CERES :: Browsing by Author "Partridge, Ivana K."

Browsing by Author "Partridge, Ivana K."

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Open Access
Acquisition and interpretation of dielectric data for thermoset cure monitoring
(Cranfield University, 2003-09) Kazilas, Michalis C.; Partridge, Ivana K.
The interpretation and modelling of the dielectric response of thermosetting materials during cure was the main focus of this study. The equivalence of complex permittivity and complex impedance in terms of information content was outlined in a series of case studies covering the separate effects of dipolar movements and charge migration as well as the combined effect of the two polarisation mechanisms. Equivalent electrical circuits were used in order to model the evolution of the complex impedance during cure. A numerical method that can model consecutive spectra throughout the cure was developed. The method is based on Genetic Algorithms and requires only input from the modelling of the initial spectra. Complex impedance spectra were collected during the cure of a commercial epoxy resin formulation under isothermal and dynamic heating conditions. The spectra were analysed and modelled. The modelling was successful over the whole frequency range of the measurements (1 Hz – 1 MHz). The analysis of the estimated model parameters showed that charge migration dominates the dielectric response in a wide frequency range. In addition, the modelling algorithm also distinguished between the effects of electrode polarisation and dipolar movements in the signal. A new equivalent circuit was used in order to map the frequency regions where the each one of the three phenomena that together comprise the dielectric signal can be monitored most effectively. A chemical cure kinetics model was developed for the studied system. A correlation between the maximum point of the imaginary impedance spectrum and the reaction conversion was established. A mathematical model, based on a simple linear dependence of the dielectric signal on conversion and temperature, was built. The model predictions agreed well with the experimental data. The aim of simplifying the interpretation of the dielectric signals led to the development of a new experimental technique. Temperature Modulated Dielectric Analysis employs temperature modulations superimposed on an underlying thermal profile in order to separate the influence on the signal of the temperature alone from that of the cure reaction. The early study carried out here shows that such measurements are feasible and reveals important issues for its further development.
Open Access
Analysis and evaluation of mechanical performance of reinforced sandwich structures: X-CorTM and K-CorTM
(Cranfield University, 2005-12) Marasco, Andrea I.; Partridge, Ivana K.
X-CorTM and K-CorTM are foam based lightweight structural cores reinforced with ZFiber ® rods oriented in a truss pattern. They can generate sandwich structures which possess strength- and stiffness-to-weight ratios such to compete with aerospace grade honeycomb constructions. The enhanced tailoring ability to specific design needs, the flexibility in reinforcement type and arrangement, the variety between closed cell foamfilled or hollow core configurations for ultimate weight savings or structural multifunctionality, while utilising manufacturing procedures similar to traditional honeycomb sandwich structures (low cost out-of-autoclave manufacturing techniques included) make these novel materials an attractive alternative. The process of their implementation into current engineering practice requires a parallel comparison with existing competitor cores and a critical evaluation of their performance, identifying advantages and disadvantages. This study represents one of the first attempts to create a rigorous methodology for the analysis and evaluation of their mechanical behaviour and manufacturing sensitivities. The balance of out-of-plane properties (shear and compression), fundamental for a sandwich core material, has been investigated. The material energy absorption capacity for the aforementioned loading cases, as well as for in-plane crushing was evaluated. For this purpose, a new quasi-static test for progressive crushing of flat sandwich laminates was designed successfully. The experimental data gathered validate proposed analytical models which allowed further deductions on core parameters influence to be made. Those parameters were the pin insertion angle, pin lay-out, pin density and the role of the foam. A local-global FE modelling approach for Z-pinned sandwich cores is also provided and validated for X-CorTM structures. Structural differences between XCorTM and K-CorTM are at the base of a diverse mechanical response; their performance is sensitive to the manufacturing process, as it determines the quality of the pin-skin and pin-adhesive film interfaces. An ‘improved’ manufacturing technique designed for XCorTM resulted in a sandwich panel able to offer the same mechanical performance of a Nomex® honeycomb structure for a 25% of weight saving.
