To see the other types of publications on this topic, follow the link: Short fibre.
Dissertations / Theses on the topic 'Short fibre'
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 'Short fibre.'
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
Fan, Yuan-Heng. "Fibre orientation and stiffness prediction in short fibre-reinforced thermoplastics." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339669.
Full text
2
Carling, Michael John. "Fracture mechanics of short fibre composites." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46986.
Full text
3
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
4
Wilson, K. A. "xtrusion of short fibre reinforced polyethylene pipes." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/10400.
Full textAbstract:
Short fibre
reinforced thermoplastic pipe was
produced by an extrusion process which oriented the fibre
reinforcement
predominantly into the pipe hoop direction.
The fibre reinforcement was
thereby used to maximise the
internal
pressure resistance and resistance to crack
propagation of the pipe in the axial direction.
Careful selection of materials and
development of
a suitable
compounding method enabled polyethylene, glass
fibres and a
coupling agent to be combined such that fibre
length retention and effective coupling gave worthwhile
improvements in the physical properties over the
polyethylene matrix polymer.
Extrusion
configurations developed were based
upon the use of motionless dies having a diverging mandrel,
and other
methods, to bring about melt hoop expansion. Die
geometry was varied to assess the influence of such factors
as melt
expansion ratio, divergence angle and die land
length.
_ Study of the complex fibre orientation
distribution
produced during extrusion and the die geometry
variables has
led, with the application of the classical
particle rotation theory proposed by Jeffrey, to the
development of predictive computer software for different
die
configurations. Predictions have been found
to
agree qualitatively with measured fibre orientation '
distributions in
pipes.
Physical testing has enabled characterisation of
a
range of pipes produced under different conditions having
different levels of fibre reinforcement and with different
fibre orientation distributions.
5
Wilson, K. A. "Extrusion of short fibre reinforced polyethylene pipes." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/10400.
Full textAbstract:
Short fibre reinforced thermoplastic pipe was produced by an extrusion process which oriented the fibre reinforcement predominantly into the pipe hoop direction. The fibre reinforcement was thereby used to maximise the internal pressure resistance and resistance to crack propagation of the pipe in the axial direction. Careful selection of materials and development of a suitable compounding method enabled polyethylene, glass fibres and a coupling agent to be combined such that fibre length retention and effective coupling gave worthwhile improvements in the physical properties over the polyethylene matrix polymer. Extrusion configurations developed were based upon the use of motionless dies having a diverging mandrel, and other methods, to bring about melt hoop expansion. Die geometry was varied to assess the influence of such factors as melt expansion ratio, divergence angle and die land length. _ Study of the complex fibre orientation distribution produced during extrusion and the die geometry variables has led, with the application of the classical particle rotation theory proposed by Jeffrey, to the development of predictive computer software for different die configurations. Predictions have been found to agree qualitatively with measured fibre orientation ' distributions in pipes. Physical testing has enabled characterisation of a range of pipes produced under different conditions having different levels of fibre reinforcement and with different fibre orientation distributions.
6
Eriksson, Axel. "Fatigue Injection Moulded Short Fibre Reinforced Polymers." Thesis, KTH, Hållfasthetslära (Inst.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254600.
Full textAbstract:
In order to keep up with the increasing demand of fuel-efficiency in the transportationindustry, the interest of making the vehicles as lightweight as possible is steadilyincreasing. One of the ways of reducing the weight is to introduce an anisotropicmaterial as Short Fibre Reinforced Polymers (SFRP) as a replacement for structuralparts made out of metals. To meet the modern vehicle design process which strivestowards a more simulation driven workflow, the need for accurate simulations offibre reinforced composites is of importance.This thesis aims to evaluate and find a working process for fatigue analysis of injectionmoulded SFRP components. To evaluate the fatigue analysis procedure anexisting SFRP component has been studied. The component is the front bracket thatmounts the roof air deflector to the roof on Scania trucks. To correlate the fatigue lifeestimation from the fatigue analysis, experiments were performed at ÅF Test Centerin Borlänge.The anisotropic behaviour is modelled using the commercial software Digimat togetherwith an injection simulation provided by Scania, to estimate the fibre orientationand thereby the material behaviour of the SFRP component. The fatigue analysiswas conducted by performing a coupled structural analysis between Digimat-Abaqus and then import the resulting stress- and strain-fields into the fatigue postprocessornCode DesignLife. The stress is then cyclic tested towards experimentallydetermined S-N curves determined in Digimat.Due to restriction of available fatigue data for the plastic in the front bracket, a fatiguematerial model for a plastic containing the same fibres and matrix but witha different fibre amount was implemented. The fatigue data were scaled using theUTS method to get a good characterisation of the real-life material behaviour of theplastic of the front bracket component.From the correlation between the fatigue analysis and performed experiments, itwas shown that the simulated fatigue life was conservative compared to the fatiguelife determined from the experiments. However, the correlation between the fatigueanalysis and experiments is not fully captured but gives a better estimation of thefatigue life compared to performing the fatigue analysis using an isotropic materialmodel.
7
Cushley, Anna T. "The prediction of fibre orientation in short fibre reinforced thermoplastic injection mouldings." Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281060.
Full text
8
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.
9
Zak, Gennady. "Rapid layered manufacturing of short-fibre-reinforced parts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/NQ41353.pdf.
Full text
10
Yang, Fan. "Low cost short wavelength radio over fibre systems." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608898.
Full text
11
Schmidt, Castellani Carlos Eduardo. "All-fibre wavelength versatile short pulsed laser sources." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24135.
