minor damages and cracks were observed in buildings near stable slurry trenches, because the soil deformation was high. The existing structures inside the cities have been constructed on shallow or deep foundations and this research was oriented to study the effect of diaphragm wall installation on the existing adjacent piled foundation. Very limited studies were made to investigate such an effect. At Cambridge university centrifuge model tests were conducted to investigate the effect of slurry reduction on single piles. Field observation was conducted in several projects and showed the settlement and deformation of buildings located on deep foundation during the diaphragm wall trenching. Numerical analysis was conducted using FLAC 3D to simulate the laboratory and the available field works. FLAC 3D is a commercial software and it depend in its analysis on finite difference method. The purpose of the simulation was to verify the used numerical analysis method. The results from the numerical analysis were in a good agreement with the available field data results, and they were also in good agreement with the laboratory test results regarding soil settlement but it was not in such good agreement when they were compared regarding the pile. Generally, from the verification the numerical analysis method is considered to be reliable. A parametric study was performed using the verified numerical analysis method. The flexible nature of the numerical analysis allows to simulate different cases and to study a variety of parameters. The output of the parametric study was the pile deflection, the bending moment and the shaft friction. The study was divided into three main parts while each part contains several parameter combinations. The first part studied the effect of the single and double panel(s) on the single pile group that has different piles numbers and formations. The second and third parts studied the effect of multiple panels on connected pile groups and piled raft foundation, respectively. Generally, the studied parameters can be divided into three main groups. The first is related to the trench which includes the panel dimension, the number of panels and the slurry level inside the panel. The effect of slurry pressure reduction at some levels inside the trench was also studied. The second group concerned the soil type and ground water level. The third group is related to the deep foundation which includes pile characteristics, location, and formation within the group. The results from the parametric study showed that the pile behavior was greatly affected by panel length, groundwater level, slurry level inside the trench and steadiness of the slurry pressure. The piles were also affected by the different stages of construction related to the pile location from the constructed panel. The piles within the group act together so they behave different from each other according to their position. The effect of the pile on the trench stability is presented through a simple analytical approach which is based on the wedge analysis. The analytical approach provided equations that calculate the factor of safety in two and three dimensions. The pile location was governing the equation that calculate the factor of safety because the pile could be fully inside the failure wedge or intersect with the failure surface. A comparative study was conducted to find out the effect of the different pile location and other parameters on the safety factor. Generally, this comparative study showed that the pile located within the failure wedge reduces the factor of safety, while the pile that intersects the failure surface could increase it. The pile row near a trench that contains piles inside the failure wedge and others intersects the failure surface act together to balance the failure wedge. The factor of safety results of some cases from the analytical approach were also compared with those calculated from the numerical analysis. In general, the factor of safety from the numerical analysis was higher than that calculated from the proposed analytical approach. This research helped to understand the trenching effect on the ground surface and on the nearby piled foundations. It provided charts that could help to predict the soil deformation and earth pressure coefficient which could be used in the design. It showed through the parametric study the precautions that should be taken into consideration during trenching process near piled foundation. This research provided a design method for the slurry trench panel near piled foundation.

The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required. In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem. Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process. With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process. With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.

