New heating techniques are required to better control heat transfer between heating tools and a composite towpreg in the automated fiber placement process. This dissertation suggests new heating techniques with liquid and rigid contact heat sources, and compares them with a widely used gas heat source for the fiber placement process. A thin towpreg composite model needs to be developed to describe the heat transfer. Subsequently, the response of the towpreg with each heat source was compared from manufacturing speed and energy efficiency viewpoints. The most promising heat source was developed for heat transfer modeling between a moving towpreg and dynamic heat source in the automated fiber placement. Through the heat transfer model, both the temperature controllability of the towpreg and manufacturing speed could be investigated. In addition, an accurate compaction process is needed in response to the growing demand for better composite processing. Since the errors in compaction mechanisms and robotic machinery in fiber placement have not been discussed in the literature, experimental investigation to address possible reasons for the variations in the compaction force was conducted with a compaction mechanism. A clearer understanding of the physical compaction process can lead to controllable process parameters for consistent ply compaction, such that the final parts quality can be enhanced. Even though this dissertation investigates the thin thermoset fiber placement process, the proposed approach could be universally applicable to other composite-fabrication processes. / Ph. D.

In this study structural design, analysis and composite manufacturing applications for a tactical UAV, which was designed and manufactured in Aerospace Engineering Department of Middle East Technical University (METU), is introduced. In order to make an accurate structural analysis, the material and loading is modeled properly. Computational fluid dynamics (CFD) was used to determine the 3D pressure distribution around the wing and then the nodal forces were exported into the finite element program by means of interpolation from CFD mesh to finite element mesh. Composite materials which are mainly used in METU TUAV are woven fabrics which are wetted with epoxy resin during manufacturing. In order to find the elastic constants of the woven fabric composites, a FORTRAN code is written which utilizes point-wise lamination theory. After the aerodynamic load calculation and material characterization steps, linear static and dynamic analysis of the METU TUAV&rsquo / s wing is performed and approximate torsional divergence speed is calculated based on a simplified approach. Lastly, co-cured composite manufacturing of a multi-cell box structure is explained and a co-cured multi-cell box beam is manufactured.

The aim of this study is to describe the conceptual design, performance analysis to validate the design and manufacturing steps of Middle East Technical University Tactical Unmanned Air Vehicle (METU TUAV). The system requirements are adopted from a market study and assumed as is. Utilizing competitor search and conceptual design methodology, the rough parameters of the aircraft are defined and a performance analysis is conducted to validate the requirements. After the design team is content that the design is meeting the requirements, material and production techniques are evaluated. The male and female molds of the aircraft are manufactured with glass fibre fabric and special mold resin. Using the female molds / with glass, carbon and aramid fibre materials and epoxy matrix / utilizing wet-layup and vacuum bagging techniques the METU TUAV is manufactured. Wing, tail and fuselage skins are manufactured first and the reinforcing structures are integrated and cured inside the skins. Then the skins are assembled and the separate components are obtained. The rear landing gear and tail booms are also manufactured from carbon fibre composites. The individual parts are assembled together in special alignment jigs and the METU TUAV is completed.

