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Tate J.S.,Texas State University | Akinola A.T.,Texas State University | Sprenger S.,Nanoresins AG
International SAMPE Symposium and Exhibition (Proceedings) | Year: 2010

Wind power has capability to become a major contributor to America's electricity supply over the next three decades. Wind turbine power ratings have steadily increased with an average of 1.5+ MW. This has been accomplished primarily by increasing the blade length, which increases power by the square of the blade length. Polymer matrix composites (E-glass/epoxy) dominate the wind turbine blade market because of their low cost, superior fatigue characteristics, high specific stiffness, and ability to make complex geometries. Wind turbines blade failure is a major issue as failure rates are as high as 20% within three years. Major causes of wind turbine blades are manufacturing errors, bad bonds, delamination and voids, leading-edge erosion, and trailing-edge splits. The cyclic bending and twisting of wind turbine blades in the operation is termed as fatigue. The mechanical (especially fatigue) performance of existing material system can be enhanced by addition of nanoparticles in epoxy resin. The major objective of this research is to develop a material system that has enhanced fatigue performance compared to existing systems of wind turbine blades. This solution not only would reduce wind turbine blade failures, but also would help in building longer but lighter blades. Further this solution can be implemented for other applications, such as helicopter rotor blades, which has similar loading as that of wind turbine blades.


Zhang H.,CAS National Center for Nanoscience and Technology | Tang L.,CAS National Center for Nanoscience and Technology | Zhang Z.,CAS National Center for Nanoscience and Technology | Gu L.,Chery Automobile Co. | And 2 more authors.
Tribology International | Year: 2010

Hybrid nanocoatings are one of the most attractive topics in nanomaterials which have achieved the transition from fundamental researches to practical applications. In the present study, a urethane-acrylate oligomer was mixed with varied concentrations of nanosilica particle sol, spin-coated onto polycarbonate substrate and finally cured by ultraviolet (UV) rays. The morphology, mechanical properties and wear resistance of the resultant hybrid coatings were systematically investigated. Infrared spectroscopy (IR) analysis was performed to determine the eventual curing extent of the mixtures studied. The transmission electron microscopy (TEM) micrographs revealed almost perfect dispersion of the nanosilica particles within organic matrices, which ensured the excellent transparence of the hybrid coatings. Nanoindentation was further conducted to determine the mechanical properties, i.e. hardness, elastic modulus and their nanoparticle loading dependence. The short-term wear resistance was characterized by a pencil hardness tester. Moreover a universal micro-tribotester (UMT) was applied to investigate the long-term performance. As a result, about 20% decrease in coefficient of friction (COF) was achieved by the coating filled with 40 wt% nanosilica particles, compared to that of the unfilled coating. Under the same fretting test conditions, the wear rate in terms of wear volume of the hybrid coating containing 40 wt% nanoparticles was about 70 times lower than that of the neat coating, confirming the wear-reduction capability of the nanoparticles. The related wear mechanisms were discussed based on worn-surface observations. © 2009 Elsevier Ltd. All rights reserved.


Hsieh T.H.,Imperial College London | Kinloch A.J.,Imperial College London | Taylor A.C.,Imperial College London | Sprenger S.,Nanoresins AG
Journal of Applied Polymer Science | Year: 2011

Silica nanoparticles and multiwalled carbon nanotubes (MWCNTs) have been incorporated into an anhydride-cured epoxy resin to form "hybrid" nanocomposites. A good dispersion of the silica nanoparticles was found to occur, even at relatively high concentrations of the nanoparticles. However, in contrast, the MWCNTs were not so well dispersed but relatively agglomerated. The glass transition temperature of the epoxy polymer was 145°C and was not significantly affected by the addition of the silica nanoparticles or the MWCNTs. The Young's modulus was increased by the addition of the silica nanoparticles, but the addition of up to 0.18 wt % MWCNTs had no further significant effect. The addition of both MWCNTs and silica nanoparticles led to a significant improvement in the fracture toughness of these polymeric nanocomposites. For example, the fracture toughness was increased from 0.69 MPam 1/2 for the unmodified epoxy polymer to 1.03 MPam 1/2 for the hybrid nanocomposite containing both 0.18 wt % MWCNTs and 6.0 wt % silica nanoparticles; the fracture energy was also increased from 133 to 204 J/m 2. The mechanisms responsible for the enhancements in the measured toughness were identified by observing the fracture surfaces using field-emission gun scanning electron microscopy. © 2010 Wiley Periodicals, Inc.


