Die Polyurethane stellen eine extrem vielgestaltige Kunststoffklasse dar, außerdem zählen sie, von den Produktionskosten her, zu den höherwertigen Kunststoffen. Ersteres erschwert die Entwicklung von Recyclingverfahren, letzteres ist der Grund, weshalb trotzdem seit längerem an Wiederverwertungsmethoden für Polyurethane gearbeitet wird. Eine ganze Reihe von Verfahren existieren bereits und werden mit Erfolg angewendet. Da es aber immer noch PURTypen gibt, die bisher nicht erfolgreich wiederverwertet werden können, besteht weiterhin Bedarf an zusätzlichen Verfahren. Bei der Hydrolyse von Polyurethan-Abfällen wird das Material unter Zugabe von Wasser weitgehend in seine Ausgangsbestandteile zerlegt. Aufgrund einiger schwierig zu bewältigender Verfahrensschritte wird die Hydrolyse bisher nur im Labor- und Technikumsmaßstab angewendet. In dieser Arbeit wurde nun ein Hydrolyseverfahren entwickelt, bei dem die Auftrennung in die Bestandteile nur bis zu einem bestimmten Grad durchgeführt wird, also ein partieller Abbau stattfindet. Der partielle hydrolytische Abbau wurde in einem Doppelschneckenextruder ausgeführt. Die Produkte („hygrothermisch a bgebautes P olyur ethan“; HA-PUR) wurden durch Bestimmung des unlöslichen Rückstands und der Viskosität, mittels Infrarotspektroskopie sowie mit Hilfe der Thermogravimetrie mit angeschlossener Massenspektrometrie charakterisiert. Ausgehend von den Eigenschaften des Zwischenproduktes HA-PUR wurde nach Anwendungsmöglichkeiten gesucht. HA-PUR lässt sich hervorragend mit Duromeren mischen. Diese Tatsache wurde genutzt, um die heute als Zähmodifikator für Duromere gebräuchlichen, aber teuren funktionalisierten Flüssigkautschuke durch ein preisgünstiges Recyclingprodukt zu ersetzen. Tatsächlich wirkte sich ein Zusatz von HA-PUR zu Duromeren günstig auf deren mechanische Eigenschaften, wie Bruchzähigkeit, Bruchenergie und Schlagzähigkeit aus. Weiterhin konnte HA-PUR auch als Härter für Epoxidharze eingesetzt werden. Die kautschukähnlichen Eigenschaften von HA-PUR legten dessen Verwendung als Füllstoff in Kautschukrezepturen nahe. In Anteilen von 10-20 Gew.-% bewirkte HA-PUR bei einigen Kautschuksorten eine beschleunigte Vulkanisation sowie eine Verbesserung der mechanischen Eigenschaften. Im Falle einer Verschlechterung des Eigenschaftsprofils war es möglich, diese durch geringfügige Variationen der Rezeptur auszugleichen. HA-PUR besitzt gewisse thermoplastische Eigenschaften. Daher wurde auch die Möglichkeit erprobt, es als Zähmodifikator für Polyoxymethylen (POM) einzusetzen. (Die Verwendung von thermoplastischem Polyurethan für diese Zwecke ist heute bereits Stand der Technik.) Bei Zusatz von 5 Gew.-% HA-PUR wurde eine leichte Erhöhung der Schlagzähigkeit festgestellt. This work was aimed at studying the hygrothermal decomposition of polyester urethanes and the usability of the products in thermosets, rubbers and thermoplastics. Polyurethanes (PUR) are one of the most versatile groups of plastic materials. The variety of PUR types reaches from flexible foams and rigid foams over thermoplastic elastomers to adhesives, paints and varnishes. This variety is one of the reasons, why the development of cost-efficient reycling methods is very difficult. On the other hand, the production of PUR is rather expensive - compared to the mass-produced plastic materials like the polyolefins. This fact was the reason for the development of recycling methods for PUR since the 60s. The recycling routes for PUR can be devided in mechanical and chemical methods. Mechanical methods cover e.g. grinding of PUR waste, compression moulding, adhesive pressing, bonding. Chemical methods (also called feedstock recycling) change the chemistry of the material. A third group of recycling methods is the recovery of energy. This can mean simple incineration of the PUR waste or the decomposition by pyrolysis or hydrogenation and the combustion of the products. Chemical methods are e.g. glycolysis and hydrolysis. Glycolysis, which is already used on a commercial scale, means the decomposition of PUR by diols (e.g. glycol) at elevated temperatures through a transesterification reaction. The reaction products are polyols which are similar to the virgin components and can be directly used for the manufacture of new PUR. Amines can be products of side reactions of the glycolysis. Hydrolysis of polyurethane waste means decomposition of the material to its virgin components by treatment with water at elevated temperatures. The products are polyols and amines which are related to the virgin isocyanates. After purification, the polyols can be used for the production of new PUR, as well as the amines - after conversion into isocyanates by phosgenation. Since there are still some problems with the processing (e.g. the separation of the amines), the hydrolysis of PUR waste has not yet been used on a commercial scale. In this work, a process of hydrolysis has been worked out which does not lead to the virgin components. The formation of these virgin components can be avoided by stopping the process before reaching the state of complete decomposition. This partial hygrothermally decomposition was carried out in a twin-screw extruder at temperatures between 150 and 250 °C and addition of 10 wt.