The high functionality epoxy resins tetraglycidyl-4,4’-diaminodiphenyl-methane(TGDDM) and triglycidyl-p-aminophenol (TGPAP) are the main components in most aerospace grade epoxy resin formulations. Owing to their high reactivity and high viscosity, TGDDM and TGPAP pose difficulties when used in wet layup composite manufacturing. As such, these resins are often modified to achieve the desired performance both in the liquid and cured states. The main objective of this thesis is to optimise a low viscosity multi-component epoxy resin formulation suitable for use as an aerospace grade composite matrix. The formulation will allow for the addition of high levels of thermoplastic to improve the fracture toughness of the resin whilst also maintaining resin processability. Through the use of thermal analytical techniques this thesis aims to study the effects of varying the TGDDM/TGPAP ratio, incorporation of a low viscosity bi-functional epoxy resin, the diglycidyl ether of bisphenol F (DGEBF) and changes to the stoichiometric ratio (r)between reactive groups of the epoxy resin and amine hardener (4,4’-diaminodiphenylsulphone, DDS) in multi-component epoxy resin formulations. Resin formulations were optimised using factorial experimental design (FED). Results from two FED’s showed curing multi-component resins at a low stoichiometric ratio significantly increased the processing window whilst also increasing the glass transition temperature (Tg) of the cured resin. No apparent benefit could be assigned to the inclusion of TGDDM owing to its poor processability and a Tg similar to TGPAP. Up to 60% DGEBF was incorporated in a multi-component resin formulation whilst still attaining a Tg greater than 220°C. Its inclusion at 60% had the additional benefit of increasing the processing window by 48 minutes over TGPAP, an increase of 62%. Two optimised resin formulations, 100% TGPAP (100T) and a binary mix of 60% DGEBF and 40% TGPAP (60D) were taken forward to study the effects of adding a thermoplastic toughener (polyethersulphone, PES) in incremental amounts up to 50wt%. SEM images showed all toughened 100T resins had a phase separated morphology whilst all 60D resins were homogenous. The phase separation seen in 100T did not improve the matrix fracture toughness when loaded at 10 wt% and 30 wt% PES. Only when 50 wt% PES was added did fracture toughness increase in comparison to the homogenous 60D resins. Through factorial experimental design two epoxy resin formulations which excluded TGDDM were optimised with a low stoichiometric ratio. The optimum aerospace formulation is dependent on the desired processability and fracture toughness of the resin. High DGEBF-containing formulations give the longest processing windows whilst the 100% TGPAP formulation toughened with 50% PES has the highest fracture toughness.

Global awareness and preservation have spurred increasing interest in utilizing environmentally friendly materials for high-performance structural applications. Biocomposites pose an appealing solution to this issue and are characterized by their sustainable lifecycles, biodegradable qualities, light weight, remarkable strength, and exceptional stiffness. Many of these structural qualities are found in applications that exhibit flexural loading conditions, and this study focuses on improving the bending performance of engineered biocomposite structures. The current application of biocomposites is increasing rapidly, so this expanding research explores other natural constituent materials for biocomposite structures under flexural loading. The renewable material investigated in this study was experimentally and numerically validated by optimizing the mechanical characteristics of bamboo fibers in biocomposite structures under flexural loading conditions through various thermal and organic chemical treatment methods. Therefore, bending performance of a biocomposite truss and I-beam are analyzed to demonstrate the benefits of utilizing optimally treated bamboos in their design. To accomplish this goal, the first task consisted of treating bamboos by thermal and chemical means to determine the resulting effects on the compressive and tensile mechanical properties through experimental testing. Results indicated a significant improvement in strength, stiffness, and weight reduction. An extensive analysis determined the optimal treatment method that was utilized for flexural loading conditions. The second task entailed studying the flexural behavior of the optimally treated bamboo in two geometric configurations, a hollow cylinder and veneer strip, to determine the resultant properties for the truss and I-beam structure. The effect of node location on flexural performance was also studied to establish design guidelines for the applied structures. Bending tests indicated that node location affects the strength and stiffness of the hollow cylindrical configuration but has minimal effects on the veneer strip. Observations discovered by this study were employed into the designs of the applied structures that yielded excellent mechanical performance through flexural testing. The final task required conducting a finite element analysis in Abaqus/CAE on the performance of each structural application to validate experimental results. A conclusive analysis revealed good agreement between the numerical method and experimental result.

<p>  </p> <p>Thermal shrinkage in advanced composite manufacturing causes residual stress in a cylindrical anisotropic segment. The residual stress later induces a spring-in angle when  the temperature change is negative. The superposition method in the finite element method (FEM) by ABAQUS©  proves that only the residual stress in the circumferential direction controls the spring-in angle and induces the radial residual stress. To predict the angle change, the residual stress is firstly determined by using the closed-loop geometry in FEM and then implemented into the cylindrical cross-ply symmetric laminate segment. Consequently, the geometry creates the spring-in angle under the traction-free surface. The angle change is in good agreement with the Radford equation and is found to depend on the coefficient of thermal expansion (CTE) in the circumferential and radial directions rather than other material properties and geometry dimensions. </p> <p>The study found a new limitation of the Radford equation, in that it is accurate when the part is anisotropic symmetric laminate, but not when it is unsymmetric. The accuracy of the Radford equation is further explored with the double curve geometry. Using the superposition method, the circumferential residual stress along the major curve is found to have an influence on the angle change not only of the major curve, but also of the minor curve. The negative temperature change produces the spring-in angle on the major curve, and both spring-in and -off angles on the minor curve, which rely on the radius ratio. In addition, the spring-in angle on the major curve is coincident with the Radford equation. In sum, knowing the spring-in angle is very helpful in designing a tool in advanced composite manufacturing, and the superposition method and the Radford equation are applicable to predict the spring-in angle.</p>

