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1
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.
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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.
2
Mahmood, Amjed Saleh. "Processing-performance relationships for fibre-reinforced composites". Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/4181.
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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.
3
Kretsis, George. "Mechanical characterisation of hybrid glass/carbon fibre-reinforced plastics". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46982.
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Berg, Jolyon. "The role of fibre coatings on interphase formation in glass fibre epoxy resin composites". Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245546.
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Hsieh, Feng-Hsu. "Nanofiber reinforced epoxy composite". Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1146149557.
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Xiao, Keqin. "Fracture behaviour of rubber-modified epoxies and their carbon fibre-reinforced composites". Thesis, The University of Sydney, 2000. https://hdl.handle.net/2123/27762.
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Prickett, Andrew C. "Intralaminar cracking of fibre reinforced composites : a fracture mechanics and ToF-SIMS study". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/798035/.
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Sirivedin, Suparerk. "Micromechanics of progressive failure in carbon fibre-reinforced composites using finite element method". Thesis, King's College London (University of London), 2001. https://kclpure.kcl.ac.uk/portal/en/theses/micromechanics-of-progressive-failure-in-carbon-fibrereinforced-composites-using-finite-element-method(825de9c4-f644-4b2f-b6d1-95569f46c0a5).html.
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Ghazali, Habibah. "Dual-Capsule Based Self-Healing of Epoxy and Carbon-Epoxy Laminated Composite". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15387.
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Since the year 2000, researchers have made extensive efforts to develop novel materials with self-healing ability by embedment of microencapsulated self-healing agents. The motivation behind these studies is to heal the crack once it occurs and to slow down crack growth in the materials. These materials were designed with the capability of repairing damage/fracture autonomously whenever it happens, and the materials subsequently recover their original properties. Many of the early-developed healing systems focused on the healing of polymers and their fibre-reinforced composites with a room temperature-curing system. Because of the difficulty in applying resins with microcapsules normally around 100 μm in size to reinforcing fibres during the fabrication process of composites and due to the limited space between the plies, most studies have adopted a low fibre volume fraction for ease of processing and fabrication. The realisation to structural composites containing a high fibre volume fraction was less studied. In general, a high fibre volume fraction is a critical factor for achieving high specific strength and high specific modulus of the resultant composites. Firstly, this study aims to develop a diglycidyl ether of bisphenol A (DGEBA) epoxy as the self-healing agent and characterise its capability in healing the elevated temperature-cured epoxy, epoxy-based adhesive joints, and carbon-fibre reinforced epoxy composites. A dual-capsule self-healing system containing DGEBA epoxy and mercaptan as its hardener, microencapsulated in similar sizes, was developed to be embedded into the base epoxy resin. This healing system was chosen to match that of the matrix of composite laminates fabricated in this study for its superior thermal stability. Although the DGEBA epoxy/mercaptan self-healing system has been reported to provide the epoxy with room temperature healing, the high viscosity imposed by the healing agent has made room temperature healing conditions less reliable for healing of composite laminates of a high fibre volume fraction, where the amount of the embedded microcapsules is constrained by fibres. Therefore, the effect of healing temperature on viscosity and healing efficiency in the base epoxy is studied to obtain the improved healing conditions. It was found that the better healing performance for this healing system is achieved at 70°C since the viscosity of DGEBA epoxy is much lower at this temperature. With a better flow behaviour, the healing agent has a better capacity to flow and spread onto crack surfaces. Apart from that it was also found that the formed healant film covering thin cavity between two crack surfaces is critical for the healing performance, and at the elevated temperature of 70°C, the full recovery in fracture toughness (KIC) is achieved for Mode I fracture in the epoxy. The dual-capsule self-healing system was then extended to heal delamination in carbon fibre (CF)/epoxy (EP) composite laminates after Mode I interlaminar fracture. One of the main focuses of this study is centred on CF/EP composite laminates embedded with the dual-capsule and with a high fibre volume fraction fabricated using the vacuum assisted resin infusion technique, with the aims to effectively heal delamination as well as matrix microcracking once they occur. Here, it was demonstrated that by properly modulating the amount of microcapsules dispersed on reinforcing CF fabrics, CF/EP composite laminates with a fibre volume fraction as high as 65% can be achieved. The self-healing performance after Mode I delamination in CF/EP composite laminates with the dual-capsule self-healing system of two different sizes (average 123 µm and 65 µm, respectively) of microcapsules was investigated. Effects of incorporating microcapsules on baseline properties of the composite laminates were investigated, and it was found that such incorporation first leads to some reduction in the baseline properties of the laminates. The CF/EP laminate with large size (123 µm) microcapsules shows 4.6% reduction in the original Mode I interlaminar fracture toughness (GIC) as compared to that of the base laminate; while the CF/EP laminate with small size (65 µm) microcapsules shows a reduction of 36.9%. Healing efficiency is characterised by the recovery in the Mode I critical stress intensity factor (KIC) measured using width-tapered double cantilever beam (WTDCB) specimens. Although the full recovery was achieved for the base laminate injected with the same healing agent, the healing efficiency with only 54% recovery was achieved for the laminate with the small size microcapsules, with the maximum being 57% in some cases. In the case of large size microcapsules, the healing efficiency increased to 69% recovery with the maximum being 80% in some cases. It was also observed that the recovery in Mode I interlaminar fracture toughness was directly correlated with the amount of healant film covering the fracture surfaces, with the highest healing efficiency obtained for the laminate with the largest film. In the following study, the self-healing performance after Mode II delamination in CF/EP laminates containing the dual-capsule self-healing system was investigated. The effect of incorporation of the microcapsules on Mode II interlaminar fracture toughness (GIIC) of CF/EP laminates was characterised using end-notched flexure (ENF) specimens. In contrast to the Mode I delamination tests, the results indicated that the Mode II interlaminar fracture toughness (GIIC) of the base CF/EP laminate was improved (up to 48%) with the incorporation of the dual-capsule self-healing system. When healed at 70°C, the dual-capsule self-healing system also provided the laminate with healing capability on Mode II delamination with 63% recovery in GIIC. Observation on the fracture surfaces also revealed that the healing efficiency varies directly with the concentration of healant and the healing of interlaminar region after Mode II fracture. Finally, the self-healing epoxy adhesive was developed using this dual-capsule self-healing system. The healing system was incorporated into a commercial two-part room temperature-cured epoxy adhesive. The addition of 3 wt% microcapsules in concentration into adhesive of 172 (± 50) μm in thickness was shown to increase the baseline lap-shear strength by 28%. The results also revealed an increment to the baseline fracture toughness (GIC) of the epoxy adhesive, with improvement as high as 80% for adhesive with thickness of 273 (±66) μm, measured using tapered-double cantilever beam (TDCB) specimens. The increase in fracture toughness was mainly attributed to enhanced plastic deformation of the host adhesive as well as the crack path deflection caused by the poor adhesion between the microcapsules and the epoxy adhesive. The healing efficiency based on the recovery in the original crack initiation and crack propagation fracture toughness is 52% and 74% respectively.
