Carbon fibre-reinforced plastics (CFRP) are widely used in aerospace, automobile and other structural applications due to their superior mechanical and physical properties. CFRP outperform conventional metals in high strength-to-weight ratio. Usually, CFRP parts are manufactured near to net-shape;however,machining is unavoidable when it comes to assembly. Drilling the holes are essential to facilitate riveting and bolting of the components. However, conventional drilling (CD) induces different types of damages such as cracking, fibre pull-out, sprintling and delamination due to the abrasive nature, inhomogeneity and anisotropy of CFRP. A novel technique, ultrasonically-assisted drilling (UAD) is hybrid machining technique in which highfrequency (typically above 20 kHz) vibration are superimposed on a standard twist drill bit in axial direction using ultrasonic transducer. UAD has shown several advantages such as thrust force reduction, improving surface quality and lower bur-formation in drilling of conventional metals. UAD has also effectively been used for drilling brittle materials.

Carbon-fibre reinforced polymer (CFRP) laminates are widely used in various engineering applications, such as in race cars and aircrafts, because they are light, stiff and strong. They commonly contain stress raisers in the form of holes and notches (for mechanical joining methods, routing of pipes and cables etc.) and are also often subjected to complex combined multi-axial stress conditions during service. Yet their notched multi-axial fracture behaviour remains largely unexplored. This is the main contribution of the thesis. First, a novel loading fixture for applying a wide range of in-plane loading modes is developed based on the popular Arcan’s method. Termed the ‘modified Arcan rig’, it utilises friction gripping to transfer loads into tabbed specimens. This loading fixture is used to test centre-notched multi-directional CFRP laminates under different combinations of tension and shear stresses. Together with penetrant-enhanced X-ray CT and laminate de-ply, the fracture behaviour of quasi-isotropic CFRP specimens is investigated for the following loading modes: pure tension, pure compression, in-plane shear, and combined tension and shear. Two notch geometries (sharp notch and circular hole) are investigated to allow for an assessment of the role of stress concentration upon strength and damage development to be performed. Three distinct fracture modes are observed in a tensile/compressive-shear stress space (termed Mechanism A, Mechanism B and Mechanism C). It is observed that quasi-isotropic specimens with a central sharp notch are consistently stronger than equivalent specimens with a central circular hole (for all stress states investigated). An underlying micromechanical explanation concerning the effects of damage upon strength is proposed. Second, a finite element (FE) model is developed using the commercial FE program, Abaqus FEA to simulate the observed progressive damage and failure in the quasi-isotropic specimens. The FE model employs independent material property data as inputs. Overall, good correlation between the simulations and the experiments is obtained, validating the FE strategy. The capabilities of the model are extended to predict the notched fracture behaviour of the specimens under combined compression and shear loading, for which experimental work has not been done by the author, but for which literature data exists. Finally, the effect of laminate lay-up upon the notched multi-axial fracture behaviour of the CFRP specimens is explored by considering a 0° ply-dominated lay-up, a ±45° ply-dominated lay-up and a cross-ply lay-up, alongside the quasi-isotropic lay-up. Experiments reveal that all lay-ups exhibit Mechanisms A, B and C. However, the extent of damage in each Mechanism as well as the regime in which each Mechanism operates in (in the failure envelopes) strongly depend on the lay-up of the specimen. As expected, the tensile strengths and compressive strengths increase with the proportion of 0° plies. Surprisingly, the shear strengths do not scale with the proportion of ±45° plies; the specimen geometry and material orthotropy are attributed as reasons for this. In contrast to the case of the quasi-isotropic lay-up, the extent of subcritical damage induced by the circular hole is not always lower than that induced by the sharp notch for the other lay-ups. The difference in the extent of damage between both notch geometries is reflected in the notched strengths of the lay-up in question. These experimental observations are adequately predicted by the FE strategy, which further validates it as a reliable predictive tool for composite fracture.

