Endre søk
Begrens søket
1234567 151 - 200 of 1232
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 151.
    Cameron, Christopher John
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Wennhage, Per
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Numerisk akustik.
    Rahmqvist, Sven
    Saab Automobile AB.
    Structural: acoustic Design of a Multi-functional Sandwich Body Panel for Automotive Applications2008Inngår i: Proceedingsof the 8th International Conference on Sandwich Structures / [ed] A. J. M. Ferreira, 2008, s. 896-907Konferansepaper (Annet vitenskapelig)
  • 152.
    Carlson, Tony
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Multi-functional composite materials: CFRP thin film capacitors2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The use of lightweight materials in structural applications is ever increasing. Today, lightweight engineering materials are needed to realise greener, safer and more competitive products. A route to achieve this could be to combine more than one primary function in a material or component to create multi-functionality, thus reducing the number of components and ultimately the overall weight. This thesis presents an approach towards realising novel multi-functional polymer composites. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. In papers I and II, capacitors have been manufactured using different papers and polymer films as dielectric separator employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/polymer film adhesion. The manufactured materials were evaluated for mechanical performance by ILSS and tearing tests and electrical performance by measuring capacitance and dielectric breakdown voltage. In paper III the concept was extended in a parametric study using the most promising approach with a polymer film as dielectric separator. Three thicknesses of PET (50, 75 and 125 µm) were used as dielectric separator with carbon fibre/epoxy pre-pregs as structural electrodes. PET was chosen due to availability in different thicknesses as well as the frequent use in ordinary capacitors making it a suitable candidate. As in paper I and II, plasma treatment was used to improve the PET/epoxy adhesion. The capacitor materials were evaluated for mechanical performance by tensile tests and ILSS and for electrical performance by measuring capacitance and dielectric breakdown voltage. The multifunctional materials shows good potential for replacing steel and other materials with lower specific mechanical properties but cannot match the high specific mechanical performance of mono-functional materials. Both mechanical and electrical performance could have large benefits from developing new separator materials adapted for use in multifunctional applications and could be an interesting field for extended research.

  • 153.
    Carlson, Tony
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Multifunctional composite materials: Design, manufacture and experimental characterisation2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The use of lightweight materials in structural applications is ever increasing. Today, lightweight engineering materials are needed to realise greener, safer and more competitive products. A route to achieve this could be to combine more than one primary function in a material or component to create multifunctionality, thus reducing the number of components and ultimately the overall weight. This thesis presents approaches towards realising novel multifunctional polymer composites, which simultaneously can carry mechanical loads and store electrical energy. For this purpose, structural capacitor and battery materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. In papers I and II, structural capacitors have been realised using different papers and polymer films as dielectric separator and employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/polymer film adhesion. The manufactured materials were evaluated for mechanical performance by interlaminar shear strength (ILSS) and tearing tests and electrical performance by measuring capacitance and dielectric breakdown voltage.In paper III the concept was extended in a parametric study using the most promising approach with a polymer film as dielectric separator. Three thicknesses of PET (50, 75 and 125 μm) were used as dielectric separator with carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used to improve the PET/epoxy adhesion. The capacitor materials were evaluated for mechanical performance by tensile and ILSS tests and for electrical performance by measuring capacitance and dielectric breakdown voltage. The multifunctional materials show good potential for replacing steel and other materials with lower specific mechanical properties but cannot match the high specific mechanical performance of monofunctional materials.Paper IV explores the effects of matrix cracking on the structural composite capacitormaterials performance. The structural capacitor materials were made from carbonfibre/epoxy pre-pregs as structural electrodes with thermoplastic PET as dielectricseparator as done in paper III. A method to induce and to measure the effect of matrixcracks on electrical properties was developed and used. The method is based on asimple tensile test and proved to be quick and easy to perform with consistent results.The structural capacitor material was found to maintain its capacitance even aftersignificant intralaminar matrix cracking in the CFRP electrodes from high tensilemechanical loads.Paper V explores another possible route for electrical energy storage in structural composites in the form of structural composite batteries. A laminated design approach would result in too long distances for ion mobility to give any useful energy storage with very low power density. Therefore, the work in this paper was focused on making each individual carbon fibre in a tow into a battery. Thus, realising a large number of batteries connected in parallel within a composite material. This is done by electro polymerisation of a solid polymer electrolyte onto the surface of the carbon fibres. The resulting sleeve of polymer is typically 500 nm thick making it thin enough to achieve useful electrical performance even with the relatively low ion conductivities of the employed solid polymer electrolytes. This paper demonstrates a new way forward to realise intrinsic multifunctional composite battery materials.

  • 154.
    Carlson, Tony
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    An experimental study into the effect of damage on the capacitance of structural composite capacitors2013Inngår i: Journal of Multifunctional Composites, ISSN 2168-4246, Vol. 1, nr 2, s. 91-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the work to characterise the effects of tensile induced matrix cracks on capacitance of structural composite capacitor materials. The study is based on earlier work within the field of multifunctional materials where mechanical and electrical properties have been characterised. Effects of damage on electrical properties have, however, not been covered by earlier studies. The structural capacitor materials were made from carbon fibre/epoxy pre-pregs as structural electrodes with thermoplastic PET as the dielectric separator. NaOH etching was used as a route for improved adhesion between the epoxy and PET to ensure matrix cracking in the CFRP electrodes occurred prior to delamination between the electrodes and the PET separator. A method to induce and measure the effect of the matrix cracks on electrical properties was successfully developed and used in this study. The method is based on a simple tensile test and proved to be quick and easy to perform with consistent results. The structural capacitor material was found to maintain its capacitance even after significant intralaminar matrix cracking in the CFRP electrodes from high tensile mechanical loads.

