Dissertations / Theses on the topic 'Fibre-reinforced composites'
To see the other types of publications on this topic, follow the link: Fibre-reinforced composites.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Fibre-reinforced composites.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bisanda, Elifis T. N. "Sisal fibre reinforced composites." Thesis, University of Bath, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278675.
Full text
2
Farooq, Mohammed. "Development of FRP based composite fibre for fibre reinforced cementitious composites." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57668.
Full textAbstract:
This thesis describes a method of development of a novel fibre based on fibre reinforced polymers (FRP), for use fibre reinforcement in concrete. Thermosetting epoxy resin matrix were reinforced with E-glass, S-glass, and Carbon fibre to produce different types of composite fibres. The FRP panels were produced using the Vacuum Infusion technique, and then cut to different fibre sizes. The volume fractions of reinforcements within the FRP fibre were controlled by using woven and unidirectional fabrics. The number of layers of reinforcing fibres were also changed, to obtain the optimal thickness of the fibres. The FRP material was characterized by means of tensile tests and microscope image analysis. Four different compositions of FRP were produced with tensile strengths ranging from 195 MPa to 950 MPa. The different combinations in geometry broadened the total number of fibres investigated to 12. Single fibre pullout tests were performed to obtain the fundamental fibre-matrix interfacial bond parameters for the different FRP fibres. The FRP fibres, being hydrophilic, along with having a unique rough surface texture, showed a good bond with cement matrix. A bond strength superior to industrially available straight steel fibres and crimped polypropylene fibres has been observed. The 3 best fibres were then chosen to examine the flexural behaviour FRP fibre reinforced concrete beams. The optimized FRP fibres, one each of Glass FRP and Carbon FRP were then further investigated to study the effect of matrix maturity, temperature, fibre inclination, and loading rate on the fibre-matrix interfacial behaviour using single fibre pullout tests. Scanning Electron Microscope (SEM) analysis was carried out to identify the effect of above-mentioned factors on the surface characteristics of the fibre. An attempt was also made to optimize the fibre-matrix interface to achieve an optimized failure mechanism by coating the fibre with oil. The ability of the fibre to transfer stresses across a cracked section over extended periods has been investigated by means of fibre-relaxation tests. Finally, to assess durability, the fibres were conditioned at high pH and high temperature after which single fibre pullout, direct tension tests, & SEM analysis were conducted.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
3
Shawkataly, Abdul Khalil H. P. "Acetylated plant fibre reinforced composites." Thesis, Bangor University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267327.
Full text
4
Ho, Christopher Sui-keung. "Mesostructure quantification of fibre-reinforced composites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ49722.pdf.
Full text
5
Dyer, S. J. R. "Elastic anisotropy in fibre reinforced composites." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373548.
Full text
6
Wooldridge, Andrew. "Fibre reinforced composites via coaxial electrospinning." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/95272/.
Full textAbstract:
This study shows that an all-thermoplastic (nano- or micro-fibre) polymer can be created using coaxial electrospinning to create fibre mats akin to pre-impregnated fabric, which can be formed into a composite without the addition of other materials. This has not yet been accomplished by using the coaxial electrospinning production process. Experimentation to investigate the maximum fibre volume ratio found that these composites were successfully formed at 0.73 fibre volume fraction, which is higher than the maximum found in traditionally formed composites (0.60 – 0.70). The formation of the composite from the fibre mats was investigated, and found that the composites formed at the lowest temperature and pressure (70 °C and 1 bar) exhibited the higher tensile strength, up to 84 % higher than at other temperatures and pressures. Higher pressure and temperature caused deformation in the reinforcing fibres, resulting in lower tensile strength. The composites were shown to have more consistent Young’s modulus and higher tensile strength compared to a composite made from the same materials, but with the fibres and matrix materials produced separately, and combined during the composite forming procedure. The finalised composite produced in this research exhibited an average Young’s Modulus of 2.5 GPa, ultimate tensile strength of 33.2 MPa, and elongation at break of 3.8 %.
7
Jia, Weiwei. "Polylactic acid fibre reinforced biodegradable composites." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/polylactic-acid-fibre-reinforced-biodegradable-composites(732904c8-584b-4fbb-b68a-3cf14dc84e9f).html.
Full textAbstract:
Polylactic acid (PLA) is a well-known biodegradable and sustainable polymer, derived from renewable agricultural sources. Its high price in the past limited its applications to mainly biomedical materials such as bone fixation devices. As the growth of awareness in global environment protection and sustainable development, PLA has attracted increased attention and development. Nowadays, the applications of PLA have been broadened into plastics, textiles and composites etc. Composites have been widely used in industrial applications for several decades, due to their high strength-to-weight ratio and good structural properties. However, most traditional composite materials are composed of two distinct fossil fuel based components. They are not eco-friendly and are difficult to recycle. This study aims at the development of PLA biodegradable composites and the optimisation of the processing parameters to achieve the best mechanical properties of PLA self-reinforced composites (PLA-SRC) for various end-uses. A variety of polymer analytical techniques were used to evaluate crystallinity, thermal properties, and chemical structures of the PLA reinforcement and matrix. Further study was carried out to assess the effects on mechanical properties of PLA-SRC caused by the processing temperature, pressure and holding time. The composites produced at high temperature and/or high pressure have significantly better matrix penetration (fibre wetting), which enhances mechanical properties. However, holding time was found to have no significant effect on the properties of PLA-SRC.
8
McCombe, Greg. "Fibre Reinforced Composites with Integrated Electromagnetic Functionality." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525467.
Full text
9
Moukhomodiarov, Rinat R. "Asymptotic models for incompressible fibre-reinforced composites." Thesis, University of Salford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402110.
Full text
10
Shyha, Islam Saad Elsayed Mohamed. "Drilling of carbon fibre reinforced plastic composites." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1353/.
Full textAbstract:
Following an extensive literature survey focusing on the machinability of carbon fibre reinforced plastics (CFRP), three main phases of experimental work were undertaken to evaluate the drilling of CFRP and associated stack materials. Phase 1 and 2 involved small diameter holes (1.5 mm) in thin CFRP laminates (3 mm thick) while Phase 3 addressed the feasibility of one-shot drilling (6.35 mm diameter holes) in multilayer workpiece stacks comprising titanium, CFRP and aluminium. Machinability was assessed in terms of tool life/wear, force/torque, hole size and geometrical accuracy, workpiece surface integrity and chip morphology.
11
Crawley, Christopher Anthony. "Thermoforming of continuous fibre-reinforced thermoplastic composites." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263704.
Full text
12
Alimuzzaman, Shah. "Nonwoven flax fibre reinforced PLA biodegradable composites." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/nonwoven-flax-fibre-reinforced-pla-biodegradable-composites(186ac2dd-0c03-497e-b984-853044fdee59).html.