Die Zustandsbewertung von Kabeln mit vernetzter Polyethylen-Isolierung (VPE) ist seit vielen Jahren eine große Herausforderung, da die Alterungsmechanismen nicht vollständig geklärt sind. Die Zuverlässigkeit der Ergebnisse von Verfahren zur Bewertung des integralen Zustandes der VPE-isolierten Mittelspannungskabel wird kontrovers diskutiert oder teilweise in Frage gestellt. Bei Kenntnis des Alterungsverhaltens und der wirkenden Einflussfaktoren kann Verlustfaktor tan δ der VPE-Mittelspannungskabel wichtige Hinweise auf den Zustand geben. Bei der Bewertung des Zustandes auf Basis des Verlustfaktors tan δ müssen die in der VPE-Hauptisolierung befindlichen Zuschlagstoffe berücksichtigt werden. In Abhängigkeit der Zugaben von Homo- oder Co-Polymeren ist ein grundsätzlich unterschiedliches Alterungsverhalten möglich, das zu Fehlinterpretation führen kann. Die messtechnisch gewonnenen Aussagen wurden über ein Dreischicht-Modell bestätigt, mit dem das elektrische Verhalten der Kabelisolierung verifiziert werden konnte. In der Arbeit werden wesentliche Schlussfolgerungen zur Auswirkung thermischer Beanspruchungen über der Einsatzdauer formuliert. Es wird ein Verfahren vorgestellt, mit dem es perspektivisch möglich sein kann, den Zustand eines VPE-Kabels abzuschätzen. Das Verfahren reduziert den Einfluss der messspezifischen Faktoren.:Inhaltsverzeichnis i Abkürzungsverzeichnis i Symbolverzeichnis iii Kurzfassung v Danksagung vi 1 Einleitung 1 1.1 Motivation 1 1.2 Bisherige Anwendungen der Verlustfaktormessungen an VPE-Kabeln 3 1.3 Zielsetzung der Arbeit 6 1.4 Struktur der Arbeit 8 2 Eigenschaften von VPE-Kabeln 11 2.1 Aufbau der VPE-Kabel 11 2.2 Entwicklung der Kunststoff-Kabeltechnologie 12 2.3 Struktur und Morphologie von PE/VPE-Isolierungen 15 2.4 Zusammensetzung und Eigenschaften der halbleitenden Schichten 18 2.5 Alterungsmechanismen bei VPE-Kabeln 19 3 Dielektrische Eigenschaften von VPE-Kabeln 23 3.1 Dielektrischer Verlustfaktor 23 3.2 Polarisationsmechanismen der PE/VPE-Isolierung 23 3.3 Leitungsmechanismen im Polyethylen 25 3.4 Ersatzanordnungen zur Nachbildung des Verlustfaktors 28 3.5 Dreischicht-Modell zur Nachbildung des Verlustfaktors 35 3.5.1 Aufbau des Simulations-Dreischicht-Modells 43 3.5.2 Materialparameter der drei Kabelhauptschichten 45 4 Verlustfaktormessungen an VPE-Kabeln 49 4.1 Messeinrichtungen zur Verlustfaktormessung 49 4.1.1 Frequenzbereichsspektroskopie (FDS-Messung) 49 4.1.2 Vektorielle Impedanzmessung (VI-Messung) 50 4.2 Umfang der Prüfobjekte 51 4.3 Konfektionierung der VPE-Kabel 53 4.4 Aufnahme einer Verlustfaktor-Referenzkurve 56 4.5 Störeinflüsse auf die Messung des Verlustfaktors 56 4.5.1 Äußere Einflüsse 57 4.5.2 Innere Einflüsse 58 4.6 Versuchsvorbereitung und -durchführung 62 4.6.1 Einfluss der Temperaturabhängigkeit auf den Verlustfaktor 62 4.6.2 Einfluss der thermischen Beanspruchung auf den Verlustfaktor 62 4.6.3 Einfluss der Einwirkung von Wasser auf den Verlustfaktor 63 5 Auswertung und Diskussion der Messergebnisse 66 5.1 Frequenzabhängigkeit des Verlustfaktors 66 5.1.1 Neuwertige VPE-Kabel 66 5.1.2 Betriebsgealterte VPE-Kabel 73 5.2 Spannungsabhängigkeit des Verlustfaktors 76 5.2.1 Spannungsabhängigkeit im Frequenzbereich 40 – 280 Hz 76 5.2.2 Spannungsabhängigkeit bei einer Frequenz von 0,1 Hz 79 5.3 Einflussfaktoren auf den frequenzabhängigen Verlustfaktor 81 5.3.1 Temperaturabhängigkeit des Verlustfaktors 81 5.3.2 Abhängigkeit des Verlustfaktors von der thermischen Beanspruchung 90 5.3.3 Abhängigkeit des Verlustfaktors von der Wasserlagerung 94 6 Zusammenfassung und Ausblick 97 Anhang 103 Abbildungsverzeichnis 105 Tabellenverzeichnis 109 Literaturverzeichnis 110 Thesen 129