  • 155.
    Carlson, Tony
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Carbon fibre composites capacitors for short term electric energy storage in structural applications2011Inngår i: 18th International Conference on Composites Materials, ICCM 2011: Jeju; South Korea; 21 August 2011 through 26 August 2011, 2011Konferansepaper (Fagfellevurdert)
  • 156.
    Carlson, Tony
    et al.
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Plasma treatment: a route for improved adhesion between pet and epoxy in multifunctional composite capacitors?2012Inngår i: Proceedings of the 15th European Conference on Composite Materials / [ed] Marino Quaresimin; Laszlo Kollar; Leif Asp, Venice, 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an approach towards realising novel multifunctional polymer composites. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The capacitors were made using three thicknesses of DuPont Mylar A thermoplastic PET as dielectric separator employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/PET adhesion employing a number of treatment times, 5, 10, 15, 20 and 25s. The manufactured materials have been mechanically and electrically tested to evaluate their multifunctional efficiency. Plasma treatment have been shown to give some improvements to the interlaminate shear strength but not to any significant degree

  • 157.
    Carlson, Tony
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structural carbon fibre composite/PET capacitors: Effects of dielectric separator thickness2013Inngår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 49, s. 16-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an approach towards realising novel multifunctional polymer composites with combined structural and electric energy storing ability. A series of structural capacitors were made using three thicknesses of DuPont Mylar A thermoplastic PET as a dielectric separator employing carbon fibre/epoxy pre-pregs as structural electrodes. Plasma treatment was used as a route for improved epoxy/PET adhesion. The manufactured materials were mechanically and electrically tested to evaluate their multifunctional efficiency.The multifunctional materials developed show good potential for replacing steel, aluminium and other materials with lower specific mechanical properties but do not match the high specific mechanical and electrical performance of monofunctional composites and capacitors.

  • 158.
    Carlson, Tony
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ordéus, Daniel
    Swerea SICOMP AB.
    Wysocki, M.
    Swerea SICOMP AB.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    CFRP structural capacitor materials for automotive applications2011Inngår i: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, nr 6/7, s. 311-316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy prepreg woven lamina separated by a polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and tearing force. The developed structural carbon fibre reinforced polymer (CFRP) capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.

  • 159.
    Carlson, Tony
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ordéus, Daniel
    Swerea SICOMP AB.
    Wysocki, Maciej
    Swerea SICOMP AB.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Structural capacitor materials made from carbon fibre epoxy composites2010Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, nr 7, s. 1135-1140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy pre-preg woven laminae separated by a paper or polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and interlaminar shear strength. The developed structural CFRP capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.

  • 160.
    Castro, Daniele Oliveira
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. MoRe Research Örnsköldsvik AB, Örnsköldsvik, Sweden.
    Karim, Zoheb
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. MoRe Research Örnsköldsvik AB, Örnsköldsvik, Sweden.
    Medina, Lilian
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Häggström, J. -O
    Carosio, F.
    Svedberg, A.
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Söderberg, Daniel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    The use of a pilot-scale continuous paper process for fire retardant cellulose-kaolinite nanocomposites2018Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 162, s. 215-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured materials are difficult to prepare rapidly and at large scale. Melt-processed polymer-clay nanocomposites are an exception, but the clay content is typically below 5 wt%. An approach for manufacturing of microfibrillated cellulose (MFC)/kaolinite nanocomposites is here demonstrated in pilot-scale by continuous production of hybrid nanopaper structures with thickness of around 100 μm. The colloidal nature of MFC suspensions disintegrated from chemical wood fiber pulp offers the possibility to add kaolinite clay platelet particles of nanoscale thickness. For initial lab scale optimization purposes, nanocomposite processing (dewatering, small particle retention etc) and characterization (mechanical properties, density etc) were investigated using a sheet former (Rapid Köthen). This was followed by a continuous fabrication of composite paper structures using a pilot-scale web former. Nanocomposite morphology was assessed by scanning electron microscopy (SEM). Mechanical properties were measured in uniaxial tension. The fire retardancy was evaluated by cone calorimetry. Inorganic hybrid composites with high content of in-plane oriented nanocellulose, nanoclay and wood fibers were successfully produced at pilot scale. Potential applications include fire retardant paperboard for semi structural applications.

  • 161. Challamel, Noel
    et al.
    Girhammar, Ulf Arne
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Boundary-Layer Effect in Composite Beams with Interlayer Slip2011Inngår i: Journal of Aerospace Engineering, ISSN 0893-1321, E-ISSN 1943-5525, Vol. 24, nr 2, s. 199-209Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An apparent analytical peculiarity or paradox in the bending behavior of elastic-composite beams with interlayer slip, sandwich beams, or other similar problems subjected to boundary moments exists. For a fully composite beam subjected to such end moments, the partial composite model will render a nonvanishing uniform value for the normal force in the individual subelement. This is from a formal mathematical point of view in apparent contradiction with the boundary conditions, in which the normal force in the individual subelement usually is assumed to vanish at the extremity of the beam. This mathematical paradox can be explained with the concept of boundary layer. The bending of the partially composite beam expressed in dimensionless form depends only on one structural parameter related to the stiffness of the connection between the two subelements. An asymptotic method is used to characterize the normal force and the bending moment in the individual subelement to this dimensionless connection parameter. The outer expansion that is valid away from the boundary and the inner expansion valid within the layer adjacent to the boundary (beam extremity) are analytically given. The inner and outer expansions are matched by using Prandtl's matching condition over a region located at the edge of the boundary layer. The thickness of the boundary layer is the inverse of the dimensionless connection parameter. Finite-element results confirm the analytical results and the sensitivity of the bending solution to the mesh density, especially in the edge zone with stress gradient. Finally, composite beams with interlayer slip can be treated in the same manner as nonlocal elastic beams. The fundamental differential equation appearing in the constitutive law associated with the partial-composite action in a nonlocal elasticity framework is discussed. Such an integral formulation of the constitutive equation encompassing the behavior of the whole of the beam allows the investigation of the mechanical problem with the boundary-element method.

  • 162.
    Chatterjee, Sanjukta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Structural and Physical Effects of Carbon Nanofillers in Thermoplastic and Thermosetting Polymer Systems2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ever since the discovery of carbon nano materials like carbon nanotube (CNT) and graphene, this class of materials has gained significant attention due to their exotic properties. The principle idea of my present research project is to understand the novel improvements induced in polymer matrices with inclusion of the nanofillers. This thesis is thematically divided into three parts.

    In the first part we introduce principle materials that we use for preparation of composites. Methods of nanofiller preparation and different nanocomposites as previously reported in literature are discussed to formulate the basis of our study. Different dispersion techniques are discussed which facilitate uniform nanofiller distribution. A variety of experimental methods are described which were employed to investigate the structure and properties of the composites.

    In the second part we discuss in details polyamide-12 (PA12) composites using CNT and graphene as fillers. A marked improvement is recorded in the toughness of the films with incorporation of CNT, dispersed in PA12 using a surfactant. Electrical percolation is also achieved in the otherwise insulating matrix. With PA-12 fibers we explored the effect of fiber processing and CNT incorporation in the mechanical properties. Extensive wide angle x-ray diffraction was carried out to interpret the structural modifications brought about by CNT in the matrix.

