A novel photocrosslinkable and melt processible terpolymer precursor for carbon fibers has been successfully synthesized and characterized. The terpolymer was synthesized by an efficient emulsion polymerization route and has a typical composition of acrylonitrile/ methyl acrylate/acryloyl benzophenone in the molar ratio of 85/14/1. This thesis describes a systematic variation of the polymerization variables in the emulsion polymerization which may further enhance the system. In particular, the effects of chain transfer agent, initiator, and surfactant concentration on the polymer properties were studied. / Master of Science

Low velocity drop weight impact tests were conducted on carbon/epoxy laminates under various magnitudes of uniform tensile stress. The composite plates were 8 ply (+45,0,- 45,90)_s laminates supported in a clamped-clamped/free-free configuration. Tensile preloads from near zero to approximately 60% of ultimate breaking strength were applied to specimens which were impacted at energies of 3.4, 4.5 and 6 Joules (2.5, 3.3 and 4.4 ft- Ibs). The amount of damage induced into the specimen was evaluated using instrumented impact techniques, x-ray inspection and cross-sectional photomicroscopy. Some static indentation tests were performed to examine if the impact events utilized in this study were of a quasi-static nature and also to gain insight into the shape of the deflected surface at various preload/transverse load combinations. Load-displacement curves from these tests were compared to those of the impact tests as was damage determined from x-ray inspection. The finite element technique was used to model the impact event and determine the stress field within the laminae. Results showed that for a given impact energy level, more damage was induced into the specimen as the tensile preload was increased. The majority of damage observed consisted of back face splitting of the matrix parallel to the fibers in that ply, associated with delaminations emanating from these splits. Tensile preloads tended to increase the length of these splits. The analysis showed qualitatively the results of tensile preloads on maximum load of impact, maximum transverse deflection and first failure mode and location. / Ph. D.

This bachelor’s thesis investigates the feasibility of designing a lightweight, aero-dynamic child bike trailer using composite materials for its main structural ele-ments. The project encompasses theoretical design, finite element analysis (FEA),and computational fluid dynamics (CFD) to optimize the structure for weight re-duction and improved aerodynamics while ensuring strength. Key considerationsinclude material selection, laminate stiffness, and manufacturing methods. Thestudy provides a plan for future prototype development. Findings suggest that acomposite-based design can significantly reduce weight and enhance aerodynamicperformance compared to traditional materials and structural design.

This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material. Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.

This work correlates the chemistry of phenol-formaldehyde (PF) resins, its functionalities with their microstructural and mechanical properties in composite materials. The main focus is put on the development of the pores in dependence on the chemical composition of the resins and their influence on the structure of the material. Chemical characteristics of the synthesized resins are analyzed and physical/mechanical properties of the matrices based on PF resins are determined. Differences in the chemical properties are detected e.g. by FT-IR and NMR spectroscopy. They indicate the existence of similar molecular basic structure units, but different network conditions of the resins. DSC investigations point on different reaction mechanisms and temperatures; they reveal also their changed thermal behavior. The bulk matrix behavior differs from that of the composite based on the same resin due to the three dimensional stress and strain fields in the composites. The structure of the CFRP composites is strongly depended on the fiber/matrix interaction. The fiber matrix bonding (FMB) strength controls the load transfer via shear forces and therefore the segmentation of the fiber bundles.:1 Introduction 2 Theoretical Overview 2.1 Phenol-Formaldehyde Resins 2.1.1 Overview 2.1.2 Reactions of phenol-formaldehyde resin 2.1.2.1 Addition reaction 2.1.2.2 Condensation reaction 2.1.2.3 Curing 2.1.3 Application of phenol-formaldehyde resin 2.2 Carbon-Fiber 2.2.1 PAN type carbon fiber 2.2.2 Pitch type carbon fiber 2.2.3 Application of carbon fiber 2.3 Composites 2.3.1 Carbon fiber composites 2.3.2 Matrix 2.3.3. Interfaces 2.3.3.1 Carbon fiber side interface between carbon fiber and matrix 2.3.3.2 Matrix side interface between carbon fiber and matrix 2.3.3.3 Toughening of fiber-reinforced polymer 3 Goal and Works 3.1 Problem and Motivation 3.2 Objective and Works plan 4 Experiments and Methods 4.1 Materials 4.1.1 Chemical reagents 4.1.2 Carbon fiber weave 4.2 Synthesis of Resin 4.3 Fabrication of Matrix 4.4. Measurement methods and Experimental approach 4.4.1 Chemical analysis 4.4.2 Microstructure characterization 4.4.3 Mechanical test 5 Chemical characterization of modified phenol-formaldehyde resin 5.1 Fourier Transformed Infrared spectroscopy (FT-IR) 5.1.1 Introduction 5.1.2 Preparation and Measurement 5.1.3 Results and Discussion 5.2 Nuclear Magnetic Resonance spectroscopy (NMR) 5.2.1 Liquid 13C Nuclear Magnetic Resonance spectroscopy 5.2.1.1 Introduction 5.2.1.2 Preparation and Measurement 5.2.1.3 Results and Discussion 5.2.2 Solid 13C CP-MAS Nuclear Magnetic Resonance spectroscopy 5.2.2.1 Introduction 5.2.2.2 Preparation and Measurement 5.2.2.3 Results and Discussion 5.3 Simultaneous Thermal Analysis (STA) 5.3.1 Introduction 5.3.2 Preparation and Measurement 5.3.3 Results and Discussion 5.3.3.1 Simultaneous Thermal Analysis 5.3.3.2 Different Scanning Calorimetry 5.4 Conclusion 6 Microstructural Characterization 6.1 Porosity 6.1.1 Introduction 6.1.2 Preparation and Measurement 6.1.3 Results and Discussion 6.1.3.1 Density 6.1.3.2 Porosity 6.2 Morphology 6.2.1 Introduction 6.2.2 Preparation and Measurement 6.2.3 Results and Discussion 6.2.3.1 Optical Microscopy 6.3.3.2 Scanning Electron Microscopy 6.3.3.2.1 Observation of the bulk matrix 6.2.3.2.2 Structural observation of the composite 6.3 Conclusion 7 Mechanical Properties 7.1 Hardness test 7.1.1 Introduction 7.1.2 Preparation and Measurement 7.1.3 Results and Discussion 7.2 Micro-bending test 7.2.1 Introduction 7.2.2 Preparation and Measurement 7.2.3 Results and Discussion 7.3 Conclusion 8 Summary and Conclusion 8.1 Summary 8.2 Conclusion 9 References