Der Scanning-Antastabweichung kommt in der Überprüfung und Bewertung von taktil-scannenden 3D-Koordinatenmessgeräten fortwährend eine große Bedeutung zu. Sie bildet unter anderem die Basis für die Geräteauswahl, die Messsystemanalyse und die Bestimmung von Messunsicherheiten. Dabei entscheiden spezifische Wirkbeziehungen innerhalb des Gesamtsystems aus Koordinatenmessgerät und Messobjekt über die Aussagekraft abgeleiteter Kennwerte sowie die Vereinbarkeit der Herausforderungen der Fertigungsmesstechnik in einer vorgegebenen Messaufgabe. In dieser Arbeit wird eine Vorgehensweise zur Bestimmung der spezifischen, oberflächenbedingten Scanning-Antastabweichung unter Berücksichtigung der Einflussgrößen Sensor, Scanning-Parameter, Tasterkonfiguration und Gestaltabweichungen des Messobjektes vorgestellt. Ziel dessen ist es, bestehende Kenntnisse zur Wirkungsweise definierter Einflussgrößen zu erweitern und einen neuen, erweiterten sowie anwendungsorientierten Ansatz für die Überprüfung und Bewertung von Koordinatenmessgeräten zu bieten. Dies bildet den Ausgangspunkt für die Vergleichbarkeit und Reproduzierbarkeit von Messergebnissen. Die Basis zugehöriger Untersuchungen bilden vorangegangene Forschungsprojekte sowie Empfehlungen und Hinweise aus Literatur und Herstellerinformationen. Daraus abgeleitete Haupteinflussgrößen definieren den Rahmen der Versuchsreihen zur Klärung formulierter zentraler Forschungs-fragen. Ausgehend von den Untersuchungen an einem festgelegten Basis-Koordinatenmessgerät wird die Übertragbarkeit erarbeiteter Erkenntnisse auf alternative Sensoren überprüft und Ergebnisse auf systematische und zufällige Abweichungsanteile hin analysiert. Durch den Vergleich „annähernd-idealer“ sowie „zielmarktorientierter“ Oberflächen zeigt sich, dass Wirkbeziehungen zwischen den untersuchten Haupteinflussgrößen, beispielsweise unter Variation der Scanning-Geschwindigkeit, erst durch das Vorhandensein nicht-idealer Oberflächeneigenschaften auftreten oder durch diese derart verstärkt werden, dass sie sich von zufälligen Messabweichungen abheben. Die Bewertung der erfassten Messdaten erfolgt dabei anhand der abgeleiteten Geradheitsabweichung in Bezug auf zugrundeliegende Referenzmessungen sowie vergleichender prozentualer Betrachtungen und abgeleiteter Grenzwerte. Zentrale Erkenntnis der Hauptuntersuchungen am Basis-Koordinatenmessgerät ist, dass durch verschiedene Tasterorientierungen klare und explizit unterschiedliche Wirkbeziehungen zwischen den Haupteinflussgrößen auftreten, was über bisherige Forschungsergebnisse weit hinausgeht. Dies konnte auch durch die Verifikationsmessungen bestätigt werden. Sensorübergreifend sind derartig klare Wirkbeziehungen nicht zu detektieren. Auch zum Basis-Koordinatenmessgerät vergleichbare sensorspezifische Abhängigkeiten sind anhand der durchgeführten Messreihen nicht formulierbar. Es ist allerdings auch zu konstatieren, dass jede der untersuchten Einflussgrößen, unter Ausnahme der Antastkraft, durch Messabweichungen belegbare Auswirkungen hat. Die Erkenntnisse und Potentiale dieser Arbeit bieten somit eine umfängliche Basis für die Weiterentwicklung der Bewertungs- und Entscheidungsgrundlagen der taktil-scannenden 3D-Koordninatenmesstechnik, welche durch eine verbesserte Vergleichbarkeit, ein umfassenderes Wissen zu Mess- beziehungsweise Antastabweichungen sowie gesteigerte Effizienz gekennzeichnet sind.