    The final part of the thesis deals with a thermosetting polymer, epoxy composites. CNT, Graphene and also a mixture of the two nanofillers were used as reinforcing agents. Appreciable improvement was recorded in the mechanical properties, electrical and thermal conductivity of the composites. Detailed optical and electron microscopy was carried out to get a vivid idea of the micro-structure and dispersion.

    The presented work demonstrates the significant ability of carbon nanofillers to reinforce polymer matrices enhancing their mechanical, electrical and thermal properties and opening a wide horizon for a variety of applications.

  • 163.
    Chatterjee, Sanjukta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    The size and synergy effects of graphene nanoplatelets andcarbon nanotubes in mechanical properties of epoxy composites.Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We study mechanical reinforcement in a widely used epoxy matrix with the addition of graphenenanoplatelets (GnPs) and various mixture ratios of carbon nanotubes (CNTs) withGnPs. Two different dimensions of GnPs were used with flake sizes of 5 mm and 25 mm toinvestigate the influence of nanofiller size on the composite properties. In the GnP reinforcedcomposites, the bigger flakes showed greater reinforcement at all GnP concentrations. The influenceof size on properties is significant as bigger flakes actively control the failure mechanismsin the composite. In the mixture samples, highest CNT content (9:1) showed significantimprovement in fracture toughness of 76 %. For composites with mixtures of CNTs andGnPs, the CNT:GnP ratio is an interesting factor significantly influencing the properties ofthe epoxy matrix. The combination of high aspect ratio of CNTs and larger surface area ofGnPs contribute to the synergistic effect of the CNT-GnP hybrid samples. Thermal conductivityconsistently increases with the incorporation of GnPs in the matrix. Transmission electronmicroscopy (TEM) images confirm the uniform nanofiller dispersion achieved in thecomposites with GnP. For the hybrid samples the CNTs are seen to align themselves on theGnP flakes creating an inter-connected strong nanofiller network in the matrix. The homogenousnanofiller dispersions have been achieved by high shear calendaring which is a methodcapable of being industrially scaled up.

  • 164. Chatterjee, Sanjukta
    et al.
    Reifler, F A
    Chu, B T T
    Hufenus, R
    Investigation of crystalline and tensile properties of carbon nanotube-filled polyamide-12 fibers melt-spun by industry-related processes2012Inngår i: Journal of Engineered Fibers and Fabrics, ISSN 1558-9250, E-ISSN 1558-9250, Vol. 7, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper addresses the influence of carbon nanotubes (CNT) on the structure and mechanical properties of high tensile strength thermoplasticpolymer fibers. Polyamide (PA) fibers with different draw ratios, with and without CNTs as fillers, and having mechanical properties close to industrial standards were spun in a pilot melt spinning plant. The morphology of the fibers was investigated using optical microscopy, nuclear magnetic resonance (NMR) and 2-D wide angle x-ray diffraction (WAXD). Differential scanning calorimetry (DSC) was carried out to get an estimation of the crystallinity. For a concise interpretation of the results of tensile measurements performed on the fibers, a parameter was developed to account for the detrimental influence of polymer extrusion on their mechanical properties. CNTs seem to act as sites for the growth of un-oriented crystalline domains converted from oriented regions, without yielding a mechanical reinforcing effect.

  • 165. Chatterjee, Sanjukta
    et al.
    Wang, J W
    Kuo, W S
    Tai, N H
    Salzmann, C
    Li, W L
    Hollertz, R
    Nüesch, F A
    Chu, B T T
    Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites2012Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 531, s. 6-10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Influence of reinforcements on mechanical and thermal properties of graphene nanoplatelets/epoxy com-posites is investigated. Amine functionalized expanded graphene nanoplatelets (EGNPs) were dispersed within epoxy resins using high-pressure processor followed by three roll milling. Functionality on the EGNPs was confirmed with FTIR and micro-Raman spectroscopy. Bending and nano-mechanical testingwas performed on the composites. Incorporation of EGNPs improved the flexural modulus and hardness of the composite and increased fracture toughness by up to 60%. Marked improvement was observed inthermal conductivity of the composites reaching 36% at 2 wt.% loading. Functionalized EGNPs exhibited significant improvements indicating favorable interaction at EGNPs/polymer interface.

  • 166. Chen, F.
    et al.
    Monnier, X.
    Gällstedt, M.
    Gedde, U.W.
    Hedenqvist, M.S.
    Wheat gluten/chitosan blends: A new biobased material2014Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 60, s. 186-197Artikkel i tidsskrift (Fagfellevurdert)
  • 167.
    Chen, Kai
    et al.
    Nanjing University of Science and Technology, Peoples R China; Nanjing University, Peoples R China.
    Guo, Rui
    Nanjing University of Science and Technology, Peoples R China.
    Ma, Chunguang
    Nanjing University of Science and Technology, Peoples R China.
    Dai, Tingyang
    Nanjing University, Peoples R China.
    Ye, Sunjie
    Nanjing University, Peoples R China.
    Lu, Yun
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhu, Jinsong
    Nanjing University, Peoples R China.
    Jiang, Wei
    Nanjing University of Science and Technology, Peoples R China.
    Self-Assembled Core-Shell Polymer Dielectric Prepared by Solution Casting Process2009Inngår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 113, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Giant permittivity at 1 MHz, which slightly changes with temperatures, is observed in a polymer composite. The dielectric spectroscopy demonstrates that the samples are electrically heterogeneous. The microstructure observation and the ingredient analysis evidence they self assemble the conducting cores surrounded by the insulating shells. The giant-dielectric phenomenon is therefore attributed to the percolation effect. The electrically heterogeneous microstructure with effective permittivity values about 10 000 can be fabricated by a simple solution casting process in air. The composite is an attractive option to the currently used printing dielectric and the future flexible electronics.