Full textAbstract:
Pulsed lasers operating in the picosecond or femtosecond regimes find a wide range of applications in optical sciences, such as spectroscopy, laser surgery, material processing and optical communications. Among the existing sources of short-pulses, mode-locked fibre lasers play an important role mainly due to their robust and compact nature, and also due to their ability to generate outputs over a wide range of repetition-rates, pulse durations, pulse shapes, peak powers and optical wavelengths. Considering the case of wavelength versatility, Raman amplification can be used to fill the spectral gaps that are not covered by the emission band of traditional rare-earth doped elements such as ytterbium and erbium, allowing the generation of light at unconventional wavelengths. Additionally, another contribution has come from the recent development of new nanomaterials such as graphene and carbon nanotubes that can be used as saturable absorbers over a broadband wavelength range. The experimental work reported in this thesis is mainly focused in combining the wavelength versatility allowed by Raman gain and carbon nanotubes and graphene to generate short-pulsed fibre lasers at different wavelengths. High power ytterbium and erbium lasers and also a high power Raman laser operating at 1450 nm are used as pump sources to seed the Raman gain and carbon nanotubes and graphene are the saturable absorbers used as mode-lockers. All the fibres utilized in the oscillators are highly non-linear single mode silica fibres doped with GeO2. The lasers operate in the dissipative soliton regime, generating chirped pulses with durations on the order of hundred of picosecond that are suitable for external compression. We demonstrate for example an erbium-pumped Raman oscillator generating 500 ps pulses that are linearly compressed to 2 ps. The results presented in this document are a contribution towards making fibre based lasers more universal devices in terms of wavelength operation.
12
Hoto, N. A. (Nceba Antony). "Bugweed, a short fibre source of high potential." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53315.
Full textAbstract:
Thesis (MFor ) -- University of Stellenbosch, 2003.ENGLISH ABSTRACT: The bulk of paper grades destined for the printing industry are produced on modern paper machines which continuously become wider and faster. In order to improve printability, print quality and dimensional stability, such papers contain a large percentage of mineral pigments either in the form of internal loading or external coatings. Although mineral pigments exercise a substantial beneficial effect on paper surface quality, unfortunately these minerals do not contribute towards sheet strength and machine runnability. Today's papermakers are faced with the dilemma of producing highly filled and coated printing papers with low grammages on faster running paper machines, but often lacking the required quality of fibre resources to secure a smooth runnability of such at high speeds. Standard fibre furnishes will have to be upgraded with special types of reinforcing fibres in order to meet the demands of sheet strength and machine runnability. The investigation had succeeded to identify a new suitable fibre resource, which would satisfy the demand of a reinforcing type natural material.
AFRIKAANSE OPSOMMING: Die oorgrootte meerderheid tipes papier wat vir die drukkersbedryf bestem is, word op moderne papiermasjiene vervaardig wat steeds breër en vinniger word. Om die drukbaarheid, drukkwaliteit en dimensionele stabiliteit te verbeter, bevat sulke papiere groot hoeveelhede minerale pigmente wat in die vorm van interne ladings of as eksterne bestrykings teenwoordig is. Alhoewel minerale pigmente -n merkbare voordelige effek op die papier oppervlakte-kwaliteit uittoefen, dra sulke pigmente ongelukkig nie by tot die sterkte en loopvermoë van die papier nie. Die hedendaagse papiervervaardiger word konfronteer met die dilemma om swaar gevuldeen bestrykte drukpapiere met lae oppervlaktegewig op vinniger lopende papiermasjiene te vervaardig. Dit gebeur dikwels sonder die beskikbaarheid van die nodige hoëkwaliteit veselbronne om te verseker dat die loopvermoë van die papier teen hoë spoed nie benadeel word nie. Standaard veselsamestellings salopgegradeer moet word met spesiale tipe versterkingsvesels om aan die uitdaging van hoë velsterkte en masjien-Ioopvermoë te voldoen. Hierdie ondersoek het daarin geslaag om 'n nuwe geskikte veselbron te dentifiseer en wat aandie behoeftes van 'n versterkingsvesel sal voldoen.
13
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.
14
Boskovic, Aleksandra. "Short pulses and optical nonlinearities in fibres." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244282.
Full text
15
Wong, Yuk Lun. "Short optical pulses from injection lasers." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293009.
Full text
16
Graham, Andrew. "An infrared study of amosite asbestos." Thesis, Edinburgh Napier University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286122.
Full text
17
Mulligan, D. R. "The effect of fibre-bundling on the mechanical properties of a short-fibre composite." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313260.
Full textAbstract:
It has been suggested that the use of fibre bundles rather than individual fibres can improve the toughness properties of a short-fibre composite. Previous experimental work on this topic employed materials in which bundles were impregnated prior to manufacture or materials with poorly defined fibre-bundling. This study is the first to consider the mechanical properties of a series of materials where the bundles have been impregnated during manufacture of the material, and the materials tested contained a well-defined proportion of fibres within bundles of a known size. A novel manufacturing technique has been developed that can be used to produce short carbon fibre reinforced polypropylene materials with a controlled proportion of fibres in bundles. Materials manufactured in this work contained 0 %, 25 %, 50 %, 75 % and 100 % of the fibres in bundles. The fibres had a length of 5 mm or 10 mm and the bundles contained either 1000 or 6000 fibres. An increase in the proportion of fibres within bundles results in a decrease in the tensile modulus of the short-fibre composites. This decrease was less severe for materials containing bundles with a greater aspect ratio or laminates with a greater thickness. A model for the modulus of the materials has been developed which illustrates some of the effects of fibre-bundling on the structure of a short-fibre composite. For the materials studied, tensile strength of materials containing bundles was one quarter of the tensile strength of the filamentised material. Only one combination of fibre length and bundle size resulted in a clear increase in toughness, as measured by JJ, compared to the filamentised material and this increase appears to be due to areas of unreinforced matrix in the material. Materials containing both filamentised fibres and fibre bundles had relatively low values of J, The fracture surfaces were imaged and three distinct ways in which a bundle may fail have been identified. Discussion of the fracture mechanisms active in these materials concludes that the use of fibre-bundling to improve toughness is unlikely to be effective due to the mechanism that has been proposed
18
Mohd, Ishak Zainal Afirin. "Mechanical properties of short carbon fibre reinforced nylon 6.6." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256817.
Full text
19
Green, Stuart. "Creep behaviour of short glass fibre reinforced nylon 66." Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279696.
Full text
20
Wilson, Alan. "Interrogation techniques for short gauge length optical fibre sensors." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266987.
Full text
21
Elsmere, Stephen Paul. "Semiconductor seeded fibre amplified sources of ultra short pulses." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/161221/.