Full textAbstract:
The awareness of environmental sustainability drives the composite industry to utilize natural fibres. Natural fibres are a readily available resource with a relatively low price. In this study natural fibre flax reinforced polylactic acid (PLA) biocomposites were made using a new technique incorporating an air-laying nonwoven process. Flax and PLA fibres were blended and converted to fibre webs in the air-laying process. Composite prepregs were then made from the fibre webs. The prepregs were finally converted to composites by compression moulding. The relationship between the main process variables and the properties of the biocomposite was investigated. It was found that with increasing flax content, the mechanical properties increased. As the moulding temperature and moulding time increased, the mechanical properties decreased. The physical, thermal and morphological properties of the biocomposites were also studied. The appropriate processing parameters for the biocomposites were established for different fibre contents. The biodegradability and water absorption properties of the composites were evaluated. The composites were incubated in compost under controlled conditions. The percentage weight loss and the reduction in mechanical properties of PLA and biocomposites were determined at different time intervals. It was found that with increasing flax content, the mechanical properties of the biocomposites decreased more rapidly during the burial trial. The increasing of flax content led to the acceleration of weight loss due to preferential degradation of flax. This was further confirmed by the surface morphology of the biodegraded composites from Scanning Electron Microscope (SEM) image analysis. This study also investigated the manufacturing of 3D PLA/Flax nonwoven prepregs by using a new system of 3D nonwoven web formation, and 3D biocomposite was made using these prepregs. A new mould unit for web and a new aluminium mould for biocomposite were developed. The physical properties of 3D biocomposites were investigated and it was found that there is no significant difference between 2D and 3D biocomposites in density and void content. The effects of fibre content and processing variables on the crushing behaviour, energy absorption and failure mode of 3D shell biocomposites were experimentally studied.
13
Mahmood, Amjed Saleh. "Processing-performance relationships for fibre-reinforced composites." Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/4181.
Full textAbstract:
The present study considers the dependence of mechanical properties in composite laminates on the fibre architecture. The objective is to characterise the mechanical properties of composite plates while varying the fibre distribution but keeping the constituent materials unchanged. Image analysis and fractal dimension have been used to quantify fibre distribution and resin-rich volumes (RRV) and to correlate these with the mechanical properties of the fibre-reinforced composites. The formation, shape and size of RRV in composites with different fabric architectures is discussed. The majority of studies in literatures show a negative effect of the RRV on the mechanical behaviour of composite materials. RRV arise primarily as a result of (a) the clustering of fibres as bundles in textiles, (b) the stacking sequence, and/ or stacking process, (c) the resin properties and flow characteristics, (d) the heating rate as this directly affects viscosity and (e) the consolidation pressure. Woven glass and carbon/epoxy fabric composites were manufactured either by the infusion or the resin transfer moulding (RTM) process. The fractal dimension (D) has been employed to explore the correlation between fabric architecture and mechanical properties (in glass or/ carbon fibre reinforced composites with different weave styles and fibre volume fraction). The fractal dimension was determined using optical microscopy images and ImageJ with FracLac software, and the D has been correlated with the flexural modulus, ultimate flexural strength (UFS), interlaminar shear strength (ILSS) and the fatigue properties of the woven carbon/epoxy fabric composites. The present study also considers the dependence of fatigue properties in composite laminates on static properties and fibre architecture. Four-point flexural fatigue test was conducted under load control, at sinusoidal frequency of 10 Hz with amplitude control. Using a stress ratio (R=σmin/σmax) of 0.1 for the tension side and 10 for the compression side, specimens were subjected to maximum fatigue stresses of 95% to 82.5% step 2.5% of the ultimate flexural strength (UFS). The fatigue data were correlated with the static properties and the fibre distribution, in order to obtain a useful general description of the laminate behaviour under flexural fatigue load. The analysis of variance (ANOVA) technique was applied to the results obtained to identify statistically the significance of the correlations. Composite strength and ILSS show a clear dependence on the fibre distribution quantified using D. For the carbon fabric architectures considered in this study, the fatigue properties of composite laminates have significant correlations with the fibre distribution and the static properties of the laminates. The loss of 5-6 % in the flexural modulus of composite laminates indicates an increasing risk of failure of the composite laminates under fatigue loads. The endurance limits, based on either the static properties or the fibre distribution, were inversely proportional to the strength for all laminates.
14
Chapman, Benjamin James. "Continuous fibre reinforced thermoplastic pipes." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285377.
Full text
15
Durrant, George. "The forging of saffil fibre reinforced aluminium." Thesis, University of Bath, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317301.
Full text
16
Bunpot, Mai-Ngam. "Strength prediction in short fibre-reinforced thermoplastics." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326535.
Full text
17
Winfield, P. H. "Toughness development in fibre reinforced metals." Thesis, Cranfield University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259794.
Full text
18
Manarakis, George S. "Properties and applications of fresh fibre reinforced concrete." Thesis, University of Aberdeen, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262346.
Full textAbstract:
Concrete is possibly the most widely used man-made construction material in the world. Low cost, versatility and adequate compressive strengths are reasons for the popularity of concrete construction. In the present investigation various properties of polyproplene and steel fibre reinforced cementitious composites in their plastic state, which influence slipforming (Chapter 3), such as early age shrinkage (Chapters 4, 5) and uniaxial tensile strength (Chapter 6) are investigated, while properties of the same mixes in their hardened state such as compressive and tensile splitting strength are also determined (Chapter 9). Three new experimental apparatae were developed during this investigation - one for the determination of the tensile stress-strain curve of fresh concrete (Chapter 6) and two for the investigation of early age shrinkage cracking of fresh concrete (Chapter 7). Theoretical aspects relating to the obtained experimental results were also considered (Chapters 6, 8). The experimental data was analysed by a digital computer with the aid of five FORTAN 77 computer programmes which were written by the author specifically for this purpose (Chapter 10).
19
Davenport, Simon Bruce. "Fatigue response of fibre reinforced aluminium-lithium laminates." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261787.
Full text
20
Shipton, Paul David. "The compounding of short fibre reinforced thermoplastic composites." Thesis, Brunel University, 1988. http://bura.brunel.ac.uk/handle/2438/5788.
Full textAbstract:
It is generally accepted that the mechanical properties of short fibre reinforced thermoplastics do not correspond with the high mechanical properties of fibres used to reinforce them. A study is made into the methods of compounding reinforcing fibres into thermoplastics to produce short fibre reinforced thermoplastics of enhanced properties. The initial method chosen for investigation is the twin screw extrusion compounding process. Variables such as fibre feeding arrangement and extrusion screw design are found to be factors influencing the properties of carbon and glass reinforced nylon 6,6. Use is made of computer programs to predict properties, assess compound quality and estimate fibre-matrix bond strength. Investigations indicate that the presence of reinforcing fibres with enhanced lengths does not result in the predicted property increases. The reasons for this shortfall are believed to lie in unfavourable fibre orientation in injection mouldings and the reduced strain to break of these materials. Short Kevlar reinforced thermoplastics are compounded and their mechanical properties assessed. The reasons for the poor mechanical properties for these materials are identified as a poor bond strength between fibre and matrix, the formation of points of weakness within the fibres by the compounding and moulding processes and the coiled arrangement of fibres present in injection mouldings. A method suitable for the routine assessment of fibre-matrix bond strength is used to examine combinations of fibre and thermoplastic matrix. A comparison is made of the values derived from this method with values calculated from stress-strain curves of injection mouldings. This allows an understanding of the nature of the fibre-matrix bond yielded by compounding and injection moulding steps. A description is given of a novel method designed to overcome the limitations of conventional compounding routes to produce long fibre reinforced injection moulding feedstock. Further work is necessary before this method is a feasible production technique.
21
Das, Shumit. "The interlaminar response of Z-fibre reinforced composites." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421868.
Full text
22
Hejda, Marek. "Deformation micromechanics of single glass fibre reinforced composites." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491333.