The article at hand presents a novel approach to accelerating the early strength development of mineralimpregnated carbon-fibre composites (MCF) by electrical Joule heating. MCF were produced with a metakaolin-based geopolymer suspension and subsequently cured using Ohmic heating under systemically varied voltages and durations. The MCF produced were characterised in respect of their mechanical and morphological properties. Threepoint-bending and uniaxial tension tests yielded significant enhancement of MCF mechanical properties due to curing within only a few hours. Thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), environmental scanning electron microscope (ESEM) as well as micro-computed tomography (μCT) confirmed advanced geopolymerisation by the electrical heating process and a strong sensitivity to parameter selection. After only two hours of resistance heating MCF could demonstrate tensile strength of up to 2800 MPa, showing the great potential for applying the Joule effect as a possibility to enhance the strength development of geopolymer-based MCF. Moreover, the applied method offers a huge potential to manufacture automated fast out-of-oven cured MCF with a variety of shapes and dimensions.

Samhället ändras konstant men detta innebär inte bara en förändring för människorna i samhället utan också att nya krav ställs på konstruktionen som brukas av människorna. Många byggnadskonstruktioner kan därmed behöva en förstärkning efter en viss tid. Behovet av en förstärkning kan bero på flera orsaker exempelvis ändrat nyttjande. Det är mer fördelaktigt med en förstärkning av konstruktionen än att den rivs ner och byts ut för att klara av dagens krav. Syftet med detta examensarbete är att undersöka förstärkning av betongkonstruktioner med hjälp av kolfiberkomposit. I rapporten presenteras beräkningar som gjordes för att undersöka tillökningen i böjoch tvärkraftskapacitet efter en utförd förstärkning. Parallellt med beräkningarna kontrollerades och utvecklades befintliga mallar som finns för denna metod. För att kunna uppnå syftet undersöktes två hypotetiska betongkonstruktioner. Ena konstruktionen är en plattramsbro som modellerades i FEM programmet Brigade Standard. Beräkningar på plattramsbron gjordes med avseende på böjande moment. Den andra konstruktionen som undersöktes är en T-balk som är en del utav ett bjälklag. På T-balken granskades tvärkraftskapaciteten innan och efter en utförd förstärkning med kolfiber. I resultatet redovisas mängden kolfiber som erfordras för att uppnå önskad kapacitet hos konstruktionerna. I resultatet redogörs också kapaciteten som uppnås efter kolfiberförstärkningen. / The society changes constantly, but this does not only affect the inhabitants of the society, but also that new demands are made on the construction used by the people. Many constructions may therefore require reinforcement after a certain amount of time. The need for reinforcement may be due many different reasons for example to altered use, corrosion to internal reinforcement or may be due to design errors, accidents or new standards. It is more beneficial to reinforce the structure than to tear it down and replace it to meet current requirements. The purpose of this thesis is to investigate carbon fiber reinforced polymer, CFRP, as a method to strengthen concrete structures. The report presents calculations that were made to investigate the increase in bending and shear capacity after a performed reinforcement. Alongside the calculations, existing templates for this method were checked and developed. In order to achieve the purpose, two hypothetical concrete structures were investigated. One design is a frame bridge modeled in the FEM program Brigade Standard. Calculations on the frame bridge were made with respect to bending. The other construction that was investigated is a T-beam. On the Tbeam, shear capacity was examined before and after reinforced carbon fiber reinforcement. The result present the amount of carbon fiber required to achieve the desired capacity of the structures. The result also describes the capacity achieved after carbon fiber reinforcement.