Full textAbstract:
Semiconductor Seeded Fibre Amplified Sources of Ultra Short Pulses By Stephen Paul Elsmere This thesis reports upon an experimental investigation of passively mode-locked optically pumped vertical-external-cavity surface-emitting semiconductor lasers (VECSEL). Mode-locked VECSELs are a compact source of ultra-short pulses at GHz repetition rates, with pulse lengths as short as 190 fs being generated directly from the laser. The VECSEL is a power scalable device offering spectral versatility through band gap engineering of semiconductor gain material. Here, for the first time the technique of frequency resolved optical gating (FROG) has been used to record a second harmonic spectrogram of the VECSEL pulse train, from which the phase information of non-transform limited sub-picosecond pulses has been retrieved. I also report the characterisation of a single stage VECSEL seeded ytterbium-doped fibre amplifier, capable of increasing the average power of a VECSEL from 20 mW to over 1.5 W while maintaining the sub-picosecond duration of the pulse train. The amplifier is capable of operating at any repetition rate obtainable with a VECSEL, amplification is demonstrated here with 1 GHz and 6 GHz seeds. Finally, the nonlinear evolution of VECSEL pulses inside a single stage fibre amplifier has been investigated. Computer modelling of the linear gain and nonlinear pulse propagation within a single fibre has been used to design an amplifier capable of producing pulses with a parabolic profile. The modelling reveals that a parabolic amplifier would produce spectrally broader linearly chirped pulses which could be compressed to below 100 fs, with average powers > 3 W. An experimental realisation of the parabolic amplifier will require a seed with average power greater than 100 mW, this could be achieved with a re-growth of an existing sample, QT1544.
22
Hsu, Che-Yuan. "Experimental determination of fibre orientation distribution and prediction of stiffness in short fibre-reinforced thermoplastics." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243399.
Full text
23
Haberer, Marc E. "Fibre-resin mixing and layer formation subsystems for the rapid manufacturing of short-fibre-reinforced parts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58838.pdf.
Full text
24
Merritt, P. A. "Interferometric dispersion measurements on short lengths of monomode optical fibre." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379397.
Full text
25
Stanford-Beale, Christopher Andrew. "High temperature deformation of short fibre reinforced aluminium based composites." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315905.
Full text
26
Ioannou, Ioannis. "A study on the numerical characterisation of short fibre composites." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8608/.
Full text
27
Henkrichová, Jana. "Krátkovláknové kompozity pro stomatologické aplikace, jejich příprava a charakterizace." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-295696.
Full textAbstract:
This diploma thesis studies short fiber reinforced composites for dental applications. Barium particulate filler, nanosilica and short glass and polyvinylalcohol fibers were added to the matrix consisting of four dimethacrylate types of monomers. The effect on material properties was observed. For characterization of different types of composite materials following methods were used: thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), three point bending test for notched and un-notched samples and scanning electron microscopy (SEM). Viscoelastic properties, modulus of elasticity and strength, critical values of stress intensity factor and strain energy release rate and polymerization shrinkage of composite materials were determined. It is possible to improve these properties of composite materials by adding short fibres to particulate reinforced composite. To make this modification more efficient, it is necessary to change surface treatment of fibres and preparation method of short fiber reinforced composites. Viscosity of material has raised after adding short fibers and processing of these types of dental material in dental laboratory is considered difficult to provide.
28
Hinzen, Marcus, and Wolfgang Brameshuber. "Improvement of Serviceability and Strength of Textile Reinforced Concrete by using Short Fibres." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244046356375-03273.
Full textAbstract:
Nowadays, thin-walled load bearing structures can be realised using textile reinforced concrete (BRAMESHUBER and RILEM TC 201-TRC [1]). The required tensile strength is achieved by embedding several layers of textile. By means of the laminating technique the number of textile layers that can be included into the concrete could be increased. To further increase the first crack stress and the ductility as well as to optimize the crack development, fine grained concrete mixes with short fibres can be used. By a schematic stress-strain curve the demands on short fibres are defined. Within the scope of this study, short fibres made of glass, carbon, aramid and polyvinyl alcohol are investigated in terms of their ability to fit these requirements. On the basis of these results, the development of hybrid fibre mixes to achieve the best mechanical properties is described. Additionally, a conventional FRC with one fibre type is introduced. Finally, the fresh and hardened concrete properties as well as the influence of short fibres on the load bearing behaviour of textile reinforced concrete are discussed.
29
Ghasripoor, Farshad. "Friction and wear of a short fibre reinforced aluminium-silicon alloy." Thesis, Brunel University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278286.
Full text
30
Jollands, M. C. "Mechanical properties and structure of extruded short glass fibre-filled polyethylene." Thesis, Cranfield University, 1990. http://dspace.lib.cranfield.ac.uk/handle/1826/10394.
Full textAbstract:
The work described in this thesis concerns the mechanical properties and structure of extruded short glass Fibre-Filled polyethylene. High density polyethylene was compounded with E-glass and coupling agent, and extruded into 110 m diameter pipe, using a normal production extruder, by Stewarts & Lloyds Plastics, Huntington. A normal die and a novel die, based on the Monsanto expanding mandrel die, were used to produce pipes with varying fibre orientation distributions (FED).
The structure of the pipe was analysed in terms of density, crystallinity, glass weight Fraction, and Fibre length and orientation distributions. Various mechanical properties were measured, to confirm the structure results, namely tensile creep and compression modulus, and tensile strength.
3-point bending tests of pipe were undertaken. The measured deflections under load were
compared with simple bending theory and finite element analysis predictions. Kc, a Jc,-testing of samples was undertaken. JC-testing was not successful, so Kc testing was adopted.
The Kc results are analysed in terms of FOD and test seed, and it is shown that alignment in the direction of load does not allays produce the most resistance to crack growth. Fatigue testing of impact tension and slant-edge cracked specimens was undertaken, with crack growth at several angles to extrusion. Results are very different for samples produced with the different dies, and also depend on fibre length, glass volume fraction, angle to extrusion, and test stress amplitude.
31
Taverner, Domino. "Generation and manipulation of short optical pulses in fibre based systems." Thesis, University of Southampton, 1996. https://eprints.soton.ac.uk/398738/.
