A conceptual design methodology was produced and subsequently coded into a Visual C++ (GUI) environment to facilitate the rapid comparison of several possible configurations to satisfy High Altitude Long Endurance (FIALE) unmanned aircraft (UAV) missions in the Low Speed (propeller driven aircraft) regime. Several comparative studies were performed to verify the applicability of traditional design methods. The traditional computational design methodologies fail in several areas such as high aspect ratio wing weight estimation and design, low Reynolds number wing design, high altitude engine performance, low Reynolds number drag estimation, unmanned aircraft design, and the conceptual design of unconventional configurations. The methodology developed for this thesis was robust enough to allow not only for consideration of these areas of inadequacy in traditional methods, but also to allow for the inclusion of advancements in the relevant technologies as they become more widely available. The following configurations were evaluated for suitability to the Low Speed HALE UAV application: conventional, canard, twin boom, multiple fuselage (conventional or canard), tandem wing, multiple fuselage tandem wing or flying wing configuration. The configurations were compared on the basis of aircraft endurance for takeoff weights ranging from 2,000 to 20,000 pounds and wing loadings ranging from 5 to 25 lbs1fe. Initial drag estimates were made using traditional parabolic drag estimation techniques. A more refined drag buildup was performed using a vortex lattice drag estimation for the lift induced drag (for all lifting components) and calculated skin friction coefficients for the parasite drag. Statistically based methods were used for other components of drag having much smaller contributions. In addition, a statistical approach was taken to the weight estimation of the major aircraft components. However, this approach made comparison of alternative configurations more difficult. Thus wing bending moments trends were evaluated and utilized in the development of weight saving values for multiple fuselage wing weight estimation. The comparative performance of each configuration is justified with direct reference to the terms in the Breguet Endurance equation. Validation was performed where possible on all modules and segments associated with the methodology, as well as for the macroscopic results. In addition, parametric studies on endurance were performed for the conventional configuration for geometric characteristics and operating conditions directly and indirectly effecting the calculated endurance and generalized results presented. Finally, a case study was performed to demonstrate this capability. A new relation was developed for aircraft empty weight prediction, a low speed airfoil figure of merit was proposed, and new constants were offered for UAV fuselage length prediction. In addition, horizontal and vertical tail volume coefficients were proposed for all of the Low Speed HALE UAV configurations considered. It was determined that the multiple fuselage configurations showed comparatively superior endurance performance across a range of takeoff weights, with several other configurations demonstrating marginal endurance improvements. Finally, a highly flexible and robust computer based conceptual design methodology was developed and validated enabling the quick comparison of a greater number of possible configurations to satisfy a given mission for Low Speed HALE UAV's and providing detailed drag and weight breakdown data.

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To manufacture a high precision component, the aircraft industry in particular, employs computer numerical control machining to produce the aircraft components. However, it has often been found that problems of distortion occur when thin and slender components are manufactured this way. It is believed that the distortion arises due to the re-distribution of the residual stress field that was present in the original component in addition to the effects of cutting forces and temperatures that were induced during the machining process. At present, the process to produce a component with acceptable tolerance limits is one of trial and error. This often consumes a lot of time and produces considerable material wastage. The finite element method has been used to develop a methodology to model the actual machining process that produced the aircraft component. The finite element model that has been developed so far was able to demonstrate the effects of redistribution of the residual stresses on the distortion of the final machined component. It was found that the final component distorted differently when the materials were simply removed from a solid billet with different material removal sequences. A preliminary investigation on the effects of cutting temperature and forces has also been made. The investigation showed that such effects could not be totally ignored as they significantly affect the distortion of the final component. In addition to modelling the machining process, a methodology has also been developed to introduce and simulate the clamps and machine worktable that are part of the machining process. Although there is a considerable amount of work relating to modelling machining processes, there has not been any previous attempt to address the problem as a whole as described in this thesis. It is hope that the work undertaken here would be able to provide a stepping-stone to such attempts in future. However, further experimental data would be required to complement a more refined model in the attempt to accurately predict the distortion in machined components. It is believed that it would be possible to then extend the developed methodology to minimise the distortion by changing the machining sequence and the shape of the material to be removed. This would reduce the timescales involved to correct the problems of distortion and eliminate material wastage.

Environmental factors, such as noise and emissions have begun to play a significant role in the design of new aircraft. Although advances in propulsion technology have reduced source noise levels significantly over the past few decades, it is becoming increasingly difficult to project similar advances for the next few decades. It is likely however that some noise benefits may come from improvements in aircraft performance and from changes in operational procedures. In order for such developments to be analysed at the conceptual design stage, an integrated conceptual aircraft design and aircraft noise model is required that enables the designer to rapidly assess the effect of key design parameters on reference noise levels and noise contour area.