An investigation on the application of basalt fibre reinforced polymer (BFRP) and carbon fibre reinforced polymer (CFRP) bars as longitudinal reinforcement for simple and continuous concrete slabs is presented. Eight continuously and four simply concrete slabs were constructed and tested to failure. Two continuously supported steel reinforced concrete slabs were also tested for comparison purposes. The slabs were classified into two groups according to the type of FRP bars. All slabs tested were 500 mm in width and 150 mm in depth. The simply supported slabs had a span of 2000 mm, whereas the continuous slabs had two equal spans, each of 2000 mm. Different combinations of under and over FRP (BFRP/CFRP) reinforcement at the top and bottom layers of slabs were investigated. The continuously supported BFRP and CFRP reinforced concrete slabs exhibited larger deflections and wider cracks than the counterpart reinforced with steel. The experimental results showed that increasing the bottom mid-span FRP reinforcement of continuous slabs is more effective than the top over middle support FRP reinforcement in improving the load capacity and reducing mid-span deflections. Design guidelines have been validated against experimental results of FRP reinforced concrete slabs tested. ISIS¿M03¿07 and CSA S806-06 equations reasonably predicted the deflections of the slabs tested. However, ACI 440¿1R-06 underestimated the deflections, overestimated the moment capacities at mid-span and over support sections, and reasonably predicted the load capacity of the continuous slabs tested. On the analytical side, a numerical technique consisting of sectional and longitudinal analyses has been developed to predict the moment¿curvature relationship, moment capacity and load-deflection of FRP reinforced concrete members. The numerical technique has been validated against the experimental test results obtained from the current research and those reported in the literature. A parametric study using the numerical technique developed has also been conducted to examine the influence of FRP reinforcement ratio, concrete compressive strength and type of reinforcement on the performance of continuous FRP reinforced concrete slabs. Increasing the concrete compressive strength decreased the curvature of the reinforced section with FRP bars. Moreover, in the simple and continuous FRP reinforced concrete slabs, increasing the FRP reinforcement at the bottom layer fairly reduced and controlled deflections.

The goal of the European Union is to make strides towards a circular economy. This means recycling or re-using as much of the material in the economic system as possible. The wind industry faces a great challenge in the years to come as huge quantities of increasingly larger wind turbines reach the end of their service-life. When old wind turbines have been decommissioned, most parts are scrapped and recycled into other applications. The turbineblades however are made from glass- and carbon fibre polymers and are not as easily recycled. Recent bans of putting the blades into landfills steer the industry toward finding new applicationfor the old wind turbine blades. Re-purposing the blades as bridges, shelters, houses and towers has been suggested, as well as re-cycle the material or recover the blades as energy. Regardless of what method is preferred, the wind turbine blades need to be transported to a re-purpose or recycling facility. Because of the distribution of wind turbines within countries, the optimal location of such facilities can be hard to evaluate. The centre-of-gravity method (evaluating the centre-of-mass) has been suggested as a way of evaluating the optimal location of such facilities. The method is built upon the assumption that the wind turbine blade can be easily downsized, transported and accommodated in a single transport. In order to achieve this, the present thesis has compared and evaluated different methods of segmenting the wind turbine blade (mechanical, thermal and chemical) as well as different loading and compressing methods. The mechanical separation methods tend to be more suitable than the thermal and chemical counterparts. The choice of loading methods is dictated by the resulting fraction size of the wind turbine blade after separation. The mass density of the resulting blade could be increased with a suitable way of compression (hydraulic or gravity).