I dagsläget är de flesta broar i Sverige tillverkade med betong eller stål. Dessa broar är många gånger förknippade med stora kostnader som ofta beror på underhåll och reparation. FRP, som står för Fiber Reinforced Polymer, är ett relativt nytt material i bärande stommar men är ett väl etablerat material i förstärkningssammanhang. I Europa och i synnerhet Nederländerna finns det flertal broar byggda i FRP. Men på grund av brist på normer och regelverk att luta sig emot sker det sällan någon form av brokonstruktion med FRP i Sverige. Detta examensarbete syftar till att undersöka befintliga normer och studera hur materialet FRP används vid förstärkning och konstruktion av broar. Vidare syftar även arbetet till att undersöka egenskaperna hos FRP som byggmaterial och jämföra det med konventionella material som stål och betong. FRP, också benämnd fiberkomposit, är ett kompositmaterial som kan sammanställas på flera olika sätt. Genom olika material som kombineras och olika tillverkningsprocesser som används kan man på så sätt ge individuell utformning till materialet för dess användning. Fördelarna med FRP är många, men i allmänhet har det god styrka, god beständighet samtidigt som det har en låg vikt. Detta resulterar i att inom brokonstruktion så ger det strukturen en minskad egenvikt, vilket i sin tur underlättar en mängd olika saker. Detta arbete visar på att FRP-material har fördelaktiga egenskaper och kan i vissa situationer vara mer gynnsamt att använda än stål eller betong. Dock som tidigare påpekat saknas det specifika Eurokoder för detta material. Däremot är vi säkra på att introduktionen av en ny Eurokod samt med uppmuntran från myndigheter kommer användningen av FRP inom brokonstruktion utan tvekan öka. / At present, most bridges in Sweden are made with concrete or steel. These bridges are often associated with high costs, which often depend on maintenance and repair. FRP, which stands for Fiber Reinforced Polymer, is a relatively new material in load-bearing structures but is a well- established material in the context of reinforcement. In Europe and in particular the Netherlands, there are several bridges built in FRP. But due to a lack of norms and regulations to lean against, there is rarely any kind of FRP bridge construction in Sweden. The aim of this thesis is to examine existing norms and study how the material FRP is used in the reinforcement and construction of bridges. Furthermore, this thesis also aims to investigate the properties of FRP as building material and compare it with conventional materials such as steel and concrete. FRP, also called fiber-composite, is a composite material that can be assembled in several different ways. Through various materials that are combined and different manufacturing processes used, one can thus provide individual designs for the material. The benefits of FRP are many, but generally it has good strength, good durability while having a low weight. This results in that within bridge construction, it gives the structure a reduced self-weight, which in turn facilitates a variety of things. This thesis shows that FRP materials have advantageous properties and in some situations can be more favorable to use than steel or concrete. However, as previously pointed out, there are no specific Eurocodes for this material. However we are sure that the introduction of a new Eurocode and encouragement from authorities will undoubtedly increase the use of FRP in bridge construction.