This investigation completed the verification of a three-dimensional resin transfer molding/resin film infusion (RTM/RFI) process simulation model. The model incorporates resin flow through an anisotropic carbon fiber preform, cure kinetics of the resin, and heat transfer within the preform/tool assembly. The computer model can predict the flow front location, resin pressure distribution, and thermal profiles in the modeled part. The formulation for the flow model is given using the finite element/control volume (FE/CV) technique based on Darcy's Law of creeping flow through a porous media. The FE/CV technique is a numerically efficient method for finding the flow front location and the fluid pressure. The heat transfer model is based on the three-dimensional, transient heat conduction equation, including heat generation. Boundary conditions include specified temperature and convection. The code was designed with a modular approach so the flow and/or the thermal module may be turned on or off as desired. Both models are solved sequentially in a quasi-steady state fashion. A mesh refinement study was completed on a one-element thick model to determine the recommended size of elements that would result in a converged model for a typical RFI analysis. Guidelines are established for checking the convergence of a model, and the recommended element sizes are listed. Several experiments were conducted and computer simulations of the experiments were run to verify the simulation model. Isothermal, non-reacting flow in a T-stiffened section was simulated to verify the flow module. Predicted infiltration times were within 12-20 percent of measured times. The predicted pressures were approximately 50 percent of the measured pressures. A study was performed to attempt to explain the difference in pressures. Non-isothermal experiments with a reactive resin were modeled to verify the thermal module and the resin model. Two panels were manufactured using the RFI process. One was a stepped panel and the other was a panel with two `T' stiffeners. The difference between the predicted infiltration times and the experimental times was 4 to 23 percent. / Master of Science

The LHC (Large Hadron Collider) will have a long shut down in the years of 2019 and 2020, referred to as LS2. During this stop the LHC injector complex will be upgraded to increase the luminosities, which will be the first step of the high luminosity LHC program (which will be realized during LS3 that takes place in 2024-2026). The LHCb experiment, whose main purpose is to study the CP-violation, will during this long stop be upgraded in order to withstand a higher radiation dose, and to be able to read out the detector at a rate of 40MHz,compared to 1MHz at present. This change will improve the trigger efficiency significantly. One of the LHCb sub-detectors the Trigger Tracker (TT), will be replaced by a new sub-detector called UT. This report presents the early stage design (preparation for mock-up building) of the box that will be isolating the new UT detector from the surroundings and to ensure optimal detector operation. Methods to fulfill requirements such as light and gas tightness, Faraday-cage behavior and condensation free temperatures, without breaking the fragile beryllium beam pipe, are established. / LHC (Large Hadron Collider) kommer under åren 2019-2020 att ha ett längre driftstopp. Under detta driftstopp så kommer LHC's injektionsanordningar att uppgraderas för att kunna sätta fler protoner i circulation i LHC, och därmed öka antalet partikelkollisioner per tidsenhet. Denna uppgradering kommer att vara första steget i "High Luminocity LHC"-programmet som kommer att realiseras år 2024-2026. LHCb-experimentet, vars främsta syfte är att studera CP-brott, kommer också att uppgraderas under stoppet 2019-2020. Framför allt så ska avläsningsfrekvensen ökas från dagens 1MHz till 40MHz, och experimentet ska förberedas för de högre strålningsdoser som kommer att bli aktuella efter stoppet 2024-2026. En av LHCb's deldetektorer, TT detektorn, kommer att bytas ut mot en ny deldetektor som kallas UT. Den här rapporten presenterar den förberedande designen av den låda som ska isolera UT från dess omgivning och försäkra optimala förhållanden för detektorn. Kraven på den isolerande lådan och tillvägagångssätt för att uppfylla dessa krav presenteras. / LHCb, LS2 and LS3 Upgrade