Open Access
Automated manufacture of 3D reinforced aerospace composite structures
(2012-03-05T00:00:00Z) Dell'Anno, Giuseppe; Partridge, Ivana K.; Cartié, Denis D. R.; Hamlyn, A.; Chehura, Edmon; James, Stephen W.; Tatam, Ralph P.
Purpose- This study is part of the FP7 project ADVITAC and focuses on exploring an innovative combination of cutting edge technologies to be implemented within automated processes for composite parts manufacturing. The objective is the design of a production route for components with tailored fibre orientation and ply lay-up, with improved damage tolerance thanks to through-the-thickness reinforcement and integrated health monitoring systems based on optical fibres technology. Design/Methodology/Approach- The proposed technologies are described in detail and their compatibility and potential for integration are discussed. A set up for on-line monitoring of infusion and curing processes of carbon/epoxy laminates preformed by dry fibre placement technology is proposed, and a preliminary study of their mechanical performance is presented. The possibility of reinforcing through-the-thickness preforms manufactured with dry slit tapes automatically laid-up and consolidated by laser heating is investigated. Findings- Improved knowledge of interaction/compatibility between the discussed technologies and scope for application. Research limitations/implications- The paper reports the technical potential and practical feasibility of the proposed integrated production process. Limited quantitative evaluations on the materials performance are provided. The analysis of the technologies involved represents the early outcome of the ongoing ADVITAC project. Practical implications- This study contributes to the identification of a new generation of composite architecture which allows production cost and weight savings while retaining the level of quality suitable for demanding structural applications, with particular relevance to the aerospace field. Originality/value- This paper investigates for the first time the practical possibility of designing a single automated process involving dry fibre placement, tufting and optical fibre sensor monitoring for the production of complex composite components.
Open Access
Blends of epoxy resin with polycarbonate and CTBN rubber
(1991-03) Jayle, L.; Partridge, Ivana K.
The study described in this thesis examines how the toughenability of a difunctional epoxy resin cured with a diamine hardener is affected by the presence of a dissolved polycarbonate in the epoxy matrix, when that matrix is modified by CTBN rubber particles. The compatibility between the epoxy resin and four different polycarbonate types is investigated. Influence of polycarbonate content and of the type of polycarbonate upon the mechanical properties and morphology of polycarbonate or rubber-polycarbonate modified epoxy systems is considered. Toughenability of the epoxy matrix is found not to be improved by the presence of dissolved polycarbonate. Study of chemical interactions between polycarbonate and epoxy resin and polycarbonate and hardener shows a degradation of the polycarbonate by the epoxy resin and also by the diamine hardener. Failure of the polycarbonate to increase the toughenability of the epoxy matrix is considered to be related to this degradation. Toughness properties of polyethersulfone modified epoxy systems are also considered.
Open Access
Bridging mechanisms of through-thickness reinforcement in dynamic mode I&II delamination
(Elsevier, 2017-04-13) Cui, Hao; Yasaee, Mehdi; Kalwak, Gordon; Pellegrino, Antonio; Partridge, Ivana K.; Hallett, Stephen R.; Allegri, Giuliano; Petrinic, Nik
Z-pin through-thickness reinforcement is used to improve the impact resistance of composite structures; however, the effect of loading rate on Z-pin behaviour is not well understood. The dynamic response of Z-pins in mode I and II delamination of quasi-isotropic IM7/8552 laminates was characterized experimentally in this work. Z-pinned samples were loaded at both quasi-static and dynamic rates, up to a separation velocity of 12 m/s. The efficiency of Z-pins in mode I delamination decreased with loading rate, which was mainly due to the change in the pin misalignment, the failure surface morphology and to inertia. The Z-pins failed at small displacements in the mode II loading experiments, resulting in much lower energy dissipation in comparison with the mode I case. The total energy dissipation decreased with increasing loading rate, while enhanced interfacial friction due to failed pins may be largely responsible for the higher energy dissipation in quasi-static experiments.