-% of water. The material used for this process was polyester-PUR waste from the footwear industry and was ground into particles of 1-3 mm size. The products („hygrothermally decomposed polyurethane“; HDPUR) were characterized by determination of the insoluble residue and melt viscosity. The hygrothermal decomposition was traced by infrared spectroscopy and by thermogravimetry combined with mass spectrometry. These examinations allowed a monitoring of the decomposition degree. Further, some information about the chemical processes during decomposition could be obtained. Based on the specific properties (consistency upon decomposition stage, compound containing primary and secondary amines) of HD-PUR attempts were made to check its use in selected thermoset, rubber and thermoplastic combinations. HD-PUR is quite well miscible with thermosets such as epoxy resins (EP) phenolic resins (PF), and unsaturated polyester resins (UP). This fact was utilized for replacing the expensive functionalized liquid rubbers, which are used for toughening of thermosets, by this costefficient recycling product. The mixing of HD-PUR, especially with EP, leads to a clear improvement of the mechanical properties like fracture toughness, fracture energy, and impact toughness. Due to this promising results, the emphasis for further investigations was placed on experiments with HD-PUR in EP. Two EPs (one trifunctional and one tetrafunctional) of Ciba were used. Examinations of fracture surfaces by scanning electron microscopy gave some information about the phase structure and the toughening mechanism. Dynamic-mechanical thermoanalysis made it possible - apart from the investigation of other mechanical properties - to determine the crosslink density which was then correlated with the fracture mechanical data. The addition of HD-PUR in small amounts (up to 20 wt.-%) led to improved toughness along with only slightly reduced stiffness. It should be noted, that even mixtures with 80 wt.-% HD-PUR gave a curable resin yet with reduced stiffness and temperature resistance. HD-PUR alone could act as hardener for epoxy resins. Further, one phenolic resin, one unsaturated polyester resin,and one vinylester-urethane hybrid resin were examined. The results were, compared to the experiments with EP, less promising. Due to its rubber-like properties, especially when extruded at lower temperatures, HD-PUR seemed to be qualified for using as polymeric filler and extender in rubber recipes. Five sorts of rubbers (natural rubber, nitrile-butadiene-rubber, styrene-butadiene-rubber, epoxidized rubber and fluoro rubber) were mixed with HD-PUR in ratios of 10-20 wt.-%. If possible, standard recipes without further additives were used. The changes of the rheological properties and the vulcanization behaviour were checked. The results showed, that HD-PUR not only could be regarded as neutral filler, but also as a kind of reactive plasticizer which could influence the vulcanization behaviour and the mechanical properties. Indeed, the vulcanization rate and the tear strength of natural rubber was increased. If there was any deterioration of the performance, this could be compensated by small variations of the related recipes. Some experiments were conducted with regard to the comparison of two different vulcanization systems and two different grades of carbon black. The applicability of HD-PUR as modifier for thermoplastics has been checked by adding HD-PUR to poly(oxymethylene) (POM). The modification of POM with thermoplastic PUR is already the state of the art. Due to its thermoplastic properties, HD-PUR should be suitable for this application. Mixing of HD-PUR with POM was possible in amounts from 5 - 40 wt.-%. If 5 wt.-% of HD-PUR was added, the impact toughness of POM was slightly increased. Higher amounts of HD-PUR led to a decrease of impact toughness, tensile strength and Young’s modulus. Future works could provide the complete clarification of the chemical reactions during the hygrothermal decomposition.The related information could serve for improved process control and for extending the decomposition on PURs of polyether type. Further, the applicability of HD-PUR as toughening agent for other (brittle) materials should be checked. The modification of thermoplastics still offers a wide field of applications. Also the use of HD-PUR as reactive filler in rubber recipes could be worked out. Finally, some other applications for HD-PUR, e.g. as pressure sensitve adhesive, as sealing material or for sound and vibration damping could be tested.