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Approved for public release, distribution is unlimited / Present-day high power microwave devices suffer from a lack of reliable, reproducible cathodes for generating the requisite GW-level electron beam in a vacuum. Standard explosive emission cathode pulse durations have been limited to 10's or 100's of ns due to the expansion of cathode-generated plasma and the ensuing impedance collapse that debilitates microwave output. Traditional thermionic cathodes do not suffer from this drawback of plasma generation, but have not yet been able to provide the required emission current densities explosive emission cathodes are capable of. It is expected that if the plasma could be made cooler and less dense, explosive emission would be more stable. Cesium iodide (CsI) has been found to slow the impedance collapse in many explosive emission cathodes. Herein we will experimentally examine diode impedance collapse, gas production, and cathode conditioning in an effort to perform an evaluation of explosive cathode performance in a typical thermionic electron gun environment. These results will then be used to help demarcate the parameter space over which these CsI-coated carbon fiber cathodes are viable candidates for the electron beam source in next-generation high power microwave devices. / Lieutenant, United States Navy

Im Luftfahrtbereich haben sich kohlenstofffaserverstärkte Kunststoffe (CFK) wegen ihrer hohen spezifischen Festigkeiten und Steifigkeiten längst als Konstruktionswerkstoffe etabliert. In der Großserienfertigung von Automobilkarosserien kommt diese Materialgruppe jedoch nur zögerlich zum Einsatz. Offensichtlich sprechen noch viele Argumente für den Einsatz von metallischen Werkstoffen: Denn auch Leichtmetalle und pressgehärtete Stähle ermöglichen immer höhere Leichtbaugrade, ohne dabei signifikante Kostensteigerungen zu generieren. Zudem sind Fertigungs- und Montageabläufe für Metallkarosserien etabliert und weitgehend frei von Entwicklungsrisiken. Vor diesem Hintergrund erscheint es schwer, mit neuen Leichtbaumaterialien und den zugehörigen Bauweisen einen Durchbruch erzielen zu können. Dabei zeigt das Produktsegment der Supersportwagen schon deutlich, dass zusätzliche Leichtbaupotentiale durch beanspruchungsgerecht gestaltete und optimierte CFK-Strukturen für den Automobilbau eröffnet werden. Bislang lassen sich derartig optimierte CFK-Strukturen jedoch kaum wettbewerbsfähig in Großserie realisieren. An dieser Stelle ergeben sich Chancen und zugleich neue Herausforderungen für die Produktentwickler: Zum einen sind Faserverbundbauweisen zu erarbeiten, mit denen die Leichtbaupotentiale von CFK weitgehend ausgereizt werden. Zum anderen ist die automatisierte Fertigung bei hohen Taktraten zu ermöglichen. Die Lösung beider Teilaufgaben setzt den Einsatz geeigneter materialspezifischer Konstruktionsmethoden voraus.

[pt] Neste trabalho é realizado o estudo experimental de oito vigas de concreto armado de seção T (cm bw=15cm e cm h=40cm), com 300 cm de comprimento, biapoiadas e com a mesma armadura longitudinal, reforçadas à força cortante com compósitos de fibras de carbono (CFC). As mesmas foram divididas em duas séries de quatro vigas, com uma viga de referência para cada série, onde a taxa de armadura transversal interna foi maior para a Série I do que para a Série II. Para as três vigas reforçadas de cada série variou-se o número de camadas do reforço em CFC por meio de estribos em U, os quais foram ancorados longitudinalmente por meio de faixas desse compósito. A colagem do CFC foi executada após o surgimento das primeiras fissuras diagonais no trecho de maior cortante. Os resultados dos ensaios mostraram que as vigas reforçadas apresentaram um aumento mínimo de resistência à força cortante de 36% em relação às respectivas vigas de referência, e que a ruptura de todas as vigas ocorreu por tração diagonal, com o descolamento do CFC na região de sua ancoragem. O modelo cinemático e do ACI-440 (2001) apresentaram resultados mais próximos aos dos ensaios realizados para a resistência total da força cortante. O resultado experimental da parcela da força cortante resistida pelo CFC apresentou resultados superiores aos calculados por diversos modelos teóricos, e os resultados mais consistentes foram os modelos da FIB-Bulletin 14 (2001) e Khalifa e Nanni (2002). A análise de diversos parâmetros mostrou que o fator de efetividade Vf do reforço diminui quando a rigidez E(f)P(f) do CFC aumenta, portanto, há um menor acréscimo de resistência total à força cortante. / [en] This analysis involves the experimental study of eight reinforced concrete beams of T section ( cm bw=15cm e h=40cm), with cm 300cm of length, bisupported and with the same longitudinal reinforcement, strengthened for shear force with carbon fiber composites (CFC). They were divided in two series of four beams, with a reference beam for each series, where the internal transversal reinforcement ratio was greater for Serie I than Serie II. For the three strengthened beams of each series the number of layers of the reinforcement in CFC made by U stirrup varied, which were anchored longitudinally by stirrups of this composite. The CFC glue was done after the first diagonal cracks in the shear region. The results of the tests showed that the strengthened beams had a minimum increase of shear force of 36% in relation to the respective reference beams and the rupture of them occurred due to diagonal tension, with the CFC debonding in the region of its anchorage. The cinematic (upper-bound solution) and ACI-440 (2001) model presented results close to the experimental results for the shear strength. The experimental result of the shear force parcel resisted by the CFC presented superior results to the calculated by diverse theoretical models, and the most consistent ones were FIB-Bulletin 14 (2001) and Khalifa and Nanni (2002) models. The analyses of diverse parameters showed that the strengthening effectiveness Vf decreases when the rigidity E(f)P(f) of CFC increases, therefore there is a lesser increase of total strength to the shear force.