Zur Untersuchung der Faser-Matrix-Haftung in Faser-Kunststoff-Verbunden werden neben makromechanischen Methoden wie dem Querzug und der Drei-Punkt-Biegung mikromechanische Methoden an Einzelfaser-Modellverbunden eingesetzt. Zu letzteren Methoden zählen bspw. der Tropfenabscherversuch, der Einzelfaserauszugversuch (engl. single-fibre pull-out test, SFPO) und der Einzelfaserfragmentierungsversuch (engl. single fibre fragmentation test, SFFT). Bei ihrem Einsatz ist zu beachten, dass sich unterschiedliche Einflussgrößen auf ihre Ergebnisse auswirken können. In der vorliegenden Arbeit wird eine ausführliche Literaturübersicht mit einem detaillierten Überblick zu einer größeren Anzahl verschiedener Einflussgrößen durchgeführt. Daraus werden die Einflussgrößen Härtungsdauer, Feuchtigkeit, freie Faserlänge und Abzugsgeschwindigkeit als Untersuchungsgegenstände dieser Arbeit erarbeitet. Wesentliche aus dieser Arbeit resultierende Ergebnisse und Schlussfolgerungen sind nachstehend zusammengefasst. Härtungsdauer: Bei SFFT-Untersuchungen an Keramikfaser/Epoxidharz-Prüfkörpern wird ein degressiver Anstieg der Faser-Matrix-Haftung über der Härtungsdauer beobachtet. Die Ergebnisse geben Hinweise darauf, dass sich die Härtungsdauer beim SFFT und SFPO prinzipbedingt unterschiedlich auswirkt (aufgrund destruktiver bzw. konstruktiver Überlagerungen von Eigenspannungen und Prüfkraft-induzierten Spannungen). Feuchtigkeit: SFPO-Untersuchungen an Kohlenstoffaser/Epoxidharz-Prüfkörpern nach einmonatiger Konditionierung in feuchtem (50 %rF, 23 °C) bzw. trockenem Klima (0 %rF, 23 °C) belegen eine feuchtebedingt verringerte Haftung. Daraus wird geschlussfolgert, dass eine schwankende Luftfeuchtigkeit auch in diesem eingegrenzten klimatischen Spektrum (bspw. in teilklimatisierten Laboren) als wichtiger potentieller Störfaktor zu beachten ist. Prüfparameter: Auf Basis des Hooke’schen Gesetzes kann für den SFPO gezeigt werden, dass die freie Faserlänge die Maximalkraft beeinflusst und die Einflüsse der freien Faserlänge und der Abzugsgeschwindigkeit auf die Maximalkraft in Zusammenhang stehen. Beides wird anhand von SFPO-Untersuchungen an Glasfaser/Epoxidharz-Prüfkörpern bestätigt. Ferner wird aus den Untersuchungen geschlussfolgert, dass eine Geschwindigkeitserhöhung von 0,01 µm/s auf 0,1 µm/s zur Reduzierung der Versuchsdauer – im vorliegenden Fall von 30 45 min auf 6 8 min – vertretbar ist. Darüber hinaus werden anhand von Fehlerverstärkungsfaktoren differenzierte Aussagen zum Einfluss fehlerhaft bestimmter Eingangsdaten auf die Berechnung der lokalen Grenzflächenscherfestigkeit generiert.
For investigating fibre-matrix adhesion in fibre-polymer composites, macromechanical methods such as transverse tensile and three-point bending tests can be applied as well as micromechanical methods for which single-fibre model composites are used. The latter category of methods includes microbond, single-fibre pull-out (SFPO) and single-fibre fragmentation tests (SFFT). When applying these methods, it needs to be considered that their results can be affected by different influencing factors. In the present thesis, an extensive literature survey with a detailed overview of a larger number of influencing factors is conducted. Based on this overview, the factors curing time, moisture, free fibre length and test speed are acquired as objects of investigation of this thesis. Main results and conclusions of this work are summarised below. Curing time: Results from SFFT investigations on ceramic fibre/epoxy-specimens exhibit a degressive increase of fibre-matrix adhesion with curing time. This indicates that curing time affects SFFT and SFPO results differently due to different underlying principles (based on destructive and, respectively, constructive superposition of internal stresses and load-induced stresses). Moisture: SFPO specimens (carbon fibre/epoxy) are conditioned in humid (50 %rH, 23 °C) and dry climate (0 %rH, 23 °C) for one month prior to testing. The results show lower adhesion due to moisture. It is concluded that uncontrolled humidity, even in this limited climatic spectrum, needs to be considered as an important potential factor of influence (e.g. in partially climatised laboratories). Test parameters: Based on Hooke’s law, it is demonstrated for the SFPO that a) the free fibre length affects the maximum force and b) the effects of the free fibre length and the test speed on the maximum force are interrelated. Both is confirmed with results from SFPO investigations on glass fibre/epoxy-specimens. Furthermore, it is deduced from the above investigations that an increase in test speed from 0.01 µm/s to 0.1 µm/s is legitimate for reducing test duration – in the present case from 30 45 min to 6 8 min. In addition, the effect of erroneously determined input data on the calculation of the local interfacial shear strength is studied using conditions numbers (a measure for the propagation of error). With this, differentiated statements are generated.