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Item type:Publication, Access status: without files , Charakterisierung der Dispersionsgüte von Carbon Nanotubes in Polymer-Nanokompositen(Wiley-VCH, 2011-06-01); ; ; ; Pegel, SvenA practical overview of possibilities and limits to characterize the state of dispersion of carbon nanotubes (CNT) in polymer based nanocomposites is given. The most important and widely available methods are discussed with practical employment in mind. One focus is the quantitative characterization of the state of dispersion in solid samples using microscopy techniques such as optical microscopy or transmission electron microscopy. For dispersions of CNTs in aqueous media, solvents or monomers a sedimentation analysis is presented. This way dispersability and dispersion state of CNTs can be assessed. Indirect methods such as electrical conductivity measurements and rheological tests, dynamic differential scanning calorimetry and mechanical test are discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Publicationtype: Journal Article11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fracture behaviour of fumed silica/epoxy nanocomposites(Elsevier, 2008-09-20); ; ; ; The paper shows the results of an experimental programme oriented to the manufacturing and characterisation of nanocomposites based on epoxy resin modified with fumed silica nanoparticles (0.1, 0.3 and 0.5 vol.%) with different surface treatments (unmodified, AMEO and GLYMO). The resulting degree of dispersion and the interfacial adhesion were investigated by TEM and SEM. Previous tensile and fracture toughness properties are discussed together with new results on the fatigue behaviour under mode I loading. The fracture toughness KIc turned out to be significantly increased and a positive trend towards the improvement in the crack propagation threshold under fatigue was observed.Publicationtype: Journal Article17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fundamental aspects of nano-reinforced compositesThe present paper highlights the potential of the CNTs as nanofillers in polymers, but also stresses out the limitations and challenges one has to face dealing with nanoparticles in general. The relation between particle size, separation and volume content is described analytically. The dominating effect of manufacturing route (sonication, mech. stirring and calendering) and surface properties of carbon nanotubes (CNTs), influencing the resulting degree of dispersion and interfacial adhesion, were intensively investigated by transmission electron microscopy (TEM). The resulting (fracture) mechanical properties of the CNT/epoxy composites were investigated for volume contents below 1%. The fracture toughness KIc turned out to be significantly increased (45%) adding only 0.3% of amino-functionalised double-walled carbon nanotubes (DWCNT-NH2).Publicationtype: Journal Article26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Glass-fibre-reinforced composites with enhanced mechanical and electrical properties - Benefits and limitations of a nanoparticle modified matrixNanoparticles and especially carbon nanotubes (CNTs) provide a high potential for the modification of polymers. They are very effective fillers regarding mechanical properties, especially toughness. Furthermore, they allow the implication of functional properties, which are connected to their electrical conductivity, into polymeric matrices. In the present paper, different nanoparticles, as fumed silica and carbon black, were used to optimise the epoxy matrix system of a glass-fibre-reinforced composite. Their nanometre-size enables their application as particle-reinforcement in FRPs produced by the resin-transfer-moulding method (RTM), without being filtered by the glass-fibre bundles. Additionally, an electrical field was applied during curing, in order to enhance orientation of the nanofillers in z-direction. The interlaminar shear strengths of the nanoparticle modified composites were significantly improved (+16%) by adding only 0.3 wt.% of CNTs. The interlaminar toughness GIc and GIIc was not affected in a comparable manner. The laminates containing carbon nanotubes exhibited a relatively high electrical conductivity at very low filler contents, which allows the implication of functional properties, such as stress-strain monitoring and damage detection.Publicationtype: Journal Article23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multiwall carbon nanotube/epoxy composites produced by a masterbatch processA masterbatch process based on a minicalander (three-roller mill) and a vacuum dissolver was developed in order to produce multiwall carbon nanotube/epoxy composites with loading fractions of 0.5, 1.0, and 2.0 wt.%. TEM and SEM analyses were performed to investigate the dispersion results. A contrast imaging in the SEM backscattering mode revealed a homogeneous distribution of carbon nanotubes in the whole volume of the material. Furthermore, an interesting correlation was found to exist between the network structure formed by the nanotubes in the epoxy matrix and the appearance of fracture surface of the nanocomposites. Furthermore, the nanocomposites exhibited an electrical conductivity in the regime of some 10-2 S/m.Publicationtype: Journal Article21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Evaluation and identification of electrical and thermal conduction mechanisms in carbon nanotube/epoxy compositesNanostructured modification of polymers has opened up new perspectives for multi-functional materials. In particular, carbon nanotubes (CNTs) have the potential to realise electrically conductive polymers with improved or retaining mechanical performance. This study focuses on the evaluation of both, the electrical and thermal conductivity of nanoparticulate filled epoxy resins. We discuss the results with regard to the influence of the type of carbon nanotube (SWCNT, DWCNT and MWCNT), the relevance of surface-functionalisation (amino-functionalisation), the influence of filler content (wt% and vol%), the varying dispersibility, the aspect ratio and the specific surface area.Publicationtype: Journal Article19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of surface treatment on mechanical behaviour of fumed silica/epoxy resin nanocompositesThe present paper shows the potential of fumed silica as nano-reinforcements in polymers, by considering the limitations and challenges one has to face dealing with nanoparticles in general. The dominating effect of the manufacturing route and surface properties of fumed silica influencing the resulting degree of dispersion and the interfacial adhesion were investigated by electron microscopy (TEM, SEM). The resulting (fracture-) mechanical properties of the fumed silica/epoxy composites were investigated for volume contents of 0.5 vol% and below. Independent of the surface modification, static and dynamic modulus decreased slightly by adding the fumed silica. Hence, the fracture toughness K Ic turned out to be significantly increased (54%) adding only 0.5 vol% of surface modified fumed silica.Publicationtype: Journal Article25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of different carbon nanotubes on the mechanical properties of epoxy matrix composites - A comparative studyCarbon nanotubes (CNTs) in general are considered to be highly potential fillers to improve the material properties of polymers. However, questions concerning the appropriate type of CNTs, e.g., single-wall CNTs (SWCNT), double-wall CNTs (DWCNT) or multi-wall CNTs (MWCNT), and the relevance of a surface functionalisation are still to be answered. This first part of the study focuses on the evaluation of the different types of nanofillers applied, their influence on the mechanical properties of epoxy-based nanocomposites and the relevance of surface functionalisation. The nanocomposites produced exhibited an enhanced strength and stiffness and even more important, a significant increase in fracture toughness (43% at 0.5 wt% amino-functionalised DWCNT). The influence of filler content, the varying dispersibility, the aspect ratio, the specific surface area and an amino-functionalisation on the composite properties are discussed and correlated to the identified micro-mechanical mechanisms.Publicationtype: Journal Article23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Production and properties of glass fibre-reinforced polymer composites with nanoparticle modified epoxy matrixIncreasing the mechanical performance, e.g. strength, toughness and fatigue properties of composites is the objective of many ongoing research projects. Nanoparticles, e.g. carbon nanotubes (CNTs) and fumed silica provide a high potential for the reinforcement of polymers. Their size in the nanometre regime make them suitable candidates for the reinforcement of fibre reinforced polymers, as they may penetrate the reinforcing fibre-network without disturbing the fibre-arrangement. In this work, glass fibre-reinforced epoxy composites with nanoparticle modified matrix systems were produced and investigated. GFRPs containing different volume fractions of the nanofillers were produced via resin transfer moulding. Matrix dominated mechanical properties of the GFRP laminates could be improved by the incorporation of nanoparticles. The addition of only 0.3 wt.% CNTs to the epoxy matrix increased the interlaminar shear strength from 33.4 to 38.7 MPa (+16%). Furthermore, the application of electrically conductive nanoparticles enables the production of conductive nanocomposites. This offers a high potential for antistatic applications and the implementation of functional properties in the composite structures. The effects of different filler types and volume fractions on the electrical properties of the GFRPs were investigated. GFRPs containing 0.3 wt.% of CNTs, for example, exhibit an anisotropic electrical conductivity. Furthermore, an electrical field was applied to the composites during curing. The effects on the resulting electrical and mechanical properties are discussed.Publicationtype: Conference Paper24 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of nano-modification on the mechanical and electrical properties of conventional fibre-reinforced compositesCarbon nanotubes (CNTs) exhibit a high-potential for the reinforcement of polymers. The mechanical properties of potential matrices of fibre-reinforced polymers (FRP), such as epoxy resins, were significantly increased by low contents of carbon nanotubes (CNT) (tensile strength, Young's modulus and fracture toughness). Nano-particle-reinforced FRPs, containing carbon black (CB) and CNTs could successfully be manufactured via resin transfer moulding (RTM). A filtering effect of the nano-particles by the glass-fibre bundles was not observed. The glass-fibre-reinforced polymers (GFRP) with nanotube/epoxy matrix exhibit significantly improved matrix-dominated properties (e.g. interlaminar shear strength), while the tensile properties were not affected by the nano-fillers, due to the dominating effect of the fibre-reinforcement. The GFRP containing 0.3 wt% amino-functionalised double-wall carbon nanotubes (DWCNT-NH2) exhibit an anisotropic electrical conductivity, whereas the conductivity in plane is one order of magnitude higher than out of plane.Publicationtype: Journal Article25