Full textAbstract:
The current work presents for the first time the application of luminescence spectroscopy in following the micromechanical deformation of glass fibre reinforced composites; this has been achieved using luminescence-active glass fibres prepared from glass doped with small amounts of Sm3+. Glass prepared in this way exhibited several relatively sharp and intense luminescence peaks observed in the range 550 nm to 700 nm. The luminescence band located at 648 nm was used for the calibration of the local strain state of the fibre due to its distinctive linear shift towards lower wavelengths with increasing strain and the factors affecting this shift were studied in detail. The fragmentation of both untreated and silane-treated Sm3+ doped glass fibre has been followed in detail and the behaviour analysed using a classical shear-lag analysis. Silane treatment slightly enhanced adhesion between glass fibre and epoxy resin, which was confirmed by a supplementary fragmentation study, which employed carbon nanotubes dispersed in the silane agent as an additional strain sensor. This work has demonstrated luminescence spectroscopy as a new significant development in the ability to follow local mechanics of the interface between glass fibres and transparent resins.
23
Daniel, Adrian Matthew. "Interfacial properties of fibre reinforced ceramic matrix composites." Thesis, University of Warwick, 1994. http://wrap.warwick.ac.uk/56665/.
Full textAbstract:
A review of ceramic matrix composites development over the past thirty years is presented, with emphasis placed on their application in gas turbine engine components. The fracture mechanics of brittle solids are outlined and the toughening mechanisms operating within continuous fibre reinforced ceramic matrix composites are discussed. The importance of the fibre-matrix interface in governing the overall mechanical properties of a composite is highlighted with respect to the micromechanical properties of interface debond fracture surface energy OJ and frictional shear stress t. Current techniques for measuring OJ and t are listed, together with their inherent disadvantages. The requirement for a micro-indentation system that can be used to measure interfacial properties via individual fibre pushing experiments across a wide range of composite systems, is discussed. The development of a unique Scanning Electron Microscope (SEM) based microindentation system is described in detail. It enables dynamic, high magnification imaging of the indentor tip and specimen contact point, and continuously records applied load and tip displacement throughout the indentation cycle. A piezoelectric load cell, coupled to a specifically developed amplifier, enables load resolution of 2mN measured up to the maximum possible of 20N. Novel capacitance displacement gauge design gives a resolution of lOnm over a l00pm range. The instrument has been used successfully to measure the interface micromechanical properties across a wide range of silicon carbide fibre reinforced glass and glass ceramic matrix composites. This data has been correlated with interface structural information obtained via Transmission Electron Microscopy (TEM) and SEM. Effects of oxidation, fatigue testing and interface pre-synthesis via fibre coating, have been measured. Fibres with diameters ranging from 7JJ;mto 150pm have been tested to demonstrate the versatility of the device for interfacial property measurement across the full range of modem ceramic matrix composites. Successful attempts have been made to correlate changes in the interfacial OJ and t to changes in overall composite mechanical behaviour. Theoretical requirements for values of G, that introduce toughness to composites have been discussed and compared to those determined by experiment. Variation of t and its effect on matrix micro-cracking and the tough!brittle property transition of a composite has been measured. Other applications that exploit the instrument's high resolution and imaging capability have been demonstrated. They include hardness and modulus measurement of individual phases in heterogeneous materials, and direct observation of controlled crack growth in ceramic composites. Ideas for the development of the instrument into a more versatile SEM based mechanical test facility are proposed.
24
Knight, Matthew G. "Numerical modelling of particulate and fibre reinforced composites." Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/7387.
Full textAbstract:
This thesis presents research into the micromechanical modelling of composite materials using numerical techniques. Composite materials are generally examined from two points of view: macromechanics and micromechanics, owing to their inherent heterogeneous nature. In this research, the material behaviour is examined on a microscopic scale, as the properties of interest, i.e. strength and toughness, are dependent on local phenomena. In general, the strength and toughness of composite materials are not as well understood as the simpler elastic properties, because in many cases the modes of failure under a given system of external load are not predictable in advance. Previous research in this field has typically involved specially designed experiments, theoretical/statistical studies, or the use of numerical models. In this study, advanced implementations of numerical methods in continuum mechanics, i.e. the boundary element and the finite element methods are employed to gain a greater understanding of composite behaviour. The advantage of using numerical methods, as opposed to experimental studies, is that the geometric and material characteristics can be investigated parametrically, in addition to the reduced time and expense involved. However, to model the complete behaviour of real composites is still not possible, due to the degree of complexity and uncertainty involved in modelling the various mechanisms of damage and failure, etc. and also due to the immense computational cost. Therefore, simplified models must be employed which are limited by their assumptions. For the preliminary studies within this thesis, geometrically simplified models are presented to provide an understanding of the influence of embedding second phase inclusions on the local stress fields, and also to validate the numerical techniques with readily available analytical solutions. These models are then extended to accommodate additional phenomena, such as inclusion interaction, spatial inclusion arrangement, material formulation, i.e. consisting of two- and three-phases of various material properties. The influence of such factors on the local stress concentrations, which play an important role in determining the strength of the composite, is analysed through a series of parametric studies. The localised toughening of composites is also considered through novel investigations into the interaction between a propagating crack with inclusions and microcracks. Through the development of the numerical models a more realistic representation of composite behaviour is achieved, which in tum, provides an improved knowledge of the factors that control strength and toughness. Such information is invaluable to composite material designers, who presently rely heavily on experimental studies to develop composite materials.
25
Papworth, Adam John. "Squeeze-casting of fibre reinforced metal matrix composites." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364201.
Full text
26
Ren, Guogang. "Fibre reinforced ceramic moulding composites manufacture and characterisation." Thesis, Queen Mary, University of London, 1999. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1710.
Full textAbstract:
Ceramic materials have considerable attraction for use in applications where the service temperatures are high and where fire performance and non-combustibility are important. Unfortunately most monolithic ceramic materials are extremely brittle which limits their use for structural applications. The development of fibre and particulate reinforced ceramic composites provides a route to achieving increased toughness in the materials, although this is often at the expense of ultimate strengths and/or the process-ability of the materials. Many reinforcing fibres used with ceramics are inherently expensive and manufacturing routes to produce fibre reinforced materials can involve high processing temperatures and are consequently expensive. A key goal of this research therefore is to develop a new type of ceramic matrix composites that combine toughness, strength and process-ability to provide a cost effective structural material. The research described in this thesis has been concerned with the development and characterisation of a series of ceramic compounds that can be moulded at modest temperatures( 130-160" C) and pressures in a manufacturing system that replicates dough moulding compounds (DMC) as used for polymeric matrix composites. The conventional polyester matrix of polymeric DMC has been replaced by a soluble inorganic system which is compounded with fibres, fillers and hardening agents to produce a paste-like or doughy substance The handle-ability of the material is determined by the viscosity of the matrix and the type or amount of fillers and additives present. The research has involved a careful set of experiments in which the formulation of the ceramic DMC has been systematically varied in order to achieve an optimum viscosity for storage and handling together with a further series of experiments studying the hardening and cure of the compounds. The mechanical properties of the compounds have been measured and additional formulation changes have been introduced to maintain desirable processing characteristics while improving mechanical properties, and in particular the impact resistance using instrumented falling weight impact machines. Finally the fire properties of the compounds have been studied using cone calorimetry and indicative furnace testing. The structure of the compound has been studied throughout the programme with various microscopic techniques and thermal analysis systems used to characterise the materials, their dispersion and changes that occurred during processing and after high temperature exposure. The final result of the programme has been the identification of a range of material formulations that can provide a tough moulding compound, capable of high temperature service use, that possesses useful structural properties and which can be processed cheaply at modest temperatures using low cost materials.
27
Grove, Stephen Michael. "Anisotropy of heat conduction in fibre-reinforced composites." Thesis, University of Plymouth, 1985. http://hdl.handle.net/10026.1/2749.
