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

Machine learning algorithms for efficient process optimisation of variable geometries at the example of fabric forming

Für einen optimalen Betrieb erfordern moderne Produktionssysteme eine sorgfältige Einstellung der eingesetzten Fertigungsprozesse. Physikbasierte Simulationen können die Prozessoptimierung wirksam unterstützen, jedoch sind deren Rechenzeiten oft eine erhebliche Hürde. Eine Möglichkeit, Rechenzeit einzusparen sind surrogate-gestützte Optimierungsverfahren (SBO1). Surrogates sind recheneffiziente, datengetriebene Ersatzmodelle, die den Optimierer im Suchraum leiten. Sie verbessern in der Regel die Konvergenz, erweisen sich aber bei veränderlichen Optimierungsaufgaben, etwa häufigen Bauteilanpassungen nach Kundenwunsch, als unhandlich. Um auch solche variablen Optimierungsaufgaben effizient zu lösen, untersucht die vorliegende Arbeit, wie jüngste Fortschritte im Maschinenlernen (ML) – im Speziellen bei neuronalen Netzen – bestehende SBO-Techniken ergänzen können. Dabei werden drei Hauptaspekte betrachtet: erstens, ihr Potential als klassisches Surrogate für SBO, zweitens, ihre Eignung zur effiziente Bewertung der Herstellbarkeit neuer Bauteilentwürfe und drittens, ihre Möglichkeiten zur effizienten Prozessoptimierung für variable Bauteilgeometrien. Diese Fragestellungen sind grundsätzlich technologieübergreifend anwendbar und werden in dieser Arbeit am Beispiel der Textilumformung untersucht. Der erste Teil dieser Arbeit (Kapitel 3) diskutiert die Eignung tiefer neuronaler Netze als Surrogates für SBO. Hierzu werden verschiedene Netzarchitekturen untersucht und mehrere Möglichkeiten verglichen, sie in ein SBO-Framework einzubinden. Die Ergebnisse weisen ihre Eignung für SBO nach: Für eine feste Beispielgeometrie minimieren alle Varianten erfolgreich und schneller als ein Referenzalgorithmus (genetischer Algorithmus) die Zielfunktion. Um die Herstellbarkeit variabler Bauteilgeometrien zu bewerten, untersucht Kapitel 4 anschließend, wie Geometrieinformationen in ein Prozess-Surrogate eingebracht werden können. Hierzu werden zwei ML-Ansätze verglichen, ein merkmals- und ein rasterbasierter Ansatz. Der merkmalsbasierte Ansatz scannt ein Bauteil nach einzelnen, prozessrelevanten Geometriemerkmalen, der rasterbasierte Ansatz hingegen interpretiert die Geometrie als Ganzes. Beide Ansätze können das Prozessverhalten grundsätzlich erlernen, allerdings erweist sich der rasterbasierte Ansatz als einfacher übertragbar auf neue Geometrievarianten. Die Ergebnisse zeigen zudem, dass hauptsächlich die Vielfalt und weniger die Menge der Trainingsdaten diese Übertragbarkeit bestimmt. Abschließend verbindet Kapitel 5 die Surrogate-Techniken für flexible Geometrien mit variablen Prozessparametern, um eine effiziente Prozessoptimierung für variable Bauteile zu erreichen. Hierzu interagiert ein ML-Algorithmus in einer Simulationsumgebung mit generischen Geometriebeispielen und lernt, welche Geometrie, welche Umformparameter erfordert. Nach dem Training ist der Algorithmus in der Lage, auch für nicht-generische Bauteilgeometrien brauchbare Empfehlungen auszugeben. Weiter zeigt sich, dass die Empfehlungen mit ähnlicher Geschwindigkeit wie die klassische SBO zum tatsächlichen Prozessoptimum konvergieren, jedoch kein bauteilspezifisches A-priori-Sampling nötig ist. Einmal trainiert, ist der entwickelte Ansatz damit effizienter. Insgesamt zeigt diese Arbeit, wie ML-Techniken gegenwärtige SBOMethoden erweitern und so die Prozess- und Produktoptimierung zu frühen Entwicklungszeitpunkten effizient unterstützen können. Die Ergebnisse der Untersuchungen münden in Folgefragen zur Weiterentwicklung der Methoden, etwa die Integration physikalischer Bilanzgleichungen, um die Modellprognosen physikalisch konsistenter zu machen

