Automated Fibre Placement with In-Situ Ultraviolet Curing and On-The-Fly Resin Impregnation

Vehicle emissions contribute to up to one third of the world's air pollution [1]. Reducing vehicle weight is crucial to reducing these emissions. Composite materials offer high specific strength-to-weight ratios which make them ideal for lightweight applications; however, existing composite manufacturing is slow and expensive. Automated Fibre Placement (AFP) is a state-of-the-art composite manufacturing process but is limited by the low complexity of parts it can produce; the cost, size and speed of the actuation systems; expensive and sensitive material options; and numerous pre and post-processes required in order to complete a part. This research proposes a new and efficient composite manufacturing process that addresses these limitations by combining AFP technology with in-situ ultraviolet (UV) curing and on-the-fly fibre and resin impregnation (UVAFP). The body of this thesis focused on proving the process concept and building robust predictive models for the technology. It was proposed that reducing the size of the placement head would increase the capability of this technique to manufacture more complex parts. It was shown that by optimising the placement head clearance angle, placement head width and the compaction roller radius the minimum placement radius and arc length could be as small as 100mm and 90 degrees respectively. It was also demonstrated that industrial robots were sufficiently accurate and repeatable to act as placement articulators for AFP. The feed rate, path interpolation point filtering and spindle speed were optimised to achieve a path following accuracy of less than 0.042mm. By increasing the tension in the tow and compaction force, dry fibre tows were shown to be a suitably dimensionally stable replacement for expensive towpregs with minimal gaps and overlaps. Dry glass fibre tows and bulk vinylester resin impregnated on-the-fly was chosen as an inexpensive and versatile material system and consolidation approach for use in UVAFP. The material system was shown to have comparable mechanical properties to aluminium and steel but lighter with equivalent properties to composites manufactured by traditional techniques. Rapid impregnation times were demonstrated up to 2160 mm/sec. High intensity UV light curing eliminated the need for post process curing and shortened the cure time and increased layup speeds. When the UV light was applied in a ply-by-ply in-situ approach, the cure time was measured to decrease the current thermal cure cycle length by 43.75% and the degree-of-cure was increased by 1.3% (as measured indirectly by the interlaminar shear strength). By characterising the process parameters the effect on degree of cure and degradation could be controlled and predicted. A degree of cure in excess of 99% was achieved, providing equivalent material properties to traditional thermal cured composites while minimising peak exposure temperatures, thus reducing mass loss caused by thermo-oxidative degradation. UVAFP was demonstrated to be a viable composite manufacturing process capable of producing high quality components and addressing the limitations of current AFP systems. The technology was shown to address efficiency shortfalls and make composite manufacturing economical and accessible to vehicle manufacturers searching for manufacturing process solutions for lightweight

Fiber-Reinforced Plastics

This book deepens the study and knowledge on fiber-reinforced plastics (FRPs), which are composite materials made of a polymer matrix reinforced with fibers. The fibers are usually glass, carbon, or aramid, although other fibers such as paper, wood, or asbestos are sometimes used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, and phenol-formaldehyde resins are still in use. Among, the most prominent applications of FRPs are in the aerospace, automotive, marine, and construction industries. The development of FRPs has a very promising future with a marked annual increase and with a wide range of sources. This book presents comprehensive information on FRPs and their wide variety of applications in the industry worldwide

Process–Structure–Properties in Polymer Additive Manufacturing

Additive manufacturing (AM) methods have grown and evolved rapidly in recent years. AM for polymers is an exciting field and has great potential in transformative and translational research in many fields, such as biomedical, aerospace, and even electronics. Current methods for polymer AM include material extrusion, material jetting, vat polymerisation, and powder bed fusion. With the promise of more applications, detailed understanding of AM—from the processability of the feedstock to the relationship between the process–structure–properties of AM parts—has become more critical. More research work is needed in material development to widen the choice of materials for polymer additive manufacturing. Modelling and simulations of the process will allow the prediction of microstructures and mechanical properties of the fabricated parts while complementing the understanding of the physical phenomena that occurs during the AM processes. In this book, state-of-the-art reviews and current research are collated, which focus on the process–structure–properties relationships in polymer additive manufacturing

Development of the in situ forming of a liquid infused preform (ISFLIP) process : a new manufacturing technique for high performance fibre reinforced polymer (FRP) components