Fast Scan Cyclic Voltammetry (FSCV) is an electrochemical technique, based on ramping a voltage through a microelectrode and measuring the resulting redox current to obtain information about an electroactive molecule. FSCV can be used for the detection of dopamine, which is a vital neurotransmitter. Dopamine is central to conditions such as Parkinson’s disease. The purpose of this thesis was to evaluate if a new type of highly biocompatible microelectrode, called tube electrode, can be used to detect dopamine using FSCV and determine how they compare to standard carbon fibre microelectrodes (CFMEs). In order to achieve this, three main tasks were set and fulfilled. First, a station for in-vitro FSCV was set up and CFMEs of varying sizes were used to detect dopamine at different concentrations. Secondly, the same trials were done with tube electrodes. Finally, the results of the tubes were compared to the CFMEs. In total, four CFMEs and four tube electrodes were investigated. The dopamine concentrations ranged from 20 nM to 40 μM. In short, the results indicate that the tubes generally have lower sensitivity than the CFMEs but better linearity between the increasing dopamine concentration and the resulting current. The tubes also had a marginally higher concentration threshold for dopamine detection. The main challenge encountered was a decrease in sensitivity over time. Here, further investigations are necessary to map the causes responsible. In conclusion, the tube electrodes are able to detect dopamine in-vitro, with concentrations relevant for in-vivo sensing, with a performance comparable to CFMEs. However, further studies are necessary before the tube electrodes can be used for dopamine detection in-vivo. / Fast Scan Cyclic Voltammerey (FSCV) är en elektrokemisk teknik, baserad på att ändra en spänning genom en mikroelektrod och sedan mäta den resulterande redox-strömmen för att få information om en elektroaktiv molekyl. FSCV kan användas för detektering av dopamin, som är en livsviktig signalsubstans. Dopamin har en central roll vid tillstånd så som Parkinsons sjukdom. Syftet med detta examensarbete var att utvärdera om en ny typ av mycket biokompatibel mikroelektrod, kallad tubelektrod, kan användas för att detektera dopamin genom FSCV och fastställa hur de jämför sig med vanliga kolfibermikroelektroder (KFME). För att uppnå detta sattes och uppfylldes tre huvuduppgifter. Först upprättades en station för in-vitro FSCV där KFME med varierande storlek användes för att detektera olika koncentrationer dopamin. Sedan gjordes samma försök med tubelektroder. Slutligen jämfördes resultaten med de från KFME. Totalt testades fyra KFME och fyra tubelektroder. Dopaminkoncentrationerna sträckte sig från 20 nM till 40 μM. Kort sagt indikerar resultaten att tuberna generellt hade lägre känslighet än KFME men bättre linjäritet mellan den ökande dopaminkoncentrationen och den resulterande strömmen. Tuberna hade även något högre koncentrationströskel för detektionen av dopamin. Den största utmaningen som påträffades var en minskning i känslighet över tid. Här krävs vidare undersökningar för att helt förstå de bakomliggande anledningarna. Slutsatsen är att tuberna kan detektera dopamin in-vitro, med koncentrationer som är relevanta för mätningar in-vivo, och med en prestation jämförbar med den för KFME. Dock krävs mer studier innan tubelektroderna kan användas för att detektera dopamin in-vivo.

Fiber reinforced plastics are composite materials that offer a lower weight, while still mechanically perform at least as good as conventional materials such as steel. This makes them attractive for the automotive industry since the implementation of them in e.g. a car frame would enable the manufacturers to sell a more fuel efficient vehicle to the customer. The manufacturing of composites is however more energy intense than for steel and the recycling capabilities are limited. This encourages the car designer to regard the product from a macro-perspective, spanning from the extraction of the resources needed to produce the material, to the phase where the product which the material constitutes is disposed. By analyzing such a macro-perspective, the life cycle energy of a product system can be estimated. Since the life cycle energy is correlated to the component design, an optimization problem can be established where the objective function to be minimized is the total life cycle energy. The component design can be expressed in terms of optimization design variables, yielding that the minimum energy is achieved by the optimal design. This methodology is called life cycle energy optimization (LCEO). The aim of this thesis is to apply this method and present a comparison between different materials and recycling strategies for a load carrying frame component provided by Volvo Cars. The materials studied are carbon fiber reinforced plastics (CFRP), glass fiber sheet moulding compound (GF-SMC) and conventional steel. A Python model consisting of five life cycle phases where each phase was described by a function was implemented. Each function uses the component geometry and material properties as an input and gives the energy of the phase as an output. By summing the outputted energies, the life cycle energy is obtained. The distribution of the results is visualized with bar plots. The results show that the least energy demanding option is to manufacture the component in GF-SMC and process the end-of-life product mechanically. If the fiber degradation is taken into account, the most efficient strategy is to manufacture the component in CFRP and recycle it using solvolysis. This thesis shows that the LCEO methodology can be used as a tool for designers to include the recyclability in an early phase of the product development. Future challenges concern the development of industrial recycling of fiber reinforced plastics where the fiber degradation is minimized. / Fiberförstärkta polymerplaster är kompositmaterial som erbjuder en lägre vikt än konventionella material som stål, samtidigt som de bibehåller den mekaniska prestandan. Detta gör dem intressanta för fordonsindustrin då nyttjandet av dem skulle möjliggöra tillverkare att sälja bränsleeffektivare bilar. Tillverkningen av sådana kompositer är dock mer energikrävande än den för stål och deras återvinningsmöjligheter är begränsade. Detta skapar för fordonsformgivaren ett incitament att beakta produkten i ett makroperspektiv som sträcker sig från utvinningen av naturresurserna för att skapa materialet, till slutskedet av produktens avsedda användning. Genom att bestämma hur den ackumulerade energin är fördelad i ett sådant makroperspektiv kan den total livscykelenergin beräknas. Eftersom livscykelenergin är kopplad till komponentens formgivning, kan ett optimeringsproblem med livscykelenergin som målfunktion att minimeras ställas upp. Komponentens formgivning kan uttryckas som optimeringsproblemets designvariabler. Den design som ger den lägsta livscykelenergin blir därmed den optimala formgivningen. Denna metod kallas livscykelenergioptimering (LCEO). Målet med detta examensarbete är att tillämpa denna metod på en lastbärande bilkomponent tillhandahållen av Volvo Cars och genomföra en jämförelseanalys mellan olika material samt återvinningsstrategier. Materialen som undersöks är kolfiberförstärkt härdplastkompist (CFRP), sheet moulding compound med glasfiber (GF-SMC) och konventionellt stål. Den Pythonimplementerade modellen består av fem livscykelfaser där varje fas uttrycks om en funktion med komponentgeomterin samt materialegenskaperna som indata och ger energiåtgången för fasen som utdata. Genom att summera energierna erhålls livscykelenergin och genom att presentera resultaten i ett stapeldiagram kan livscykelenergidistributionen visualiseras. Resultaten visar att det minst energikrävande alternativet är att tillverka komponenten i GF-SMC och återvinna produkten genom mekanisk bearbetning. Om hänsyn tas till fiberslitage blir den optimala lösningen att tillverka komponenten i CFRP och återvinna den genom solvolys. Detta arbete visar att LCEO- metoden, i ett tidigt skede, kan användas som ett verktyg av formgivare för att inkludera hur väl en produkt kan återvinnas. Framtida utmaningar består av att utveckla återvinningen av fiberförstärkta härdplaster industriellt, så att fiberslitaget minimeras.