  • 168. Chen, Xiangrong
    et al.
    Murdany, Deni
    Liu, Dongming
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Mattias
    Gubanski, Stanislaw M.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Suwarno, S.
    AC and DC Pre-stressed Electrical Trees in LDPE and its Aluminum Oxide Nanocomposites2016Inngår i: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 23, nr 3, s. 1506-1514Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Resistance of pure low density polyethylene (LDPE) and its aluminum oxide nanocomposites (up to 3.0 wt%) to degradation by electrical treeing under AC stress and DC pre-stress is analyzed. The experiments were carried out on wire-plane electrode specimens before and after exposure to thermal and DC electro-thermal ageing at 80 degrees C. The obtained results showed enhanced resistance of the nanocomposites to electrical tree inception under AC stress and the tree inception voltage (TIV) increased with nanoparticles content. It has been shown that there was an improved partial discharge (PD) resistance in the nanocomposites compared to the unfilled LDPE. The results also showed that the AC TIV in the nanocomposites consistently increased with the ageing and especially the DC electro-thermally aged specimens had about 30% higher the AC TIV as compared to the unaged material. This effect is attributed to significantly reduced mobility of charge carriers in the nanocomposites. The DC pre-stressed electrical trees generated in the investigated materials were of filamentary-branch structure and the branch channels content increases with the addition of nanoparticles. The mean tree number of the DC prestressed electrical trees decreased in the LDPE and its nanocomposites while the mean maximum tree length increased with the ageing treatments. It is postulated that material recrystallization and a very high electric field level on the wire electrode during the DC pre-stressed electrical tree test are the main reasons for the observed effects.

  • 169.
    Chen, Yu-Hsiang
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Rogström, Lina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Roa, JJ
    Departament de Ciència dels Materials i Enginyería Metal·lúrgica, Universitat Politècnica de Catalunya, EEBE-Campus Diagonal Besòs, Barcelona, Spain.
    Zhu, Jianqiang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Schramm, Isabella
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten. Functional Materials, Department of Materials Science, Campus D3.3, Saarland University,Saarbrücken, Germany.
    Johnson, LJS
    Sandvik Coromant, SE-126 80 Stockholm, Sweden.
    Schell, N.
    Helmholtz-Zentrum Geesthacht (HZG), Geesthacht, Germany.
    Muecklich, F.
    Functional Materials, Department of Materials Science, Campus D3.3, Saarland University, Saarbrücken, Germany.
    Anglada, M. J.
    Departament de Ciència dels Materials i Enginyería Metal·lúrgica, Universitat Politècnica de Catalunya, EEBE-Campus Diagonal Besòs, Barcelona, Spain.
    Odén, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska fakulteten.
    Thermal and mechanical stability of wurtzite-ZrA1N/cubic-TiN and wurtzite-ZrA1N/cubic-ZrN multilayers2017Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 324, s. 328-337Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase stability and mechanical properties of wurtzite (w)-Zr(0.25)A1(0.75)N/cubic (c)-TiN and w-Zr(0.25)A1(0.75)N/c-ZrN multilayers grown by arc evaporation are studied. Coherent interfaces with an orientation relation of c-TiN (111)[1-10]IIw-ZrAlN (0001)[11-20] form between ZrA1N and TiN sublayers during growth of the w-ZrAIN/c-TiN multilayer. During annealing at 1100 degrees C a c-Ti(Zr)N phase forms at interfaces between ZrA1N and TiN, which reduces the lattice mismatch so that the coherency and the compressive strain are partially retained, resulting in an increased hardness (32 GPa) after annealing. For the w-ZrAIN/c-ZrN multilayer, there is no coherency between sublayers leading to strain relaxation during annealing causing the hardness to drop. The retained coherency between layers and the compressive strain in the w-ZrAIN/c-TiN multilayer results in superior fracture toughness compared to the w-ZrAIN/c-ZrN multilayer as revealed by cross-sectional investigations of damage events under scratch and indentation tests. (C) 2017 Elsevier B.V. All rights reserved.

    Fulltekst tilgjengelig fra 2019-05-25 16:49
  • 170.
    Chieh-Yi, Kuo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Fabrication and Optical Properties of ZnO Nanocrystal/GaN Quantum Well Based Hybrid Structures2012Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
    Abstract [en]

    Optical properties of hybrid structures based on zinc oxide nanocrystals (NCs) and Gallium Nitride quantum well (QW) has been studied. The ZnO NCs thin films on the top of GaN QW structures were fabricated using spin coating. The surface morphology was characterized by scanning electron microscopy (SEM). We have performed temperature dependence time-resolved photoluminescence (TRPL) measurements of the bare AlGaN/GaN QW structures and hybrids, containing ZnO NCs. It was found that at some temperatures the QW PL decay has shorter decay time in the presence of ZnO NCs thin film compared to the bare QW. The effect was stronger for the samples with thinner cap layers. The results are discussed in terms of three models such as exciton nonradiative energy transfer (NRET), tunneling effect, and piezoelectric field influence on the QW exciton energy.

  • 171.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Averianova, N.
    Gibadullin, M.
    Petrov, V.
    Leirset, Ingebjörg
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Micro-structural characterisation of homogeneous and layered MFC nano-composites2013Inngår i: Micron, ISSN 0968-4328, E-ISSN 1878-4291, Vol. 44Artikkel i tidsskrift (Fagfellevurdert)
  • 172.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Brodin, Malin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Karlsen, Trond
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Wood pulp fibres and nanocellulose: Characterization and application in biocomposite materials2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A composite can be defined as a material composed of two or more components having distinct morphology and chemistry, and giving synergetic effects. In this paper the term biocomposite is used, referring to i) a material having at least one bio-component (e.g. wood pulp fibres and nanofibrils) or ii) biomaterials intended for biomedical applications. The utilization of wood pulp fibres in composite materials has gained major interest during the last years. There are various wood pulp fibres that can be used as reinforcement in composites, e.g. thermo-mechanical pulp (TMP), chemi-thermo-mechanical pulp (CTMP) and kraft pulp fibres. Depending on the pulping process (TMP, CTMP or kraft pulp), the pulp fibres differ greatly with respect to the fibre morphology and chemistry. Kraft pulp fibres have been one of the most used raw materials for producing nanocellulose. Nanocellulose from wood refers to various cellulose nano-materials such as cellulose nanocrystals and nanofibrillated cellulose. Nanofibrillated cellulose is composed of a major fraction of structurally homogeneous nanofibrils having typical widths in the nanometre scale and lengths in the micrometre scale. Wood pulp fibres and nanofibrils have been proposed as reinforcement in composite materials. Some of the major motivations have been the potential improvements by using fibres and nanofibrillated materials with respect to e.g. strength, biodegradability and functionality. The purpose of the present work is to review some advances in biocomposite research and development, including three focus areas; structured biocomposites, flexible biocomposites and biomaterials.

