Filmische und soziale Raumentwürfe im experimentellen ethnografischen Dokumentarfilm anhand der Filmpraxis von Trinh T. Minh-ha

Eine Erschliessung von Raum zwischen und abseits konventioneller Paarkonstellationen ist Teil der Agenda von Trinh T. Minh-ha. In der vorliegenden Arbeit beschäftige ich mich im Genaueren mit den Filmarbeiten RE-ASSAMBLAGE (1981) und SURNAME VIET GIVEN NAME NAM (1989). Dabei analysiere ich filmische Raumkonstitutionen und befrage diese nach deren Potential de-kolonialisierende und feministische Filmpraxen zu generieren. Somit begreife ich die Organisation von filmischem Raum als Display spezifischer sozialer Räume. Zunächst skizziere ich in Kapitel 1 eine historische Kontextualisierung ethnografischer Filmpraxen und gehe in Kapitel 2 näher auf Trinhs Woman Native Other ein, mittels dessen ich Sprache als widerständigen Ort verhandle. Dabei führe ich spezifische Begrifflichkeiten als konkrete „Verhandlungsorte“ vor. So wie ich Sprache als materiellen Ort und Artikulation sozialer Kämpfe begreife, versuche ich auch Film als in kulturelle und soziale Gefüge eingebettetes Medium zu verstehen. Die Frage nach Raumentwürfen in Trinhs Filmarbeit stellt den Haupt-Analyseaspekt dar. Dabei denke ich Raum sowohl in seiner (pro-)filmischen Materialität als auch auf konzeptionelle Weise und frage schliesslich nach der Konstitution dessen. Raum verstehe ich dabei nie als ein neutrales Medium, das irgendwo draussen existiert, sondern als Manifestation verschiedenster Formen von Wissen und sozialen Institutionen. Schon der Begriff des Raumes selbst ist ja an eine Historie gebunden, die auf verschiedene Formen von Wissensproduktionen rekurriert. Jegliche theoretische Bemühung in Bezug auf Raum ist daher geographisch, sozial, institutionell verortet und schreibt sich wiederum in diese ein. Sowohl die theoretischen als auch filmischen Arbeiten Trinh Thi Minh-ha´s sind Ausdruck ihres politischen Kampfes, der- wie sie diesen selbst verortet- an (Be)Grenzen(-ungen) stattfindet und durch welchen sich durch Verschiebungen hegemonialer Verhältnisse neue „Zwischen-Räume“ auftun lassen. So wie Trinh das Ich als intertextuell und vielschichtig begreift, versteht sie auch Kultur(en) als hybride und in sich heterogene soziale Gebilde. Wie sich diese Auffassungen Trinhs innerhalb ihrer filmischen Raumkonzepte manifestieren, stellt die Motivation der vorliegenden Arbeit dar. Dabei habe ich (filmisch-räumliche) Repräsentation als machtvolle Strategie begriffen, die –indem diese zum Beispiel mit gängigen Sehkonventionen bricht- (selbst-)ermächtigende politische Wirkungen zu erzielen vermag

Processing of thick section epoxy powder composite structures

The use of epoxy powder as the primary matrix in thick fibre-reinforced composite parts is investigated. The characteristics of three epoxy powders are assessed using several experimental techniques, focusing on their curing behaviour. At least one epoxy powder is shown to have advantageous characteristics for manufacturing thick-section composites. Material models are developed which can describe the processing behaviour (cure kinetics, viscosity change, etc.) of an epoxy powder. The cure kinetics model makes use of an additional rate constant to better describe the rate of cure at both high and low temperatures. The chemorheological model is based on an existing model for toughened epoxies. A one-dimensional simulation tool for manufacturing thick-section composite laminates is developed in MATLAB. The simulation tool employs a resin flow model for vacuum-bag-only prepregs to describe the infusion process and subsequent thickness change. This thickness change is coupled to a model for through-thickness heat transfer which can be solved numerically for various thermal boundary conditions. The model is used to explore the suitability of epoxy powders for the manufacturing thick-section composite structures. The aforementioned simulation tool is validated against experimental results for thick-section composite laminates. The experiments are carried out using a modified heated tool and test apparatus which apply known thermal boundary conditions. A linear variable differential transformer is used to measure the thickness change of each laminate during testing, while thermocouples are used to measure the temperatures at various positions within each laminate. The results of the tests show good agreement with the one-dimensional simulation tool. Additional simulations are performed to investigate the influence of material format, thickness change, and heating methods. Methods for reducing thermal and cure gradients are explored also. A method is outlined for implementing the process models within commercial finite element software, Abaqus FEA. User subroutines for heat transfer and thermal expansion are used to define the various process models. One-dimensional simulations are validated, and a convergence study is performed on time step size and element size. Simulations show the effect of in-plane heating for glass-fibre and carbon-fibre laminates, and the processing of a wind turbine blade root section is investigated. Overall, it is shown that thick-section composite structures can be manufactured using a low-cost commodity epoxy powder from the coating industry, and that these structures do not suffer from the risk of uncontrolable thermal events