A problem is not a problem anymore if no solution exists; therefore, in the present dissertation, a novel manufacturing technique, the In Situ Forming of a Liquid Infused Preform (ISFLIP), is proposed as a solution to some typical problems that manufacturing of Fibre Reinforced Polymer (FRP) parts through Vacuum Infusion (VI) involves, such as not taking advantage of the full potential of FRPs, long processing times and lack of reproducibility. ISFLIP is a hybrid process between VI and diaphragm forming in which a flat preform of a stack of reinforcement fabrics is firstly impregnated with a low viscosity matrix and, then, formed over a mould while the matrix is still in the low viscosity state. Being focused on high performance FRPs and shell components, from simple to complex double curvature shapes, a number of trade-offs between VI and diaphragm forming were overcome to lay the foundations from which ISFLIP ability to manufacture FRP components has been proven. In order to adopt a VI manufacturing methodology that fitted ISFLIP targets, important contributions to more general VI have also been made in terms of part quality optimization, addressing the major concern that void content is in VI, with competitive manufacturing times. An effective vacuum degassing procedure in which bubble formation is enhanced through high speed stirring, and a non-conventional filling and post-filling strategy are proposed for this purpose. Eventually, void content was virtually eliminated and post-filling time minimized without affecting fibre content. In ISFLIP, textile preforms are formed together with a series of auxiliary materials (plastic films and sheets, textile fabrics and knitted meshes), most of them showing different in-plane deformation mechanisms. Forming performance of preforms, as well as final part quality, are severely affected by interactions between all these materials different in nature. Uncertainties on this respect and an initial evaluation of attainable shapes were also addressed to define a more focused research plan to the final goal, still distant, of implementing ISFLIP in a real production environment. Results obtained throughout the research project give cause for reasonable optimism in ISFLIP potential and future prospects.Un problema deja de ser un problema si no existe solución; por lo tanto, en esta disertación, una novedosa técnica de fabricación, el Conformado In Situ de una Preforma Infusionada con resina Líquida (ISFLIP, por sus siglas en inglés), se propone como solución a algunos problemas típicos relacionados con la fabricación de piezas de Polímero Reforzado con Fibra (FRP) a través de la Infusión por Vacío (VI), problemas tales como el desaprovechamiento de todo el potencial de los FRPs, largos tiempos de procesado y falta de reproducibilidad. ISFLIP es un proceso híbrido entre la VI y el conformado por membrana elástica en el que una preforma plana formada a partir de un apilado de tejidos de refuerzo es en primera instancia impregnada con una resina de baja viscosidad y, entonces, conformada sobre un molde mientras que la matriz permanece todavía en el estado de baja viscosidad. Estando centrado en los FRPs de altas prestaciones y en componentes con formas tipo concha, desde curvaturas simples hasta formas con doble curvatura complejas, un número importante de compensaciones entre la VI y el conformado por membrana se han ido superando para asentar las bases a partir de las cuales se ha probado la capacidad de ISFLIP para fabricas componentes de FRP. Con la vista puesta en implementar una metodología de fabricación por VI que cumpliese los objetivos definidos para ISFLIP, también se han realizado importantes contribuciones de carácter más general relacionadas con la VI en términos de optimización de parámetros de calidad de las piezas, abordando la gran preocupación que la porosidad final supone en la VI, y consiguiendo unos tiempos de fabricación competitivos. Con este propósito se han propuesto un proceso de desgasificación por vacío muy efectivo en el que se favorece la nucleación de burbujas mediante la agitación a alta velocidad, y una prometedora y no convencional estrategia de llenado y post-llenado de la preforma. Finalmente, se consiguió virtualmente eliminar la porosidad atrapada en las piezas, minimizando el tiempo de post-llenado sin afectar la fracción de fibra contenida. En ISFLIP las preformas textiles se conforman junto con una serie de materiales auxiliares (films y hojas plásticas, mallas y tejidos textiles), que muestran diferentes mecanismos de deformación en plano. El conformado de las preformas y el acabado final de las piezas se ve severamente afectado por todas las interacciones entre todos estos materiales diferentes en naturaleza. También se han abordado las incertidumbres que surgen al respecto y una evaluación inicial de las geometrías abarcables para definir un plan de investigación más concreto con el que poder afrontar la meta final, todavía distante, de implementar ISFLIP en un entorno productivo real. Los resultados obtenidos a lo largo de este proyecto de investigación permiten ser razonablemente optimistas en cuanto al potencial de ISFLIP y sus expectativas

Structural Framework for Flight: NASA's Role in Development of Advanced Composite Materials for Aircraft and Space Structures