Zhang H.,CAS National Center for Nanoscience and Technology | Zhang H.,University of Chinese Academy of Sciences | Tang L.,CAS National Center for Nanoscience and Technology | Zhou L.,CAS National Center for Nanoscience and Technology | And 2 more authors.
Composites Science and Technology | Year: 2011

We applied two kinds of silica nanoparticles, i.e. colloidal and pyrogenic ones, to improve the performance of transparent coatings on polymer substrates. The urethane-acrylate oligomer was mixed with varied concentrations of silica nanoparticles, spin-coated onto polycarbonate substrate and finally cured by ultraviolet rays. The resultant thickness of the coatings can be controlled in the range of 20-30 μm. The transmission electron microscopy revealed that both silica nanoparticles presented different dispersion states, i.e. mono-dispersion for the colloidal nanoparticles and floc-like dispersion for the pyrogenic ones. In comparison with the colloidal nanoparticles filled coatings, the pyrogenic ones exhibited much improved modulus, hardness and wear resistance, but slightly decreased optical properties such as transmittance, haze and gloss. The nanoparticle morphology, amorphous structure, dispersion state and particle-matrix interfacial bonding relating to these properties were discussed in the present study. © 2010 Elsevier Ltd.


Manjunatha C.M.,Imperial College London | Taylor A.C.,Imperial College London | Kinloch A.J.,Imperial College London | Sprenger S.,Nanoresins AG
Journal of Reinforced Plastics and Composites | Year: 2010

A thermosetting epoxy polymer was modified by incorporating 9 wt% of a CTBN rubber microparticles. The stress-controlled CA tensile fatigue behavior at stress ratio, R = 0.1 for both the neat and the modified epoxy was investigated. The addition of rubber particles increased the epoxy fatigue life by a factor of about three to four times. The rubber particle cavitation and plastic deformation of the surrounding material was observed to contribute to the enhanced fatigue life of the epoxy polymer. Then, the neat and the rubber-modified epoxy resins were infused into a quasi-isotropic, lay-up E-glass fiber, non-crimp fabric in a RIFT set -up to fabricate GFRP composite panels. Further, the stress-controlled CA tensile fatigue tests at stress ratio, R = 0.1 were performed on both of these GFRP composites. Matrix cracking and stiffness degradation was continuously monitored during the fatigue tests. Similar to bulk epoxy fatigue behavior, the fatigue life of GFRP composites increased by a factor of about three times due to the presence of rubber particles in the epoxy matrix. The suppressed matrix cracking and the reduced crack propagation rates in the rubber-modified matrix contribute towards the enhanced fatigue life of GFRP composites employing a rubber-modified epoxy matrix. © The Author(s), 2010.


Manjunatha C.M.,Imperial College London | Taylor A.C.,Imperial College London | Kinloch A.J.,Imperial College London | Sprenger S.,Nanoresins AG
Composites Science and Technology | Year: 2010

An anhydride-cured thermosetting epoxy polymer was modified by incorporating 10 wt.% of well-dispersed silica nanoparticles. The stress-controlled tensile fatigue behaviour at a stress ratio of R = 0.1 was investigated for bulk specimens of the neat and the nanoparticle-modified epoxy. The addition of the silica nanoparticles increased the fatigue life by about three to four times. The neat and the nanoparticle-modified epoxy resins were used to fabricate glass fibre reinforced plastic (GFRP) composite laminates by resin infusion under flexible tooling (RIFT) technique. Tensile fatigue tests were performed on these composites, during which the matrix cracking and stiffness degradation was monitored. The fatigue life of the GFRP composite was increased by about three to four times due to the silica nanoparticles. Suppressed matrix cracking and reduced crack propagation rate in the nanoparticle-modified matrix were observed to contribute towards the enhanced fatigue life of the GFRP composite employing silica nanoparticle-modified epoxy matrix. © 2009 Elsevier Ltd. All rights reserved.


Hsieh T.H.,Imperial College London | Kinloch A.J.,Imperial College London | Masania K.,Imperial College London | Sohn Lee J.,Imperial College London | And 2 more authors.
Journal of Materials Science | Year: 2010

The present paper investigates the effect of adding silica nanoparticles to an anhydride-cured epoxy polymer in bulk and when used as the matrix of carbon- and glass-fibre reinforced composites. The formation of 'hybrid' epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms. The fracture energy of the bulk epoxy polymer was increased from 77 to 212 J/m2 by the presence of 20 wt% of silica nanoparticles. The observed toughening mechanisms that were operative were (a) plastic shear-yield bands, and (b) debonding of the matrix from the silica nanoparticles, followed by plastic void-growth of the epoxy. The largest increases in toughness observed were for the 'hybrid' materials. Here a maximum fracture energy of 965 J/m2 was measured for a 'hybrid' epoxy polymer containing 9 wt% and 15 wt% of the rubber microparticles and silica nanoparticles, respectively. Most noteworthy was the observation that these increases in the toughness of the bulk polymers were found to be transferred to the fibre composites. Indeed, the interlaminar fracture energies for the fibre-composite materials were increased even further by a fibre-bridging toughening mechanism. The present work also extends an existing model to predict the toughening effect of the nanoparticles in a thermoset polymer. There was excellent agreement between the predictions and the experimental data for the epoxy containing the silica nanoparticles, and for epoxy polymers containing micrometre-sized glass particles. The latter, relatively large, glass particles were investigated to establish whether a 'nano-effect', with respect to increasing the toughness of the epoxy bulk polymers, did indeed exist. © 2009 Springer Science+Business Media, LLC.