10
Magrini, Michael A. "Fiber reinforced thermoplastics for ballistic impact". Birmingham, Ala. : University of Alabama at Birmingham, 2010. https://www.mhsl.uab.edu/dt/2010m/magrini.pdf.
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Zhou, Gang. "Preparation, structure, and properties of advanced polymer composites with long fibers and nanoparticles". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173287075.
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Green, Keith Jamahl. "Multiscale fiber reinforced composites using a carbon nanofiber/epoxy nanophased matrix processing, properties, and thermochemical behavior /". Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2007m/green.pdf.
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Thiagarajan, C. "Smart characterisation of damage in carbon fibre reinforced composites under static and fatigue loading condition by means of electrical resistivity measurements". Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309660.
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Bozkurt, Emrah Tanoğlu Metin. "Mechanical and thermal properties of non-crimp glass fiber reinforced composites with silicate nanoparticule modified epoxy matrix/". [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/makinamuh/T000517.pdf.
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Thesis (Master)--İzmir Institute of Technology, İzmir, 2006Keywords: polymer composites, Nanoparticles, glass fiber, mechanical properties, thermal properties. Includes bibliographical references (leaves 75-79).
15
Bettelli, Mercedes Amelia. "Effect of Induction-Heat Post-Curing on Residual Stresses in Fast-Curing Carbon Fibre Reinforced Composites". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80527.
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Manufacturing induced shape distortions is a common problem for composite materials. Due to the non-isotropic nature of carbon fibre reinforced polymers (CFRP) unavoidable deformations occur during part production. During fabrication of polymer composites, the material obtains its final shape at elevated temperatures. The curing process involves a transition from the liquid state to the solid, glassy state, allowing bonding between fibres and matrix. As the material cools the mismatch in thermal expansion coefficients and cure shrinkage obtained during the matrix polymerization leads to residual stresses on the mechanical level within composite part. There is a great interest from the aircraft and automotive industries, to increase the ability to understand development of shape distortions and residual stresses during the cure, since these deformations often lead to dissatisfaction of tolerances and it is essential to predict the deformations beforehand in order to compensate time and cost. In this context, a study of residual stresses during the curing process of thermosetting resin composites is presented. A methodology is proposed for predicting the formation and development of manufacturing- induced residual stresses. The present project reports on a comprehensive experimental study on the dependency of different short curing cycles on the build-up of residual stresses in a carbon fibre/fast-curing epoxy system and evaluate of post-curing methods through induction heating and oven post-curing with unidirectional [904] and unsymmetrical [9020] laminates. It includes characterization in thermo-elastic properties and degree-of-cure of the material by Thermal bending test, thermal expansion test, mechanical tensile test and Differential Scanning Calorimetry (DSC) in non-post-cured and post-cured laminates. The results showed slight variation in the thermal properties and not effect in the mechanical properties at different cure and post-curing conditions. Analytical data by Laminate Analysis program validated the experimental thermo-elastic data with analytical simulations. In addition, it is shown improvements in the temperature distributions in the post-curing by induction heating with different experimental set-ups, however, oven post-curing showed a more systematic system, higher heat efficient a low cure temperature, with more consistent mechanisms of shape distortions and residual stresses compared to induction heating. These findings are relevant for the future development of prediction methods for process induced deformations of Fast Curing Epoxy Resins (FCER).
16
Zhang, Mei. "The effects of contamination on the mechanical properties of carbon fibre reinforced epoxy composite materials". Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299084.
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Abessalam, Qutaiba. "Investigation into the modes of damage and failure in natural fibre reinforced epoxy composite materials". Thesis, University of East London, 2011. http://roar.uel.ac.uk/2632/.
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The aim of the research is to develop new high performance composite materials that would potentially compete with existing man made materials and to investigate the physical, mechanical and thermal properties of crushed (powdered) olive stones (pits) reinforced epoxy composites. This research focuses on development of a new range of sustainable reinforced polymer composite materials using powdered olive pits as a novel filler material to be used with synthetic resins. A full review has been made of the previous work on different types of natural fibres and fillers used as reinforcement for synthetic polymers. This project attempts to clarify the advantages and limitations resulted from using these fibres/ fillers and endeavours to provide explanation on the mechanical behaviour of these materials. Prior to investigating the mechanical properties of the powdered olive pits-epoxy composites the density and the mechanical properties of the olive pits were fully characterised. The influence of the untreated and treated powder loading (weight fraction) on the void content and the mechanical properties of the composites was examined using different tests, including flexural, tensile, microhardness and impact testing. The composites showed significant improvements in mechanical properties including flexural strength (139%) and flexural modulus (149%), tensile strength (121%) and tensile modulus (46%), microhardness (170%), and impact strength (167%) following treatment of the olive pits powder with 2% Al 100 coupling agent. Composites consisting of epoxy resin reinforced with untreated powder exhibited weaker powder to matrix interfacial bonding compared to those with treated powder composites. The improvements in properties have been attributed to the treatment of the powder with coupling agent, which has resulted in enhanced powdermatrix interaction. Hence it was possible to develop an experimental model of the behaviour of these materials subjected to the above mentioned testing conditions. Furthermore different thermal analysis techniques including dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) have been used to investigate the influence of the coupling agent on the olive pits powder composites properties by carefully analysing the changes in the thermal properties of the composites; glass transition temperature increased by 38%, tan delta peak decreased by 50%, and room temperature storage modulus improved by 17% and loss modulus peak decreased by 60%. The corroborated mechanical and thermal analysis results support the formation of a strong and efficient interfacial bond between the filler and epoxy matrix. The influence of powder content and interfacial bond strength on the damage and failure mechanisms operating in the different samples subjected to the destructive testing regime have been examined using optical and scanning electron microscopy (SEM).