  • 173.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Miettinen, A
    Hendriks, C.L.L
    Gamstedt, K
    Kataka, M
    Structural characterisation of kraft pulp fibres and their nanofibrillated materials for biodegradable composite applications2011Inngår i: Nanocomposites and Polymers with Analytical Methods, InTech , 2011Kapittel i bok, del av antologi (Fagfellevurdert)
  • 174.
    Chinga-Carrasco, Gary
    et al.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Solheim, O.
    Lenes, M.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Larsen, Å.
    A method for estimating the fibre length in fibre-PLA composites2013Inngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 250Artikkel i tidsskrift (Fagfellevurdert)
  • 175.
    Chiu, NingWei Justin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Recent Development in Phase Change Materials for Thermal Energy Storage2012Inngår i: BIT's 1st Annual World Congress of Advanced Materials 2012: Innovation, Cutting-Edge and Smartness / [ed] International Research Center of International Talent, Beijing China, 2012, s. 299-300Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Phase change materials (PCMs) have in the past years been in the center of research focus as an energy saving alternative. They have large potential for use in applications where intermittent energy sources are present and where shift of energy supply from user demand in time and in space is required. Examples are solar heating, night time ambient air cooling, and waste heat utilization amongst others. The materials store and release heat through change of phase from solid to liquid in endothermic process and from liquid to solid in exothermic process.

    There are currently two major axes of PCM development driven application-wise. In passive thermal energy storage (TES) systems where the predominant role of PCMs is to serve as insulating material, thermal properties of the PCMs are tailored towards low thermal conductivity so as to limit heat transfer rate. In active TES, however, the research interest has been put in ameliorating the overall thermal power output. Various methods are dispersion of highly conductive particles, impregnation of PCM in graphite matrices, and novel design of heat exchanger apparatus.

    The second research axe lies in improvement of material compatibility with the considered applications. Inorganic PCMs are characterized with subcooling effect, this means start of heat release well below the phase change temperature. While this can be used in the advantage for long term seasonal heat storage, in active cold storage systems where the working temperature range is relatively small, subcooling is to be limited in order to provide efficient thermal charge and discharge cycle. Furthermore, efforts have been put in limiting phase separation; this has a predominant role in assuring the energy storage stability for repeated charge/discharge cycles.

    This presentation will provide insights to the recent material development in the field of thermal energy storage.

  • 176.
    Chniga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Miettinen, Arttu
    Luengo Hendriks, Cris L.
    Gamstedt, Kristofer E.
    Kataja, Markku
    Structural characterisation of kraft pulp fibres and their nanofibrillated materials for biodegradable composite applications2011Inngår i: Nanocomposites and polymers with analytical methods / [ed] Cuppoletti John, InTech, 2011Kapittel i bok, del av antologi (Fagfellevurdert)
  • 177.
    Cho, O-R
    et al.
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Khartsev, S.I.
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Grishin, A.M.
    Department of Condensed Matter Physics, Royal Institute of Technology.
    Lindbäck, Ture
    Preparation of Na0.5K0.5NbO3/La0.6Sr 0.2Mni.2O3/LaAIO3 thin film structures by pulsed laser deposition1999Inngår i: Multicomponent oxide films for electronics: symposium held April 6 - 8, 1999, San Francisco, California, U.S.A ; [contains papers presented at Symposium BB, Multicomponent oxide films for electronics held at the 1999 MRS Spring Meeting] / [ed] Marilyn E. Hawley, Warrendale, Pa: Materials Research Society, 1999, s. 149-154Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on ferroelectric/giant magnetoresistive Nao.sKo.sNbCVLao.oSrojMniO} (NKN/LSMO) heterostructures gro\vn onto LaAlOj (001) single crystal using KrF pulsed laser ablation of stoichiometric ceramic target. Main processing parameters have been optimized to obtain smooth LSMO template layer, avoid NKN-LSMO interdiffusion, preserve NKN stoichiometry against the lost of volatile potassium and sodium and achieve reasonable reliability of NKN film performance. X-ray diffraction 0- 20 scans and rocking curves evidence for single-phase content and high c-axis orientation both in template LSMO and top NKN layers. Ferroelectric measurements yield remnant polarization P, of 1.5 (.iC/cm2 and spontaneous polarization Ps of 7 jiC/cm2 at electric field strength of 130 kV/cm. At room temperature, dielectric permittivity e' and dissipation factor tancJhave been found to vary from 595 to 555 and 0.046 to 0.029 respectively in the frequency range of 0.4 to 20 kHz. At 10 kHz dielectric permittivity linearly increases from 410 to 650 in the temperature range 77 K to 415 K while the dissipation factor below 320 K does not exceed 3%

  • 178. Cho, S.-W.
    et al.
    Gällstedt, M.
    RISE, Innventia.
    Johansson, E.
    Hedenqvist, M.S.
    Injection-molded nanocomposites and materials based on wheat gluten2011Inngår i: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, nr 1, s. 146-152Artikkel i tidsskrift (Fagfellevurdert)
  • 179. Cho, S.-W.
    et al.
    Gällstedt, Mikael
    RISE., Innventia.
    Hedenqvist, M.S.
    RISE., Innventia.
    Properties of wheat gluten/poly(lactic acid) laminates2010Inngår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 58, nr 12, s. 7344-7350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laminates of compression-molded glycerol-plasticized wheat gluten (WG) films surrounded and supported by poly(lactic acid) (PLA) films have been produced and characterized. The objective was to obtain a fully renewable high gas barrier film with sufficient mechanical integrity to function in, for example, extrusion-coating paper/board applications. It was shown that the lamination made it possible to make films with a broad range of glycerol contents (0-30 wt %) with greater strength than single unsupported WG films. The low plasticizer contents yielded laminates with very good oxygen barrier properties. In addition, whereas the unsupported WG films had an immeasurably high water vapor transmission rate (WVTR), the laminate showed values that were finite and surprisingly, in several cases, also lower than that of PLA. Besides being a mechanical support (as evidenced by bending and tensile data) and a shield between the WG and surrounding moisture, the PLA layer also prevented the loss of the glycerol plasticizer from the WG layer. This was observed after the laminate had been aged on an "absorbing" blotting paper for up to 17 weeks. The interlayer adhesion (peel strength) decreased with decreasing glycerol content and increasing WG film molding temperature (130 °C instead of 110 °C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 °C) did not, however, have a major effect on the final peel strength.