Analyse der Vernetzungskinetik von Duroplasten und deren Bedeutung für das Beschichten und Verkleben pflanzen-basierter Werkstoffe

Within the scope of the present cumulative doctoral thesis six scientific papers were published which illustrates that modern reaction model-free (=isoconversional) kinetic analysis (ICKA) methods represents a universal and effective tool for the controlled processing of thermosetting materials. In order to demonstrate the universal applicability of ICKA methods, the thermal cure of different thermosetting materials having a very broad range of chemical composition (melamine-formaldehyde resins, epoxy resins, polyester-epoxy resins, and acrylate/epoxy resins) were analyzed and mathematically modelled. Some of the materials were based on renewable resources (an epoxy resin was made from hempseed oil; linseed oil was modified into an acrylate/epoxy resin). With the aid of ICKA methods not only single-step but also complex multi-step reactions were modelled precisely. The analyzed thermosetting materials were combined with wood, wood-based products, paper, and plant fibers which are processed to various final products. Some of the thermosetting materials were applied as coating (in form of impregnated décor papers or powder and wet coatings respectively) on wood substrates and the epoxy resin from hempseed oil was mixed with plant fibers and processed into bio-based composites for lightweight applications. From the final products mechanical, thermal, and surface properties were determined. The activation energy as function of cure conversion derived from ICKA methods was utilized to predict accurately the thermal curing over the course of time for arbitrary cure conditions. Furthermore the cure models were used to establish correlations between the cross-linking during processing into products and the properties of the final products. Therewith it was possible to derive the process time and temperature that guarantee optimal cross-linking as well as optimal product propertiesIm Rahmen der vorliegenden kumulativen Doktorarbeit wurden sechs wissenschaftliche Arbeiten bzw. Paper veröffentlicht, in denen gezeigt wurde, dass moderne Methoden der (Reaktions-)modellfreien (="isoconversional") kinetischen Analyse (ICKA) ein universelles und effektives Werkzeug für die kontrollierte Verarbeitung chemisch vernetzender Werkstoffe darstellen. Um die universelle Anwendbarkeit der ICKA-Methoden zu demonstrieren, wurde die Vernetzung von Werkstoffen mit sehr unterschiedlicher chemischer Zusammensetzung (Melamin-Formaldehyd-Harze, Epoxidharze, Polyester/Epoxid-Harze und Acrylat/Epoxidharze) analysiert und mathematisch modelliert. Einige der Werkstoffe basierten auf nachwachsenden Rohstoffen (Hanfsamenöl-Epoxidharz, Leinsamenöl-Acrylat/Epoxidharz). Mit den ICKA-Methoden ließen sich nicht nur einstufige sondern auch komplexe mehrstufige Vernetzungsreaktionen präzise modellieren. Die analysierten Werkstoffe wurden mit verschiedenen pflanzlichen Materialien (Holz, Holzwerkstoffe, Papier, Pflanzenfasern) kombiniert und zu Produkten verarbeitet. Einige der vernetzenden Werkstoffe wurden (in Form imprägnierter Dekorpapiere, Pulver- bzw. Nass-Lacke) für die Beschichtung Holz-basierter Substrate eingesetzt, andere (Hanfsamenöl-Epoxidharz) wurden mit Pflanzenfasern vermischt und zu Verbundwerkstoffen für Leichtbauanwendungen verarbeitet. Von den Produkten wurden mechanische, thermische und Oberflächen-Eigenschaften ermittelt. Die aus der ICKA abgeleitete Aktivierungsenergie als Funktion des Vernetzungsumsatzes wurde eingesetzt, um für beliebige Prozessbedingungen den zeitlichen Verlauf der Vernetzung exakt vorherzusagen. Darüber hinaus wurden die Vernetzungskinetik-Modelle verwendet, um Zusammenhänge zwischen der Vernetzung während der Verarbeitung zu Produkten und den Eigenschaften der Produkte herzustellen. Damit ließen sich Verarbeitungs-Zeit und -Temperatur ableiten, die zu einer optimalen Vernetzung und zu optimalen Produkteigenschaften führte