18
Parker, Melanie A. "Flexural Response of Masonry Elements Strengthened with Epoxy-Bonded Elastomeric Fiber Reinforced Films". Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19836.
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The structural response of unreinforced masonry elements strengthened with
hybrid elastomeric/fiber materials was investigated through material characterization and
flexural experiments. Material characterization tests were performed on various
unreinforced and reinforced elastomeric materials to identify those materials that were
best suited for use as structural retrofits. After material characterization was completed,
the three most promising material systems were selected for further investigation,
including one unreinforced elastomer film and two reinforced elastomer films with fiber
orientations at 0/90° and +/- 45° relative to the major axis of the masonry elements. A
series of four-point bending tests were performed on the selected masonry and epoxy
bonded elastomer/fiber hybrid retrofits to determine the structural response of the
composite systems. The experimental load-deformation response was used, along with
material characterization results, in the development of a semi-empirical model to predict
the static moment capacity of the strengthened masonry system. This model will be used in
the development of reliable design criteria for masonry walls strengthened with these
advanced materials.
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Cormier, Daniel. "Repair of Conductive Layer on Carbon Fibre Reinforced Polymer Composite with Cold Gas Dynamic Spray". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33160.
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Carbon fibre reinforced composites are known for their high specific strength-to-weight ratio and are of great interest to the aerospace industry. Incorporating these materials into the fuselage, like in Boeing's 787 "Dreamliner", offers considerable weight reduction which increases flying efficiency, and reduces the cost of flying.
In flight, aircraft are often subject to lightning strikes which, in the case of composites, can result in localized melting given the high resistive nature of the material. Aerospace carbon fibre composites often incorporate a metallic mesh or foil within the composite layers to dissipate the electrical charge through the large aircraft. The damage to the aircraft is minimized but not always eliminated. This research aims to elaborate a practical technique to deposit thin layers of conductive material on the surface of aerospace grade composites. Using Cold Gas Dynamic Spray (CGDS), such coatings could be used to repair damaged components.
An experimental research approach was used to develop metallic coated composites. Using the CGDS equipment of Centerline (SST-P), specific parameters (such as gas temperature and stagnation pressure) were determined for each type of metallic coating (tin-based & copper-based). The use of bond coats was explored in order to attain the desired coatings. Once optimized, these coatings were evaluated with respect to their corrosive, adhesive, and electrical properties following industry standards.
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Khasawneh, Firas Abdallah. "Characterization of drillability of sandwich structure of carbon fiber reinforced epoxy composite over titanium alloy". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5871.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 13, 2007). Vita. Includes bibliographical references.
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Turmel, J.-P. "Effect of phase separation in Epoxy/PEI matrix on the mixed - mode I/II delamination behaviour of unidirectional glass fibre reinforced composites". Thesis, Cranfield University, 1995. http://dspace.lib.cranfield.ac.uk/handle/1826/11335.
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The study reported in this thesis investigates the relationships between the
morphology of PEI/epoxy blends reinforced with glass fibres and their fracture
properties.
Hot stage optical microscopy is used to study the phenomenon of phase
separation in the thermosetting blends in the presence of glass, carbon and
aramid fibres. Phase separation is shown to be unaffected by the presence of
aramid and carbon fibres, but is affected by the presence of glass fibres, to a
degree which mainly depends on the PEI concentration. Other parameters like
cure temperature, the nature of the glass fibre surface and fibre volume fraction
are also examined. The most striking feature is the initiation and development
of an epoxy-rich layer around the fibres for blends modified with 15 wt % PEI.
This concentration corresponds to a co-continuous network of PEI-rich particles
embedded in an epoxy-rich matrix.
The effects of morphologies formed during phase separation on the
fracture properties of glass fibre-reinforced composites are studied using the
mixed-mode bending test rig developed by NASA. Extensive scanning electron
microscopy (SEM) observations provide qualitative support to the delamination
results. They show that different micro-mechanisms of deformation can occur,
depending on the matrix microstructure and the fibre/matrix interfacial strength.
SEM observations show that cusps are not only present under mode II
loading, but also under mixed-mode I/II loading. They reveal that the spatial
density and angle of cusps depend on the applied loading mode, the interfacial
strength and the nature of the matrix itself. These observations are the base of
a model which describes the delamination behaviour of composites from pure
mode Ito pure mode II loading.
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Turmel, Denis Jean-Pierre. "Effect of phase separation in epoxy/PEI matrix on the mixed-mode I/II delamination behaviour of unidirectional glass fibre reinforced composites". Thesis, Cranfield University, 1995. http://dspace.lib.cranfield.ac.uk/handle/1826/11335.
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The study reported in this thesis investigates the relationships between the morphology of PEI/epoxy blends reinforced with glass fibres and their fracture properties. Hot stage optical microscopy is used to study the phenomenon of phase separation in the thermosetting blends in the presence of glass, carbon and aramid fibres. Phase separation is shown to be unaffected by the presence of aramid and carbon fibres, but is affected by the presence of glass fibres, to a degree which mainly depends on the PEI concentration. Other parameters like cure temperature, the nature of the glass fibre surface and fibre volume fraction are also examined. The most striking feature is the initiation and development of an epoxy-rich layer around the fibres for blends modified with 15 wt % PEI. This concentration corresponds to a co-continuous network of PEI-rich particles embedded in an epoxy-rich matrix. The effects of morphologies formed during phase separation on the fracture properties of glass fibre-reinforced composites are studied using the mixed-mode bending test rig developed by NASA. Extensive scanning electron microscopy (SEM) observations provide qualitative support to the delamination results. They show that different micro-mechanisms of deformation can occur, depending on the matrix microstructure and the fibre/matrix interfacial strength. SEM observations show that cusps are not only present under mode II loading, but also under mixed-mode I/II loading. They reveal that the spatial density and angle of cusps depend on the applied loading mode, the interfacial strength and the nature of the matrix itself. These observations are the base of a model which describes the delamination behaviour of composites from pure mode Ito pure mode II loading.
23
Chan, Kathleen Joyce. "Investigation of Processing Conditions and Viscoelastic Properties on Frictional Sliding Behavior of Unidirectional Carbon Fiber Epoxy Prepreg". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/86444.
