Due to the complexity of designing advanced composite parts, many software tools have been developed to aid the designer and reduce design cycle time. Draping is one of those tools and is used to predict the fiber angles throughout the part. This application of draping is to simulate the actual hand layup process that a technician would go through while creating a multi-layered laminate composite part. This method is the first to use plies as an underlying surface for draping instead of just using an offset mold surface. This method can visualize full 3D ply geometry taking into account the thicknesses of the underlying plies and their drop-off regions which a designer could use to avoid superimposing ply drop-offs. Physical testing showed that this method predicts ply drop-off regions reasonably well and allows the designer to visualize the final shape of the laminate. The method also provides for re-ordering of the plies while keeping their cut-out shape the same because of its reverse-process draping technique. Three methods of draping were explored in order to find the best method. Multiple test parts were created with specific features that are difficult to drape. The method to drop fabric to the surface was the most versatile while a method published by Wang was the best for convex surfaces and superior to spread-type draping. No one method worked well for all surfaces.

The purpose of this study was to develop a composite manufacturing process that would be able to deliver Class A surface finished products in the context of mould manufacturing methods. The problem required solving was to overcome the time needed to prepare Class A surfaces, by developing a composite manufacturing process that will deliver Class A surface finished products straight from the mould. The process was aimed at the entire development process, from mould and plug design up to the finished product. A literature study and a factory mould survey were conducted with a view to obtain the necessary insights into surface finishing and composite manufacturing. These surveys were followed by seven constructional tests which determined the most appropriate solutions for the proposed manufacturing processes. Test 1 was used to determine a quality finish standard for composites from the sanding grits used to finished composite surfaces versus surface roughness values used in other industries. The standard determined that a P800 finish has a roughness between 0.200 and 0.150 um and constitutes a Class A3 finish. P1000 to P1200 have a roughness between 0.150 um to 0.100 um and constitutes a Class A2 finish. Finally a P2000 and higher have a roughness of 0.100 um and lower and constitutes Class A1 surface finish. After the standard was set, the tests for finishing of the moulds, plugs and parts commenced. Test 2 was conducted on the CNC manufacturing of plugs out of Nuceron651 tooling board. Tool path parameters were varied in a matrix. The samples with the best surface finish value were cut with a step-over of 0.5 and feed of 800 mm/min. These parameters were found to be the most influential. Test 2 and 4 revealed that the plug surface finishing should commence with conventional 2K paint finishing, with a possibility of acrylic split surface. This process produced projected mould surfaces between 0.150 um and 0.200 um, which can be categorised as Class A-3. Test 5 and 6 determined methods for improving the mould surface quality and durability. It was established that the tooling gelcoat should be applied whilst being heated and backed with at least two layers of glass veil and a steady increase of GSM of structural glass fibres to prevent print-through. Test 3 determined that the mould corners could be strengthened with rovings pressed into the corner. It was also established that the moulds surfaces will require finishing after demoulding. The final moulds were manufactured from a fibreglass composite structure with tooling gelcoat surface. A number of guidelines and a set process were developed in order to produce moulds with a surface finish of average 0.9 um, equivalent to Class A1. Release agents were tested in Test 7, and the Loctite Frekote 770-NC release system was deemed appropriate for use with In Mould Coating (IMC) of 2K Paint. These elements were all synthesised into plug, mould and part manufacturing processes. The proposed processes were validated by the manufacturing of a JS instrument panel, which delivered a Class A2, 0.175 um, finish with IMC of 2K paint. With only a minor sanding of P3000 grit and polishing, the part was made into a Class A1 surface, measured at 0.63 um. The study proved that it is possible to produce Class A finished part with IMC. This method can provide a solution aimed at the elimination of P600 and lower finishing of composite parts manufactured with IMC. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

The purpose of this study was to develop a composite manufacturing process that would be able to deliver Class A surface finished products in the context of mould manufacturing methods. The problem required solving was to overcome the time needed to prepare Class A surfaces, by developing a composite manufacturing process that will deliver Class A surface finished products straight from the mould. The process was aimed at the entire development process, from mould and plug design up to the finished product. A literature study and a factory mould survey were conducted with a view to obtain the necessary insights into surface finishing and composite manufacturing. These surveys were followed by seven constructional tests which determined the most appropriate solutions for the proposed manufacturing processes. Test 1 was used to determine a quality finish standard for composites from the sanding grits used to finished composite surfaces versus surface roughness values used in other industries. The standard determined that a P800 finish has a roughness between 0.200 and 0.150 um and constitutes a Class A3 finish. P1000 to P1200 have a roughness between 0.150 um to 0.100 um and constitutes a Class A2 finish. Finally a P2000 and higher have a roughness of 0.100 um and lower and constitutes Class A1 surface finish. After the standard was set, the tests for finishing of the moulds, plugs and parts commenced. Test 2 was conducted on the CNC manufacturing of plugs out of Nuceron651 tooling board. Tool path parameters were varied in a matrix. The samples with the best surface finish value were cut with a step-over of 0.5 and feed of 800 mm/min. These parameters were found to be the most influential. Test 2 and 4 revealed that the plug surface finishing should commence with conventional 2K paint finishing, with a possibility of acrylic split surface. This process produced projected mould surfaces between 0.150 um and 0.200 um, which can be categorised as Class A-3. Test 5 and 6 determined methods for improving the mould surface quality and durability. It was established that the tooling gelcoat should be applied whilst being heated and backed with at least two layers of glass veil and a steady increase of GSM of structural glass fibres to prevent print-through. Test 3 determined that the mould corners could be strengthened with rovings pressed into the corner. It was also established that the moulds surfaces will require finishing after demoulding. The final moulds were manufactured from a fibreglass composite structure with tooling gelcoat surface. A number of guidelines and a set process were developed in order to produce moulds with a surface finish of average 0.9 um, equivalent to Class A1. Release agents were tested in Test 7, and the Loctite Frekote 770-NC release system was deemed appropriate for use with In Mould Coating (IMC) of 2K Paint. These elements were all synthesised into plug, mould and part manufacturing processes. The proposed processes were validated by the manufacturing of a JS instrument panel, which delivered a Class A2, 0.175 um, finish with IMC of 2K paint. With only a minor sanding of P3000 grit and polishing, the part was made into a Class A1 surface, measured at 0.63 um. The study proved that it is possible to produce Class A finished part with IMC. This method can provide a solution aimed at the elimination of P600 and lower finishing of composite parts manufactured with IMC. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Der Einsatz kohlenstofffaserverstärkter Kunststoffe im Strukturleichtbau ziviler Luftfahrzeuge wird erheblich durch Produktionsautomatisierung getrieben. Einzelne Komponenten der für die Verarbeitung der duroplastischen Werkstoffe genutzten Automated-Fiber-Placement Anlagen bieten jedoch noch erhebliches Potential für die Steigerung der Leistungsfähigkeit des Prozesses. Insbesondere ist der prozessspezifische Entwicklungs- und Kenntnisstand des Erwärmungssystems gegenüber der Verfahrensvariante mit thermoplastischen Werkstoffen weniger fortgeschritten. So weisen die dort genutzten Diodenlaser Vorteile in der Reaktionszeit, der Homogenität der Erwärmung und ihrer Regelbarkeit gegenüber den im AFP genutzten Infrarotstrahlern auf. Letztere haben jedoch einen geringeren Bauraumbedarf sowie geringere Kosten und Sicherheitsanforderungen. Um die Vorteile beider Erwärmungssysteme für das AFP zu kombinieren, wurde in dieser Arbeit ein neuartiges Erwärmungssystem entwickelt. Kernstück des Lösungsansatzes ist dabei die Nutzung von LEDs als Strahlungsquellen. Grundlegende Prozess- und Materialuntersuchungen ermöglichen die Auswahl geeigneter LEDs und deren Anordnung zu einem prozessgerechten LED-Strahler. Dessen anlagentechnische Integration zu einer Strahlereinheit ermöglicht eine aktive Kontrolle des Profils der abgegebenen Strahlung, um ohne weitere Hilfsmittel eine Anpassung an unterschiedliche Prozessgegebenheiten zu erlauben. Zur Erprobung wurde die Strahlereinheit in eine Versuchsumgebung, welche den AFP-Prozess vereinfachend auf Labormaßstab abbildet, integriert. Die Baumraumbeschränkungen üblicher Infrarotstrahlersystem finden hierbei Berücksichtigung. In der Erprobung wurden bidirektionale Laminate hergestellt und die erzielte Oberflächentemperatur gemessen. Dabei zeigte sich, dass das neuartige Erwärmungssystem sehr gut geeignet ist, den benötigten Wärmeeintrag für den Prozess zuverlässig zu liefern. Anschließend wurde in weiteren Versuchen festgestellt, dass das vorliegende System prinzipiell bereits in der Lage ist, den Anforderungen eines industriellen Prozesses in puncto erzielbarer Ablegegeschwindigkeit gerecht zu werden. Zudem konnte gezeigt werden, dass die Reaktionszeit beim Anfahren und Stoppen des Ablegekopfes durch eine aktive Kontrolle des Profils der abgegebenen Strahlung kurzgehalten und so ein sehr gut kontrollierbares Erwärmungsverhalten erzielt werden kann. Da für eine robuste Prozessgestaltung auch eine präzise Vorhersage der Erwärmung des Materials vonnöten ist, wurde ein numerischen Modell des Energieeintrags und der dadurch verursachten Erwärmung entwickelt. Dabei war es zudem das Ziel, die lokale Verteilung des eingebrachten Wärmestroms zu analysieren und mit dem neuartigen Erwärmungssystem vorhersehbar zu beeinflussen. Dazu wurde ein optisches Modell entwickelt, welches auf numerischer Basis den Energieeintrag jeder einzelnen LED in das Substrat zu bestimmen gestattet. In der anschließenden Simulation wurde eine Konfiguration ermittelt, welche eine nahezuhomogene Verteilung der eingebrachten Wärmeleistung über der bestrahlten Fläche ermöglicht. Die Berechnungsergebnisse konnten zudem auf rein optischer Basis mit sehr guter Übereinstimmung experimentell validiert werden. Der so bestimmte Wärmestrom wurde zudem als Eingangsgröße für ein Prozessmodell der Erwärmung genutzt. Für dieses Prozessmodell wurde ein erweiterter zweidimensionaler Ansatz genutzt, um den dreidimensionalen Erwärmungsvorgang effizient abzubilden. In der abschließenden Validierung zeigte sich eine prinzipiell hohe Übereinstimmung von Theorie und Experiment. Die Fähigkeit des neuartigen LED-Erwärmungssystems, die Temperaturgradienten normal zur Ablegerichtung im bestrahlten Substrat gezielt einstellen zu können, wurde dabei bestätigt. Das im Rahmen der vorliegenden Arbeit entwickelte, neuartige LED-Erwärmungssystem ermöglicht durch die Kombination der Vorteile von Infrarotstrahlern und Diodenlasern wesentliche Fortschritte für die Weiterentwicklung des industriellen AFP. So ergeben sich durch die Verwendung standardisierter LEDs und dem damit ermöglichten flexiblen Aufbau des Erwärmungssystems Möglichkeiten zur Kostensenkung in der Entwicklung neuer Ablegeanlagen. Der Betrieb und die Wartung solcher