Full textAbstract:
This thesis presents experimental and computational work on a variety of fibre based systems covering the generation, transmission, manipulation and amplification of short optical pulses (hundreds of femtoseconds to tens of picoseconds). The construction and characterisation of an all-polarisation-maintaining fibre figure-8, passively mode-locked laser is presented. This was the first all-fibre passively mode-locked cavity constructed entirely of high birefringence, polarisation maintaining components. This enabled the generation of a single polarisation Eigen-state within the cavity, resulting in a source of high quality 2.3ps-6ps solitonic pulses with excellent environmental stability, despite the considerable length of the device (395m). A computational model of a dispersion compensated standard fibre link using a fibre based four-wave mixing, midpoint spectral inversion (MPSI) technique was developed to provide qualitative and quantitative support to a 50km experimental system for the transmission of 6ps solitonic pulses. This model was then used to provide an estimate of the limitations to such systems presented by higher order dispersion, the results suggesting that links greater than 2500km at single channel bit-rates of 50GBit/s could be feasible. The development of photorefractive fibre Bragg gratings has produced one of the most important and flexible fibre devices. Experimental and computational investigations of the interaction of short pulses with both uniform and linearly chirped gratings are presented, giving a useful insight into their dispersive effects and limitations for their use in more complex systems. The importance of apodisation for reducing the energy scattering from pulses after multiple reflections was clearly demonstrated through numerical modelling of such systems. The application of long, linearly chirped fibre Bragg gratings to the compensation of chromatic dispersion in step-index fibres at potential bit-rates approaching 50GBit/s was demonstrated experimentally with the transmission of 16ps pulses over 100km. The use of two cascaded 4cm gratings exploited the linearity of these devices to further push the limits of compensation available. One of the few limitations of fibre based short pulse sources is the relatively low pulse energies produced. This problem had been tackled through the use of chirped pulse amplification (CPA) to circumvent the limitations imposed by fibre nonlinearities to amplification in EDFAs, however the problems of energy extraction from the amplifier fibre remained. The development and application to CPA of a large mode-area EDFA designed to improve pulse energy extraction is presented. The generation of 32?J pulses directly from the amplifier represented a significant increase in both energy and pulse quality over previously reported systems, demonstrating the potential of such amplifier designs for a range of high energy/intensity pulse applications.
32
Isaac, Leslie Thomas. "Puffer circuit breaker diagnostics using novel optical fibre sensors." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263762.
Full text
33
Wilkinson, Simon B. "Residual stress and through depth modulus properties of short fibre reinforced composites." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308979.
Full text
34
Chisholm, Karen E. "Fabrication and application of short and novel structure in-fibre Bragg gratings." Thesis, Aston University, 2000. http://publications.aston.ac.uk/7993/.
Full textAbstract:
This thesis presents details on progress made in the fabrication and application of short and novel structure fibre Bragg gratings. The basic theoretical concepts of in-fibre Bragg gratings and photosensitive mechanisms are introduced together with an overview of fabrication methods and applications presented to date. The fabrication of fibre Bragg gratings using a quadrupled Nd:YAG laser is presented and some of the issues of grating fabrication using a fabrication using a phasemask are investigated, including the variation of the separation of the fibre and phasemask, and other alignment issues. A new apodisation technique is presented, enabling the production of gratings with a wide range of spectral profiles. The technique is used to investigate the design and fabrication of length limited fibre Bragg gratings for use in telecommunication systems as filters. Application to devices designed for use in WDM systems is presented. The use of fibre Bragg gratings as high spatial resolution distributed sensors is investigated. Grating sensing arrays comprising very short apodised gratings are demonstrated and Chirped Moiré gratings are implemented as distributed sensors achieving high spatial resolution with miniature point sensing sub-elements. A novel grating sensing element designed to imitate an interferometer is also presented. Finally, the behaviour of gratings fabricated in Boron-Germania-co-doped fibre is investigated, revealing atypical behaviour of the Bragg wavelength during ageing.
35
Barhum, Rabea, and Viktor Mechtcherine. "Mechanical Behaviour under Tensile Loading of Textile Reinforced Concrete with Short Fibres." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77896.
Full textAbstract:
This treatise addresses the influence of the addition of short dispersed and integral fibres made of alkali-resistant glass on the fracture behaviour of textile-reinforced concrete (TRC). A series of uniaxial, deformation-controlled tension tests was performed to study the strength-, deformation-, and fracturebehaviour of thin, narrow plates made of TRC both with and without the addition of short fibres. Furthermore, uniaxial tension tests on specimens reinforced with only short fibres and single-fibre pullout tests were carried out to gain a better understanding of crack-bridging behaviour, which suppresses crack growth and widening. Various effects of the addition of short fibre on the stress-strain relationship and cracking behaviour of TRC were observed and discussed with reference to microscopic investigation of fractured surfaces.
36
Alkoles, Omar M. S. "Mechanical behaviour and fracture toughness of unfilled and short fibre filled polypropylene both drawn and undrawn. Experimental investigation the effect of fibre content and draw ratio on the mechanical properties of unfilled and short glass fibre filled polypropylene." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5510.
Full textAbstract:
The goal of this research is to investigate the combined effects of glass fibre reinforcement and molecular orientation in polypropylene-short glass fibre composites. Specimens have been fabricated using the injection moulding process and drawn using a small die drawing rig. The effects of die drawing on the fibre composites are complex, with the drawing process orienting both the polymer molecules and the glass fibres. This may be accompanied by the creation of voids in the polymer matrix and their destruction in the compressive stress field thus restoring the interfacial contact area between fibre and matrix. Unfilled and short glass fibre filled polypropylene specimens, with fibre content 7% wt, 13%wt, 27%wt, and 55%wt, were injection moulded prior to the die drawing process. An experimental program of die drawing within an oven at elevated temperature was conducted for polypropylene filled to various levels and at different strain rates. The specimens drew to draw ratios in the range ¿=1.41 to ¿=5.6. Mechanical characterization of the test materials has been conducted by examining the tensile stress strain and fracture behaviour under uniaxial conditions. The influence of glass fibre content and drawing conditions (draw ratio) on the fracture toughness and crack propagation was investigated using the double edge notched fracture test. The notch lengths ranged from 1.5 to 2.5 mm for 10 mm wide specimens. The critical stress intensity factor increased as the fibre content increased up to a limiting filler level. The fracture toughness of both unfilled and fibre filled polypropylene were found to be highly dependent on draw ratio. The results were analysed to find out the optimal draw ratio and fibre content that yielded the maximum modulus, strength and fracture toughness. Data showed that, at a given draw ratio, modulus, strength and fracture toughness increased with increasing fibre content to a maximum and then decreased. The optimum material was obtained at a draw ratio of 2.5 and filler loading 13wt%.