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The quality of continuous fiber reinforced polymer matrix composite parts and structures depends strongly on the friction during the composite forming process. The two major types of friction that cause deformations during this process are ply-ply friction and tool-ply friction. One of the challenges in the composite forming process is the occurrence of wrinkling and shape distortion of the fabric caused by the surface differences between the forming tool and surface of the laminate. Frictional measurements of composites can vary widely depending on processing parameters, measurement technique, and instruments used.
In this study, a commercial rheometer was used to evaluate tool-ply friction of unidirectional carbon fiber epoxy prepreg at various contact pressures, temperatures and sliding velocities. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G'), loss modulus (G"), and loss factor (tan δ) were used to determine the critical transition events (such as gelation) during cure. An understanding of changes in viscoelastic properties as a function of time, temperature, and cure provides insight for establishing a suitable processing range for compression forming of prepreg systems.
Surface imaging results were coupled with rheological results to qualitatively examine the effects of processing parameters on prepreg distortions. Changes in gap height over the measurement interval qualitatively describe the changes in contact area and contact mechanisms between the tool-ply surfaces. The results indicate that friction behavior of the prepreg system is a contribution of adhesive and frictional forces, where increase in viscosity, reduction in gap height, and cure of the sample correlate to higher friction values.Master of Science
The quality of composite parts and structures depends strongly on the friction present during the composite forming process. One of the major challenges in the forming process is the occurrence of wrinkling and shape distortions of the fabric caused by the surface differences between the forming tool and material. The presence of these defects can compromise the final material property and lead to failure when in use. Frictional measurements of composites can vary widely depending on processing parameters, measurement technique, and instruments used. The extent of interaction between the tool and surface of the material depends on the tooling height, and by extension, contact area, which cannot easily be monitored with traditional test designs. A commercial rheometer was used in this study to evaluate tool-ply friction of unidirectional carbon fiber epoxy prepreg at various contact pressures, temperatures, and sliding velocities. Gap height and torque were monitored to provide information on the frictional dependence of processing parameters. In addition, surface-imaging results were coupled with rheological results to examine the relationship between friction and fiber distortions. The understanding of changes in material property with respect to the tooling process is the key to optimizing the composite forming process.
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チェン, フオン ウェン, i Nguyen Tien Phong. "Study on the effects of green micro/nano fiber addition on mechanical properties of carbon fiber reinforced epoxy composites". Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12614789/?lang=0, 2013. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB12614789/?lang=0.
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Rahman, Md Arifur. "Fabrication and Mechanical Characterization of Novel Hybrid Carbon-Fiber/Epoxy Composites Reinforced with Toughening/Self-Repairing Nanofibers at Interfaces". Thesis, North Dakota State University, 2012. https://hdl.handle.net/10365/26735.
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This research was aimed at fabrication and characterization of novel hybrid carbon-fiber/epoxy composites reinforced with toughening/self-repairing nanofibers at interfaces. For interfacial toughening, continuous electrospun polyacronitrile (PAN) and carbon nanofibers (CNFs) were incorporated between carbon fabrics to form the ultrathin toughening interlayers after resin infusion and curing. Mode I interlaminar fracture tests showed that PAN nanofibers can noticeably enhance the fracture toughness of Epon 862 based composites, while the toughening results were scattered for SC-15 resin based system. Furthermore, core-shell dicyclopentadiene (DCPD)/PAN nanofibers mats were fabricated by coelectrospinning, which were inserted between carbon fabrics and formed the ultrathin self-repairing interlayers after resin infusion and curing. Three-point bending tests showed up to 100% recovery of the flexural stiffness of pre-damaged composite specimens by the core-shell nanofibers. The research demonstrated novel high-strength, self-healing lightweight structural composites for broad applications.
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Seghini, Maria Carolina. "Mechanical Analysis and Fibre/Matrix Interface Optimization for Next Generation of Basalt-Plant Fibre Hybrid Composites". Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0003.
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La prise de conscience mondiale des enjeux environnementaux a conduit à l’émergence de composites«verts», dans lesquels les fibres naturelles sont amenées à remplacer les fibres synthétiques. Ces nouveaux matériaux offrent des alternatives écologiques aux composites synthétiques traditionnels mais sont difficilement utilisables pour des applications semi-structurales ou structurales. Une solution possible à ce problème est le développement des composites hybrides, en combinant ensemble fibres naturelles et synthétiques. Dans ce cadre, l'objectif de cette étude était de développer des composites hybrides à base de fibres de basalte et de lin. Les composites hybrides ont été élaborés par moulage par infusion sous vide avec une matrice époxy. À des fins de comparaison,des composites 100% à fibres de lin et100%à fibres de basalte ont également été produits. Une caractérisation mécanique quasi-statique et dynamique amontré que l'hybridation permet d’obtenir un composite avec des propriétés mécaniques intermédiaires comparées à celles des composites à fibres de lin ou de basalte. Cependant, l’analyse approfondie des dommages a montré la nécessité d'optimiser la qualité d'adhésion de l'interface fibre/matrice afin d'accroître les performances mécaniques des composites hybrides obtenus. Pour cette raison, différents traitements de modification de surface ont été développés et étudiés pour les fibres de lin et de basalte. Un traitement physique par plasma (Plasma Enhanced Chemical Vapor Deposition) a été appliqué aux fibres de lin et de basalte. Les fibres de lin ont également été soumises à deux traitements chimiques utilisant des espèces enzymatiques et du CO2supercritique. Les effets des traitements sur la stabilité thermique, la morphologie et les propriétés mécaniques des fibres de lin et de basalte ont été étudiés. L’adhérence fibre/matrice a été analysée en réalisant des tests de fragmentation sur des composites monofilamentaires. La qualité de l'adhésion entre les fibres et les matrices époxy et vinylester a été évaluée en termes de longueur critique de fragment, de longueur de décohésion interfaciale et de résistance au cisaillement interfacial. La micto-tomographie haute résolution a été utilisée pour analyser les mécanismes d'endommagement lors des tests de fragmentation. Pour les deux types de fibres, les meilleurs résultat sont été obtenus grâce au traitement par plasma. Ce traitement a consisté à déposer un revêtement homogène de tétravinylsilane à la surface des fibres de basalte et de lin, ce qui a permis une augmentation significative de l’adhérence fibre/matrice, ouvrant ainsi la voie à la prochaine génération de composites hybrides plus respectueux de l’environnement et utilisables pour des applications semi-structuralesGlobal awareness of environmental issues has resulted in the emergence of “green” composites, in which natural fibres are used to replace synthetic ones. However, in semi-or structural applications, it can be inconvenient to use composites based on natural fibres. A possible