Green composite material made from Typha latifolia fibres bonded with an epoxidized linseed oil/tall oil-based polyamide binder system

Here, we report the mechanical and water sorption properties of a green composite based on Typha latifolia fibres. The composite was prepared either completely binder-less or bonded with 10% (w/w) of a bio-based resin which was a mixture of an epoxidized linseed oil and a tall-oil based polyamide. The flexural modulus of elasticity, the flexural strength and the water absorption of hot pressed Typha panels were measured and the influence of pressing time and panel density on these properties was investigated. The cure kinetics of the biobased resin was analyzed by differential scanning calorimetry (DSC) in combination with the iso-conversional kinetic analysis method of Vyazovkin to derive the curing conditions required for achieving completely cured resin. For the binderless Typha panels the best technological properties were achieved for panels with high density. By adding 10% of the binder resin the flexural strength and especially the water absorption were improved significantly

Influence of thermo-analytical and rheological properties of an epoxypowder coating resin on the quality of coatings on medium densityfibreboards (MDF) using in-mould technology

Powder coating of engineered wood panels such as medium density fibreboards (MDF) is gaining industrial interest due to ecological and economic advantages of powder coating technology. For transferring powder coating technology to temperature-sensitive substrates like MDF, a thorough understanding of the melting, flowing and curing behaviour of the used low-bake resins is required. In the present study, thermo-analysis in combination with iso-conversional kinetic data analysis as well as rheometry is applied to characterise the properties of an epoxy-based powder coating. Neat resin and cured powder coating films are examined in order to define an ideal production window within which the resin is preferably applied and processed to yield satisfactory surface performance on the one hand and without exposing the carrier MDF too high a temperature load on the other hand to prevent the panel from deteriorating in mechanical strength. In order to produce powder coated films of high surface gloss – a feature that has not yet successfully been realized on MDF with powder coatings – a new curing technology, in-mould surface finishing, has been applied

High-gloss surfaces by powder coating and hot pressing of veneered particle board

In the powder coating of veneered particle boards the highly reactive hybrid epoxy/polyester powder transparent Drylac 530 Series from TIGER Coatings GmbH & Co. KG, Wels, Austria was used. Curing is accelerated by a mixture of catalysts reaching curing times of 3 min at 150 °C or 5 min at 135 °C which allows for energy and time savings making Drylac Series 530 powder suitable for the coating of temperaturesensitive substrates such as MDF and wood

Powder coating of veneered particle board surfaces by hot pressing

The powder coating of veneered particle boards by the sequence electrostatic powder application –powder curing via hot pressing is studied in order to create high gloss surfaces. To obtain an appealingaspect, veneer Sheets were glued by heat and pressure on top of particle boards and the resulting surfaceswere used as carrier substrates for powder coat finishing. Prior to the powder coating, the veneeredparticle board surfaces were pre-treated by sanding to obtain good uniformity and the boards werestored in a climate chamber at controlled temperature and humidity conditions to adjust an appropriate electrical surface resistance. Characterization of surface texture was done by 3D microscopy. The surfaceelectrical resistance was measured for the six veneers before and after their application on the particleboard surface. A transparent powder top-coat was applied electrostatically onto the veneered particleboard surface. Curing of the powder was done using a heated press at 130◦C for 8 min and a smooth, glossy coating was obtained on the veneered surfaces. By applying different amounts of powder thecoating thickness could be varied and the optimum amount of powder was determined for each veneer type