Open Access
Conductive Carbon Nanotube Thermosetting Polyester Nanocomposites
(Cranfield University, 2009) Battisti, Andrea; Partridge, Ivana K.; Skordos, Alexandros A.
A commercial unsaturated polyester resin has been used in combination with commercial multiwalled carbon nanotubes (MWNTs) to study the effects of this nanofiller on the electrical properties of the mix in the liquid state, during the cure and in the solid state. The level of addition of the nanotubes ranged from 0.05 to 0.3 wt%. The dispersion of the filler particles in the matrix was carried out combining triple roll milling, horn sonication and high shear mixing. Qualitative optical and electronic microscopy characterisation supports the development of novel techniques for real-time quantitative assessments of dispersion quality. Fitting of shear dependent viscosity, measured between 0.1 and 100 s-1, to Carreau's model has been shown to provide an indicator of the state of nanotube dispersion in the mixture. Additionally, liquid electrical conductivity measurements offer the option of on-line monitoring, providing a promising tool for process optimisation. The formation of an effective conductive network of nanotubes during the cure was investigated by combining impedance spectroscopy measurements and equivalent circuit modelling with two parallel RC circuit in series with each other. This allows in-situ observation of the key phenomenon responsible for the electrical conductivity of the nanocomposite, namely the filler re-aggregation during cure. Optimisation of dispersion and cure parameters results in a nanocomposite showing conductive behaviour in the solid state, achieving DC conductivity of 0.13 S/m at 0.30 wt% loading. The percolation threshold was estimated to occur at 0.026 wt% filler loading. The conductivity achieved is comparable to state-ofthe-art epoxy thermosetting nanocomposites based on use of carbon nanotubes of equivalent quality. Successful laboratory scale trials demonstrated the suitability of the materials in copper electroplating and resistance heating. An industrial scale up trial of a 40 kg batch was carried out, using the dispersion and the monitoring techniques developed in the study.
Open Access
Coupon scale Z-pinned IM7/8552 delamination tests under dynamic loading
(Elsevier, 2019-08-01) Cui, Hao; Mahadik, Yusuf; Hallett, Stephen R.; Partridge, Ivana K.; Allegri, Giuliano; Ponnusami, Sathiskumar A.; Petrinic, Nik
Dynamic impact onto laminated composite structures can lead to large-scale delamination. This can be mitigated by the introduction of through-thickness reinforcement, such as z-pins. Here, mode I & II and mixed-mode delamination tests have been designed and conducted at high loading rate, for both unpinned and Z-pinned coupons to study the effect of rate of loading. It was found that the Z-pins were not effective in delaying the dynamic crack initiation or resisting the dynamic propagation of delaminations shorter than 5 mm. However, the further growth of cracks was substantially delayed by Z-pinning, especially for the pure mode I and mode I dominated failure modes. On the other hand, the effectiveness of Z-pins in shear tests was relatively modest. The mode I dominated delamination resistance of Z-pinned laminates was found to be sensitive to the loading rate.
Open Access
Cure Induced Property Changes and Warpage in Thermoset Resins and Composites
(Cranfield University, 2003-03) Zarrelli, M.; Partridge, Ivana K.
