by Deborah L. Christiansen / Typescript / Ph. D. Florida State University 1999 / Includes bibliographical references (leaves 101-113)

A two-dimensional finite element model for the infiltration of a dry textile preform by an injected resin has been verified. The model, which is based on the finite element/control volume technique, determines the total infiltration time and the pressure increase at the mold inlet associated with the RTM process. Important input data for the model are the compaction and permeability behavior of the preform along with the kinetic and rheological behavior of the resin. The compaction behavior for several textile preforms was determined by experimental methods. A power law regression model was used to relate fiber volume fraction to the applied compaction pressure. Results showed a large increase in fiber volume fraction with the initial application of pressure. However, as the maximum fiber volume fraction was approached, the amount of compaction pressure required to decrease the porosity of the preform rapidly increased. Similarly, a power law regression model was used to relate permeability to the fiber volume fraction of the preform. Two methods were used to measure the permeability of the textile preform. The first, known as the steady state method, measures the permeability of a saturated preform under constant flow rate conditions. The second, denoted the advancing front method, determines the permeability of a dry preform to an infiltrating fluid. Water, corn oil, and an epoxy resin, Epon 815, were used to determine the effect of fluid type and viscosity on the steady state permeability behavior of the preform. Permeability values measured with the different fluids showed that fluid viscosity had no influence on the permeability behavior of 162 E-glass and TTI IM7/8HS preforms. Permeabilities measured from steady state and advancing front experiments for the warp direction of 162 E-glass fabric were similar. This behavior was noticed for tests conducted with corn oil and Epon 815. Comparable behavior was observed for the warp direction of the TTl 1M7/8HS preform and corn oil. Fluid/fiber interaction was measured through the use of the single fiber pull-out test. The surface tension of both the corn oil and Epon 815 was determined. The contact angle between these two fluids and glass and carbon fibers was also measured. These tests indicated that the glass fiber had a lower contact angle than the carbon fiber and therefore is wet out better than the carbon fiber by both fluids. This result is attributed to the sizing commonly used on the carbon fibers. Mold filling and flow visualization experiments were performed to verify the analytical computer model. Frequency dependent electromagnetic sensors were used to monitor the resin flow front as a function of time. For the flow visualization tests, a video camera and high resolution tape recorder were used to record the experimental flow fronts. Comparisons between experimental and model predicted flow fronts agreed well for all tests. For the mold filling tests conducted at constant flow rate injection, the model was able to accurately predict the pressure increase at the mold inlet during the infiltration process. A kinetics model developed to predict the degree of cure as a function of time for the injected resin accurately calculated the increase in the degree of cure during the subsequent cure cycle. / Master of Science

Die Entwicklung von Geweben mit gestreckten Fadenlagen ist Gegenstand aktueller Forschungen, die vielfach Sondermaschinen für ganz spezielle Anwendungen hervorbringen. Eine systematische Analyse und Optimierung der unter Berücksichtigung der Verbundeigenschaften existiert nach bekanntem Stand des Wissens nicht. Ziel der Dissertation ist es, diese Lücke zu schließen und einen Beitrag zur Etablierung von Geweben mit gestreckten Fadenlagen in Faserverbundwerkstoffen zu leisten. Die Arbeit basiert zum Teil auf den Ergebnissen, die in der Zeit von 2006 – 2012 am Institut für Textilmaschinen und textile Hochleistungswerkstofftechnik der Technischen Universität Dresden im Rahmen verschiedener AiF und DFG Vorhaben entstanden sind. Weiterführende Überlegungen wurden 2015 – 2017 im Rahmen eines Promotionsstudiums an der Professur für Textile Technologien der Technischen Universität Chemnitz angefertigt. Wie anhand konkreter Ausführungsbeispiele gezeigt wird, stößt das Weben insbesondere für Anwendungen im Faserverbundleichtbau an technologisch bedingte Grenzen. Es erfolgt zunächst eine Gegenüberstellung konventioneller Flächenbildungsverfahren und der Anforderungen seitens der Endanwender, insbesondere aus dem Bereich der Verbundwerkstoffindustrie, gleichermaßen. Daraus wird ein Anforderungsprofil für ein anforderungsgerechtes Flächenbildungsverfahren abgeleitet und konstruktive Lösungsvorschläge zu dessen Umsetzung aufgezeigt. / The development of non-crimped-fabrics (NCF) is subject of current research activities. These often led to special machines for very special applications. There is no systematic analysis and optimization of the properties of composites based on the state of the art. The aim of this dissertation is to close this gap and to contribute to the establishment of woven NCF in fiber-reinforced composites. The work is based partially on the results obtained at the Institut für Textilmaschinen und textile Hochleistungswerkstofftechnik der Technischen Universität Dresden from 2006 to 2012 within the framework of various AiF and DFG projects. Further reflections were made between 2015 and 2017 as part of a doctoral study at the Chair of Textile Technologien der Technischen Universität Chemnitz. As shown from examples of the design, weaving is reaching technological limits, especially for applications in composite construction. First of all, conventional surface formation methods are compared with the requirements of end users, especially from the composites industry. From this, a requirement profile is derived for a requirements-based surface formation process and constructive proposals for solutions for its implementation are identified.