Thesis (MScEng)--Stellenbosch University, 2013. / AFRIKAANSE OPSOMMING: Saamgestelde materiale het baie gewilde materiale in die lugvaart- en motor industrië geword as gevolg van die gewigsbesparende voordele wat dit inhou. Kostes en ander verwerkingsprobleme het tradisioneel die wydverspreide gebruik van spesifiek termoplasties-versterkte vesels in hierdie areas verhinder. Baie van die vervaardigingsprobleme (spesifiek lang siklusse) is aangespreek met die aanvang van termoplastiese matriks materiaal soos Polyphenolien Sulfied (PPS). Hierdie materiaal voldoen ook aan die lugvaart-industrie se brand-, rook- en giftigheidstandaarde. Termoplastiese saamgestelde materiale kan byvoorbeeld gevind word op komponente in vliegtuie se binneruimtes en ook die voorste rand van die vlerke. Hierdie komponente is hoogs vatbaar vir impakskade. Die hoë sterkte en styfheid tot gewig verhoudings van saamgestelde materiale laat toe vir dun materiaal dwarssnitte. Komponente is dus kwesbaar vir uit-vlakkige impak beladings. Saamgestelde materiale kan ook intern deur hierdie beladings beskadig word en kan nie met die blote oog waargeneem kan word nie. Dit is dus nodig om die skade weens hierdie beladings tydens normale gebruik akkuraat te voorspel. Verder sal dit nuttig wees om die struktuur se gedrag te bepaal in toepassings waar byvoorbeeld passasier veiligheid krities is, soos op vliegtuig ruglenings tydens noodlandings. In hierdie studie is die potensiële vervaardigingsvoordele van termoplastiese saamgestelde materiale gedemonstreer. Daarbenewens is 'n uit-vlakkige impak deur 'n sagte liggaam herbou in 'n laboratorium omgewing. Die primêre doelwit van hierdie studie was om die impak numeries te modelleer. Vervaardigingsvoordele van `n vesel versterkte termoplastiese laminaat is gedemonstreer deur die vervaardiging van 'n konkawe, agt laag laminaat uit 'n vooraf gekonsolideerde geweefde doek. Die totale verwerkingstyd van die plat laminaat na 'n konkawe laminaat was minder as vyf minute. 'n Eenvoudige plat laminaat en 'n konkawe laminaat is onderwerp aan 'n lae snelheid impak deur 'n sagte projektiel. Die impak is gemodelleer deur die evaluering van drie modelleringsmetodes vir die saamgestelde paneel. Die evalueringskriteria het o.a. ingesluit of laminaat se volle gedrag suksesvol gemodelleer kon word met behulp van slegs 2D dop elemente. Die reaksie van die saamgestelde paneel en gepaardgaande faling is met wisselende vlakke van sukses deur die drie geëvalueerde modelle voorspel. Die faling van tussen-laminêre bindings (verwys na as delaminasie) kon nie deur enige van die modelle voorspel word nie. Twee van die modelle het egter in-vlak faling met redelike akkuraatheid voorspel. / ENGLISH ABSTRACT: Due to weight saving advantages composite materials have become a highly popular material in the aerospace and automotive industries. Traditionally processing difficulties and costs have been a barrier to widespread composite material use in these industries. With the advent of thermoplastic matrix materials such as Polyphenoline Sulphide (PPS) the processing difficulties (especially long cycle times) experienced with traditional thermosetting resins can be addressed while maintaining aerospace Fire-Smoke and Toxicity (FST) approval. Thermoplastic composites can for example be found on aircraft interior components and leading edges of the wings. These areas are highly susceptible to impact damage. The high strength- and stiffness to weight ratios of composites allows for thin material cross sections. This leaves the components vulnerable to out-of-plane impact loads. Composite materials may also be damaged internally by these loads, leaving the damage undetectable through visual inspections. It may therefore be necessary to predict the amount of damage a component would sustain during normal operation. Additionally, it would be useful to predict structural response of these materials in applications where passenger safety is crucial, such as aircraft seat backrests during emergency landings. In this study the potential processing benefits of thermoplastic composite materials were demonstrated. Additionally an out-of-plane impact from a soft bodied projectile was reconstructed in a laboratory environment. The primary objective was to numerically model the impact event. Processing benefits of thermoplastics were demonstrated by producing a single curvature eight layered laminate from a pre-consolidated woven sheet. The total processing time from flat panel to a single curvature panel was below five minutes. A simple flat laminate and a single curvature laminate were subjected to a low velocity drop weight impact load from a soft bodied projectile. These impact events were modelled by evaluating three modelling methods for the composite panel structural response and damage evolution. Part of the evaluation criteria included whether laminate failure could be modelled successfully using only 2D shell elements. The response of the composite panel and accompanying failure were predicted with varying levels of success by the three evaluated models. The failure of interlaminar bonds (referred to as delamination) could not be predicted by either model. However two of the models predicted in-plane failure with reasonable accuracy.