In the automotive industry, the market share of innovative and individual product variants has increased dramatically in recent years. The vehicle-independent requirements relating to quality and equipment are growing. Summarizing, the expenditure on product development is rising, forcing car producers to reduce development times and costs. The need for reengineering of the product development process is increasingly being met by virtual product development. A key factor is the reduction of time- and cost-consuming prototype tests by pre-designing automotive components virtually. The prerequisite for this are numerical methods which meet a high quality standard and allow predictive statements to realize concept decisions on the basis of calculation results. Questions of product liability are becoming increasingly important and may also concern test results based on numerical results in future. An example of these methods of calculation is the crash calculation using the finite elements method, which is being used increasingly to improve passive safety within the general context of reengineering. In view of the growing requirements relating to occupant safety, this method of calculation, which is established highly efficient in the design of the body-in-white, will have to be improved in a way, that realizes a virtual design of interior safety components in the future. This will include especially simulating the complex material behaviour of the materials used in the vehicle interior. Describing these materials with sufficient material models affords a high quality of reproduction, which often can only be achieved at considerable cost and effort. This paper introduces a general process for the methodical integration of these new materials in the crash calculation. The objectives of the integration process are to improve and assure detail reproduction quality, as well as to increase efficiency using standardizable material modelling procedures. The integration process will be developed on the basis of the so-called Quality Improvement Paradigm and subdivided into four phases: the planning phase, the performance phase, the evaluation phase and the know-how acquisition phase. During the planning phase, the necessary fundamental data on the material, the areas of application of the material within the vehicle and the associated application boundary conditions will be formulated. Targets will be defined for the integration process on the basis of these fundamentals. They will include a clear definition of assumptions regarding material behaviour and requirements relating to the planned material model. Under consideration of the validity of these assumptions and requirements, further action will be described in a project plan and assessed on the basis of a risk appraisal. Material characterization, as well as material modelling and validation will take place in the performance phase of the integration process. Material characterization involves formulating all the fundamental data required for development of the model so that material behaviour can be described. The first step - material modelling - involves examining the models existing in commercial calculation programs and literature, and validating their suitability for detail reproduction of material behaviour. The objective is to select a model that can be used for crash calculation in the productive development process, or for the necessary further developments. Further development of the model will be subdivided into formulation of the materials equation, implementation of the materials equation in the finite element tool and verification of development steps. The implemented material model has to be validated. During the evaluation phase of the process, the process steps will be analyzed in detail and validated. The quality of the developed material model will be proved. This will include a definition of quality specifications for the model and for components to be designed by numerical simulation. The final step in the integration process is the know-how acquisition phase, which serves to improve the quality of material models and leads to a long-term improvement of the process efficiency. In addition to empirical process data acquisition, this phase will include saving all experimental and numeric data. In addition, know-how will be derived by using the material model in the productive development process. The integration process will be shown for the first time within this paper by using a polymer brittle foam with high energy absorption capacity as an example. The fundamental data required for this purpose will be formulated in the process planning phase. The foams are synthetically manufactured materials with a low specific weight and a cellular. The material behaviour of the foams is affected by the properties of the basic