The aim of the present work was to investigate the evolution of thermal and mechanical properties during the polymerisation of a thermosetting resin that is typical those used as the matrix in advanced composites. The mechanism of the cure reaction was studied using differential scanning calorimetry (DSC) in both dynamic (thermal scanning) and isothermal modes, and procedures for correlating the two types of calorimetric data were developed. The model finally chosen encapsulates the diffusion- controlled mechanism of reaction by establishing a one-to-one relationship between the degree of cure and the glass transition temperature, which is assumed to be a structural parameter during the polymerisation. A detailed experimental investigation of specific heat capacity, thermal conductivity, secondary transformations (gelation and vitrification), thermal and chemical volume changes and stress relaxation moduli was carried out to establish a suitable database for the resin. Where possible, a closed analytical model was employed; alternatively, an interpolation procedure was developed evaluate the changes in a selected property during a more complex temperature profile. Experimental equipment was developed to perform shrinkage measurements on the neat resin system; the results obtained were later compared with experimental data from standard liquid dilatometry tests. A simulation of the curing of a bi-material cantilever beam is presented as a test case highlight the influence of property changes on the final curvature. Sample curvature during the experiment was recorded using a digital camera and then analysed using graphical software. The correlation between the observed values of curvature and the results of a finite element based simulation was used to validate the kinetics model and property modelling for the chosen thermosetting resin.
Open Access
Cure modelling and monitoring of epoxy/amine resin systems
(Cranfield University, 1998-03) Karkanas, Panagiotis I.; Partridge, Ivana K.
Thermoanalytical techniques and dielectric analysis were used in this study to describe and characterise the cure processes occurring during the isothermal and dynamic cures of four epoxy/amine resin systems. The complexity of the cure reactions was illustrated by results from DSC and FTIR experiments and was attributed to the variety of chemical reactions between the epoxy and the amine groups. Several phenomenological and mechanistic cure kinetics models were constructed, based on the cure reaction mechanisms, in order to simulate the degree of conversion during the cure. A one-to-one relationship was established between the degree of cure and the glass transition temperature of the curing resin, which was finther used in the construction of chemoviscosity models and in a simulation of the viscosity advancement during the cure. A number of mathematical techniques were utilised to evaluate the parameters involved in all the models, varying from simple linear regression methods to complex non-linear least squared estimation procedures. An in-situ dielectric monitoring technique was used in combination with the above mentioned chemorheological models, to investigate the feasibility of a quantitative correlation between the changes in the dielectric signal, the cure advancement and the major physical transformations, namely gelation and vitrification. The imaginary impedance response of the curing resin, as measured by the dielectric technique, showed good agreement with the degree of conversion, depicting all the crucial characteristics of the curing mechanism, such as autocatalysis and diflusion. The endset of the cure reaction was also identified from the endset of the conductivity changes and correlated to the vitrification time. The analytical chemorheological models developed in this study to describe the cure processes for some epoxy/amine resin systems, along with the dielectric monitoring technique used, suggest that a real-time link between the above mentioned models and the cure monitoring technique can be achieved. This would greatly enhance the predictive capability of the technique and form the basis of a future feedback-loop control system.
Open Access
Delamination of Z-pinned carbon fibre reinforced laminates
(Elsevier Science B.V., Amsterdam., 2005-05-17T00:00:00Z) Denis, D. R.; Cartié, Manos Troulis; Partridge, Ivana K.
The paper outlines the current status of mechanical testing, identification of failure mechanisms and data analysis related to delamination cracking in high performance laminates made via the prepreg/autoclave route, strengthened in the through-thickness direction by Z-pinning. The applied loading cases under consideration are limited to Mode I and Mode II. Sample preparation, test methodologies and applicability of data reduction schemes are considered, with data obtained from within the range of aerospace and Formula 1 grades of carbon fibre / epoxy composites. Micromechanisms of failure in the three dimensional tests specimens are shown to be dependent on the architecture of the fibre reinforcement (i.e. unidirectional versus woven fabric prepregs), particularly in the case of Mode II loading.
Open Access
Designing with z-pins : locally reinforced composite structures
(Cranfield University, 2008-11) Lander, James K.; Partridge, Ivana K.