Currently the system development of aircraft engineering concentrates its focus on the reduction of energy consumption more than ever before. As a consequence, the efficiency of subsystems inside the aircraft is highlighted. According to previous investigations the simplification/unification of conventional multifaceted board energy systems by means of electric power management is the most promising way concerning aircraft global efficiency improvement. The main aim of the present work was to optimize a multi-device, heavy duty EHA-System by introducing of a comprehensive perspective. In order to achieve the final, non-plus-ultra improvement level, the attributes of architecture, hardware and operation method were combined in an interactive manner, whereas particular attention has been paid to the mutual enhancing influences. The maximum reduction of losses, the minimizing of consumption and weight optimization can be achieved concurrently when the physical coherences between the involved subsystems are understood and their hidden potentials are exploited. This can only be achieved in one way and the detail follows: The most effective way to reduce both manufacturing effort and weight is to introduce a multiple-allocation philosophy. The highest reliability possible can be achieved by novel cascade-nested system architecture and strict restraining of the control logic. By employing an ultra-low-loss hardware concept, the energy efficiency can be maximized at a necessary minimum own weight. Last but not least, possibly the most important cognition is that an intelligent operation method will improve the actual system and influence the entire system positively and with a lower effort. The final conclusion is that the only and reasonable way to achieve an ultimate optimized solution of an actuation system is an all-encompassing consideration. Eventually it was to recognize that the final result is nothing but ultimate lightweight architecture, i.e. a non-plus-ultra solution. / Gegenwärtig konzentriert sich die Technologieentwicklung für Flugzeuge auf die Reduktion des Energieverbrauchs mehr denn je zuvor. Hierfür ist die Effizienz der an Bord befindlichen, nicht propulsiven Subsysteme neben der Wirkungsgradverbesserung der Triebwerke von zentraler Bedeutung. Laut vorangegangenen Untersuchungen und Studien ist die Vereinfachung bzw. Vereinheitlichung der Vielfalt der konventionellen Bordenergiesysteme durch ein adäquates Energiemanagement unter Verwendung von Elektrizität der aussichtsreichte Weg zur Effizienzverbesserung auf der Gesamtflugzeugebene. Durch die Elektrifizierung wurden die einzelnen Geräte zwar zuverlässiger und energieeffizienter als je zuvor aber gleichzeitig erheblich schwerer, sodaß ein signifikanter Verlust an Nutzlasten auf Gesamtflugzeugebene hervorgerufen wird. Das Hauptziel der vorliegenden Arbeit war es, ein Schwerlast-EHA-System mit mehrfachen Betätigungseinheiten durch Einführung von umfassenden Perspektiven zu optimieren. Durch Einführung der sog. ganzheitlichen Leichtbauweise demonstriert die Arbeit, wie das Subsystem mit mehreren Endgeräten ultimativ optimiert werden kann, ohne Abstriche an Gewichtsbilanz u/o Kompromiß mit der Energieeffizienz zu machen. Um eine wahrhaftige Optimierung, d.h. die Erreichung des ultimativen, Nonplusultra-Verbesserungslevels zu erreichen, wurden die Systemarchitektur, die Hardware und die Operationsmethode interaktiv kombiniert, wobei die besondere Aufmerksamkeit auf die interaktiven, zur Verbesserung führenden Einflüsse gelegt wurde. Die Minimierung des Energieverbrauchs und die ultimative Gewichtsoptimierung gleichzeitig können erreicht werden, wenn die physikalischen Zusammenhänge zwischen den involvierten Subsystemen verstanden und ihre verborgenen Potentiale ausgenutzt werden. Der einzige und vernünftige Weg zur Erreichung der ultimativen Optimierung eines Betätigungssystems ist eine allumfassende Betrachtung, also eine ganzheitliche Betrachtungs- bzw. Vorgehensweise.