materials and the characteristics of the cellular structure. Mechanical behaviour is characterized by the compressive plateau- or crush-stress over a large compression strain and by a low elastic recovery rate after pressure relief. The usual areas of application with regard to occupant protection are the headliner trim, the instrument panel and the side door trim. These foams are also used in bumpers for vehicle protection in lower impact collisions and for pedestrian safety. Regardless of the area of application, polymer brittle foams are primarily subjected to compressive stresses. As a result of the formulated fundamental data, it is necessary to account for the changes in mechanical properties in dependence on varying conditions, such as strain rate, temperature and the application of force - characterized by varying sample and impactor geometries - in order to characterize the material. Classifying polymer brittle foams, two representative materials are determined which are used for material characterization. The thermoplastic and closed-cell particle foam system Noryl® EF will be considered in addition to the thermoset and nearly open-cell polyurethane-based Bayfill® EA foam system. Based on the procedure defined by the integration process, the material characterization will be realized by material tests such as the uniaxial compression test and the shear test, as well as application-oriented basic tests in accordance with the actual area of application of the foams. These tests will be conducted under varying application boundary conditions. Evaluation and analysis of the test results shows that the material behaviour of the two foam systems can be described by an elastic-plastic approach. The main characteristic of this approach is the dependence of plasticity on the first and second stress invariants which is represented by a closed yield surface the multiaxial stress space. The material behaviour observed, is heavily dependent upon the application boundary conditions strain rate and temperature, as well as the density of the foam system. Failure of the Bayfill® EA also occurred when it was subjected to tensile and shear stresses, which have a strong influence on the behaviour of components under application-oriented loads. The examination of existing material models which have the potential to reproduce the polymer brittle foam, leads to the selection of a model developed for aluminium foams by Professor N. Fleck at Cambridge University. The material model will be improved based on the results of the material characterization. This further development necessitates adapting the flow rule, introducing a law for the strain rate dependency of the material behaviour and formulating a damage model for modelling the failure mechanism of brittle polymer foams. The modified material model will be implemented as a user material in the ABAQUS/Explicit finite elements program and validated on the basis of the material tests and application-oriented tests. The potential of the integration process will be established during the evaluation phase. Though being of a pilot nature, this process supports the quality-controlled modelling of polymer brittle foams to a high degree. This is clearly reflected in the detailed process descriptions which allow a target-oriented distribution of labour among the development partners involved. Thus, the material characterization will be performed in close cooperation with IVW GmbH and material modelling will be carried out in cooperation with HKS Inc. The transparency and reproducibility of the process are also essential for long-term quality improvement and assurance. Analysis of the model validation in the evaluation phase leads to an acceptance of the developed material model for numerical simulation of the material behaviour of polymer brittle foams. A prerequisite for use is compliance with various quality specifications for the material model and for components to be designed based on numerical simulation. The components are required to exhibit a homogeneous density distribution and little scatter within defined bounds of production. The main requirement for use of the material model is quality-controlled calibration of the material parameters. The necessary material tests must be conducted on the foam system used for the component. The parameters also have to be validated by applicationoriented basic tests. Calibration and the validation should be supervised by the component manufacturer and carried out by a test institute with the necessary equipment and experience. Following the implementation of the integration process, two different calculation models which are representative of the area of application of the foams - the bumper test according to NHTSA, Part 581 and the head impact test according to FMVSS 201 – demonstrate the productive use.