Hsieh T.H.,Imperial College London | Kinloch A.J.,Imperial College London | Masania K.,Imperial College London | Taylor A.C.,Imperial College London | Sprenger S.,Nanoresins AG
Polymer | Year: 2010

The present paper considers the mechanical and fracture properties of four different epoxy polymers containing 0, 10 and 20wt.% of well-dispersed silica nanoparticles. Firstly, it was found that, for any given epoxy polymer, their Young's modulus steadily increased as the volume fraction, v f, of the silica nanoparticles was increased. Modelling studies showed that the measured moduli of the different silica-nanoparticle filled epoxy polymers lay between upper-bound values set by the Halpin-Tsai and the Nielsen 'no-slip' models, and lower-bound values set by the Nielsen 'slip' model; with the last model being the more accurate at relatively high values of v f. Secondly, the presence of silica nanoparticles always led to an increase in the toughness of the epoxy polymer. However, to what extent a given epoxy polymer could be so toughened was related to structure/property relationships which were governed by (a) the values of glass transition temperature, T g, and molecular weight, M c, between cross-links of the epoxy polymer, and (b) the adhesion acting at the silica nanoparticle/epoxy-polymer interface. Thirdly, the two toughening mechanisms which were operative in all the epoxy polymers containing silica nanoparticles were identified to be (a) localised shear bands initiated by the stress concentrations around the periphery of the silica nanoparticles, and (b) debonding of the silica nanoparticles followed by subsequent plastic void growth of the epoxy polymer. Finally, the toughening mechanisms have been quantitatively modelled and there was good agreement between the experimentally-measured values and the predicted values of the fracture energy, G c, for all the epoxy polymers modified by the presence of silica nanoparticles. The modelling studies have emphasised the important roles of the stress versus strain behaviour of the epoxy polymer and the silica nanoparticle/epoxy-polymer interfacial adhesion in influencing the extent of the two toughening mechanisms, and hence the overall fracture energy, G c, of the nanoparticle-filled polymers. © 2010 Elsevier Ltd.


Manjunatha C.M.,National Aerospace Laboratories, Bangalore | Sprenger S.,Nanoresins AG | Taylor A.C.,Imperial College London | Kinloch A.J.,Imperial College London
Journal of Composite Materials | Year: 2010

A thermosetting epoxy-polymer was modified by incorporating 9 wt% of carboxyl-terminated butadiene-acrylonitrile rubber microparticles and 10 wt% of silica nanoparticles. The tensile fatigue behavior at a stress ratio, R = 0.1 for both the neat-epoxy polymer (i.e., unmodified) and the hybrid-epoxy polymer was first investigated. The fatigue life of the hybrid-epoxy polymer was about six to ten times higher than that of the neat-epoxy polymer. Secondly, the neat- and the hybrid-epoxy resins were infused into a quasi-isotropic lay-up, E-glass fiber fabric via a ĝ€Resin Infusion under Flexible Tooling' set-up to fabricate glass-fiber reinforced plastic (GFRP) composite panels. The tensile fatigue tests at a stress ratio, R = 0.1 were performed on both of these GFRP composites during which the matrix cracking and stiffness degradation were routinely monitored. The fatigue life of the GFRP composite increased by about six to ten times due to employing the hybrid-epoxy matrix, compared to employing the neat-epoxy matrix. Suppressed matrix cracking and a reduced crack propagation rate were observed in the hybrid-epoxy matrix, which resulted from the various toughening micromechanisms induced by the presence of both the rubber microparticles and silica nanoparticles. These factors were considered to contribute towards the enhanced fatigue life which was observed for the GFRP composite employing the hybrid-epoxy matrix. © The Author(s), 2010.


Grant
Agency: Cordis | Branch: FP7 | Program: JTI-CS | Phase: JTI-CS-2010-1-GRA-01-028 | Award Amount: 73.44K | Year: 2010

The aim of the proposal is to modify several epoxy resin systems designed for the manufacture of fiber reinforced composites. These modifications include the use of silica nanoparticles, toughneres like core shell elastomers and combinations thereof. The modified resin systems are adapted to the processing conditions in the manufacture of the FRCs. The modifications are selected to increse significantly the performance of the FRCs by means of toughness, stiffness, fatigue etc.

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