37
Parveen, Bushra. "Fibre Orientation and Breakage in Glass Fibre Reinforced Polymer Composite Systems: Experimental Validation of Models for Injection Mouldings. Validation of Short and Long Fibre Prediction Models within Autodesk Simulation Moldflow Insight 2014." Thesis, University of Bradford, 2014. http://hdl.handle.net/10454/14865.
Full textAbstract:
End-gated and centre gated mouldings have been assessed with varying thickness and sprue geometries for the centre gate. Alternative image analysis techniques are used to measure the orientation and length of injection moulded short and long fibres composite components. The fibre orientation distribution (FOD) measurements for both geometries have been taken along the flow path. In shear flow the FOD changes along the flow path, however the FOD remains relatively constant during expansion flow. The core width and FOD at the skin within a long glass fibre (LGF) specimen is different in comparison to a short glass fibre (SGF) specimen. Fibre length measurements have been taken from the extrudate, sprue and 2 positions within the centre gate cavity. The size of the sprue has little influence on fibre breakage if the moulding is more than 1 mm thick The SGF FOD prediction models within Autodesk Simulation Moldflow Insight 2014 (ASMI) have been validated against measured SGF data. At present, by default, the models over-predict the < cos2θ > for most geometries. When the coefficients are tailored for each model, drastic improvements are seen in the FOD prediction. The recently developed SGF RSC model accurately predicts the FOD in shear, in a thin geometry, whereas the Folgar-Tucker model predicts the FOD accurately in expansion flow. The measured LGF fibre length distribution (FLD) and FOD have been validated against the LGF prediction models. The LGF models are currently under predicting the breakage and over-predicting < cos2θ >. The breakage prediction improves if measured FLD of the extrudate is input into the model.
38
Zadhoush, Ali. "The influence of defects on the mechanical properties of short fibre reinforced thermoplastics." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255673.
Full text
39
Kinsella, M. A. "Mechanics of short fibre thermoplastic based composites containing UHMWPE interlayers : a preliminary investigation." Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/7134.
Full textAbstract:
FEM has been applied to analyse the influence of interlayers on the stress distribution around cylindrical fibres in an elastic matrix. This being part of a research programme aiming to enhance the energy absorption characteristics of composites by means of interlayers from materials exhibiting high ductility under plane strain conditions, e. g. UHMWPE. The theoretical model is based on the Galerkin weighted residual finite element in conjunction with a "penalty approach". The advantage of this method for polymer composites is in its ability to cope very effectively with non-linear systems. Glass microscope slides were initially used to develop a technique for bonding the ductile layers on to glass and polyamides respectively, as well as to provide simple verifications of the applicability of the aforementioned model. Further experiments were carried out on glass fibres coated with UHMWPE from a xylene solution, in order to evaluate the applicability of the above technique and of the theoretical model in actual composite systems. Although great difficulties were encountered in achieving a well bonded uniform coating on the glass fibres the results have confirmed the viability of the approach: The impact strength of compression moulded glass reinforced Nylon plaques, measured with an instrumented falling weight apparatus was increased up to 400% with a corresponding loss in flexural modulus of only 10-15%. The ductile nature of the interfacial failure between fibres and matrix was also confirmed by SEM examination of fractured specimens. Thermal analysis results, especially from DMA indicate that an UHMWPE interlayer substantially increases the tan 8 of the short fibre composite over a wide temperature range, albeit with some reduction in modulus. There was good agreement between the flexural modulus results obtained from DMA tests and those obtained using 3 point bending at room temperature.
40
Alkoles, Omar M. "Mechanical behaviour and fracture toughness of unfilled and short fibre filled polypropylene both drawn and undrawn : experimental investigation of the effect of fibre content and draw ratio on the mechanical properties of unfilled and short glass fibre filled polypropylene." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5510.
Full textAbstract:
The goal of this research is to investigate the combined effects of glass fibre reinforcement and molecular orientation in polypropylene-short glass fibre composites. Specimens have been fabricated using the injection moulding process and drawn using a small die drawing rig. The effects of die drawing on the fibre composites are complex, with the drawing process orienting both the polymer molecules and the glass fibres. This may be accompanied by the creation of voids in the polymer matrix and their destruction in the compressive stress field thus restoring the interfacial contact area between fibre and matrix. Unfilled and short glass fibre filled polypropylene specimens, with fibre content 7% wt, 13%wt, 27%wt, and 55%wt, were injection moulded prior to the die drawing process. An experimental program of die drawing within an oven at elevated temperature was conducted for polypropylene filled to various levels and at different strain rates. The specimens drew to draw ratios in the range γ=1.41 to γ=5.6. Mechanical characterization of the test materials has been conducted by examining the tensile stress strain and fracture behaviour under uniaxial conditions. The influence of glass fibre content and drawing conditions (draw ratio) on the fracture toughness and crack propagation was investigated using the double edge notched fracture test. The notch lengths ranged from 1.5 to 2.5 mm for 10 mm wide specimens. The critical stress intensity factor increased as the fibre content increased up to a limiting filler level. The fracture toughness of both unfilled and fibre filled polypropylene were found to be highly dependent on draw ratio. The results were analysed to find out the optimal draw ratio and fibre content that yielded the maximum modulus, strength and fracture toughness. Data showed that, at a given draw ratio, modulus, strength and fracture toughness increased with increasing fibre content to a maximum and then decreased. The optimum material was obtained at a draw ratio of 2.5 and filler loading 13wt%.
41
Warnock, Robyn Ellen Civil & Environmental UNSW. "Short-term and time-dependent flexural behaviour of steel fibre-reinforced reactive powder concrete." Awarded by:University of New South Wales. Civil and Environmental, 2006. http://handle.unsw.edu.au/1959.4/23027.