This serves as a source of collated information on Composite Research over the past four decades at NASA Langley Research Center, and is a key reference for readers wishing to grasp the underlying principles and challenges associated with developing and applying advanced composite materials to new aerospace vehicle concepts. Second, it identifies the major obstacles encountered in developing and applying composites on advanced flight vehicles, as well as lessons learned in overcoming these obstacles. Third, it points out current barriers and challenges to further application of composites on future vehicles. This is extremely valuable for steering research in the future, when new breakthroughs in materials or processing science may eliminate/minimize some of the barriers that have traditionally blocked the expanded application of composite to new structural or revolutionary vehicle concepts. Finally, a review of past work and identification of future challenges will hopefully inspire new research opportunities and development of revolutionary materials and structural concepts to revolutionize future flight vehicles

Design of a Mechatronic System for the Characterization of Polymer Composite Material Properties During Molding Processes

RÉSUMÉ La fabrication de matériaux composites à la base de polymères est de plus en plus importante dans les industries aérospatiale, automobile et du sport. La principale raison de l’utilisation de ces types de matériaux est la proportion poids / résistance, mais ils peuvent également être conçus pour répondre à des exigences spécifiques en choisissant la résine polymère et le renforcement appropriés. Mais le choix des bons matériaux ne constitue que la première étape de la conception de structures composites, car le processus de fabrication est un défi technique majeur. Les paramètres de traitement optimal génèrent une structure composite dotée d'excellentes propriétés mécaniques et d'une bonne tolérance dimensionnelle. En même temps, le processus doit utiliser un minimum d'énergie et de temps de traitement. D'autre part, un ensemble inadéquat de paramètres du processus peut entraîner une pièce présentant un mauvais état de surface, des distorsions géométriques, des propriétés mécaniques insuffisantes et un temps de production prolongé. Pour améliorer la pièce fabriquée, l’ingénieur a besoin des données détaillées sur l’évolution du matériau dans le moule. La caractérisation nécessite plusieurs dispositifs dans un laboratoire standard. La méthodologie de caractérisation traditionnelle prend du temps et la configuration des expériences est difficile à reproduire. De plus, la taille de l'échantillon change d'un appareil à l'autre. En général, les équipements de laboratoire traditionnels ne peuvent pas caractériser les matériaux composites. Un échantillon représentatif de ce type de matériaux est simplement trop grand et dépasse les capacités de ces dispositifs. Les chercheurs ont tenté à plusieurs reprises de produire une meilleure stratégie de caractérisation. Cependant, pour obtenir un appareil entièrement fonctionnel, plusieurs défis technologiques doivent être résolus. L'objectif principal de ce projet de thèse est de relever ces défis et de trouver des stratégies qui permettront l'intégration de plusieurs équipements de laboratoire de caractérisation dans un seul appareil. Pour atteindre cet objectif, nous étudions les dispositifs de caractérisation proposés dans la littérature et nous en résumons les limites. Pour étayer nos conclusions, nous utilisons une machine de laboratoire capable de reproduire les conditions des cycles de fabrication standards. Nous faisons nous-mêmes l'expérience des défis liés à la fabrication d'un matériau composite. Toutes les informations collectées nous ont permis de trouver les exigences de périphérique souhaitées.----------ABSTRACT The manufacturing of polymeric composite materials is nowadays more and more common in the aerospace, automotive and sports industries. The main reason for the use of these materials is its strength to weight ratio advantages, but beyond that, is that they can be engineered to meet specific requirements by choosing the proper polymer resin and reinforcement. But choosing the right materials is just the initial step in the design of composite structures since the manufacturing process is a major engineering challenge. Optimum processing parameters generate a composite structure with excellent mechanical properties and good dimensional tolerance. At the same time, the process must use a minimum of energy and processing time. On the other hand, an inadequate set of process parameters may result in a part with bad surface finish, geometric distortions, lower mechanical properties and long production time. To improve the manufactured part, the process engineer requires detailed data about the evolution of the material inside the mold. This characterization requires of multiple laboratory characterization devices. Also, the traditional characterization methodology is time consuming and the experiments setup are difficult to reproduce. Moreover, the sample size changes from one device to the other. In general, traditional laboratory equipment cannot characterize composite materials, a representative sample of this material type is just too big and surpasses the capabilities of the traditional characterization devices. Researchers have made several attempts to produce a better characterization strategy. However, to achieve a fully functional device, several technological challenges need to be resolved. The main objective of this PhD project is to find those challenges and find strategies that will allow the integration of multiple characterization laboratory equipment into a single device. To achieve this objective, we study the proposed characterization devices in the literature and abstract those devices limitations. To support our findings, we use a laboratory scale machine capable of reproducing the conditions of regular manufacture cycles. We experience by ourselves the challenges in the manufacturing of polymer matrix composite material. All the collected information allowed us to find the desired device requirements. This thesis developed an integrated mechatronic design methodology to abstract the manufacture challenges into product requirements. The proposed methodology allowed us to understand the relationship between the different design requirements