In order to develop a program whereby people can be educated to appreciate and choose the best contemporary designs among the many textiles that are available, it is necessary to know which types of textiles, if any, among those designed in the modern manner, the public accepts, which it rejects, and the factors that influence selection. This study was made to discover those factors -- such as color, subject matter, and utility -- that determine popular choices in a representative group of well-designed modern printed textiles which were available on the Dallas market. The textiles were placed on public exhibition at the Dallas Museum of Fine Arts.

Innovative 3D spacer fabrics made from individual planes and connecting layers present great potential as complexly shaped textile preforms in lightweight composite applications. As one of the most flexible textile manufacturing methods, flat knitting enables the production of intricately shaped textile structures. The major advantages coupled with flat knitting techniques include the ability to produce multi-layer reinforcements, a diminishing waste, reducing production time and near-net shaping. This research includes the further development of flat knitting technology and the manufacturing processes of innovative, customized 3D spacer fabrics for high performance composite applications. Novel 3D spacer fabrics have been developed in different geometries using glass-polypropylene commingled hybrid yarns for complex shaped thermoplastic composite components. Reinforcement yarns have been integrated into spacer fabric structures with up to 4 reinforcement layers to improve mechanical performance. Furthermore, the successful addition of “sensor networks” created by integrating functional yarns into the 3D spacer fabrics could be used for structural health monitoring. Innovative integration concepts, which accommodate different positioning of the reinforcement yarns into the knit structures, can be used to adjust the mechanical properties of the finished knit composites. Moreover, the tensile properties have been accurately predicted based on the mathematical models formulated. The developed flat knitted 3D spacer fabrics are very promising for applications in lightweight composites, mechanical engineering, protective textiles, civil engineering and architectural designs. / Innovative 3D-Spacer Fabrics bestehend aus individuellen Deckflächen und Verbindungsstegen bieten ein großes Potential als komplex geformte textile Halbzeuge für Leichtbauverbundwerkstoffanwendungen. Mit Hilfe des Flachstrickens, welches einer der flexibelsten textilen Herstellungsprozesse ist, lassen sich komplex geformte textile Strukturen herstellen. Belastungsgerechte Verstärkungen, Abfallreduzierung, endkonturnahe Fertigung sind nur einige der großen Vorteile der modernen Flachstricktechnik. Die Forschungsarbeit beinhaltet die Entwicklung der Flachstricktechnologie und des Herstellungsprozesses für innovative 3D-Spacer Fabrics für Hochleistungsverbundwerkstoffe. Neuartige 3D-Spacer Fabrics wurden in unterschiedlichen Geometrien entwickelt, in dem Glas-/ Polypropylen Commingling-Hybridgarn für komplex geformte thermoplastische Verbundwerkstoffkomponenten eingesetzt wird. Verstärkungsfäden wurden für hochmechanische Belastungen in die Spacer-Fabric-Strukturen in bis zu 4 Verstärkungschichten integriert. Die erfolgreiche Umsetzung und Entwicklung von Sensornetzwerken durch die Integration von funktionalen Fäden in die 3D-Spacer Fabrics kann für die strukturelle Zustandsüberwachung genutzt werden. Die innovativen Integrationskonzepte erlauben die differenzierte Orientierung von Verstärkungsfäden in den Gestrickstrukturen, wodurch eine starke Beeinflussung der mechanischen Eigenschaften der Gestrickverbundwerkstoffe herbeigeführt wird. Darüber hinaus wurden die Zugeigenschaften basierend auf den entwickelten mathematischen Modellen vorhergesagt. Die entwickelten flachgestrickten 3D-Spacer Fabrics sind sehr vielversprechend beispielweise für die Anwendung in Leichtbauverbundwerkstoffen, im Maschinenbau, in Schutztextilien, im Bauingenieurwesen und Architekturdesign.