  • 180. Clemons, Craig M.
    et al.
    Rowell, Roger M.
    Plackett, David
    Segerholm, Kristoffer
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Chapter 13: Wood/nonwood thermoplastic composites2012Inngår i: Handbook of wood chemistry and wood composites, second edition / [ed] Rowell Roger M., Boca Racon, FL: CRC Press, 2012, 2, s. 473-508Kapittel i bok, del av antologi (Fagfellevurdert)
  • 181.
    Corvo Alguacil, Marina
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Substitution of thermosets by thermoplastic resins in electrical insulation applications2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 182.
    Crispin, Xavier
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Carbon nanotubes get high2016Inngår i: NATURE ENERGY, ISSN 2058-7546, Vol. 1, artikkel-id 16037Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Waste heat can be converted to electricity by thermoelectric generators, but their development is hindered by the lack of cheap materials with good thermoelectric properties. Now, carbon-nanotube-based materials are shown to have improved properties when purified to contain only semiconducting species and then doped.

  • 183. Cunha, A.G.
    et al.
    Zhou, Q.
    Larsson, P.T.
    RISE, Innventia.
    Berglund, L.A.
    Topochemical acetylation of cellulose nanopaper structures for biocomposites: Mechanisms for reduced water vapour sorption2014Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, nr 4, s. 2773-2787Artikkel i tidsskrift (Fagfellevurdert)
  • 184.
    Dahlman, Olof
    et al.
    RISE, Innventia.
    Larsson, Karolina
    RISE, Innventia.
    Thermoplastic wood hemicellulose-lactide graft-polymers and films2014Konferansepaper (Fagfellevurdert)
  • 185.
    Dahlman, Olof
    et al.
    RISE, Innventia.
    Larsson, Karolina
    RISE, Innventia.
    Thermoplastic wood hemicellulose-lactide graft-polymers and films2014Konferansepaper (Fagfellevurdert)
  • 186.
    Dahlström, Christina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Faria, Gregorio C
    Department of Materials Science and Engineering, Stanford University, São Carlos Physics Institute, University of São Paulo.
    Engström, Ann-Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Duong, Duc, T.
    Department of Materials Science and Engineering, Stanford University.
    Salleo, Alberto
    Department of Materials Science and Engineering, Stanford University.
    Structural Change of Cellulose Nanofibers in Supercapacitor Electrodes during Galvanostatic Cycling2015Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Graphene and other carbon-based materials are often used as electrodes in electrochemical double-layer supercapacitors (EDLCs), due to their ability to store electrical energy. Cellulose nanofibers (CNF) have been proven to be suitable as a dispersion agent and binder in graphite based electrodes for supercapacitor applications, especially due to their capability to improve the wet and dry strength of the electrode. At the same time the capacitance is maintained or even increased with addition of CNF. It is reasonable to believe that the addition of CNF manages to stabilize smaller graphite particles in the dispersion which results in larger internal surface area in the dry material.

     

    When the amount of CNF is around 20 wt%, (in ratio to the total mass of active material), both scanning electron microscopy and XPS analysis showed that the surface is almost completely covered with the nano-cellulose. Even with this isolating layer of cellulose it is interesting to note that the capacitance is as high as 90 F/g, compared to around 50 F/g for the lowest CNF amount of 5 wt%. However, by applying voltage pulses during the galvanostatic cycling procedure for capacitance measurements, an initial transient behavior is observed during the first cycles. Therefore the capacitance is calculated after 4000 charge and discharge curves, when curves are completely stabilized. We found that the electrode structure changes significantly during this capacitance measurement and already after a short pulse of 10 s and 0.3 V the structural change is noticeable. After cycling for 24 hours, a completely new structure emerges where large fiber-like structures are developed with diameters around 20-30 µm. The galvanostatic cycling procedure has created fiber-like cellulose structures around 1000 times larger than the initial size of the nano-cellulose.

     

    Structural properties of the electrode have often been related to the electronic properties in the supercapacitor. Our result shows that due to this change in the CNF structure, the electrode properties after galvanostatic cycling are indeed also of interest to study. This structural change might be critical to device performance and durability.    

  • 187.
    de Borst, Karin
    et al.
    University of Glasgow, UK.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Structure-€“function relationships in hardwood: Insight from micromechanical modelling2014Inngår i: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 345, s. 78-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract A micromechanical model is presented that predicts the stiffness of wood tissues in their three principal anatomical directions, across various hardwood species. The wood polymers cellulose, hemicellulose, and lignin, common to all wood tissues, serve as the starting point. In seven homogenisation steps, the stiffnesses of these polymers are linked to the macroscopic stiffness. The good agreement of model predictions and corresponding experimental data for ten different European and tropical species confirms the functionality and accuracy of the model. The model enables investigating the influence of individual microstructural features on the overall stiffness. This is exploited to elucidate the mechanical effects of vessels and ray cells. Vessels are shown to reduce the stiffness of wood at constant overall density. This supports that a trade-off exists between the hydraulic efficiency and the mechanical support in relation to the anatomical design of wood. Ray cells are shown to act as reinforcing elements in the radial direction.

  • 188.
    de Borst, Karin
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Wikete, Christoph
    Vienna University of Technology, Austria.
    Microstructure-€“stiffness relationships of ten European and tropical hardwood species2012Inngår i: Journal of Structural Biology, ISSN 1047-8477, E-ISSN 1095-8657, Vol. 177, nr 2, s. 532-542Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hardwood species exhibit a huge anatomical variability. This makes them perfect study objects for exploring relations between structural features at different length scales and corresponding stiffness properties of wood. We carry out microscopic analysis, nanoindentation tests, as well as macroscale ultrasonic and quasi-static tension tests and build a complete set of microstructural and corresponding micromechanical data of ten different (European and tropical) hardwood species. In addition, we apply micromechanical modeling to further elucidate the individual influences of particular structural features, which might appear only in a superimposed manner in experiments. The test results confirm the dominant influences of the microfibril angle on the stiffness at cell wall level and of density at the macroscopic scale. Vessels and ray cells affect the macroscopic stiffness of the wood tissue not only through their content, but also through their arrangement and shape: A ring-porous structure results in comparably higher longitudinal but lower radial stiffness than a diffuse-porous one. As for ray cells, large and particularly compactly shaped bundles might reduce the stiffness in tangential direction because of the fiber deviations they cause. Moreover, vessel and ray content might affect the relation between nanoindentation modulus and density-corrected macroscopic longitudinal stiffness.