Full textAbstract:
This thesis presents an experimental and theoretical study of the material and structural behaviour of a Steel-Fibre reinforced Reactive Powder Concrete (SF-RPC). The experimental program consisted of three phases. Phase 1 involved the development of a design mix for use throughout the remainder of the study. Phase 2 consisted of an in-depth investigation into the material properties of the mix. The final phase of the experimental component was the testing of 16 plain and prestressed SF-RPC beams. Twelve beams were tested under short-term loading to determine their cracking and ultimate moment capacity. The remaining 4 beams were used to investigate the time-dependent flexural behaviour of prestressed SF-RPC slabs. The material properties were measured using a range of short-term tests and included the compressive and flexural behaviour, static chord modulus of elasticity and crack mouth opening. In addition to the short-term tests, investigation into the time-dependent material behaviour was undertaken and included the creep and shrinkage characteristics of the material. The response of the material to various curing conditions was also investigated. The structural behaviour investigated included the short-term flexural moment-curvature response and load-deflection behaviour of beams and slabs along with the crack patterns of both plain and prestressed SF-RPC members. In addition to the investigations into the short-term flexural behaviour, a study into the time-dependent flexural behaviour was also undertaken. There are currently 2 available models for predicting the flexural response of plain and prestressed RPC cross-sections. The analytical phase of this investigation involved an evaluation of these models. Based on the experimental findings and analysis, a modified model was proposed for calculating the short-term flexural behaviour of plain and prestressed SF-RPC beams. The applicability of an age-adjusted effective modulus method for calculating the time-dependent deformations of prestressed SF-RPC slabs under various levels of sustained loads was also evaluated and found to be adequate with minor refinements.
42
Jittham, Pairote. "Optimising design for short fibre filled thermoplastics injection moulding using knowledge based engineering (KBE)." Thesis, University of Warwick, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439591.
Full text
43
Mouti, Zakaria. "Localised low velocity impact performance of short glass fibre reinforced polyamide 66 oil pans." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7843.
Full textAbstract:
This thesis focuses on the mechanical properties of short glass fibre reinforced polyamide 66 material used in automotive composite structures, and its impact resistance under localised low velocity impact. The main application of this research concerns the impact performance of an oil pan component susceptible to stone impact damage. The thesis reviews the current state-of-the-art of thermoplastic polyamide materials with an overview of the glass fibre reinforced polyamide under-the-hood components, as well as its manufacturing and processing techniques. The study explores much of the work published in the literature so as to identify the fundamental parameters determining the impact resistance. It then concentrates on assessing the mechanical properties of the material subjected to quasi-static loads and impacts considering the influence and consequences of atmospheric or weathering conditions such as the moisture and salt uptake and the variation of temperature. The experimental work employed a universal testing machine for the quasi-static tests, drop weight tower and projectile air gun to carry out the dynamic tests. The testing involves different polyamide grades and impact modifier material in small specimens and full-scale oil pan components so as to gain important insights into the material-geometrical coupling effects. In correlation with the experiments, a finite element analysis was conducted to predict capability and simulate impact events using LS-DYNA solver. The simulation allowed putting to the test and comparing different protective design features. The post-testing investigations focused on the damage assessment and failures at micro- and macro-scales on the structure using visual inspection, scanning electron microscopy and ultrasound flaw detector. This was intended to bring detailed understanding of the failure mechanisms and also shed some light into damage tolerance of typical under-the-hood thermoplastic polyamide components. Investigation results indicated that impact resistance properties of short glass fibre reinforced polyamide 66 grades are sensitive and influenced by moisture and salt uptakes, temperature ageing and air oxidation. In general, the increase of these parameters reduces the material strength but at the same time improves its strain. The study also compares different structures and shows the significant contribution of the design in terms of shock absorption and stress distribution. The proposed oil pan design with protective ribbing pattern combined with a superior material with rubbery phase considerably improves the impact resistance of the full-scale automotive component studied.
44
Yong, Ming S. "Process optimisation of squeeze cast magnesium-zinc-rare earth alloys and short fibre composites." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/15363.
Full textAbstract:
The work reported in this thesis demonstrates the potential of the squeeze casting process for the production of castings using magnesium aIloys and its composites. In particular, the studies involving composites are focused on fabrication through squeeze infiltration. These show the ability of the squeeze casting process to produce castings of high metallurgical integrity. The work offers a clear understanding of a number of key parameters for the squeeze casting process which are prerequisites for the production of high strength castings of magnesium aIloys and composites. A better understanding of the behaviour of the squeeze cast material tested at both ambient and elevated temperature has been achieved. A methodology, which aIlows the identification of optimum squeeze casting conditions, has been developed. This has been successfully used in the identification of casting conditions which produce the best tensile properties at both test temperatures. Two casting programmes, namely: primary and secondary programmes, were designed to evaluate the controlling parameters for squeeze cast magnesium alloys and composites. The investigation was conducted with two magnesium alloys: ternary RZ5DF (Mg-4.2o/oZn-RE) alloy and commercial RZ5 (MgZn- RE-Zr) alloy. Different preform systems were investigated during the primary casting programme and the results showed that 14% volume fraction alumina fibres with 5 % silica binder provided the most satisfactory results in terms of ease of fabrication, improvement in strength and cost. Applied pressures of 0.1 to 120 MPa were studied with and without the addition of fibre reinforcement. Pressures of 60 MPa and 80 MPa were found to yield optimum tensile properties in the RZ5DF alloy and its composite respectively. It was also found that a preform temperature of 600°C or above was necessary to achieve minimum resistance to magnesium infiltration at the preform surface. Other process settings, such as applied pressure duration, were also investigated. The influence of pouring and die temperature on the tensile properties was studied during the secondary casting programme. It was found that a higher pouring and intermediate die temperature provided the highest tensile properties. The mechanical properties of castings were tested at both ambient and elevated temperatures. It was found that fibre reinforcement improved the mechanical properties of the materials at ambient temperature but the most significant improvement was observed at 250°C. The effect of grain refinement (zirconium) addition on the squeeze cast magnesium alloys and composites was also investigated. The results indicated that the tensile properties in the zirconium-free RZ5DF alloy were comparable to those of the RZ5 alloy grain refined with zirconium. The influence of zirconium addition on the tensile properties of RZ5DF and RZ5 MMC was similarly reported. Heat treatment improved the properties of the alloys by a small margin and adversely affected the properties of the composite. The overall results showed that there is an opportunity to achieve a significant saving in material and process cost when producing Mg-Zn-RE alloys and composites by the squeeze casting process.
45
Zantout, B. "The production and evaluation of squeeze cast Al-alloy matrix-short ceramic fibre composites." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/22082.
Full textAbstract:
Research work on metal matrix-fibre composites has concentrated in the past on aligned fibre composites. The poor transverse strength of these composites is seen as a major hindrance to their practical use in the majority of engineering applications because stresses exist in more than one direction. Materials with isotropic properties are preferred and consequently reinforcement of composites in three dimensions will be necessary. With this objective, an investigation was conducted to assess the method of fabrication and properties of A1-a110y reinforced with short fibres (SiC and A1 203) randomly oriented in three dimensions. Two composite systems were examined: Al-4.S Cu alloy reinforced with SiC fibre; and Al-3.7S Mg alloy reinforced with A1 203 fibre. The general approach was to establish a satisfactory manufacturing method for the composites before evaluating their mechanical properties. The vortex technique was used to introduce the fibres into the molten alloy. Pre-treatment of the fibres, to induce wetting, and the use of a specially designed device for fibre separation and introduction to the molten A1-ai10ys was found to be necessary so that a uniform distribution of fibres oriented in three dimensions could be achieved. The composites were squeeze cast, under conditions which were experimentally determined, to ensure the production of pore-free castings with fine equiaxed structures. The improvement in tensile strength and ductility of the cast metal, provided by squeeze casting, would be beneficial to composite properties. Composite castings, with up to 10% volume fibre, were produced with a sound structure and with fibres that were uniformly distributed and randomly oriented in three dimensions. It was found that the reaction between the fibres and the respective molten alloy must be closely controlled so that fibre reinforcement can be realised. In this respect the optimum time of contact between the fibres and the molten alloy was experimentally defined for both composite systems. The tensile properties (UTS, 0.1% proof stress, and ductility) of the fibre-free alloys were substantially improved by squeeze casting. The addition of fibre produced further substantial improvement in the tensile properties of the squeeze cast composites, in particular elastic modulus and 0.1% proof stress. Furthermore, composite properties were isotropic. The improvement in the tensile properties of composite castings (as a result of the addition of fibre) was maintained at elevated temperatures. At 250oC, castings of both composite systems with 10% (volume) fibre had 0.1% proof stress and elastic modulus values similar to those for the fibre-free castings at room temperature. The tensile properties of the composite castings were not affected by thermal cycling (at experimental conditions). The fatigue life of the squeeze cast composite was substantially improved over and above the initial improvement in fatigue life of the fibre-free castings produced by squeeze casting. Wear of cutting tools was adversely affected by the presence of fibres.
46
Islam, Mohammad Saiful. "The Influence of Fibre Processing and Treatments on Hemp Fibre/Epoxy and Hemp Fibre/PLA Composites." The University of Waikato, 2008. http://hdl.handle.net/10289/2627.
Full textAbstract:
In recent years, due to growing environmental awareness, considerable attention has been given to the development and production of natural fibre reinforced polymer (both thermoset and thermoplastic) composites. The main objective of this study was to reinforce epoxy and polylactic acid (PLA) with hemp fibre to produce improved composites by optimising the fibre treatment methods, composite processing methods, and fibre/matrix interfacial bonding. An investigation was conducted to obtain a suitable fibre alkali treatment method to: (i) remove non-cellulosic fibre components such as lignin (sensitive to ultra violet (UV) radiation) and hemicelluloses (sensitive to moisture) to improve long term composites stability (ii) roughen fibre surface to obtain mechanical interlocking with matrices (iii)expose cellulose hydroxyl groups to obtain hydrogen and covalent bonding with matrices (iv) separate the fibres from their fibre bundles to make the fibre surface available for bonding with matrices (v) retain tensile strength by keeping fibre damage to a minimum level and (vi) increase crystalline cellulose by better packing of cellulose chains to enhance the thermal stability of the fibres. An empirical model was developed for fibre tensile strength (TS) obtained with different treatment conditions (different sodium hydroxide (NaOH) and sodium sulphite (Na2SO3) concentrations, treatment temperatures, and digestion times) by a partial factorial design. Upon analysis of the alkali fibre treatments by single fibre tensile testing (SFTT), scanning electron microscopy (SEM), zeta potential measurements, differential thermal analysis/thermogravimetric analysis (DTA/TGA), wide angle X-ray diffraction (WAXRD), lignin analysis and Fourier transform infrared (FTIR) spectroscopy, a treatment consisting of 5 wt% NaOH and 2 wt% Na2SO3 concentrations, with a treatment temperature of 120oC and a digestion time of 60 minutes, was found to give the best combination of the required properties. This alkali treatment produced fibres with an average TS and Young's modulus (YM) of 463 MPa and 33 GPa respectively. The fibres obtained with the optimised alkali treatment were further treated with acetic anhydride and phenyltrimethoxy silane. However, acetylated and silane treated fibres were not found to give overall performance improvement. Cure kinetics of the neat epoxy (NE) and 40 wt% untreated fibre/epoxy (UTFE) composites were studied and it was found that the addition of fibres into epoxy resin increased the reaction rate and decreased the curing time. An increase in the nucleophilic activity of the amine groups in the presence of fibres is believed to have increased the reaction rate of the fibre/epoxy resin system and hence reduced the activation energies compared to NE. The highest interfacial shear strength (IFSS) value for alkali treated fibre/epoxy (ATFE) samples was 5.2 MPa which was larger than the highest value of 2.7 MPa for UTFE samples supporting that there was a stronger interface between alkali treated fibre and epoxy resin. The best fibre/epoxy bonding was found for an epoxy to curing agent ratio of 1:1 (E1C1) followed by epoxy to curing agent ratios of 1:1.2 (E1C1.2), 1: 0.8 (E1C0.8), and finally for 1:0.6 (E1C0.6). Long and short fibre reinforced epoxy composites were produced with various processing conditions using vacuum bag and compression moulding. A 65 wt% untreated long fibre/epoxy (UTLFE) composite produced by compression moulding at 70oC with a TS of 165 MPa, YM of 17 GPa, flexural strength of 180 MPa, flexural modulus of 10.1 GPa, impact energy (IE) of 14.5 kJ/m2, and fracture toughness (KIc) of 5 MPa.m1/2 was found to be the best in contrast to the trend of increased IFSS for ATFE samples. This is considered to be due to stress concentration as a result of increased fibre/fibre contact with the increased fibre content in the ATFE composites compared to the UTFE composites. Hygrothermal ageing of 65 wt% untreated and alkali treated long and short fibre/epoxy composites (produced by curing at 70oC) showed that long fibre/epoxy composites were more resistant than short fibre/epoxy composites and ATFE composites were more resistant than UTFE composites towards hygrothermal ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, fracture toughness, SEM, TGA, and WAXRD test results. Accelerated ageing of 65 wt% UTLFE and alkali treated long fibre/epoxy (ATLFE) composites (produced by curing at 70oC) showed that ATLFE composites were more resistant than UTLFE composites towards hygrothermal ageing environments as revealed from tensile, flexural, impact, KIc, SEM, TGA, WAXRD, FTIR test results. IFSS obtained with untreated fibre/PLA (UFPLA) and alkali treated fibre/PLA (ATPLA) samples showed that ATPLA samples had greater IFSS than that of UFPLA samples. The increase in the formation of hydrogen bonding and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased IFSS for ATPLA system compared to UFPLA system. Long and short fibre reinforced PLA composites were also produced with various processing conditions using compression moulding. A 32 wt% alkali treated long fibre PLA composite produced by film stacking with a TS of 83 MPa, YM of 11 GPa, flexural strength of 143 MPa, flexural modulus of 6.5 GPa, IE of 9 kJ/m2, and KIc of 3 MPa.m1/2 was found to be the best. This could be due to the better bonding of the alkali treated fibres with PLA. The mechanical properties of this composite have been found to be the best compared to the available literature. Hygrothermal and accelerated ageing of 32 wt% untreated and alkali treated long fibre/PLA composites ATPLA composites were more resistant than UFPLA composites towards hygrothermal and accelerated ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, KIc, SEM, differential scanning calorimetry (DSC), WAXRD, and FTIR results. Increased potential hydrogen bond formation and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased resistance of the ATPLA composites. Based on the present study, it can be said that the performance of natural fibre composites largely depend on fibre properties (e.g. length and orientation), matrix properties (e.g. cure kinetics and crystallinity), fibre treatment and processing methods, and composite processing methods.
47
Philpott, Emma. "Development and characterisation of short fibre ceramic matrix composites processed using a twin rolling mill." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267453.
Full text
48
Benyahya, Kaoutar. "Mode group division multiplexing for short reach optical communications." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S117.
Full textAbstract:
La demande croissante du trafic de données sera alimentée par des technologies révolutionnaires telles que la réalité virtuelle (VR), la réalité augmentée (AR) et l’Internet des objets (IoT). Par conséquent, les réseaux optiques devraient répondre aux besoins de ces services en termes de débit, faible temps de réponse et grande fiabilité. En effet, les hauts débits représentent un besoin critique pour les systèmes de communication à fibre optique déployés dans les réseaux locaux ainsi que dans les centres de données. Pour ces deux applications, les systèmes basés sur la modulation d'intensité et la détection directe de cette dernière sont très attractifs en raison de leur faible coût et de leur compatibilité avec les applications à courte distance. Dans le cadre de cette thèse, nous répondons à la nécessité d’augmenter les débits pour les systèmes de communication optiques à courte distance basés sur le multiplexage de groupe de modes et la détection directe. Tout d'abord, nous visons à augmenter la capacité des fibres multimodes standard déjà déployées dans les réseaux locaux et à l’intérieur des centres de données où la distance est inférieure à 5 km. Deuxièmement, nous étendons notre solution aux applications avec des distances de déploiement plus longues telles que les connexions entre les centres de données. Dans les deux cas, les architectures des liens optiques, y compris les émetteurs, les récepteurs et les fibres optiques, sont analysées. De plus, les formats de modulation adaptés aux systèmes basés sur la détection directe tels que le format de modulation mono-porteuse 4-PAM et celui multi-porteuse DMT sont comparés dans le contexte de la transmission basée sur le multiplexage spatial. Nous avons démontré les avantages du multiplexage de groupes de modes combiné à la détection directe pour augmenter le débit transmit sur une seule fibre. Premièrement, 5 Tb / s ont été démontré sur 2,2 km de fibre multimode conventionnelle (OM2). Deuxièmement, un record de transmission de 14,5 Tb / s sur fibre OM2 est démontré au moment correspondant à sa réalisation. Enfin, 200 Gb / s sur 20 km de fibre faiblement multimode (FMF) a été démontré, ce qui étend les avantages du multiplexage par groupes de modes aux applications à longue distance par rapport aux réseaux LAN où la distance maximale est limitée à 5 kmThe ever-growing demand of data traffic will be fuelled by revolutionary technologies such as virtual reality (VR), augmented reality (AR) and Internet of things (IoT). Therefore, optical networks should support the requirements of these services in terms of high capacity, low latency and high reliability. In fact, large scale capacity is a critical need for fiber optic communication systems deployed in local area networks as well as in datacenters. For both applications, systems relying on intensity modulation and direct detection (IMDD) are highly demanded due to their low cost and compatibility with short range applications. In this thesis, we address the need of increasing the data rates for short reach optical communication systems based on mode group division multiplexing and direct detection schemes. Firstly, we focus on increasing the capacity of already deployed standard multimode fibers in local area networks and intra-datacenters communication where the distance is shorter than 5 km. Secondly, we extend our solution to longer reach applications such as inter-datacenter interconnects. In both cases, optical link architectures, including transmitters, receivers and the optical fibers are analysed. Moreover, modulation formats adapted to IMDD systems such as single carrier 4-PAM and multicarrier DMT are compared in the context of space division multiplexing transmission. In this work we demonstrated the achievable benefit of mode group multiplexing combined with IMDD schemes. First, 5 Tb/s has been achieved over 2.2 km of conventional multimode fiber (OM2). Secondly, transmission record at the corresponding time of its realization of 14.5 Tb/s over OM2 fiber is demonstrated. Finally, 200 Gb/s over 20 km of FMF has been achieved which extend the benefit of mode group multiplexing to longer reach applications compared to LAN and intra-datacenter where the maximum distance is limited to 5 km
49
Emeanuwa, P. C. "Structure and properties of internal weld lines in injection moulded thermoplastics and short fibre reinforced composites." Thesis, University of East Anglia, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376356.
Full text
50
Lasagni, Fernando A. [Verfasser]. "The role of Si on the microstructure of Al casting alloys and short fibre composites / Fernando A Lasagni." Aachen : Shaker, 2008. http://d-nb.info/1164341537/34.
Full text