Anlagen kann zudem energieeffizienter und damit günstiger gestaltet werden. Weiterhin ergibt sich durch die zuverlässigere Messung der Temperatur die Möglichkeit, robustere Regelkreise zu integrieren. Dies wird weiter begünstigt durch die schnelle Reaktion der Strahlungsquellen, was zudem eine Reduktion der Fertigungszeit insbesondere bei komplexen Bauteilen ermöglicht.:1 Einleitung und Motivation 2 Stand der Technik 2.1 Faser-Kunststoff-Verbunde in der Luftfahrt 2.2 Automatisierte Ablegeverfahren 2.3 Bestehende Erwärmungssysteme für Ablegeverfahren 2.4 LEDs als Strahlungsquellen 2.5 Vergleich der Erwärmungssysteme 3 Entwicklung eines LED-basierten Erwärmungssystems 3.1 Anforderungen, Rahmenbedingungen und Zielgrößen 3.1.1 Anforderungen 3.1.2 Rahmenbedingungen 3.1.3 Zielgrößen 3.2 Anlagenkonzept 3.3 Entwicklung eines LED-Strahlers 3.3.1 Prozessmodell zur Auslegung 3.3.2 Spektrales Absorptionsverhalten des Materials 3.3.3 Auswahl geeigneter LEDs 3.3.4 Anordnung der LEDs zu einem LED-Strahler 3.4 Weitere Komponenten und Integration des LED-Strahlers 3.4.1 Aufbau einer Steuereinheit 3.4.2 Aufbau eines Versuchsstands 3.4.3 Montagekörper der LED-Strahlereinheit 3.4.4 Integration des Erwärmungssystems 3.5 Erprobung des Erwärmungssystems 3.5.1 Ablegeversuche 3.5.2 Variieren von Geschwindigkeit und Leistung 3.5.3 Einstellen der Reaktionszeit 3.6 Ergebnisdiskussion 4 Prozessmodell zum optischen Energieeintrag 4.1 Modellentwicklung 4.1.1 Modellannahmen 4.2 Numerische Implementation 4.2.1 Abbilden der diskreten Geometrie 4.2.2 Berechnen des Wärmestroms, der Wärmestromdichte und der Bestrah- lungsstärke 4.3 Simulieren unterschiedlicher Eingangsverteilungen 4.3.1 Eingangsverteilung aus Auslegung und Ablegeversuchen 4.3.2 Einstellen unterschiedlicher Verteilungen 4.4 Validierung 4.4.1 Versuchsaufbau und -durchführung 4.4.2 Auswertung 5 Prozessmodell des Erwärmungsvorgangs 5.1 Modellentwicklung und Materialparameter 5.1.1 Anforderungen und Annahmen 5.1.2 Materialparameter 5.2 Implementierung und Berechnung 5.2.1 Implementierung 5.2.2 Berechnung und Simulationsergebnisse 5.3 Validierung des thermischen Modells 5.3.1 Methodik und Versuchsaufbau 5.3.2 Auswertung und Vergleich mit Simulationsergebnissen 6 Potenzialanalyse zum Einsatz des LED-Erwärmungssystems 6.1 Kostensenkung in der Anlagenentwicklung und im Betrieb 6.2 Verbesserung der Prozesskontrolle 6.3 Verkürzung der Prozesszeit 7 Zusammenfassung und Ausblick Literaturverzeichnis

Man-made materials such as fiber-reinforced composites (FRCs) can be tailored for optimum performance in product design applications in terms of strength and weight. The current work is aimed at studying the behaviors of composite laminates based on E-glass CSM (Chopped Strand Mat) or WRM (Woven Roving Mat) plies with a polyester resin for impact protection applications. Detailed mechanical characterization of CSM and WRM laminates till failure is carried out for tensile, compressive and shear loads by varying manufacturing process, number of plies, and laminate thickness. The effect of fiber volume fraction on mechanical properties is shown. The efficacy of CSM and WRM laminates as energy- absorbing countermeasures is studied by performing quasi-static and axial impact tests on cylindrical tubes made of the stated FRCs. In addition to load-displacement and specific energy absorption attributes, failure modes are of interest in such studies. The potential of FRC laminates for protection against projectile impact is investigated by performing low velocity impact perforation tests with a falling tup fitted with an indentor, and medium to high velocity projectile impact tests in a gas gun-based device. The valuable results generated are used for the validation of nonlinear finite element-based CAE (Computer-Aided Engineering) procedures including application of a multi-modal failure criterion for explicit dynamic analysis. The present study not only throws light on complex mechanical behavior of an important class of lightweight materials under static and dynamic loads, but also simulation tools for the design of impact safety countermeasures such as bullet-proof laminates and energy–absorbing components for automotive body structures.