  • 189.
    Dev, Apurba
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Dev Choudhury, Bikash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Abedin, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA.
    Fabrication of Periodic Nanostructure Assemblies by Interfacial Energy Driven Colloidal Lithography2014Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 24, nr 29, s. 4577-4583Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel interfacial energy driven colloidal lithography technique to fabricate periodic patterns from solution-phase is presented and the feasibility and versatility of the technique is demonstrated by fabricating periodically arranged ZnO nanowire ensembles on Si substrates. The pattern fabrication method exploits different interfaces formed by sol-gel derived ZnO seed solution on a hydrophobic Si surface covered by a monolayer of colloidal silica spheres. While the hydrophobic Si surface prevents wetting by the seed solution, the wedge shaped regions surrounding the contact point between the colloidal particles and the Si substrate trap the solution due to interfacial forces. This technique allows fabrication of uniform 2D micropatterns of ZnO seed particles on the Si substrate. A hydrothermal technique is then used to grow well-defined periodic assemblies of ZnO nanowires. Tunability is demonstrated in the dimensions of the patterns by using silica spheres with different diameters. The experimental data show that the periodic ZnO nanowire assembly suppresses the total reflectivity of bare Si by more than a factor of 2 in the wavelength range 400-1300 nm. Finite-difference time-domain simulations of the wavelength-dependent reflectivity show good qualitative agreement with the experiments. The demonstrated method is also applicable for other materials synthesized by solution chemistry.

  • 190.
    Dionisi, Filippo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner. Politecnico di Milano, Italy.
    Harnden, Ross
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Zenkert, Dan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    A model to analyse deformations and stresses in structural batteries due to electrode expansions2017Inngår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 179, s. 580-589Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to aid design of future structural battery components an analytical model is developed for modelling volume expansions in laminated structural batteries. Volume expansions are caused by lithium ion intercalation in carbon fibre electrodes. An extended version of Classical Lamination Plate Theory (CLPT) is used to allow analysis of unbalanced and unsymmetric lay-ups. The fibre intercalation expansions are treated analogously to a thermal problem, based on experimental data, with intercalation coefficients relating the fibre capacity linearly to its expansions. The model is validated using FEM and allows the study of the magnitude of interlaminar stresses and hence the risk of delamination damage due to the electrochemically induced expansions. It also enables global laminate deformations to be studied. This allows information about favourable lay-ups and fibre orientations that minimise deformations and the risk of delamination to be obtained. Favourable configurations for application to a solid state mechanical actuator are also given.

  • 191.
    Doddapaneni, Venkatesh
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    On the polymer-based nanocomposites for electrical switching applications2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Recent research demonstrated that polymer based nanocomposites (PNCs) have been engineered in order to improve the arc interruption capability of the circuit breakers. PNCs are the combination of nano-sized inorganic nanoparticles (NPs) and polymers, opened up new developments in materials science and engineering applications. Inorganic NPs are selected based on their physical and chemical properties which could make multifunctional PNCs in order to interrupt the electrical arcs effectively. In particular, we presented the PNCs fabricated by using CuO, Fe3O4, ZnO and Au NPs in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method, recently developed method to avoid NPs agglomeration, leading to good spatial distribution in the polymer matrix. Thus, several samples with various wt% of NPs in PMMA matrix have been fabricated. These PNCs have been characterized in detail for the morphology of NPs, interaction between NPs and polymer matrix, and radiative/thermal energy absorption properties. In the next stage, PNCs are tested to determine their arc interruption performance and impact on the electrical arcs of current 1.6 kA generated using a specially designed test set-up. When PNCs interact with the electrical arcs, they generate ablation of chemical species towards core of the electrical arc, resulting in cooling-down the arc due to strong temperature and pressure gradient in the arc quenching domain. This thesis demonstrates for the first time that these engineered PNCs are easily processed, reproducible, and can be used to improve the arc interruption process in electrical switching applications.

  • 192.
    Doddapaneni, Venkatesh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Ye, Fei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Gati, R.
    Toprak, Muhammet Sadaka
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Engineered PMMA-ZnO nanocomposites for improving the electric arc interruption capability in electrical switching applications: Unprecedented experimental insights2017Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 141, s. 113-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polymer inorganic nanocomposites (PINCs) have been engineered for controlling the electrical arc and to improve the arc interruption capability of the electrical switching applications, like circuit breakers. Several PINCs are fabricated by formation of ZnO quantum dots (QDs) in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method to avoid agglomeration of QDs, leading to a good spatial distribution of QDs in the polymer matrix. These PINCs have been characterized in detail for the morphology of QDs, interaction between QDs and polymer matrix, and ultraviolet (UV) radiation absorption. ZnO QDs have been assessed to have particle diameter of 3.5 nm, and their presence in the PMMA is revealed by the unique luminescence characteristics of the QDs under UV light. The presence of ZnO QDs broadened the range of UV radiation absorption of PMMA and the absorption edge is gradually shifted from 270 nm to 338 nm with step-wise loading of ZnO QDs. The PINCs are tested to determine their reproducibility and impact on the electrical arcs of current 1.6 kA generated using a specially designed test-setup. Interaction of PINCs with the electrical arcs generates ablation of chemical species towards core of the electrical arc, resulting in increase of voltage leading to cool-down the arc temperature. This experimental study demonstrates for the first time that these PINCs are reproducible, reliable and provides superior arc interruption capability.

  • 193.
    Doddapaneni, Venkatesh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Ye, Fei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Gati, Rudolf
    ABB Switzerland.
    Toprak, Muhammet Sadaka
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    New experimental insights for controlling the electrical arcs in electrical switching applications: a comparative study on PMMA nanocomposites of Au and ZnO2017Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Polymer inorganic nanocomposites (PINCs) are developed, not only due to scientific interest but also improving theelectric arc interruption process in the electrical switching applications like circuit breakers. The novelty of this work isin integrating the current developments in PINCs into electrical switching application in order to extend the limits of thepower switching devices. Several PINCs are fabricated by using pre-synthesized Au nanoparticles (NPs) of size 2.75 ±0.4 nm and poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method. Six homogeneous PINCsamples with ultra-low wt% of Au NPs varying from 0.0003 to 0.005 wt% have been fabricated. We find that thepresence of Au NPs improved the convective heat transfer and visible optical radiation absorption of PMMA. Thefabricated PINCs are tested for their arc interruption performance and the results are compared with ZnO PINCs in ourearlier work. The results of the experiments insights demonstrate the impact of PINCs on the electrical arcs and theirpotential advantages of having PINCs for the electric arc interruption process in high power switching devices.