solution to this problem is the development of hybrid composite materials, combining together plies of natural and synthetic fibres. In this framework, the aim of this research project was to develop basalt-flax fibre hybrid composites with a view to obtaining more environmentally friendly composites for semi-structural applications. Hybrid composites were produced through vacuum infusion molding with epoxy matrix.For comparison purposes, 100% flax fibre composites and 100% basalt fibre composites were also manufactured. A quasi-static and dynamic mechanical characterization showed that the hybridization allows the production of a composite with intermediate mechanical performances compared to those possessed by flax and basalt composites. However, the damage analysis has revealed the need to optimize the fibre/matrix interface adhesion quality, in order to increase the mechanical properties of the resulting hybrid composites. For this reason, different surface modification treatments have been specifically designed and investigated for flax and basalt fibres. Flax and basalt fibres were treated by the physical process of Plasma Enhanced Chemical Vapor Deposition. Flax fibres were also subjected to two chemical treatments using enzymatic species and supercritical CO2. The effects of the surface modification treatments on the thermal stability, morphology and mechanical properties of flax and basalt fibres have been investigated. The degree and extent of fibre/matrix adhesion were analyzed by micromechanical fragmentation tests on monofilament composites. The adhesion quality between fibres and both epoxy and vinylester matrices has been assessed in terms of critical fragment length, debonding length and interfacial shear strength. High-resolution μ-CT has been used to support the analysis of the damage mechanisms during fragmentation tests. For both flax and basalt fibres, the best results were obtained after the plasma polymer deposition process. This process was able to produce a homogeneous tetravinylsilane coating on the surface of basalt and flax fibres, which resulted in a significant increase in the fibre/matrix adhesion, thus paving the way for the next generation of more environmentally friendly hybrid composites for semi-structural applications
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Subagio, Bambang Sugeng. "Contribution à la modélisation de l'endommagement de fatigue en flexion dans les matériaux composites unidirectionnels". Ecully, Ecole centrale de Lyon, 1987. http://www.theses.fr/1987ECDLA008.
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Essais d'identification d'une loi locale d'endommagement de fatigue basée sur la théorie de Kachanov-Rabotnov à partir d'essais mécaniques. Intégration de cette loi dans un calcul de structure. Introduction de la notion de dispersion par l'application d'une loi de Weibull. Identification de la dispersion locale à partir de la dispersion globale par la méthode de simulation de Monte-Carlo.
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LIU, ZENG-GANG. "Comportement et modelisation des materiaux composites carbone/epoxyde en cisaillement a grande vitesse". Nantes, 1987. http://www.theses.fr/1987NANT2011.
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Ponsot, Bernard. "Influence de la matrice sur le comportement a long terme de composites carbone-epoxyde". Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0058.
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Etat de degradation en fonction du temps d'un materiau soumis a des sollicitations thermomecaniques sur des plaques unidirectionnelles et des tubes (esais, traction, fluage, eclatement, flexion). Utilisation d'emission acoustique pour suivre l'evolution de la structure. Cinetique d'endommagement
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Cuynet, Amélie. "Etude du comportement mécanique à l’impact et en post impact de matériaux composites à fibres végétales". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAA017/document.
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L'objectif du projet de thèse est d'étudier et d'analyser le comportement mécanique à l'impact et en post impact de composites à fibres végétales. Le déroulement de cette thèse nécessite : L'élaboration et la caractérisation des matériaux de l'étude : Les matériaux de l'étude seront constitués de tissus à fibres végétales (lin et/ou chanvre) imprégnées de résine thermodurcissable (de type époxyde) ou thermoplastique (de type PP ou PLA). Ceux-ci seront fabriqués sous forme de plaque par la technique d'infusion sous vide ou la technique de la thermocompression, en fonction du type de résine. La caractérisation mécanique sera effectuée à partir d'essais mécaniques statiques et d'essais d'impact avec une tour de chute (à plusieurs niveaux d'énergie). Celle-ci sera d'abord menée sur des éprouvettes modèles (non impactées et non vieillis, sans et avec renfort fibreux) puis sur des éprouvettes dégradées (impactées à chaque niveau d'énergie et vieillis en humidité et température). La caractérisation de l'endommagement : Elle permettra, à partir des analyses d'images associées aux techniques de l'émission acoustique, de localiser et d'identifier les différents mécanismes d'endommagement intervenant dans ces matériaux au cours des diverses sollicitations choisies. Cette étude conduira à définir le degré de nocivité de ces endommagements tout en associant à la démarche l'influence des paramètres microstructuraux tels que la nature du renfort fibreux et des constituants (résine et fibres). L'identification de modèles de comportement : Il s'agit de proposer une méthode d'identification des paramètres matériaux de modèles de comportement tenant compte de l'endommagement au niveau de la microstructure du matériau (résine et torons de fibres). Cette étude conduira à la mise en œuvre d'une méthode de type recalage de modèles éléments finis en utilisant les bases de données expérimentales constituées notamment des mesures de champs cinématiques. L'objectif à terme est de disposer de modèles fiables et prédictifs pour le calcul de structures de ces matériaux dans l'industrieThe purpose of this PhD project is to study and analyze the mechanical behavior during the impact and post-impact of plant-fiber based composite materials. The conduct of this thesis requires: The manufacturing and characterization of the materials involved in the study : The materials are composed of plant-fiber fabrics (flax and/or hemp) impregnated with thermosetting resin (epoxy type) or thermoplastic resin (PP or PLA). These are manufactured using the vacuum infusion process or using thermocompression, depending on the resin. The materials are plate-shaped. The mechanical characterization will be performed using static mechanical testing and impact testing with a drop tower (over several energy levels). This will be first conducted on unmodified specimens (unimpacted and unaged, with and without fiber reinforcement) then on degraded specimens (impacted with a known energy and/or aged in humidity and temperature). The characterization of damage: It will, from the analysis of the images associated to the techniques of the acoustic emission, locate and identify the various damage mechanisms that intervene in these materials during different stresses. This study will lead to define the degree of harmfulness of such damage while associating to the approach the influence of microstructural parameters such as the nature of the fiber reinforcement and the components (resin and fibers). The identification of behavioral patterns: It consists in suggesting a method to identify the material parameters of behavioral patterns while taking into account the damage level of the material's microstructure (resin and fiber strands). This study will lead to the implementation of a finite element model updating-like method using experimental databases such as kinematic field measurements. The ultimate purpose is to have reliable and predictive models in order to calculate the structures of such materials in the industry
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Brunel, Jean-Evrard. "Influence de l'endommagement sur la rupture de plaques composites en présence de surcontraintes". Paris 13, 1989. http://www.theses.fr/1989PA132008.
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On cherche à définir un critère de rupture d'éprouvettes trouées en matériau composite stratifiés croisé. Des essais de traction statique uniaxiale, menés sur 3 matériaux (T300-5208, T300-6376, T400-6376) agencés sous différentes séquences d'empilement conduisent à déterminer l'influence de la nature du renfort ou de la matrice sur les mécanismes d'endommagement.
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Nesa, Daniel. "Etude de la fissuration d'un composite unidirectionnel verre-résine". Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0093.
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Nguyen, Thanh Hai. "Contribution à l'étude du comportement thermomécanique à très haute température des matériaux composites pour la réparation et/ou le renforcement des structures de Génie Civil". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10244/document.
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Dans le domaine du renforcement et/ou de la réparation des structures en béton armé par des matériaux composites à l'aide de la méthode du collage extérieur au moyen d'un adhésif époxy, une des préoccupations de la communauté scientifique est l'intégrité structurelle de ce système dans le cas d'incendie dans lequel la haute température est une caractéristique essentielle et peut atteindre jusqu'à 1200°C. Ce travail de recherche est axé sur le comportement thermomécanique à très haute température des matériaux composites [un composite à base de polymère carbone/ époxy (Carbon Fiber Reinforced Polymer- CFRP), un composite textile/ mortier cimentaire (Textile Reinforced Concrete- TRC) et un adhésif à base d'époxy]. L'évolution des propriétés mécaniques et d'autres aspects mécaniques de ces matériaux composites avec la température a été caractérisée. Une nouvelle procédure expérimentale concernant la mesure de la déformation de l'éprouvette à l'aide du capteur laser est développée et validée. Une étude numérique et expérimentale a été réalisée dans le but de déterminer principalement la température à la rupture des joints « composite/ adhésif/ composite » sous les sollicitations mécaniques et thermiques. L'efficacité de la protection thermique de deux isolants [PROMASPRAY®T (produit commercial de la société PROMAT] et Isolant A (produit développé par le LGCIE site Tusset) a aussi été étudiée dans cette thèse. Enfin, une approche numérique, à l'aide du logiciel ANSYS, est utilisée afin de déterminer, de façon préliminaire et approximative, à l'échelle matériau, les propriétés thermiques des matériaux (composite textile/ mortier cimentaire -TRC et Isolant A)In the area of the strengthening and/or the reparation of reinforced concrete structures with composites by means of the external bonding method using an epoxy adhesive, one of the preoccupation of the scientific community is the structural integrity of this system in the event of fire in which the high temperature is the essential feature et can reach up to 1200°C. This research focuses on the thermo-mechanical behavior of composite materials [carbon/epoxy adhesive composite (or carbon fiber reinforced polymer (CFRP), textile/cementitious mortar composite (or textile reinforced concrete (TRC)] and an epoxy-based adhesive. The evolution of mechanical properties and other mechanical aspects of these materials with the temperature has been characterized. A new experimental procedure concerning the measurement of sample strain by the laser sensor is developed and validated. An experimental and numerical study has been realized in order to mainly determine the temperature at the failure of "composite/adhesive/composite" joints under thermal and mechanical loadings. The effectiveness of the thermal protection of two insulators [PROMASPRAY®T (a commercial product of the PROMAT company and the insulator A (product developed by the LGCIE site Tuset)] has also been investigated in this PhD thesis. Finally, a numerical approach, using ANSYS software, is used to determine, in the preliminary and approximate way, at material scale, thermal properties of the materials [the textile reinforced concrete (TRC) and the insulator A]
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Renault, Michel. "Tolerance a l'endommagement de composites carbone-resine et stratifies t300-914". Paris, ENMP, 1988. http://www.theses.fr/1988ENMP0109.
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Etude experimentale (essais de fatigue, essais de traction, de compression) sur des eprouvettes entaillees ou non, trouees ou non de stratifies resine epoxyde/carbone. Analyse mathematique avec des calculs par elements finis
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Bisanda, Elifis T. N. "Sisal fibre reinforced composites". Thesis, University of Bath, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278675.
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Rice, Kolten Dewayne. "Bending Behavior of Concrete Beams with Fiber/Epoxy Composite Rebar". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/9062.
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This research explores the use of carbon/epoxy and fiberglass/epoxy fiber-reinforced polymer (FRP) composite rebar manufactured on a three-dimensional braiding machine for use as reinforcement in concrete beams under four-point bending loads. Multiple tows of prepreg composite fibers were pulled to form a unidirectional core. The core was consolidated with spirally wound Kevlar fibers which were designed to also act as ribs to increase pullout strength. The rebar was cured at 121â—¦C (250â—¦F) in an inline oven while keeping tension on the fibers. Five configurations of reinforcing bars were used in this study as reinforcement in concrete beam specimens: carbon/epoxy rebar and fiberglass/epoxy rebar were manufactured on the three-dimensional braiding machine and cured in an inline oven while still under tension immediately after production; carbon/epoxy rebar was manufactured by IsoTruss industries on the three-dimensional braiding machine and was rolled and stored before curing; fiberglass/epoxy rebar was purchased from American Fiberglass; conventional No. 4 steel rebar was also purchased. All bars were embedded in 152 cm (60 in) long, 11 cm (4.5 in) wide, and 15 cm (6.0 in) tall concrete beams. Beams were tested under four-point bending loads after which three 30 cm (12 in) specimens were taken from the ends of each configuration to be tested under axial compression loads in order to investigate the effects of the concrete voids on the concrete strength. Concrete beams reinforced with BYU glass/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 5% greater compression bending stress and 11% greater tension bending stress than concrete beams reinforced with industry manufactured glass/epoxy rebar. Concrete beams reinforced with BYU carbon/epoxy rebar manufactured on the three-dimensional braiding machine exhibited 18% lower compression bending stress and 64% lower tension bending stress than concrete beams reinforced with industry manufactured carbon/epoxy rebar. BYU glass/epoxy rebar has a 3% greater stiffness and 1% greater displacement than industry manufactured glass/epoxy rebar and BYU carbon/epoxy rebar has a 40% greater bending stiffness and 19% lower displacement than industry carbon/epoxy rebar. BYU carbon/epoxy rebar has 49% lower compression bending stress, 1% lower tension bending stress, 28% lower displacement, and a 68% greater bending stiffness than BYU glass/epoxy rebar. BYU glass/epoxy rebar has 38% greater compression bending stress, 30% lower tension bending stress, 26% greater center displacement, and a 105% lower bending stiffness than conventional steel. BYU carbon/epoxy rebar has 8% lower compression bending stress, 31% lower tension bending stress, and 22% lower bending stiffness than steel. The deflections of steel reinforced concrete and BYU carbon/epoxy reinforced concrete are comparable with steel rebar displaying a 1% greater center displacement than BYU carbon/epoxy rebar.
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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.
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Lavadiya, Dayakar Naik. "Effective Properties of Randomly Oriented Kenaf Short Fiber Reinforced Epoxy Composite". DigitalCommons@USU, 2015. http://digitalcommons.usu.edu/etd/4600.
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Natural fibers have drawn attention of researchers as an environmentally-friendly alternative to synthetic fibers. Developing natural fiber reinforced bio-composites are a viable alternative to the problems of non-degrading and energy consuming synthetic composites. This study focuses on (i) the application of kenaf fiber as a potential reinforcement and, (ii) determining the tensile properties of the randomly oriented short kenaf fiber composite both experimentally and numerically. Kenaf fiber micro-structure and its Young's modulus with varying gage length (10, 15, 20, and 25.4 mm) were investigated. The variation in tensile strength of kenaf fibers was analyzed using the Weibull probability distribution function. It was observed that the Young's modulus of kenaf fiber increased with increase in gage length. Fabrication of randomly oriented short kenaf fiber using vacuum bagging techniques and hand-lay-up techniques were discussed and the tensile properties of the specimens were obtained experimentally. The tensile modulus of the composite sample at 22% fiber volume fraction was found to be 6.48 GPa and tensile strength varied from 20 to 38 MPa. Numerical models based on the micro mechanics concepts in conjunction with finite element methods were developed for predicting the composite properties. A two-step homogenization procedure was developed to evaluate the elastic constants at the cell wall level and the meso-scale level respectively. Von-Mises Fisher probability distribution function was applied to model the random orientation distribution of fibers and obtain equivalent modulus of composite. The predicted equivalent modulus through numerical homogenization was in good agreement with the experimental results.
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L, Dayakar Naik. "Effective Properties of Randomly Oriented Kenaf Short Fiber Reinforced Epoxy Composite". DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4587.
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Natural fibers have drawn attention of researchers as an environmentally-friendly alternative to synthetic fibers. Developing natural fiber reinforced bio-composites are a viable alternative to the problems of non-degrading and energy consuming synthetic composites. This study focuses on (i) the application of kenaf fiber as a potential reinforcement and, (ii) determining the tensile properties of the randomly oriented short kenaf fiber composite both experimentally and numerically. Kenaf fiber micro-structure and its Young's modulus with varying gage length (10, 15, 20, and 25.4 mm) were investigated. The variation in tensile strength of kenaf fibers was analyzed using the Weibull probability distribution function. It was observed that the Young's modulus of kenaf fiber increased with increase in gage length. Fabrication of randomly oriented short kenaf fiber using vacuum bagging techniques and hand-lay-up techniques were discussed and the tensile properties of the specimens were obtained experimentally. The tensile modulus of the composite sample at 22% fiber volume fraction was found to be 6.48 GPa and tensile strength varied from 20 to 38 MPa. Numerical models based on the micro mechanics concepts in conjunction with finite element methods were developed for predicting the composite properties. A two-step homogenization procedure was developed to evaluate the elastic constants at the cell wall level and the meso-scale level respectively. Von-Mises Fisher probability distribution function was applied to model the random orientation distribution of fibers and obtain equivalent modulus of composite. The predicted equivalent modulus through numerical homogenization was in good agreement with the experimental results.
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Treiber, Johannes W. G. "Performance of tufted carbin fibre/epoxy composites". Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/5531.
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The thesis presents a detailed analysis of the effects of one-sided access z-direction reinforcement, ‘tufting’, on the morphology and mechanical performance of the resulting MVR-444 epoxy matrix/carbon fibre fabric composites. The dry fabric architectures used are pseudo-UD, twill woven fabric and non-crimped fabric (NCF). They are tufted with a range of commercial tufting threads, using KSL KL150 tufting head mounted on a 6-axis robot arm. The main focus is on the use of a twisted carbon fibre thread, at areal tufting densities of 0.5% and 2%. The composite plates are prepared via Resin-Transfer- Moulding (RTM) route, making it possible to control the plate thicknesses. The morphological features characteristic of tufted, cured composites are described and categorised. The global and local fibre volume fractions are measured and simple models proposed that connect local increase with local fibre deviation and presence of resin rich surface loop layers. It is shown that the balance of in-plane and out-of-plane properties in tufted composites is highly dependent on the tufting parameters, but also on the fabric architecture, with the NCF option seeming the most attractive. Overall, the stiffness of tufted materials is not affected and the drop in in-plane strength of any realistic geometry combinations is below 20%. ‘Thread-less’ tufting experiments prove that the drop is not caused by fibre breakage from the passage of the needle alone. Digital image correlation (DIC) techniques is used to map out the strain field distributions during mechanical testing, increasing the accuracy of crack tip location in Mode II delamination cracking studies and confirming the mode mixity changes during deformation of tufted structures. Single-tuft experiments provide the experimental data that are required for the development and validation of analytical models. A finite element unit cell model is developed to predict in-plane elastic and failure behaviour of tufted UD and NCF composites incorporating the critical meso-structural features of fibre deviation and increased fibre volume fraction. The thesis also contains an overview of the tufting technology and some detailed information on recent manufacturing developments that were required to obtain the controlled quality specimens used in the study. A demonstration structural element was produced, in the form of a tufted omega-stiffener. A standard pull-off test demonstrates the superior load carrying and energy absorbing capacity of this strengthened structure. Details of robot programming, additional single tuft bridging results, test fixture design, derivation of the analytical bridging model and additional publications are given in appendices to the main body of the thesis.
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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.
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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.
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Wooldridge, Andrew. "Fibre reinforced composites via coaxial electrospinning". Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/95272/.
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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 %.
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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.
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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.
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Triantafyllidis, Zafeirios. "Structural enhancements with fibre-reinforced epoxy intumescent coatings". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/29514.
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Epoxy intumescent coatings are fire protection systems for steel structural elements that are widely used in applications that protection from severe hydrocarbon fires is required, such as oil and gas facilities. These polymer coatings react upon heating and expand into a thick porous char layer that insulates the protected steel element. In the typical fire scenarios for these applications, the intumescent coatings must resist very high heat fluxes and highly erosive forces from ignited pressurised gases. Hence, continuous fibre reinforcement is embedded in the thick epoxy coating during installation, so as to ensure the integrity of the weak intumesced char during fire exposure. This reinforcement is typically in the form of a bidirectional carbon and/or glass fibre mesh, thus under normal service conditions a fibre-reinforced intumescent coating (FRIC) is essentially a lightly fibre-reinforced polymer (FRP) composite material. This thesis examines the impacts of embedded high strength fibres on the tensile behaviour of epoxy intumescent materials in their unreacted state prior to fire exposure, and the potential enhancements that arise in the structural performance of elements protected with FRICs. An experimental programme is presented comprising tensile coupon tests of unreacted intumescent epoxies, reinforced with different fibre meshes at various fibre volume fractions. It is demonstrated that the tensile properties of FRICs can be enhanced considerably by including increasing amounts of carbon fibre reinforcement aligned in the principal loading direction, which can be tailored in the desired orientation on the coated structural members to enhance their load carrying capacity and/or deformability. An experimental study is presented on coated intact and artificially damaged I-beams (simulating steel losses from corrosion) tested in bending, demonstrating that FRICs can enhance the flexural response of the beams after yielding of steel, until the tensile rupture of the coatings. An analytical procedure for predicting the flexural behaviour of the coated beams is discussed and validated against the obtained test results, whereas a parametric analysis is performed based on this analytical model to assess the effect of various parameters on the strengthening efficiency of FRICs. The results of this analysis demonstrate that it is feasible to increase the flexural load capacity of thin sections considerably utilising the flexural strength gains from FRICs. Finally, a novel application is proposed in this thesis for FRICs as a potential system for structural strengthening or retrofitting reinforced concrete and concrete-encased steel columns by lateral confinement. An experimental study is presented on the axial compressive behaviour of short, plain concrete and concrete-encased structural steel columns that are wrapped in the hoop direction with FRICs. The results clearly show that epoxy intumescent coatings reinforced with a carbon fibre mesh of suitable weight can provide lateral confinement to the concrete core resisting its lateral dilation, thus resulting in considerable enhancements of the axial strength and deformability of concrete. The observed strengthening performance of the composite protective coatings is found to be at least as good as that of FRP wraps consisting of the same fibre reinforcement mesh and a conventional, non-intumescent epoxy resin. The predictive ability of existing design-oriented FRP confinement models is compared against the experimental results, and is found to be reasonably precise in predicting the peak strength of the tested columns, hence existing models appear to be suitable for design and analysis of column strengthening schemes with the proposed novel FRIC system. The research presented herein shows clearly that FRICs have a strong potential as alternative systems for consideration in the field of structural strengthening and rehabilitation, since they can provide substantial enhancements in the load carrying capacity for both applications considered. At the same time FRICs can thermally protect the underlying structural elements in the event of a fire, by intumescing and charring, thus potentially eliminating the need for additional passive fire protection that is common with conventional fire-rated FRP wrapping systems. Although this thesis provides a proof-of-concept for use of the proposed novel FRICs as structural strengthening materials, considerable additional research is particularly required to study their fire protection performance when applied to concrete substrates, to make use of the proposed hybrid functionality with confidence.
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Embrey, Leslie. "Three-Dimensional Graphene Foam Reinforced Epoxy Composites". FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3128.
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Three-dimensional graphene foam (3D GrF) is an interconnected, porous structure of graphene sheets with excellent mechanical, electrical and thermal properties, making it a candidate reinforcement for polymer matrices. GrF’s 3D structure eliminates nanoparticle agglomeration and provides seamless pathways for electron travel. The objective of this work is to fabricate low density GrF reinforced epoxy composites with superior mechanical and electrical properties and study the underlying deformation mechanisms. Dip coating and mold casting fabrication methods are employed in order to tailor the microstructure and properties. The composite’s microstructure revealed good interfacial interaction. By adding mere 0.63 wt.% GrF, flexural strength was improved by 56%. The addition of 2 wt.% GrF showed a surge in glass transition temperature (56oC), improvement in damping behavior (150%), and electrical conductivity 11 orders of magnitude higher than pure epoxy. Dip coated and mold casted composites showed a gauge factor of ~2.4 indicating electromechanically robust composite materials.
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Dhillon, Jagminder. "Coated fibre composites using rubbery and ductile fibre/matrix interlayers". Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/33043.
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Advanced composite materials possessing high specific stiffness and strength have been successfully employed as structural materials in the aerospace, military and automotive industries. Despite the advantages that composites have over other materials, further development has been restricted by their brittleness. The aim of this research project was to improve the energy absorbing capabilities of unidirectional glass fibre epoxy resin composites by coating the fibres with an interlayer. UHMWPE was used as the interlayer because of its outstanding toughness while EPDM of low modulus was used to assess the difference between energy absorption through plastic deformations (UHMWPE) and highly elastic deformations (EPDM).
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Gu, Xiaohong. "Micromechanics of model carbon-fibre/epoxy-resin composites". Thesis, University of Manchester, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488261.
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Cantwell, W. J. "Impact damage in carbon fibre composites". Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/7834.
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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.
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