Prepreg is a fibre reinforced polymer composite material often used by the aeronautical industry. The material supplier has pre-impregnated the fibre often with an epoxy resin and cured it to a semi-viscous B-stage where the material is tacky (adhesive). Manual layup of prepreg components is still common because there are only a few automated layup techniques which has limited geometric capability and high investment cost. Swerea SICOMP is a research institute which have in collaboration with partners developed a manufacturing demonstrator for automated layup of carbon fibre prepreg components based on robotic handling. The manufacturing demonstrator is able to; feed out prepreg from a spool onto a cutting table, cut the prepreg into plies, pick the plies from the cutting table and place them on a layup table, consolidate the prepreg plies on the layup table and remove the backing paper that covers one side of the prepreg. Three robustness problems has been identified and these forms the bulk of this master’s thesis. The first problem is that the robot is unable to place the plies on the cutting table with sufficient accuracy due to fluctuating position of the prepreg on the cutting table. The second problem is that the end effector used for the pick and place operation sometimes fails to pick the adhesive plies from the cutting table. The problem originates in limited holding force by the end effectors suction cups and limited capability to perform a peeling motion when picking due to the design of the end effector. The third problem is that process variables like temperature is believed to effect the robustness of the demonstrator but has not been further studied. The first problem was solved by implementing a probing routine which measures the position of the prepreg on the cutting table with an array sensor mounted to the robot. The measurement values are used to reprogram subsequent operations. The second problem seems to be solved by designing and implementing a new pick and place end effector. The new end effector has higher holding force and better capability to perform a peeling motion while picking and placing the tacky prepreg plies. Tests with the new end effector has been promising, the pick and placeoperation performs robustly, but all ply geometries was not tested and some minor adjustment is needed to further improve the placing accuracy. The third problem has not been solved but studied. A literature study reviled that temperature, relative humidity and prepreg out of freezer age is likely to effect the prepreg adhesive properties which in turn is known to effect the robustness. A test procedure has been devised to test how these variables effect the robustnessof the demonstrator. The tests should be conducted when all process steps in the demonstrator is up and running.

Cette thèse aborde la problématique de la conception optimale de structures composites stratifiées d’épaisseur variable. Les variables d’empilement définissent un problème d’optimisation combinatoire et des espaces de décisions de grande taille et potentiellement multimodaux. Les algorithmes d’optimisation stochastiques permettent de traiter ce type de problème et de tirer profit des performances et de l’anisotropie des plis composites pour l’allègement des structures composites stratifiées. Le but de cette étude est double : (i) développer un algorithme d’optimisation dédié aux composites stratifiés d’épaisseur variable et (ii) estimer le potentiel des composites stratifiés pour la maîtrise des performances aérodynamiques d’une pale de CROR composite.Dans la première partie de cette thèse, un algorithme évolutionnaire est spécialisé pour l’optimisation de tables de drapage et la gestion d’un ensemble de règles de conception représentatif des pratiques de l’industrie. Pour se faire, un encodage spécifique des solutions est proposé et des opérateurs de variations spécialisés sont développés.Dans la deuxième partie, l’algorithme est enrichi d’une technique de guidage basée sur l’exploitation d’un espace auxiliaire afin d'accroître son efficacité et d’intégrer davantage de connaissances des composites dans la résolution du problème.Finalement, la méthode est appliquée pour la conception d’une pale de CROR composite à l’échelle de la maquette de soufflerie. Au préalable, des processus itératifs de mise à froid et mise à chaud de la pale sont mis en place afin d’estimer la forme de la pale au repos et l’état de contraintes dans la pale en fonctionnement. / This thesis deals with the optimal design of variable-thickness laminated composite structures. The stacking variables define a combinatorial optimization problem and large decision spaces which are potentially multimodal. Stochastic optimization algorithms allow solving this type of problem and allow taking advantage from the performance and the anisotropic nature of unidirectional composite plies to lighten laminated composite structures.The purpose of this study is twofold: (i) developing an optimization algorithm dedicated to variable-thickness laminated composites and (ii) assessing the potential of laminated composites in influencing the aerodynamic performances of a composite CROR blade.Firstly, an evolutionary algorithm is specialized in order to optimize layup tables and handle a set of design guidelines which is representative of industrial practices. In this purpose, a specific encoding of the solutions is suggested and specialized variation operators are developed.Secondly, the algorithm is enriched with a guiding technique based on the exploitation of an auxiliary space in order to improve its efficiency and to include further composites-related knowledge for the resolution of the problem.Finally, the method is applied for the design of a reduced-scale composite CROR blade intended for wind-tunnel testing. Beforehand, iterative processes are implemented to estimate the shape of the non-operating blade and the stress state within the operating blade.

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