  • 194.
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    A combined material model for plasticity and fracture for wood2015Inngår i: Proceedings of the EUROMECH Colloquium 556 on Theoretical, Numerical, and Experimental Analyses in Wood Mechanics / [ed] Michael Kaliske, 2015Konferansepaper (Fagfellevurdert)
  • 195.
    Dorn, Michael
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Proposal for a Failure Surface for Orthotropic Composite Materials2014Inngår i: / [ed] Oñate, Eugenio and Oliver, Xavier and Huerta, Antonio, 2014Konferansepaper (Fagfellevurdert)
  • 196.
    Doroudgarian, Newsha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High Performance Bio-based Composites: Mechanical and Environmental Durability2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The presented work is a part of the ongoing effort on the development of high performance bio-based composites with enhanced durability, under static and dynamic mechanical loading including the exposure to elevated humidity. The impact of relative humidity on the performance of cellulosic fibers (natural and regenerated), bio-based resins and their composites was studied. The material performance was rated against the data for glass fiber epoxy, as the reference. The comparison of water absorption results for unreinforced resins and for composites showed that the cellulosic reinforcement is primarily responsible for the transport and uptake of moisture in the composites. The effect of chemical treatment on the cellulosic fibers, as a protection against moisture, was evaluated. However, the treatment did not improve the moisture resistance in composites significantly. Quasi-static tensile tests revealed that some of the bio-based resins and their composites performed very well and comparable to the composites of synthetic epoxy, even at high humidity. However, any structural material is supposed to hold mechanical loads over a long service time and most often in harsh environmental conditions. Hence, tension-tension fatigue tests were performed on the fiber bundles as well as on the composites. The fibers of choice as the reinforcement for further mechanical testing were regenerated cellulose fibers (RCF), mainly owing to the stable geometry and properties. Due to the high nonlinearity of RCF, the fatigue tests were limited in number and the focus was on analyzing the mechanisms underlying the fatigue behavior rather than on constructing S-N curves. Strain evolution of the bio-based composites during the dynamic fatigue was very similar to that observed in the static fatigue (creep). It confirmed the strong influence of viscoelastic and viscoplastic phenomena on the overall performance of the material under the rapid loading conditions in fatigue. Since the durability of composites greatly depends on the material’s ability to stand the internal damages (e.g. debonding, microcracking, delaminations), the interfacial properties in the bio-based composites were addressed. To investigate the fracture toughness of bio-based composites, the double cantilever beam (DCB) tests were carried out, under static and dynamic loading. Moreover, the DCB results were utilized as a measure of the fiber chemical treatment’s efficiency to improve the adhesion between RCF and the resin. The nonlinearity of RCF strongly influenced the results obtained from DCB tests, which complicated the analysis regarding the effectiveness of the fiber surface treatment. Nevertheless, this study brings forward the issues that have to be dealt with, in order to characterize and predict the performance of these composite materials with highly nonlinear reinforcing fibers. Overall, the results presented in this thesis give an insight into the behavior of bio-based composites, at various environments and under different types of mechanical loading. Based on these findings, the potential use of these materials in structural applications can be assessed.

  • 197.
    Doroudgarian, Newsha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical and environmental durability of high performance bio-based cellulosic composites2012Konferansepaper (Fagfellevurdert)
  • 198.
    Doroudgarian, Newsha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Mechanical and Environmental Durability of High Performance Bio-based Composites2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This study is an initial step within the on-going project on development of high performance bio-based composites with improved mechanical (fatigue) and environmental (elevated humidity and temperature) durability. In the presented thesis the performance of cellulosic fibers (flax and regenerated cellulose), bio-based resins (Tribest, EpoBioX, Palapreg, and Envirez) and their composites under exposure to elevated humidity has been studied. Composites reinforcement was in a form of fiber rovings and fabrics to manufacture uni-directional and cross-ply laminates. Water absorption experiments were performed at different humidity levels to measure apparent diffusion coefficient and moisture content at saturation. Effect of chemical treatment (alkali and silane) on fibers as protection against moisture was also subjected to study. The comparison of results for pristine resins and composites showed that primarily cellulosic reinforcement is responsible for moisture uptake in composites. However, fiber treatment did not improve moisture resistance in composites significantly. Mechanical testing was carried out in order to estimate the influence of humidity on behavior of these materials. Results were compared with data for glass fiber and epoxy, as reference materials. The results indicated that some of the bio-based resins and composites with these polymers performed very well and have comparable properties with composites of synthetic epoxy, even at elevated humidity.

  • 199.
    Doroudgarian, Newsha
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Anglada, Marc
    Universitat Politècnica de Catalunya.
    Mestra, Alvaro
    Universitat Politècnica de Catalunya.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Bio-based composites with different moisture contents under static and dynamic loading2013Inngår i: 6th international conference on composites testing and model identification: held 22-24 April 2013 in Aalborg, Denmark / [ed] O.T. Thomsen; Bent F. Sørensen; Christian Berggreen, 2013Konferansepaper (Fagfellevurdert)
  • 200.
    Doroudgarian, Newsha
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical behavior of bio-based composites and their constituents at different humidity levels2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    During the few past years the development of natural fiber composites for structural applications has gained the momentum. Mainly the efforts in development of these materials were focused on the composites with synthetic matrices. But most recently several bio-based resins (Tribest, EpoBioX etc.) have been introduced, allowing production of whole bio-based composites. The latest results demonstrated that these composites are comparable with glass fiber reinforced polymers in terms of stiffness. However due to variability of fiber properties and limited filament length it is complicated to arrange and control fiber alignment in composites as well as ensure stable, predictable composite properties. Therefore, another type of reinforcement with natural origin has caught attention of researchers – Regenerated Cellulose Fibers (RCF). These fibers are continuous with constant, reproducible cross-section and properties but with one significant disadvantage - they exhibit highly non-linear behavior. Thus, this reinforcement should be treated as material with time-dependent properties. Schepary developed model for time-dependent materials. This model has been successfully applied to short fiber (natural and synthetic) and long synthetic fiber composites. However, in order to apply this model, large number of time-consuming tests on studied composites must be performed. Therefore, our objective is to improve this model in such a way that only input of properties of constituents is required to predict behavior of material with any composition. Visco-elasticity and viscoplasticity has been analyzed by performing creep tests at different time steps and stress levels, and extent of damage is evaluated by performing stiffness degradation tests of fibers, matrix and composite.

1234567 151 - 200 of 1232
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf