Flush repairs to military aircraft are expected to become more prevalent as more thick skin composites are used, particularly on the surface of the fuselage, wings and other external surfaces. The use of these repairs, whilst difficult to manufacture provide an aerodynamic, ???stealthy??? finish that is also more structurally efficient than overlap repairs. This research was undertaken to improve the design methodology of scarf repairs with reduced material removal and to investigate the damage tolerance of scarf repair to low velocity impact damage. Scarf repairs involve shallow bevel angles to ensure the shear stress in the adhesive does not exceed allowable strength. This is important when repairing structures that need to withstand hot and humid conditions, when the adhesive properties degrade. Therefore, considerable amounts of parent material must be machined away prior to repair. The tips of the repair patch and the parent laminate are very sharp, thus a scarf repair is susceptible to accidental damage. The original contributions include: ??? Developed analytic means of predicting the stresses within optimised scarf joints with dissimilar materials. New equations were developed and solved using numerical algorithms. ??? Verified using finite element modelling that a scarfed insert with dissimilar modulus subjected to uniaxial loading attracted the same amount of load as an insert without a scarf. As such, the simple analytic formula used to predict load attraction/diversion through a plate with an insert may be used to predict the load attraction/diversion into a scarf repair that contains a dissimilar adherend patch. ??? Developed a more efficient flush joint with a doubler insert placed near the mid line of the parent structure material. This joint configuration has a lower load eccentricity than external doubler joint. ??? Investigated the damage tolerance of scarf joints, with and without the external doubler. The results showed that scarf joints without external doublers exhibited a considerable strength reduction following low velocity impact. Based on the observations, the major damage mechanics in the scarf joint region following impact have been identified. These results demonstrated that it is important to incorporate damage tolerance in the design of scarf repairs.

This thesis describes some of the processes and results obtained during the design and prototyping of a single seat experimental aircraft. The major aim was to maximise the Triaviation score of the aircraft. This score is a combination of the top speed, the stall speed and the rate of climb. The aircraft has been designed constructed, inspected and flown. The process of designing and prototyping is outlined in this thesis. Details are provided regarding preliminary design, numerical optimisation and the process of building the prototype. The aircraft registered VH-ZYY is a shoulder wing monoplane using a Continental IO-240 aircraft engine. The aircraft has a high power to weight ratio and light wing loading to assist it to climb well and fly slowly. Full span flaperons are used to increase the maximum coefficient of lift at the stall. The primary structure is aluminium with a carbon fibre and nomex cored cowl. All steel components have been formed with 4130 chrome molybdenum aircraft grade tubing. All hardware uses AN specification parts. VH-ZYY is registered in Australia as an Experimental aircraft.

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An approach to multidisciplinary optimization is presented which combines the Global Sensitivity Equation method, parametric optimization, and analytic technology models. The result is a powerful yet simple procedure for identifying key design issues. It can be used both to investigate technology integration issues very early in the design cycle, and to establish the information flow framework between disciplines for use in multidisciplinary optimization projects using much more computationally intense representations of each technology. To illustrate the approach, an examination of the optimization of a short takeoff heavy transport aircraft is presented for numerous combinations of performance and technology constraints. / Master of Science

The aerodynamic prediction methodology available in ACSYNT is examined through comparison with aircraft data for a variety of classes of configurations. The predictions are a synthesis of the best empirical procedures currently available. The present work presents selected results obtained from the comparison, and shows how the basic capability can be enhanced by user supplied adjustments to represent changes in technology levels when considering advanced aircraft designs. The predictions and basis for adjustments are described for a supersonic cruise vehicle, a large subsonic transport, a typical fighter, an attack aircraft, and a typical business jet. / Master of Science

In an integrated design environment, the common thread between the different design stages is usually the geometric model of the part. However, the requirements for the geometric definition of the design is usually different for each stage. The transformation of data between these different stages is essential for the success of the integrated design environment. For example, conceptual design systems usually deal with geometric dimensional parameters (e.g. length, radius, etc.) whereas preliminary design systems frequently require the geometry definition to be in the form of surface models. This dissertation presents the necessity and scope of creating and implementing methodologies to obtain dimensional geometric parameters from the surface description of an object. Since the study of geometric modeling and parametric surfaces is a new field, few classical methods are applicable. Methods and algorithms for the extraction of various geometry parameters are created. A few methods to pre-process and manipulate these surfaces before the parameter extraction methods can be applied are outlined. One of the most important applications of parameter extraction is in the field of aircraft design. There are two important aspects of geometry data conversion in the design cycle. The first is the conversion from conceptual CAD models to CFD compatible models. The second is the conversion from surface representations of CFD models to obtain component parameters (e.g. wing span, fuselage fineness ratio, moments of inertia, etc.). The methods created in this dissertation are used to extract geometric parameters of importance in aircraft design. This enables the design cycle to be complete and promotes integrated design. These methods have been implemented in the aircraft design software, ACSYNT. Examples of the conversion of data from B-spline surface models to dimensional geometric parameters using these methods are included. The emphasis of this dissertation is on non-uniform B-spline surfaces. Methods for obtaining geometric parameters from aircraft models described by characteristic points are also considered briefly. / Ph. D.

During the conceptual design phase, aircraft designers require tools to be able to quickly and accurately produce concepts that meet given requirements. These tools often take the form of computer programs and computer-aided design systems which model the shape of the airplane concept and perform various analyses. Often, a common element in these analyses is that only the exterior of the aircraft is considered. Thus a major component of aircraft design is largely overlooked: the internal layout of the airplane. This thesis describes the design and implementation of a new computer software, the Internal Layout Module, designed to enhance the ability of the aircraft designer to arrange, modify, view, and analyze the internal components of an airplane. By considering the internal layout concurrently with the external shape and size, the configurator can effectively design the smallest airplane that meets specifications. The module is coded in C++ entirely under the object-oriented paradigm to ease integration with existing code and to ensure future maintainability and extensibility. New components as varied as seats, galleys, lavatories and cargo containers have been designed for use in the Internal Layout Module and to provide a foundation for future object-oriented geometry for aircraft design. The module has been successfully integrated with the aircraft conceptual design code ACSYNT (AirCraft SYNThesis). The process of adding this new object-oriented module to existing procedural code is discussed in detail. / Master of Science

This thesis presents the algorithms and methods for transferring B-spline surface data from a final design CAD tool to a parameter based conceptual design CAD tool. Both codes store data in different ways, requiring a technique referred to as reverse parameteriation to achieve data transfer. Methods are discussed to produce surface points from generic B-spline patch definitions. These points are inverted to generate component B-spline surface data. The geometric parameters are retrieved by analyzing the B-spline surface for each component. These methods are applied to a conceptual aircraft design code, ACSYNT, which defines the B-spline geometry using dimensional parameters. This allows for aircraft created on non-parameter based systems to utilize the analysis and geometry routines of ACSYNT. / Master of Science

This thesis discusses the creation of an object-oriented method to facilitate the creation and specification of aircraft mission profiles. Mission profiles are detailed descriptions of an aircraft's flight path and its inflight mission activities. They are a vital aspect of the conceptual design process of an aircraft. The Mission Profile Input System (MPIS) created is general in nature and can be customized to be compatible with existing aircraft CAD systems. All data associated with the mission—phase parameters, phases, and mission parameters, are defined to be objects. Each data type can therefore be customized individually to meet any requirements which may be necessary to make the MPIS compatible with a host system. Customization of the MPIS is further enhanced by the nature of the design upon which it is based. An object-oriented design provides the system with a high degree of extendibility. The encapsulation and inheritance features of object-oriented design allow new types of phases and phase parameters to be simply "plugged" into the existing system. The MPIS provides the user with an interactive, Motif-like interface which is conducive to manipulating the large quantities of data inherent in specifying mission profiles. The system is based on the ISO graphics standard, PHIGS, and hence is device-independent. Moreover, the system has been implemented using the hybrid object-oriented language, C++, which is supported by a large number of computer systems. / Master of Science

In recent years, the use of computer-aided design (CAD) systems for conceptual aircraft design has greatly increased. As a result, new and better methods for creating surface models of aircraft geometry using dimensional parameters are needed. One such method, the Rule-Based Fuselage method, was suggested by Lockheed. The Rule-Based Fuselage method allows an aircraft designer to define complex aircraft fuselage geometry by specifying the fuselage profile and individual parametric cross-sections along the fuselage. This thesis describes the Rule-Based Fuselage method and discusses the implementation of the method in an interactive, object-oriented environment. Also included in this system is the Spine and Cross-Section method for creating arbitrarily shaped aircraft components. The design and implementation of both the Rule-Based Fuselage and Spine and Cross-Section methods are described. The integration of these methods with the conceptual aircraft design code, ACSYNT, is also discussed. / Master of Science