This thesis describes specific new applications of Z-Fibre ® pinning and focuses the attention onto the failure modes of locally reinforced (z-pinned) structures. Design implications of the use of localised reinforcement on structures, rather than laboratory coupons, are considered. Z-pinning reinforcement is applied to cylindrical crash tubes and I-section patch joints manufactured from woven carbon / epoxy pre-pregs. Z-pinning is shown to improve the Specific Energy Absorption (SEA) of the crash tubes by up to 76 %, the exact amount depending on the tube geometry. For the I-section patch joints, an initial increase in ultimate load carrying capability due to z-pin use is observed and, as the quantity of z- pins increases, a change in failure mode is induced. Z-pinning is also shown to enhance the damage tolerance of these. The ability to predict major changes to the structural response due to use of z-pins, and design for them accordingly, is the next step in the understanding of the technology. The design element of this study is contained in the development of a new Finite Element model using cohesive interface elements. The provision of mode II input data for this model comes from End Loaded Split (ELS) testing of the woven laminates and continued development of the Z-shear test. A new analysis for quantifying the crack sliding displacement, based on the ELS test, is developed. Z-shear testing has shown that the z-pin ‘mode II’ fracture energy is strongly affected by the amount of mode I opening of the shear surfaces. Here, new data are obtained for a fully constrained, pure mode II case. Using this modelling tool, changes in failure mode due to z-pin use can be predicted. Verification is provided by a new simulation of the I-section patch joint geometry.
Open Access
Developing cure kinetics models for interleaf particle toughened epoxies
(Society for the Advancement of Material and Process Engineering (SAMPE), 2016-12-31) Kratz, James; Mesogitis, Tassos; Skordos, Alexandros A.; Hamerton, Ian; Partridge, Ivana K.
In this study, we investigated the cure kinetics behaviour of the commercial Hexply® M21 thermoplastic interleaf epoxy resin system. Dynamic, isothermal, and cure interrupted modulated differential scanning calorimetry (mDSC) tests were used to measure the heat flow of the system, and semi-empirical models were fitted to the data. The cure kinetics model describes the cure rate satisfactorily, under both dynamic heating and isothermal conditions. The glass transition temperature was described using the DiBenedetto equation and showed that heating rate can influence formation of the network; therefore cure schedule must be controlled carefully during processing.
Open Access
Development of a rubber toughened epoxy adhesive loaded with carbon nanotubes, for aluminium – polymer bonds
(Cranfield University, 2009-06) Salinas-Ruiz , Maria del Mar; Partridge, Ivana K.
This thesis describes the formulation of a ternary thermosetting adhesive which consists of a diglycidyl ether of bisphenol-A (DGEBA) epoxy resin cured with 3,3’-diamino diphenyl sulphone (3,3’-DDS) hardener and modified through the addition of carboxyl- terminated butadiene-acrylonitrile (CTBN) rubber and multi-walled carbon nanotubes (MWCNTs). Processing implications of the novel adhesive in the film form are considered in order to manufacture bonded specimens for characterisation of the adhesive performance in structural joints. The ternary blend which represents the novel adhesive formulation is also characterised in bulk form. The cure kinetics behaviour of the novel ternary blend is investigated using differential scanning calorimetry which shows 10% reduction in the total reactivity, and therefore reduced final crosslinking density, with the addition of the carbon nanotubes. A cure kinetics model is developed for the novel ternary thermoset. From characterisation of cast samples, a toughening effect of the phase separated rubber particles is observed, from 144 to 317 J/m 2 , with a further increase to 551 J/m 2 in the presence of the carbon nanotubes. In the absence of rubber, the nanotubes alone produce a minimal effect upon the thermo-mechanical and mechanical characteristics of the resin. The morphology of the cured material is affected by the presence of the nanoparticles, resulting in the reduction of the mean rubber particle size from 3µm to below 1µm. The electrical conductivity of the cured resin samples is found to increase by six orders of magnitude, up to 3.6 x10 -3 S/m in the ternary blend for a low carbon nanotube concentration of 0.3 wt%. DCB and ELS tests are used to study the performance of the novel adhesive in a joint configuration. The adhesive joint strength is dependent on the substrate type as well as on the surface preparation. The novel adhesive is also examined under fatigue in a ‘bonded crack retarder’ application.