No description available.

The need for innovative lightweight materials are rapidly increased in the recent years, owing to their cost-effective, high-strength, environmentally-sound use of materials and process technologies, in addition to that they reduce the weight of a product. The characteristics of 3D-spacer fabrics as one of the most important lightweight materials in future are multifaceted not only owing to its extremely light materials, but also because of exceptionally high stiffness to weight ratio compared to other constructions. It is also one possible method for improving the properties of fabric-reinforced composites. It can enhance the through-the-thickness properties, such as shear strength, dimensional stability, damage, tolerance, and fracture toughness that are critical for many structural applications. Spacer fabric has been employed in high-technology applications because of its critical mechanical properties related to high tensile strength, tear strength and stiffness. Furthermore, its multidirectional structures allow with more reinforcement along the thickness direction leading to an increase in stiffness and strength properties. The fundamental aim of this thesis exists in the development of a new kind of woven spacer fabrics for the light weight composites materials, in an effort to weave spacer fabrics that can not be realized with the old technology which are mentioned above. Therefore, the work in brief focuses on two main goals: 1. Development of a new kind of spacer fabrics for composites in the lightweight constructions. 2. Development of special devices of a narrow weaving machine for standing the process of the new kind of spacer fabrics production. The slippage strength test had to be carried out for the floated warp yarns through the ground fabrics by using different elements of woven fabric structures variables represented in different fabric constructions, different weft densities and different repeats of constructions by using different materials. The importance of this test related to the backward-movement of the floated warp yarns which is the crucial stage in the weaving process of spacer fabrics during the backward-movement. The results of this test determine the required forces for the backward-movement, on the other side it is the best method to observe the behavior of structure elements during the backward movement. The results of the slippage strength had been statistically analyzed, and the weaving process for the spacer fabrics had been achieved. It was concluded that the best properties for the woven spacer fabrics and the optimum case for the weaving process on the test weaving machine had been achieved when the following items are realized: Development of the narrow weaving machine is closed in assisting operations, let-off and take-up and enhancement for take-up processes. Extra let-off and take-up devices must be constructed at the weaving machine. Extra let-off device has to be used for controlling the floated warp yarns of ground fabrics. On the other side, extra take-up and the developed take-up devices have to be used for controlling the woven spacer fabrics. The experimental results give fundamental knowledges for the next steps in research and development of woven spacer fabrics made of high-performance yarns on the wide weaving machine. / Die Ziele der Arbeit bestanden in der Entwicklung der Geometrie der Spacer Fabrics und der notwendigen Falteneinrichtung an der Bandwebmaschine. Spacer Fabrics werden ausschließlich aus zwei Deckflächen, die durch eingewebte Stege verbunden sind, gefertigt. Zur Entwicklung der Spacer Fabrics muss eine Doppelnadel-Bandwebmaschine mit zwei Webfächern eingesetzt werden. Für die Faltenwebeinrichtung werden der entwickelte Extra-Kettablass und der Extra-Abzug benötigt. Der Antrieb und die Steuerung des Extra-Abzuges erfolgen durch einen Synchronantrieb und der Antrieb und die Steuerung des Extra-Ablasses durch Pneumatik.Eine frei programmierbare Steuerung der Faltenwebeinrichtung ermöglicht eine sichere und optimierte Synchronisation zwischen Webprozess und Faltenbildung. Im Ergebnis einer systematischen Strukturentwicklung von Spacer Fabrics und der Simulation ihrer günstigen Herstellung mittles eines speziell entwickelten Slippage Strength Tests werden die optimalen Strukturen ermittelt. Die experimentellen Untersuchungen bringen grundlegende Erkenntnisse für die folgenden Forschungsschritte zur Entwicklung von gewebten Spacer Fabrics mit Hochleistungsgarnen auf Doppelgreiferwebmaschinen.