Full textAbstract:
Fibre-reinforced composites usually exhibit anisotropy of thermal as well as mechanical properties. For example, in a unidirectional carbon fibre-reinforced plastic of 60% volume fraction, the longitudinal thermal conductivity may be greater than that in the transverse direction by a factor of 50, and greater than that of the unreinforced polymer by more than two orders of magnitude. In order to evaluate the engineering applications of thermal anisotropy, this thesis concentrates on the development and validation of a generalised finite element model of heat conduction in an anisotropic medium. This uses a variational formulation of the anisotropic time-dependent heat conduction equation, and is implemented for two and threedimensional quadratic finite elements. The model may be used for the solution of problems having any combination of steady or time-dependent boundary conditions (fixed temperature, convection, radiation, heat flux and internal heat generation), as well as nonlinear properties. Anisotropy is specified by the components of the two or threedimensional thermal conductivity tensor; efficient representation of nonhomogeneous materials is achieved by the specification of properties at element integration points. Theoretical validation of the model is carried out by means of a number of mathematical solutions to orthotropic and anisotropic problems. Experimental validation is performed by comparison of calculations with measured steady-state surface temperatures on a cylindrical specimen of unidirectional carbon fibre-reinforced epoxy resin. The thermal property data for this exercise are obtained from measurements of principal thermal conductivities on absolute and comparative steady-state apparatus. The use of the finite element model in two industrial applications is briefly described. These concern thermal cycling during composite fabrication with reinforced thermoplastic tape, and an analysis of heat transfer in a composite propeller blade.
28
Diao, Hele. "Carbon fibre reinforced polymer composites with enhanced ductility." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44273.
Full textAbstract:
Carbon fibre reinforced polymers (CFRPs) have high strength and stiffness, low density, long fatigue life in the fibre direction and good corrosion resistance. Nowadays, CFRPs are been used in aeronautics, wind turbine blades, sports goods and civil industry. However, one fundamental limitation of CFRPs is their brittleness (low ductility): CFRPs fail catastrophically at a relatively low strain (1.5% to 1.8%) under the tension with little warning or residual load-carrying capacity. To overcome this weakness, there is considerable interest to enhance the ductility of CFRPs exhibiting increased failure strains under tension and more progressive, graceful failure modes. In this work, three different methods were developed to improve the ductility of unidirectional (UD) CFRPs. The first method was to introduce fibre waviness into UD composites. The fibre alignment angles of the resulting composites and control composites were assessed and it was found that fibre waviness in UD composite did result in a stepwise tensile failure mode and an enhanced strain to failure. The second method was using an air-assisted fibre tow spreading and commingling technology to manufacture continuous intermingled carbon fibre/glass fibre hybrid tows. After defining and quantifying the degree of hybridisation (at the filament level) of two carbon fibre/glass fibre hybrid tows, the one with the higher degree of hybridisation was selected to manufacture intermingled UD hybrid composites. It was found that hybridising of continuous glass and carbon fibres resulted in the composites with an increased failure strain. Moreover, these hybrid composites failed more gradually. The final method investigated for introducing ductility was the introduction of ply cuts into PEEK interleaved UD carbon fibre/PEEK composites, which were manufactured by compression moulding. The resulting cut-ply interleaved carbon fibre/PEEK composite possessed a non-linear tensile stress-strain curve and ductility strain of 0.4%, which is due to shearing of the PEEK interleaves in the overlap regions between the cut carbon fibre plies.
29
Morrisey, Ben. "Vibration Testing of Short Fibre Reinforced Polymer Composites." Thesis, KTH, Lättkonstruktioner, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261221.
Full textAbstract:
Applications of short fibre reinforced polymer composites (SFRPCs) have been rapidly increasing and most of the components made of these materials are subjected to cyclic loading. In automotive applications, “under the hood” is the harshest environmental condition for plastic-based materials with temperatures ranging from -40°C to 120°C. Components are subjected to mechanical vibrations primarily as a result of the periodic excitation and the dynamics of the engine firing. It is important, therefore, to design and test the components accurately so as to minimise the risk of component failure during the expected lifetime of the vehicle. Taking this into account, this thesis investigated if the current test methods being used at Scania ensured a valid fatigue testing of engine components made of SFRPCs. An extensive literature review was carried out detailing the work published on SFRPC fatigue to-date and the methods currently used at Scania NMBT were detailed. A series of sine and random vibration tests were then performed to characterise material behaviour in addition to Dynamic Mechanical Analysis and Scanning Electron Microscopy of failed specimens. The results of these, combined with the knowledge gathered in the literature review, resulted in a number of suggestions to adapt the current test methods with the aim of increasing their validity for SFRPCs.
30
Javanbakht, Zia. "Computational Modelling of Fibre-Reinforced Composites and Nanocomposites." Thesis, Griffith University, 2020. http://hdl.handle.net/10072/393980.
Full textAbstract:
In the current study, the major aim was to develop computationally-effective numerical procedures with the capability of modelling the thermal and mechanical response of fibre-reinforced composites. The attempt was made with a focus on the applicability of the procedures to a variety of synthetic and natural fibres with various geometrical characteristics so that a materialindependent framework is developed. The work is divided into three main stages: developing methodologies, investigating the performance of the available analytical tools, and extending the material models by numerical techniques. The finite element computational framework was used and a library of general-purpose subroutines was developed that encompassed the methodologies. Then, finite element prototypes were challenged through a variety of thermal and mechanical analyses to set up the interaction between micro- and macro-scales. Representative volume elements (RVEs) were created for a variety of short/long and aligned/randomly-oriented fibres in thermal analyses. Fibre orientation tensors were used to carry out clustering and spectral analyses in order to characterise the morphology of the heterogeneities. According to the results of sensitivity analyses, although spectral analysis seems to be less sensitive to local variation of fibre direction, it correlates better with the effective properties. Furthermore, the element elimination technique was used to indirectly model the progression of damage. This technique was used in both discrete fibre modelling and homogenised elements. It was shown that by following the latter case, mesh-independent results could be obtained. Moreover, natural fibre-reinforced composites were modelled using discrete fibre elements and a new strength-updating scheme was proposed and implemented. The numerical results showed the detrimental effect of considering length-dependent strength properties in computational modelling. Namely, the strength of fibres must be updated for the remaining portions to obtain results that are closer to the experimental one. At the final stage of the study, the localised mesoscopic data was collected through the introduced concept of auxiliary maps. Auxiliary maps of volume fraction and fibre orientation data were obtained and it was shown that their resolution should be linked to the mesh density of the model. A semi-analytical model was created to demonstrate the performance of the purposed method. The proposed models were used in single-scale elastic analyses but are able to be extended to coupled multi-scale analyses.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text
31
Liu, Tongyu. "Fibre optic sensors for strain and temperature measurements in fibre reinforced composites." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266638.
Full text
32
Farries, Pamela Mary. "Processing and properties of fibre reinforced silicon carbide composites." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/11355.
Full text
33
Hull, Brian David. "Mathematical theory of flow processes of fibre-reinforced materials." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335766.
Full text
34
Patel, Harish. "Hemp fibre reinforced sheet moulding compounds." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8783.