Open Access
Dielectric flow sensing in resin transfer moulding of carbon fibre reinforced composites.
(Maney Publishing, 2000-08-01T00:00:00Z) Skordos, Alexandros A.; Partridge, Ivana K.
An in situ dielectric technique for sensing flow is outlined and shown to be suitable for use in moulding of composites from liquid resins containing continuous conducting fibres. This work builds upon the recent development of a sensor for monitoring flow and cure in thermosetting composites with (non- conductive) glass reinforcements. The linear relationship between the position of the flow front in the mould and the electrical admittance of the sensor system, which is observed in resins with non-conductive reinforcements, was found to extend to resins containing conducting fibres. The performance of the sensor in detecting the position of the flow front was evaluated by comparison with visual observations. The capability of the sensing system to monitor the cure of the resin after mould filling was also investigated. The results demonstrate that the sensor can both locate the flow front accurately and monitor the cure, identifying vitrification in a way that is similar to conventional microdielectrometry. Data from flow measurements are output in complex number format, which offers the potential to produce a method that can be used to evaluate the performance of the sensor system quantitatively.
Open Access
Dielectric monitoring during the cure of epoxy resin blends
(Cranfield University, 1991-10) Maistros, G. M.; Partridge, Ivana K.; Block, H.
Dielectric monitoring and supporting techniques (differential Scanning calorimetry, infra-red spectrosoopy, viscometry, dynamic mechanical thermal analysis and light transmittance) were used to study the isothermal cure reaction of the CTBN rubber modified DGEBA resin/amine hardener blends. The neat system was also examined for the required knowledge of the matrix properties. The complexity of the cure kinetics was demonstrated by the use of a rapid technique for kinetic parameters evaluation. The utility of the dielectric cure monitoring is focused at the observation of evidence o phase separation, gelation and vitrification. The phase separatlon which the blends underwent during the cure was detected by the dielectric »monitoring through a permittivity increase at the low frequency response. The onset of the rapid viscosity increase leading to gelation was also indicated by the sharp decrease o the dielectric constant atlhigh frequencies. The frequency dependence of the times reach the dielectric loss peaks was used to predict successfully the vitrification times during the isothermal reactions o the blends. The in-situ nature o the technique and the basic understanding o the features appearing in the dielectric signal during the cure reaction provide the basis for the use of dielectric monitoring in the process of composite materials, manufacture.
Open Access
Dielectric monitoring of carbon nanotube network formation in curing thermosetting nanocomposites
(Iop Publishing Ltd, 2009-01-01T00:00:00Z) Battisti, Andrea; Skordos, Alexandros A.; Partridge, Ivana K.
This paper focuses on monitoring of carbon nanotube (CNT) network development during the cure of unsaturated polyester nanocomposites by means of electrical impedance spectroscopy. A phenomenological model of the dielectric response is developed using equivalent circuit analysis. The model comprises two parallel RC elements connected in series, each of them giving rise to a semicircular arc in impedance complex plane plots. An established inverse modelling methodology is utilized for the estimation of the parameters of the corresponding equivalent circuit. This allows a quantification of the evolution of two separate processes corresponding to the two parallel RC elements. The high frequency process, which is attributed to CNT aggregates, shows a monotonic decrease in characteristic time during the cure. In contrast, the low frequency process, which corresponds to inter-aggregate phenomena, shows a more complex behaviour explained by the interplay between conductive network development and the cross-linking of the polymer.
Open Access
A dielectric sensor for measuring flow in resin transfer moulding.
(Iop Publishing Ltd, 2000-01-01T00:00:00Z) Skordos, Alexandros A.; Karkanas, Panagiotis I.; Partridge, Ivana K.