Um eine weitere Zunahme der Umweltbelastung infolge des stetig anwachsenden Leergewichtes heutiger Kraftfahrzeuge zu vermeiden, wird dem vermehrten Einsatz von Faser-Kunststoff-Verbundwerkstoffen (FKV) auch für hochbelastete Sekundärstrukturen zukünftig eine zentrale Rolle beim intelligenten Fahrzeug-Leichtbau zukommen. Die hierzu erforderliche Substitution metallischer Bauweisen durch FKV-Lösungen bietet das Potential, aufgrund des herausragenden gewichtsspezifischen Eigenschaftsprofils der Werkstoffgruppe und der Möglichkeit einer weitreichenden Teile- und Funktionsintegration eine deutliche Gebrauchswerterhöhung und auch Kostenreduktion zu erzielen. Die im Rahmen dieser Arbeit durchgefüh1ie Analyse des heutigen Entwicklungsstandes von Fahrzeug-Sitzstrukturen und Fahrwerkselc1nenten in FKV-Bauweise zeigte, daß bei vorderen Pkw-Sitzen die Grenzen des mit FKV derzeit Umsetzbaren erreicht sind. Bei Pkw-Fahrwerken konnte festgehalten werden, daß bislang keine längsorientierte, nicht angetriebene Hinterachse in FKV-Bauweise ohne zusätzliches Querelement bekannt ist, obwohl diese Achsbauart zunehmend eingesetzt wird. Zielsetzung der Arbeit war es daher, innovative Ansätze für die integrierte Gestaltung vorderer Sitzstruktur-Komponenten zu entwickeln, die Leichtbau und hohe Funktionalität mit Großserienfertigung verbinden und weiter Vorschläge zur Gestaltung längsorientierter, nicht angetriebener Pkw-Hinterachsen in FKV-Bauweise zu erarbeiten. Die Arbeit geht zunächst detailliert auf die Besonderheiten der FKV-Bauweisenentwicklung im Vergleich zum klassischen Konstruktionsablauf bei metallischen Strukturen ein. Darauf aufbauend wird die werkstoff- und fertigungsgerechte Spritzgieß-Konstruktion einer oberen Lehnen-Quertraverse aus diskontinuierlich langglasfaserverstärktem Thermoplasten (DLFRP oder LFT) vorgestellt, die zwei Kopfstützen-Führungselemente und die eigentliche metallische Quertraverse integriert. Zudem ermöglicht die Funktionserweiterung der axialen Drehbarkeit des gesamten Bauteils ein verbessertes Anstellen der Kopfstütze an den Insassen-Hinterkopf. Quasi-statische und auch dynamische Kopfaufprall-Prüfungen an Prototypen zeigten eine gute Übereinstimmung mit den numerischen Simulationsergebnissen und bestätigten das geforderte „gutmütige" Versagensverhalten des Bauteils durch den Einsatz von Langfasern. Im weiteren stellt die Arbeit erstmals ein schlüssiges werkstoff- und fertigungsgerechtes Konzept für eine längsorientierte, nicht angetriebene Hinterachse in FKV-Bauweise auf der Basis eines funktionsintegrierten CFK-Doppel-Blattfeder-Elementes mit in Reihe geschalteter FKV-Drehrohrfeder-Anordnung vor. Die im Vergleich zu herkömmlichen Metallbauweisen um etwa 40 % leichtere Konstruktion verzichtet auf ein mitfederndes Querelement zur Aufnahme der Seitenkräfte und ermöglicht ein elastokinematisch basiertes In-Vorspur-Gehen des kurvenäußeren Hinterrades. Die grundsätzliche Funktionstüchtigkeit der Konstruktion konnte in ausführlichen strukturmechanischen Simulationsrechnungen nachgewiesen werden.

For most applications the used transport service providers are predetermined during the development of the application. This makes it difficult to consider the application communication requirements and to exploit specific features of the network technology. Specialized protocols that are more efficient and offer a qualitative improved service are typically not supported by most applications because they are not commonly available. In this paper we propose a concept for the realization of protocol independent transport services. Only a transport service is predetermined during the development of the application and an appropriate transport service provider is dynamically selected at run time. This enables to exploit specialized protocols if possible, but standard protocols could still be used if necessary. The main focus of this paper is how a transport service could provide a new transport service provider transparently to existing applications. A prototype is presented that maps TCP/IP based applications to an ATM specific transport service provider which offers a reliable and unreliable transport service like TCP/IP.

The quality of freeform surfaces is one of the major topics of CAD/CAM. Aesthetic and technical demands require the construction of high quality surfaces with strong shape conditions. Quality diminishing properties like dents or flat points have to be eliminated while approximation conditions must hold at the same time. Our approach combines quality and approximation criteria to a nonlinear multicriteria optimization problem and achieves an automatic approximation and fitting process.