Full textAbstract:
Glass fibres are by far the most extensively used fibre reinforcement in thermosetting composites because of their excellent cost-performance ratio. However, glass fibres have some disadvantages such as non- renewability and problems with ultimate disposal at the end of a materials lifetime since they cannot be completely thermally incinerated. The possibility of replacing E-glass fibres with hemp fibres as reinforcement in sheet moulding compounds (SMC) is examined in this thesis. The composites are manufactured with existing SMC processing techniques and similar resin formulation as used in the commercial industry. An attempt is made to enhance/optimise the mechanical properties of hemp/polyester composites. For this the fibre-matrix interface is modified via chemical modifications with alkaline and silane treatments. Influence of hemp fibre volume fraction, calcium carbonate (CaCO3)filler content and fibre-matrix interface modification on the mechanical properties of hemp fibre-mat-reinforced sheet moulding compounds (H-SMC) is studied. The results of H-SMC composites are compared to E-glass fibre-reinforced sheet moulding compounds (G-SMC). In order to get a better insight in the importance of these different parameters for the optimisation of composite performance, the experimental results are compared with theoretical predictions made using modified micromechanical models such as Cox-Krenchel and Kelly- Tyson for random short-fibre-reinforced composites. These models are supplemented with parameters of composite porosity to improve the prediction of natural fibre composite tensile properties. The influence of impact damage on the residual exural strength of the H-SMC composites is investigated to improve the understanding of impact response of natural fibre reinforced composites. The result of penetration and absorbed energies during non-penetrating impact of H-SMC composites are investigated and compared to values for G-SMC. A simple mechanistic model has been developed for H-SMC composites and is used to get an insight into the impact behaviour of these composite as well as to provide a guideline to compare the experimental results with theoretically calculated data. The fracture toughness properties in terms of the critical-stress-intensity factor KIc, and critical strain energy release rate, GIc, of H-SMC and G-SMC composites are studied using the compact tension (CT) method. It was shown that fracture toughness of H-SMC composites is significantly lower than that of glass fibre reinforced composites (G- SMC). However, results show that with an optimum combination of fibre volume fraction, (CaCO3) filler and surface treatment of the hemp fibres can result in H-SMC composites that have fracture toughness properties that can be exploited for low to medium range engineering applications. It is recommended that to further improve the fracture toughness properties of these natural fibre reinforced composites more research needs to be devoted to the optimization of the fibre-matrix interface properties and ways of reducing porosity content in these composites. Finally, environmental impact of H-SMC composite with conventional G-SMC composite for automotive and non-automotive applications was compared. The composites were assumed to be made in a traditional SMC manufacturing method. Two different types of performance requirements; i.e. stiffness and strength were investigated for both the non-automotive and automotive parts. Two different disposal scenarios: landfill and incineration of the SMC product at the end of life was considered. The LCA results demonstrate that the environmental impact of H-SMC composites is lower than the reference G-SMC composites. G-SMC composites have a significantly higher environmental impact on climate change, acidification and fossil fuels than H-SMC composites. Where as H-SMC composites have a much higher impact on land use and ecotoxicity than G-SMC composites.
35
Rao, Sanjeev. "Manufacture of cellular solids using natural fibre reinforced composites." Thesis, University of Auckland, 2009. http://hdl.handle.net/2292/5813.
Full textAbstract:
This thesis explains the manufacturing of recyclable, eco-friendly composites and their fabrication into hollow cores. The composites have been manufactured using compression moulding and extrusion techniques; each representing batch manufacturing and continuous manufacturing respectively. A statistical design of experiments based on Taguchi method has been used to study the multivariable system involved in the process of continuous extrusion. Factorial design of experiments (DoE) has been used to determine the best material formulation to obtain maximum mechanical properties. The composite sheets produced after the DoE were pelletised in a hammer mill and reprocessed by passing them through another cycle of extrusion. The effect of recycling on the mechanical properties, which were determined by performing static tests as per ASTM standards, has been investigated. The extruded composite sheets have been thermoformed into half-hexagonal and sinusoidal profiles using matched-die and roll forming processes. As the process involves bending and stretching the sheet to conform to the geometry of the mould, it is usually accompanied by large strains. These strains have been analysed using grid strain analysis, and the strain path taken during the forming operation has been determined using strain space diagrams. Due to the stretching and bending of the composite sheet during thermoforming process, a stress field is induced in the material, which upon extraction in that state, would result in either spring-forward or spring-back of the material causing dimensional instability, but by holding the part in that deformed state for a period of time will allow the stresses in the materials to relax. This time-stress information (stress relaxation behaviour) has been experimentally investigated and modelled using springs and dashpots arranged in series and parallel. The spring-back and spring-forward phenomena, occurring in the formed part upon de-moulding, have been investigated using single curvature vee-bending experiments. The profiled sheets obtained after forming have been assembled and bonded into honeycomb cores using adhesives and ultrasonic methods. These cores have been sandwiched between two wood veneer facings to form eco-friendly sandwich panels. The compressive and shear properties of these sandwich panels have been modelled and experimentally investigated. The compressive behaviour of the sisal-PP honeycomb cores has been modelled considering the honeycomb cell wall as a linear elastic specially orthotropic plate/lamina under plane stress and as a quasi-isotropic material. A finite element model of the sandwich panel has been developed in ANSYS classic finite element environment, to study the behaviour of the panel and the core, under flexural loading. Some non-structural properties such as, sound absorption, structural damping and energy absorption have been experimentally determined. The sound absorption ability of the honeycomb has been experimentally evaluated using a standing plane wave impedance tube. Three configurations; one with hollow cores, and the other two filled with polyurethane foam and wood fibres, respectively have been tried. The natural frequencies and structural damping have been experimentally determined by subjecting the sandwich beam to harmonic vibrations. The energy absorption characteristic has been experimentally determined by subjecting the honeycomb cores to quasi-static compressive loading.
36
Liu, Yan. "Nano-reinforced epoxy resin for carbon fibre fabric composites." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/nanoreinforced-epoxy-resin-for-carbon-fibre-fabric-composites(284f8361-2530-4fc8-8abe-759ff2e57891).html.
Full textAbstract:
This thesis reports a study of the effects on processing and properties of incorporating nano-scale reinforcements (multiwall carbon nanotubes, MWCNTs) in the matrix of epoxy- carbon fibre (CF) laminate composites to produce multi-scale composites (M-SC). The main aim of this research was to study the effects of MWCNTs on matrix toughening and the through-thickness properties of M-SCs based on a commonly used aerospace grade epoxy resin — triglycidyl-p-aminophenol (TGPAP) cured with diaminodiphenyl sulphone (DDS). In order to improve resin processing, diglycidyl ether of bisphenol F (DGEBF) was added into the TGPAP/DDS system as a reactive diluent. Factorial experimental design (FED) was used to optimize the composition of this tri-component system to obtain high Tg and low resin viscosity, which gave a TGPAP/DGEBF/DDS system with 30.56 wt.% of DGEBF and a chemical stoichiometry of 0.5. Three types of MWCNTs were used; as-received (AR-), base-washed (BW-) and amine functionalized (NH2-). These were shear-mixed with both the bi- and tri-component systems using a 3-roll mill to produce nanocomposite matrices (NCM). The curing behaviour, dispersion state of MWCNTs in the resin and processability of NCMs were studied to decide upon the preparation method for the final M-SC. The fracture toughness (KIC) and the flexural properties of NCM were affected by both MWCNTs and the matrix type; thus KIC increased by up to 8 % in TGPAP/DDS NCM but decreased by 23% in TGPAP/DGEBF/DDS NCM with 0.5 wt.% AR-CNTs. The addition of both non-functionalized and functionalized MWCNTs increased the flexural modulus. The failure mechanism of NCMs was found to be dominated by the size and distribution of CNT aggregates and the behaviour of MWCNTs, both those dispersed in the matrix and in aggregates. The addition of functionalized MWCNTs increased the interfacial bonding between MWCNT and epoxy resin and thus improved the mechanical properties. All the NCM systems were taken forward to manufacture M-SC using a hybrid resin film infusion (RFI)/hot press process. The fibre volume fraction and the void content could be controlled at 43 ± 5 % for M-SC with TGPAP/DDS NCM and 60 ± 6 % for M-SC with TGPAP/DGEBF/DDS NCM. M-SCs were characterised using a range of tests, including flexural, interlaminar shear strength (ILSS), mode-II interlaminar fracture toughness (GIIC), low velocity impact and compression after impact (CAI). The most obvious improvement occurred for the M-SC with tri-component system with 0.5 wt.% CNTs, whereILSS increased by 16 % upon adding NH2-CNTs and GIIC increased significantly on addition of 0.5 wt.% AR-CNTs and NH2-CNTs, by 85% and 184% respectively. However the effect of MWCNTs on other properties was at best marginal. For example, for the M-SC with TGPAP/DDS, the flexural modulus and ILSS only increased by 4.1 % and 2.3 % with 0.5 wt.% AR-CNT.