Thesis (M. Tech.) -- Central University of Technology, Free State, 2010 / The aim of this study is to produce more cost effective carbon fibre (CF) parts. To achieve this there must be a saving on materials, labour and time. Thus, a production process to produce cost effective CF moulds while saving time and money is required. This procedure must be suited for the incorporation in the small to medium production ranges. The composite industry is one of the fastest growing industries in the world. Therefore, the faster a mould can be produced, the faster the end product will reach the market. This research project investigates the possibility to sinter CF moulds on the Electro Optical Systems (EOS) Laser Sintering (LS) machine cheaper and faster than the conventional method using computer numerically controlled (CNC) machining. The surface finish produced on the LS machine is not of the same quality as a CNC machined mould, but there are ways to enhance the surface quality of a LS part to the point that it is compatible to the surface quality of a CNC machined mould. The CF moulding process uses many different types of moulding processes. However, it is not possible to use LS parts for all of the available processes to produce CF parts. In this study only one CF moulding process will be investigated, namely compression moulding. The moulds will be designed to be manufactured as cheaply and as quickly as possible. Different methods of mould adapting have been studied to find the cheapest most suitable method of mould design for the LS process.

Hydraulic systems are used in many fields of applications for different functions like energy storage in hybrid systems. Generally the mass of hydraulic systems plays a key role especially for mobile hydraulics (construction machines, trucks, cars) and hydraulic aircraft systems. The main product properties like energy efficiency or payload can be improved by reducing the mass. In this connection carbon fiber reinforced plastics (CFRP) with their superior specific strength and stiffness open up new chances to acquire new lightweight potentials compared to metallic components. However, complex quality control and failure identification slow down the substitution of metals by fiber-reinforced plastics (FRP). But the lower manufacturing temperatures of FRP compared to metals allow the integration of sensors within FRP-components. These sensors then can be advantageously used for many functions like quality control during the manufacturing process or structural health monitoring (SHM) for failure detection during their life cycle. Thus, lightweight hydraulic components made of composite materials as well as sensor integration in composite components are a main fields of research and development at the Institute of Lightweight Engineering and Polymer Technology (ILK) of the TU Dresden as well as at the Leichtbau-Zentrum Sachsen GmbH (LZS).