The development, analysis and experimental validation of a novel flow and cure sensor for use in the resin transfer moulding of composites are presented. A linear relationship is established between the flow front position in the mould and electrical admittance measurements gathered using the sensor setup, allowing accurate flow front location. The sensor performance as an indicator of flow front position is evaluated using visual verification. Its efficiency for monitoring of the curing stage is assessed by comparison of the measurements with data obtained from more conventional microdielectrometry. Experimental results demonstrate that the sensor can locate the flow front accurately. The measurement output is in the form of a complex number; this suggests a potential qualitative self-assessment method. The monitoring of the cure process using the new sensor shows performance similar to that of the established microdielectrometric techniques.
Open Access
Dynamic bridging mechanisms of through-thickness reinforced composite laminates in mixed mode delamination
(Elsevier, 2017-11-23) Cui, Hao; Yasaee, Mehdi; Hallett, Stephen R.; Partridge, Ivana K.; Allegri, Giuliano; Petrinic, Nik
Delamination resistance of composite laminates can be improved with through-thickness reinforcement such as Z-pinning. This paper characterises the bridging response of individual carbon fibre/BMI Z-pins in mixed mode delamination at high loading rate using a split Hopkinson bar system. The unstable failure process in quasi-static tests, was also captured with high sampling rate instruments to obtain the complete bridging response. The energy dissipation of the Z-pins were analysed, and it was found that the efficacy of Z-pinning in resisting delamination growth decreased with an increase in mixed mode ratio, with a transition from pull-out to pin rupture occurring. The Z-pin efficacy decreased with loading rate for all mode mix ratios, due to the changing in failure surface with loading rate and rate-dependent frictional sliding.
Open Access
Dynamic bridging response of through-thickness reinforcement in composite laminates
(International Committee on Composite Materials, 2017-12-31) Cui, Hao; Melro, António R.; Mahadik, Yusuf; Yasaee, Mehdi; Allegri, Giuliano; Partridge, Ivana K.; Hallett, Stephen R.; Petrinic, Nik
The present experimental study aims to extend the understanding of delamination crack bridging mechanisms in Z-pinned laminates subjected to highly dynamic loading conditions. The bridging response of single Z-pins was characterized with both quasi-static and high loading rate. Standard delamination tests of Z-pinned laminates were carried out at varying velocity. The experimental results at both length scales showed that Z-pin efficiency in improving delamination resistance decreases with increasing loading rate.
Open Access
Effect of carbon nanoparticle addition on epoxy cure
(Cranfield University, 2007-11) Dimopoulos, Athanasios; Partridge, Ivana K.
The thesis reports studies of cure kinetics and the glass transition temperature advancements of three commercial epoxy resin systems: MY 750 / HY 5922 (Vantico), MTM 44 -1 (ACG) and 8552 (Hexcel Composites). This investigation was conducted with the utilisation of Differential Scanning Calorimetry (DSC) and Temperature Modulated DSC (TMDSC). Appropriate phenomenological cure kinetics models were built to predict the degree of cure as a function of temperature/time profile. The validity of superposition of dynamic and isothermal experimental data was established. Rheological measurements were performed in order to determine the gelation region under given cure conditions. The cure modelling methodology was validated against an international Round-Robin exercise led by the University of British Columbia (Canada). The effects of carbon nanoparticle incorporation on the cure kinetics and the glass transition temperature advancement of two of the epoxy systems were also studied. Cure kinetics models were developed for the nanocomposites containing commercial multiwalled carbon nanotubes and a direct comparison was made with the models of the neat resin systems. The glass transition temperature advancement is shown to be affected in the early stages of the cure. The state of the dispersion of the nanoparticles was studied in order to correlate it with the observed effects upon the cure and on the morphology of the cured samples. The presence of carbon nanotube clusters is shown to have an influence on the phase separation in the MTM 44-1 resin system. As a potential industrial application of this study, optical fibre refractometers were utilised as an on-line cure monitoring technique. A good correlation was established between the measured refractive index changes during the cure and the degree of cure predicted by the above mentioned models, for the neat resin systems and their nanocomposites.

Browsing by Author "Partridge, Ivana K."

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