37
Yau, Grace Chi Ying. "Repair and strengthening of columns with fibre reinforced composites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0006/MQ34125.pdf.
Full text
38
Lee, Peter. "Blow molding behaviour of wood fibre-reinforced polypropylene composites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/MQ45434.pdf.
Full text
39
Khalil, Ahmed Amir Ghobarah Ahmed. "Rehabilitation of reinforced concrete structural walls using fibre composites /." *McMaster only, 2005.
Find full text
40
Hassan, Aziz. "Compounding and characterisation of fibre reinforced polyamide 6,6 composites." Thesis, Brunel University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361088.
Full text
41
Bond, Michael David. "Multi-scale modelling of discontinuous carbon fibre reinforced composites." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/28879/.
Full textAbstract:
Discontinuous carbon fibre composites are becoming increasingly popular in the automotive and aerospace sectors, as an alternative to textile-based fibre reinforced composites for both semi-structural and structural components. Materials are highly heterogeneous, with the random architecture leading to uncertainties when modelling and predicting mechanical performance. The microscopic characteristics are known to dominate the strength of the composite, which need to be correctly represented to improve mechanical property predictions at the macroscale. This thesis presents a multi-scale modelling approach that captures the effects of microstructural (filament level) parameters at the macro scale (component level) to predict the mechanical properties of discontinuous composite materials. In the present work, a continuum damage approach has been used to initiate and monitor failure in the models at all scales, via a user defined material (UMAT), allowing strength predictions to be made for the discontinuous material within the ABAQUS solver. Experimental testing of the material constituents (fibre bundle and matrix materials) has been performed to provide input data for the finite element analyses. Micromechanical models have been developed to calculate the properties of fibre bundles, which are used directly at the meso and macroscale. Debonding criterion has also been established and validated which has been used to demonstrate that a small interface, with a thickness of only 1% of the fibre radius, can strongly influence the stress transfer between fibre and matrix materials. Interactions between multiple fibre bundles have been considered at the mesoscale, at a range of bundle orientations and separation distances. As the separation distance between the fibre bundles decreased there was an increase in stiffness 0 f the unit cell (~1.9%) across the bundle orientations considered, however, this also coincided with greater stress concentrations (up to 9.6%) being found in the bundles aligned to the direction of loading. These stress concentrations have been used to produce a comprehensive stiffness reduction scheme at the macro scale to account for the 3D nature of the bundle interactions. A 2D macro scale model is presented for generating discontinuous random fibre architectures consisting of high filament count bundles, with interfacial debonding permitted between the bundle and matrix materials. The fibre bundles are deposited randomly in a 2D plane to provide a representative material. The model has shown that the interface between the bundle and matrix material is critical at short fibre bundle lengths (~5mm) when determining the mechanical properties of the material, with reductions in strength of up to 40% observed at low interfacial shear strengths. The results from the macro scale analysis for discontinuous materials provide predictions within ~10% for tensile stiffness and ~18% for tensile strength when compared with experimental validations.
42
Daghia, Federica <1980>. "Active fibre-reinforced composites with embedded shape memory alloys." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/962/.
Full textAbstract:
This dissertation concerns active fibre-reinforced composites with embedded
shape memory alloy wires. The structural application of active materials allows to develop adaptive structures which actively respond to changes in the
environment, such as morphing structures, self-healing structures and power
harvesting devices. In particular, shape memory alloy actuators integrated
within a composite actively control the structural shape or stiffness, thus influencing the composite static and dynamic properties. Envisaged applications
include, among others, the prevention of thermal buckling of the outer skin of
air vehicles, shape changes in panels for improved aerodynamic characteristics
and the deployment of large space structures.
The study and design of active composites is a complex and multidisciplinary topic, requiring in-depth understanding of both the coupled behaviour of
active materials and the interaction between the different composite constituents. Both fibre-reinforced composites and shape memory alloys are extremely
active research topics, whose modelling and experimental characterisation still
present a number of open problems. Thus, while this dissertation focuses on
active composites, some of the research results presented here can be usefully
applied to traditional fibre-reinforced composites or other shape memory alloy
applications.
The dissertation is composed of four chapters.
In the first chapter, active fibre-reinforced composites are introduced by
giving an overview of the most common choices available for the reinforcement, matrix and production process, together with a brief introduction and
classification of active materials.
The second chapter presents a number of original contributions regarding
the modelling of fibre-reinforced composites. Different two-dimensional laminate theories are derived from a parent three-dimensional theory, introducing
a procedure for the a posteriori reconstruction of transverse stresses along the
laminate thickness. Accurate through the thickness stresses are crucial for the
composite modelling as they are responsible for some common failure mechanisms. A new finite element based on the First-order Shear Deformation Theory and a hybrid stress approach is proposed for the numerical solution of the
two-dimensional laminate problem. The element is simple and computationally
efficient. The transverse stresses through the laminate thickness are reconstructed starting from a general finite element solution. A two stages procedure is
devised, based on Recovery by Compatibility in Patches and three-dimensional
equilibrium. Finally, the determination of the elastic parameters of laminated
structures via numerical-experimental Bayesian techniques is investigated. Two
different estimators are analysed and compared, leading to the definition of an
alternative procedure to improve convergence of the estimation process.
The third chapter focuses on shape memory alloys, describing their properties and applications. A number of constitutive models proposed in the literature, both one-dimensional and three-dimensional, are critically discussed and
compared, underlining their potential and limitations, which are mainly related
to the definition of the phase diagram and the choice of internal variables. Some
new experimental results on shape memory alloy material characterisation are
also presented. These experimental observations display some features of the
shape memory alloy behaviour which are generally not included in the current
models, thus some ideas are proposed for the development of a new constitutive
model.
The fourth chapter, finally, focuses on active composite plates with embedded shape memory alloy wires. A number of di®erent approaches can be used
to predict the behaviour of such structures, each model presenting different advantages and drawbacks related to complexity and versatility. A simple model
able to describe both shape and stiffness control configurations within the same
context is proposed and implemented. The model is then validated considering
the shape control configuration, which is the most sensitive to model parameters. The experimental work is divided in two parts. In the first part, an active
composite is built by gluing prestrained shape memory alloy wires on a carbon
fibre laminate strip. This structure is relatively simple to build, however it
is useful in order to experimentally demonstrate the feasibility of the concept
proposed in the first part of the chapter. In the second part, the making of
a fibre-reinforced composite with embedded shape memory alloy wires is investigated, considering different possible choices of materials and manufacturing
processes. Although a number of technological issues still need to be faced, the
experimental results allow to demonstrate the mechanism of shape control via
embedded shape memory alloy wires, while showing a good agreement with the
proposed model predictions.
43
Pearce, Neil Robert Lewarne. "Process-property-fabric architecture relationships in fibre-reinforced composites." Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/2596.