As the clothing industry moves away from traditional models of mass production there has been increased interest towards customised clothing. The technology to produce cost effective customised clothing is already in place however the prerequisite to customised clothing is accurate body dimensional data. In response, image capture systems have been developed which are capable of recording a three-dimensional image of the body, from which measurements and shape information may be extracted. The use of these systems for customised clothing has, to date, been limited due to issues of inaccuracy, cost and portability. To address the issue of inaccuracy a diagnostic procedure has been developed through the performance evaluation of an image capture system. By systematically evaluating physical and instrumental parameters the more relevant sources of potential error were identified and quantified and subsequently corrected to form a `closed loop' experimental procedure. A systematic test procedure is therefore presented which may be universally applied to image capture systems working on the same principle. The methodology was based upon the isolation and subsequent testing of variables that were thought to be potential sources of error. The process therefore included altering the physical parameters of the target object in relation to the image capture system and amending the configuration and calibration settings within the system. From the evaluation the most relevant sources of error were identified as the cosine effect, measurement point displacement, the dimensional differences between views and the influence of the operator in measurement. The test procedure proved to be effective in both evaluating the performance of the system under investigation and in enabling the quantification of errors. Both random and systematic errors were noted which may be quantified or corrected to enable improved accuracy in the measured results. Recommendations have been made for the improvement of the performance of the current image capture system these include the integration of a cosine effect correction algorithm and suggestions for the automation of the image alignment process. The limitations of the system such as its reliance on manual intervention for both the measurement and stitching processes, are discussed, as is its suitability for providing dimensional information for bespoke clothing production. Recommendations are also made for the creation of an automated test procedure for testing the performance of alternative image capture systems, which involves evaluating the accuracy of object replication both for multiple and single image capture units using calibration objects which combine a range of surfaces.

This investigation examines the structure-property relationships of high modulus fibres. Five fibre classes were chosen for examination. These are p-aromatic copolyamide (Armos and SVM) and poly-p-aramids (Terlon and Kevlar) obtained from rigid chain polymers; poly-m-aramids (Phenylon and Nomex) obtained from semi rigid chain polymers, and aliphatic polyamide (Capron and Nylon) and Polyethylene obtained from flexible chain polymers. The thermo-mechanical properties studied include tensile properties, thermal shrinkage, creep-recovery, stress-relaxation and residual deformation over a range of temperatures. Results show that mechanical properties are highly related to chain rigidity, orientation and crystallinity of the fibres. The presence of aromatic rings in polymer chains increase the polymer rigidity. The higher the intermolecular attractive force and chain rigidity, the greater the resistance to heat. Study of the creep-recovery properties of polyamide fibres shows that irrecoverable residual deformation for the rigid chain polymers is accumulated within a very short initial period of time (15 seconds) when the load is applied. However for semi-rigid or flexible chain polymer fibres, the residual deformation is accumulated during the whole creep process. The characteristics of tensile stress-strain properties and the accumulation of residual deformation are found to be temperature dependent, especially in the case of Armos and SVM. The mechanical properties of polyamide fibres are also influenced by moisture which is associated with intermolecular interaction. Supplementary studies using FTIR, SEM and DSC were also undertaken. FTIR was used for preliminary investigation into the intermolecular hydrogen bonding and associated moisture in fibres. The results support the explanation of the thermomechanical properties of polyamide fibres. SEM results show the fibre rupture mechanism related to the fibre structures.

Textile process and textile structures that are suitable for composites are carefully studied and chosen to have weft knitted fabrics. The aim of this research is to knit the carbon and Dyneema® fibres in circular weft knitting to fit contour shapes. Carbon/Dyneema® can also be knitted in warp knitting machines to get properties in multi axial direction. But the fabric was flat and can be used only for 2D shape products which are having less drapabiity. According to previous research, weft knitting is the best suitable for complex preforms. Before knitting these fibres properties were studied in order to avoid the damage to the carbon fibres. The carbon fibres have high bending rigidity, low resistance to friction and are very brittle. A small damage to the carbon fibre in knitting subsequently affect directly on the composite properties. The strongest manmade fibre manufactured till date is Dyneema® and these fibres could be used in composites due to its performance, properties and light weight. But, the Dyneema® fibres are expensive when compared to common polyester, so polyester fibres are used to compare the properties and cost performance ratio. The critical bending of the carbon fibres causes friction between the fibres and also between fibre and machine. This was considered carefully during the knitting of carbon fibres and the idea chosen is mentioned in this thesis. Between the two layers of Dyneema®/polyester, carbon fibres are laid circularly in unidirectional and in un-crimped condition. This makes the carbon yarn to possess good mechanical properties. The 2 layers of Dyneema®/polyester fibres exchange the loops at certain points to increase the inter-laminar strength and decrease the carbon fibre distortion. This structure helps to withstand external load. It is also lighter than the carbon composite with additional properties. This makes much more space in the future for the Dyneema® fibres in the 3D carbon composite manufacturing. The internal carbon fibres are fully covered by the Dyneema® fibres to withstand the external impact load and not to damage the carbon fibres. So the loop length, stitch density, fibre volume fractions are considered before knitting.