Structure-property relationships in high barrier multilayer film/foam systems

Thermoplastic foams nowadays are widely used in a variety of applications, such as packaging, construction, and the automotive industry because of their wide range of properties such as lightweight, excellent strength/weight ratio, insulation properties, energy absorption performance, and material cost. However, there are still issues on the gas barrier and mechanical properties in use because of the cellular structure. This work targeted to unveil the processing-structure-property relationships of three film/foam multilayer polymeric systems with diverse transport properties. The first part of the thesis (Chapter 2) focuses on the understanding of the effect of the number of layers and composition on mechanical properties and barrier properties of multilayer film/foam material with alternating ethylene-vinyl alcohol copolymer (EVOH) film layers and low-density polyethylene (LDPE) foam layers. Tensile properties of the film/foams at elevated temperatures were used to optimize thermoforming conditions. Uniaxial orientation was discovered as an efficient approach to evaluate the potential for thermoforming. Oxygen transmission showed a strong correlation with the thickness reduction which could be used as an indicator for barrier properties of the packaging materials. Film/foam materials with 32 layers demonstrated optimum performance with low oxygen transmission along with high drawing capability. In the third chapter, the previous system (Chapter 2) was innovated with high-density polyethylene (HDPE) skin layer. High oxygen and water vapor barrier film/foam system had been developed using multilayer co-extrusion technology. The film/foams contained alternating low-density polyethylene (LDPE) foam layers and ethylene–vinyl alcohol (EVOH) copolymer film layers with HDPE skin layer. The lightweight film/foams showed oxygen and water vapor transmission rate are correlated with the EVOH film layer and HDPE skin layer composition. The layered film/foam was successfully thermoformed at 80 °C with low oxygen transmission along with high drawing capability. The fourth chapter introduces a novel approach, to produce PLA/PLA multilayer film/foams structures having 16, 32, and 64 alternating layers. The lightweight multilayered PLA/PLA film/foam has a unique solid/porous alternating horizontal architecture, in which the film layers can effectively control the growth of the cells and suppress the premature rupture of cells during coextrusion process. Tensile properties at elevated temperatures of the PLA film were used to optimize thermoforming conditions. The effects of annealing temperature and time on the crystallinity and oxygen permeability of PLA/PLA multilayer film/foams were investigated. Oxygen transmission showed a strong correlation with the crystallinity of PLA/PLA multilayer film/foam. The material demonstrated high performance with low oxygen transmission which could be used as high barrier material

AN INVESTIGATION OF SIZE EFFECTS ON THIN SHEET FORMABILITY FOR MICROFORMING APPLICATIONS

The increasing demand for powerful miniaturized products for all industrial applications has prompted the industry to develop new and innovative manufacturing processes to fabricate miniature parts. One of the major challenges facing the industry is the dynamic market which requires continuous improvements in design and fabrication techniques. This means providing products with complex features while sustaining high functionality. As a result, microfabrication has gained a wide interest as the technology of the future, where tabletop machine systems exist. Microforming processes have the capability of achieving mass production while minimizing material waste. Microforming techniques can produce net-shape products with intricacy in fewer steps than most conventional microfabrication processes. Despite the potential advantages, the industrial utilization of microforming technology is limited. The deformation and failure modes of materials during microforming is not yet well understood and varies significantly from the behavior of materials in conventional forming operations. In order to advance the microforming technology and enable the effective fabrication of microparts, more studies on the deformation and failure of materials during microforming are needed. In this research work, an effort to advance the current status of microforming processes for technologies of modern day essentials, is presented. The main contribution from this research is the development of a novel method for characterizing thin sheet formability by introducing a micro-mechanical bulge-forming setup. Various aspects of analyzing microscale formability, in the form of limiting strains and applied forces, along with addressing the well known size effects on miniaturization, were considered through the newly developed method. A high temperature testing method of microformed thin sheets was also developed. The aim of high temperature microforming is to study the material behavior of microformed thin sheets at elevated temperatures and to explore the capability of the known enhancement in formability at the macroscale level. The focus of this work was to develop a better understanding of tool-sheet metal interactions in microforming applications. This new knowledge would provide a predictive capability that will eliminate the current time-consuming and empirical techniques that, and this in turn would be expected to significantly lower the overall manufacturing cost and improve product quality

Mass Production Processes

It is always hard to set manufacturing systems to produce large quantities of standardized parts. Controlling these mass production lines needs deep knowledge, hard experience, and the required related tools as well. The use of modern methods and techniques to produce a large quantity of products within productive manufacturing processes provides improvements in manufacturing costs and product quality. In order to serve these purposes, this book aims to reflect on the advanced manufacturing systems of different alloys in production with related components and automation technologies. Additionally, it focuses on mass production processes designed according to Industry 4.0 considering different kinds of quality and improvement works in mass production systems for high productive and sustainable manufacturing. This book may be interesting to researchers, industrial employees, or any other partners who work for better quality manufacturing at any stage of the mass production processes

Advanced Knowledge Application in Practice

The integration and interdependency of the world economy leads towards the creation of a global market that offers more opportunities, but is also more complex and competitive than ever before. Therefore widespread research activity is necessary if one is to remain successful on the market. This book is the result of research and development activities from a number of researchers worldwide, covering concrete fields of research

The 1st Advanced Manufacturing Student Conference (AMSC21) Chemnitz, Germany 15–16 July 2021

The Advanced Manufacturing Student Conference (AMSC) represents an educational format designed to foster the acquisition and application of skills related to Research Methods in Engineering Sciences. Participating students are required to write and submit a conference paper and are given the opportunity to present their findings at the conference. The AMSC provides a tremendous opportunity for participants to practice critical skills associated with scientific publication. Conference Proceedings of the conference will benefit readers by providing updates on critical topics and recent progress in the advanced manufacturing engineering and technologies and, at the same time, will aid the transfer of valuable knowledge to the next generation of academics and practitioners. *** The first AMSC Conference Proceeding (AMSC21) addressed the following topics: Advances in “classical” Manufacturing Technologies, Technology and Application of Additive Manufacturing, Digitalization of Industrial Production (Industry 4.0), Advances in the field of Cyber-Physical Systems, Virtual and Augmented Reality Technologies throughout the entire product Life Cycle, Human-machine-environment interaction and Management and life cycle assessment.:- Advances in “classical” Manufacturing Technologies - Technology and Application of Additive Manufacturing - Digitalization of Industrial Production (Industry 4.0) - Advances in the field of Cyber-Physical Systems - Virtual and Augmented Reality Technologies throughout the entire product Life Cycle - Human-machine-environment interaction - Management and life cycle assessmen