Full textAbstract:
The use of fibre-reinforced polymer matrix composite materials is growing at a faster rate than GDP in many countries. An improved understanding of their processing and mechanical behaviour would extend the potential applications of these materials. For unidirectional composites, it is predicted that localised absence of fibres is related to longitudinal compression failure. The use of woven reinforcements permits more effective manufacture than for unidirectional fibres. It has been demonstrated experimentally that compression strengths of woven composites are reduced when fibres are clustered. Summerscales predicted that clustering of fibres would increase the permeability of the reinforcement and hence expedite the processing of these materials. Commercial fabrics are available which employ this concept using flow-enhancing bound tows. The net effect of clustering fibres is to enhance processability whilst reducing the mechanical properties. The effects reported above were qualitative correlations. Gross differences in the appearance of laminate sections are apparent for different weave styles. For the quantification of subtle changes in fabric architecture, the use of automated image analysis is essential. Griffm used Voronoi tessellation to measure the microstructures of composites made using flow-enhancing tows. The data was presented as histograms with no single parameter to quantify microstructure. This thesis describes the use of automated image analysis for the measurement of the microstructures of woven fibre-reinforced composites, and pioneers the use of fractal dimensions as a single parameter for their quantification. It further considers the process-property- structure relationships for commercial and experimental fabric reinforcements in an attempt to resolve the processing versus properties dilemma. A new flow-enhancement concept has been developed which has a reduced impact on laminate mechanical properties.
44
Hill, Paul Spencer. "The environmental degradation of fibre reinforced pultruded polymer composites." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240930.
Full text
45
El-Hofy, Mohamed Hassan. "Milling/routing of carbon fibre reinforced plastic (CFRP) composites." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5529/.
Full textAbstract:
The research relates to a study on the routing/slotting of CFRP composites of the type used in aerospace applications. Following a literature review, 3 phases of experimental work were undertaken to evaluate the effects of key process variables on the machinability of CFRP. The influence of varying operating parameters, tool material and cutting environment were initially investigated in Phase 1 work. The results showed that use of PCD was critical and highlighted the importance of chilled air in maintaining adequate tool life and acceptable workpiece integrity. Delivery of chilled air through a single-nozzle arrangement generally led to an increase in forces and delamination with the twin-nozzle configuration showing superior workpiece surface roughness. Phase 2 work detailed the effect of workpiece lay-up configuration on cutting forces, temperature and surface integrity following slotting and routing. Plies in the 45 direction generally exhibited the highest level of surface damage following machining. Experiments in Phase 3 showed that relatively small helix angles (± 3) had a negligible effect on tool life, forces and temperature. In addition, cutters with a single relief angle were found to have lower stability in operation compared to tools with a secondary clearance angle, with detrimental effects on surface roughness.
46
Dear, Matthew Nicholas. "Fatigue in SiC fibre reinforced titanium metal matrix composites." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6603/.
Full textAbstract:
The fatigue and interfacial characteristics of a unidirectional, SiC (SCS 6), fibre reinforced Ti 6Al 4V metal matrix composite have been investigated using a series of fatigue crack propagation, total life, and interfacial characterisation techniques. A room temperature crack arrest to catastrophic failure (CA/CF) transition was quantified using the initial stress intensity factor range ΔKapp. This transition occurred between 21 and 18 MPa√m in the three point bend geometry, and was found to be dependent on volume fraction of intact fibres bridging the crack. Increasing the test temperature to 300˚C had different effects on the resistance to fatigue crack growth depending on crack opening displacements and test piece stiffness. Total life fatigue tests revealed that the dominant failure mechanism was matrix fatigue cracking and fibre bridging. The extent of fatigue crack growth and fibre bridging was dependant on the applied stress and test temperature. The introduction of a dwell period at maximum load resulted in a small reduction in the total fatigue life. Post fatigue fibre push out tests identified that fatigue caused a reduction of interfacial properties below the as received levels. This reduction of interfacial properties was dependent on fatigue test temperature and initial loading conditions.
47
Chin, Chee Seong Chin. "Experimental and computational analysis of fibre reinforced cementitious composites." Thesis, Swansea University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.585523.
Full textAbstract:
A significant amount of research has been carried out on the material and structural characteristics of fibre reinforced concrete (FRC). Chapter 1 presents a literature survey of the historical background and development of FRC. New experimental data on the direct tensile, cylinder splitting, flexural, and cube crushing strengths of both plain and fibrous concretes is provided in Chapter 2. An analytical formula for predicting the direct tensile strength of FRC has also been derived. Chapter 3 comprises two tension softening models (i.e. TSM and EMIS models) for simulating the complete pre-cracking and post-cracking responses of cementitious composite. Both models have been validated using various experimental data. Chapter 4 addresses the characterization of the fiber-matrix properties where fibre pull out tests have been conducted for various types of deformed fibres. Chapter 5 covers the nonlinear finite element modelling of the deformed fibre pull out from cementitious matrix. A fibre pullout model has been developed and validated using experimental results. Chapter 6 concentrates on the simulation of the complete loaddeflection response and failure pattern of FRC flat slab at slab-column connection. Parametric studies on the slab thickness and reinforcement ratio have been conducted. Simulations of FRC flat slab and beam structures have also been performed using the EMIS model. Chapter 7 cites the details of a general analytical model for the prediction of ultimate punching shear strength of flat slab at slab-column connection. The analytical model is shown to provide reasonably good improvement when compared to several major design codes. Additionally, a unique analytical expression that provides useful information on the failure mode of flat slab has also been derived. Finally, Chapter 8 summarizes and concludes the outcomes and achievements throughout the research and possible areas for further research are suggested.
48
Haji, Kamis Haji Elmi Bin. "Three dimensional analysis of fibre reinforced polymer laminated composites." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/three-dimensional-analysis-of-fibre-reinforced-polymer-laminated-composites(0ba2ceae-129c-4d09-bdbd-de110e7b3617).html.
Full textAbstract:
The thesis presents the structural behaviour of fibre reinforced polymer (FRP) laminated composites based on 3D elasticity formulation and finite element modeling using Abaqus. This investigation into the performance of the laminate included subjecting it to various parameters i.e. different boundary conditions, material properties and loading conditions to examine the structural responses of deformation and stress. Both analytical and numerical investigations were performed to determine the stress and displacement distributions at any point of the laminates. Other investigative work undertaken in this study includes the numerical analysis of the effect of flexural deformation of the FRP strengthened RC slab. The formulation of 3D elasticity and enforced boundary conditions were applied to establish the state equation of the laminated composites. Transfer matrix and recursive solutions were then used to produce analytical solutions which satisfied all the boundary conditions throughout all the layers of the composites. These analytical solutions were then compared with numerical analysis through one of the commercial finite element analysis programs, Abaqus. Out of wide variety of element types available in the Abaqus element library, shells and solids elements are chosen to model the composites. From these FEM results, comparison can be made to the solution obtained from the analytical. The novel work and results presented in this thesis are the analysis of fully clamped laminated composite plates. The breakthrough results of fully clamped laminated composite plate can be used as a benchmark for further investigation. These analytical solutions were verified with FEM solutions which showed that only the solid element (C3D20) exhibited close results to the exact solutions. However, FEM gave poor results on the transverse shear stresses particularly at the boundary edges. As an application of the work above, it is noticed that the FEM results for the FRP strengthened RC slab, agreed well with the experimental work conducted in the laboratory. The flexural capacity of the RC slab showed significant increase, both at service and ultimate limit states, after FRP sheets were applied at the bottom surface of the slab. Given the established and developed programming codes, exact solutions of deflection and stresses can be determined for any reduced material properties, boundary and loading conditions, using Mathematica.
49
Sudarisman. "Flexural behaviour of hybrid fibre-reinforced polymer (FRP) matrix composites." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2110.
Full textAbstract:
The flexural behaviour of three different hybrid fibre-reinforced polymer (FRP) matrix composites, i.e. S2-glass/E-glass/epoxy, TR50S carbon/IM7 carbon/epoxy, and E-glass/TR50S carbon/epoxy hybrid FRP composites, has been investigated. The main objectives of this study were to: (i) improve the flexural properties of the parent composite materials, i.e. E-glass/epoxy and TR50S carbon fibre/epoxy composites, through substitution of stronger fibres, i.e. S2-glass and IM7 carbon fibres, for the fibres of the parent composite materials, and (ii) determine the optimum stacking configurations that produced the maximum increase in flexural properties of the resulting hybrid composites. In addition to these, two secondary objectives related to the preliminary investigation of determining the optimum stacking configurations have also been established. The two secondary objectives were to: (i) determine the optimum values of the processing parameters of the composites under investigation, and (ii) determine the compressive strength and compressive modulus of the parent materials.The investigation was carried out experimentally, thus data presented and analysed were obtained from laboratory work. Optimum values of five processing parameters, i.e. (i) the concentration of matrix precursor within the solvent solution utilised to wet the fibres, (ii) the compressive pressure applied during hotpress curing, (iii) the vacuum pressure of the atmosphere inside the curing chamber, (iv) the dwell time during hot-press curing, and (v) the holding temperature during hot-press curing, have been established. The criteria for determining the optimum values of these parameters were optimum fibre content, minimum void content, and optimum flexural properties. Compressive strength and compressive modulus of the parent composite materials have also been determined.Specimens were cut from flat composite plates using a diamond-tipped circular blade saw. The longitudinal edges of the specimens were carefully polished to remove any possible edge damage due to cutting. The composite plates were produced from preforms comprised of a number of glass fibre/epoxy prepregs, carbon fibre/epoxy prepregs or a combination of these. All the fabrication procedures were carried out using manual techniques. Whilst the compressive tests were conducted in accordance with the ASTM D3410-03 standard, flexural tests were carried out according to Procedure A of the ASTM D790-07 standard. Span-to depth ratios, S/d, of 16, 32, and 64 were selected for flexural testing in order to determine the minimum value of S/d required to ensure flexural failure rather than shear failure. Fibre and void contents were evaluated from optical micrograph images of the slices perpendicular to the fibre direction of the samples.It was concluded that the optimum values of the five processing parameters under investigations were: (i) epoxy concentration, C[subscript]e ~ 50 wt%, (ii) compressive pressure, p[subscript]c ~ 1.00 MPa, (iii) vacuum pressure, p[subscript]v ~ 0.035 MPa, (iv) dwell time, t ~ 30 minutes, and (v) holding temperature, T ~ 120 °C. Compressive tests revealed that the order of compressive strength for the parent composite materials were arranged as follows: S2-glass fibre/epoxy (476 MPa), E-glass fibre/epoxy (430 MPa), IM7 carbon fibre/epoxy (426 MPa), and TR50S carbon fibre/epoxy (384 MPa). The compressive modulus of these parent composite materials were found to be ordered as follows: IM7 carbon fibre/epoxy (67.9 GPa), TR50S carbon fibre/epoxy (61.8 GPa), S2-glass fibre/epoxy (45.1 GPa), and E-glass fibre/epoxy (32.9 GPa). After considering these compressive properties, three different hybrid combinations, as mentioned earlier, were manufactured and evaluated with the prepreg layers of the fibre composites possessing higher compressive strength being placed at the compressively loaded side of the flexural specimens.Shorter beam specimens (S/d = 16) of the three hybrid systems exhibited increased flexural strength as the amount of stronger fibre content was increased, but no hybrid effect was noted. The increase appeared to follow the rule of mixtures and this was attributed to their failure mode being shear failure. For beams tested at S/d = 32 and S/d = 64, the three hybrid systems demonstrated three different trends. The S2-glass fibre/E-glass fibre/epoxy hybrid system, where the S2-glass fibre (substituted at the compressive loading face) was slightly stronger and stiffer compared to the E-glass fibre at the tensile side, demonstrated increases in flexural strength together with the presence of a hybrid effect following partial substitution of the S2-glass fibre for E-glass fibres at the compressive side. The IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, where the IM7 carbon fibre (substituted at the compressive side) was slightly stronger but significantly stiffer in compression compared to the TR50S fibre at the tensile side, exhibited a slight increase in flexural strength that appeared to obey the rule of mixtures.This result was attributed to the strength increase in the compressive side introduced by the substituted fibres not being sufficient to suppress the increase of internal compressive stress due to the increase in compressive modulus of the substituted fibres. The E-glass fibre/TR50S carbon fibre/epoxy hybrid system, where the E-glass fibre (substituted at the compressive side) was found to be slightly stronger but significantly less stiff in compression compared to the TR50S fibre at the tensile side, demonstrated a significant increase in flexural modulus and also exhibited a significant hybrid effect. The decrease in internal compressive stresses generated at the compressive side due to the decreased compressive modulus of the substituted fibre, when combined with the increase in compressive strength of the substituted fibre, was thought to led to the significant increase of flexural strength for this hybrid system.General trends observed in flexural modulus for the three hybrid systems were reasonably similar with any change in flexural modulus appearing to obey the rule of mixtures. Whilst an increase in flexural modulus was noted for higher contents of stronger fibre in the case of the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, a decrease in flexural modulus with increased quantities of stronger fibre was exhibited by the E-glass fibre/TR50S carbon fibre/epoxy hybrid system. The increase or decrease in flexural modulus was attributed to the relative stiffness in compression of the substituted fibre when compared to that of the respective parent composite materials.Unlike the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system that did not exhibit any significant trend with regards the effect of the substitution of stronger fibre at the compressive side, the E-glass fibre/TR50S carbon fibre hybrid system demonstrated a significant increase in the energy stored to maximum stress with increasing content of the stronger fibre. This increase was mainly attributed to the increased strain–to-maximum stress of the hybrid system with respect to that of the parent composite material.In addition, for the three hybrid systems under investigation, the most significant change in flexural properties was noticed following substitution of the first layer at the compressive face. The relative position with respect to the neutral plane of the substituted layer was thought to be the reason for this phenomenon. It was also noted that flexural properties increased with the increase in S/d. A change in failure morphology was noted with the change of S/d from 16 to 32. It was thus determined that a S/d ratio of at least 32 was required in order to promote flexural failure (as opposed to shear failure). For the S2-glass fibre/E-glass fibre/epoxy hybrid system, this change appeared more obvious in comparison with that the other two hybrid systems with this change being accompanied by a significant increase in flexural strength.The main general conclusions that could be drawn from this investigation were that, although the flexural modulus appeared to obey the rule of mixture, an increase in flexural strength together with the presence of a hybrid effect, would most probably be observed when the fibre substituted at the compressive side possessed a significantly lower modulus combined with significantly higher compressive strength as demonstrated by the hybrid TR50S carbon - E-glass FRP composites. The most significant change in properties was exhibited by the first layer substitution whilst increasing the value of S/d resulted in an increase of flexural strength, with S/d = 32 being determined to be sufficient in order to promote flexural failure as opposed to shear failure.
50
Singh, Mary Margaret. "Dynamic properties of fibre-reinforced polymers exposed to aqueous conditions." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385659.
Full text