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Item type:Publication, Access status: without files , Anomalous water diffusion in epoxy/carbon nanoparticle compositesWater absorption-desorption-resorption and swelling were studied for a DGEBA-based amine-cured epoxy resin filled with four types of carbon nanoparticles: multiwall carbon nanotubes (MWCNT), graphite nano-platelets (GnP), expanded graphite platelets, and carbon black. Nanocomposites are characterised by lower diffusivity (down to 20% for epoxy/GnP) and increased water sorption capacity compared to the neat epoxy. Anomalous water absorption and swelling of nanocomposites is finely described by the diffusion-relaxation model. The relaxation times, considered as quantitative indicators of changes in segmental mobility of the polymer, increased with addition of nanoparticles and decreased with temperature. Epoxy/MWCNT composites are characterised by the longest relaxation times (twofold increase) and highest Deborah numbers compared to the neat epoxy and other nanocomposites. Hydrothermal ageing effects and efficiency of nanoparticles on thermal and thermomechanical properties of the epoxy were estimated. Water uptake in nanocomposites is accompanied by several competing processes: plasticization, after-cure, and physical ageing of the polymer matrix.Publicationtype: Journal Article186 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Relaxation-driven water diffusion in epoxy resin filled with various carbon nanoparticles(Curran Associates, Inc., 2018); ; ; ; Water sorption-desorption-resorption and swelling were studied for a model epoxy system based on DGEBA resin and triamine curing agent. Four types of carbon nanofillers were incorporated into the epoxy matrix: multiwall carbon nanotubes, graphite nano-platelets, expanded graphite platelets, and carbon black. Two-stage sorption and swelling behaviour was observed for all types of nanocomposites. An extent of the anomalous sorption depends on temperature, time and history of the test, and type of the filler. Diffusion-relaxation model of Berens and Hofenberg finely described sorption and resorption experimental curves, while desorption of all samples obeyed the Fick's law. The only additional parameter - relaxation time of polymer network - was introduced into general equations. The relaxation time increased with the addition of nanofillers and decreased with temperature increase. Dynamic mechanical thermal analysis was done to evaluate the plasticizing effect due to the absorbed water and to give an insight into the structural changes of the nanocomposites caused by their hydrothermal ageing. Water absorption resulted in plastification of the polymer that appeared in drop of glass transition temperature and lowering and broadening of tan δ peak, while after-cure and physical ageing effects appeared in the increased storage modulus.Publicationtype: Conference Paper1107 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fracture, failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy compositeAerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7-15 mg/cm3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. The present study investigates the fracture and failure of AG/epoxy composites and its energy absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ~133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ~19% in KIC for AG/epoxy composites with 0.45 wt% of AG. Observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.Publicationtype: Journal Article73 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Toughening mechanisms in polymer nanocomposites: from experiments to modelling(Elsevier, 2015-12-02); ; ; A successful exploitation of nanocomposite materials founds on the development of models capable of predicting the macroscopic mechanical behaviour as a function of the nanostructure. To this end the most critical issue to overcome is the identification of the inherent mechanisms at the very nanoscale which might depend on the type, the morphology and the functionalisation of the nanofilleras well as on the loading conditions. Within this scenario, this work aims to review the main damage mechanisms reported in the literature for nano-reinforced thermosetting polymers, to include new insights and to discuss predictive models incorporating these mechanisms.Publicationtype: Journal Article61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Failure mechanisms, electrical and thermal conductivity of Aerographite/epoxy compositeAerographite (AG) is a novel hierarchical carbon nanomaterial formed by a 3D-network of directly interconnected thin-walled graphite layers with densities in rage of 0.2-15 mg/cm3 [1]. AG is synthesized using a single-step CVD process on ZnO templates where simultaneous deposition of graphitic layers and etching of Zn takes place. Despite the ultra-low density, Aerographite's unique morphology consisting of tubular, interconnected graphitic hollow tetrapods enables infiltration with a polymeric matrix. Aerographite/epoxy nanocomposites have been prepared using a novel, proprietary vacuum assisted infiltration technique. The density and the electrical conductivity of the neat AG used for the preparation of the composite is ~12 mg/cm3 and 2-3 S/m respectively. Optical investigations confirm that the 3D interconnected structure remains in-tact during the infiltration process. The composite after infiltration with epoxy was characterized for its electrical and mechanical properties. The electrical conductivity of AG/composite was 7-8 S/m for 0.85-0.88 wt% of AG content. Preliminary results on fracture toughness (KIC) showed an enhancement of 19 % in KIC for AG/epoxy composite with 0.45 wt% of AG. Observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. Evidence of increased energy absorption were observed through compression tests and via interaction of crack front with an AG network through photoelasticity experiments.Publicationtype: Conference Paper68 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , New functions in polymer composites using a nanoparticle-modified matrix(William Andrew is an imprint of Elsevier, 2015-05-26); ; ; Fiber-reinforced composites have superior properties compared to conventional structural materials. They already gain a very high standard, resulting in application in the aerospace and other important industries, however, there is still room for further improvement. These aim toward manufacturing, cost reduction during material processing, application, and last but not least superior material properties.Nanocomposites (polymers filled with nanoparticles as carbon nanotubes, graphene, etc.) have been under investigation in the last decade and they resulted in tremendous improvements in mechanical properties, as fracture toughness or electrical conductivity.Nanocomposites used as matrix for fiber-reinforced polymers (FRPs) have the potential to improve overall mechanical properties as interlaminar shear stress, first-ply failure, impact and compression after impact, etc. At the same time, the polymer matrix being an isolator by nature can be turned into an electrically conductive material. This additional function can not only be used for electric charge ablation but also be used for sensing deformation and/or damage. Especially, their potential for strain sensing applications with electrical conductivity methods can be used to investigate the electromechanical response of nanocomposites or FRP deformation when subjected to mechanical load.An integration of carbon nanoparticles into the matrix of FRPs not only improves the overall properties, they turn into a multifunctional material. Superior mechanical properties combine with sensing capabilities. Composite materials can even better compete with conventional structural materials, respectively, are an even more attractive alternative.Publicationtype: Book Part80 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The effect of carbon nanoparticles on the fatigue performance of carbon fibre reinforced epoxy(Elsevier, 2014-09-01); ; ; ; The aim of this study is to investigate the influence of different types of carbon nanoparticles like multi-wall carbon nanotubes (MWCNT) and few layered graphene (FLG) on the damage mechanisms of carbon fibre reinforced epoxy (CFRP) under fatigue loading up to the high cycle regime. Specimens were manufactured from in-house made prepregs to ensure good and reproducible nanoparticle distribution within the CFRP and penetration of the fibre rovings. The quasi-static mechanical properties of the crossply laminates were not affected by the nanoparticle modification. The fatigue life, however, increased significantly for both types of carbon nanoparticles, being most pronounced for FLG at high fatigue loads. Scanning electron microscopy-analysis revealed enormous plastic deformation of the matrix due to the nanoparticles. The fatigue life increasing effect was discussed by means of energy absorption. Nanoparticle-based damage mechanisms in CFRP were displayed and differences due to the varying nanoparticle structures identified.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fracture toughness and failure mechanism of graphene based epoxy composites(Elsevier, 2014-04-01); ; ; ; The present study investigates the effect of addition of three different types on carbon nano-fillers on fracture toughness (KIC) and failure mechanism of epoxy based polymer nano-composites. The carbon nano-fillers were dispersed in the epoxy matrix using a three-roll mill and the three nano-fillers used for this experiment were (i) thermally reduced graphene oxide (TRGO); (ii) graphite nano-platelets (GNP); and (iii) multi-wall carbon nano-tubes (MWCNT). The fracture toughness was measured as a function of weight percentage of the filler using single edge notch three-point-bending tests. The toughening effect of TRGO was most significant resulting in 40% increase in KIC for 0.5wt% of filler. On the other hand, the enhancements in toughness were 25% for GNP/epoxy and 8% for MWCNT/epoxy. Investigations on fracture surface revealed that crack pinning or bi-furcation by TRGO and crack face separation initiated from TRGO contributed to enhance the fracture toughness. Based on the observations, a schematic explaining the crack propagation in graphene/epoxy composite and the interaction of crack front with graphene particles was proposed.Publicationtype: Journal Article35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Development of nano-particle modified polymer matrices for improved fibre reinforced composites(2014); In this work, different types of graphene filler were dispersed in epoxy matrix, to prepare a graphene based epoxy nano-composite and compared with carbon nanotube reinforced epoxy system. The effect of filler addition on mechanical, electrical and thermal properties of the nano-composites was studied. The interaction between the fillers was studied by intermixing different fillers by means of bi-filler epoxy composites. The main object of the current study is to understand the failure mechanisms and toughening effects of graphene based fillers in epoxy composites.Publicationtype: Doctoral Thesis637 950 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Preparation and characterization of graphite nano-platelet (GNP)/epoxy nano-composite : mechanical, electrical and thermal propertiesEpoxy based polymer nano-composite was prepared by dispersing graphite nano-platelets (GNPs) using two different techniques: three-roll mill (3RM) and sonication combined with high speed shear mixing (Soni-hsm). The influence of addition of GNPs on the electrical and thermal conductivity, fracture toughness and storage modulus of the nano-composite was investigated. The GNP/epoxy prepared by 3RM technique showed a maximum electrical conductivity of 1.8 × 10-03 S/m for 1.0 wt% which is 3 orders of magnitude higher than those prepared by Soni-hsm. The percentage of increase in thermal conductivity was only 11% for 1.0 wt% and 14% for 2.0 wt% filler loading. Dynamic mechanical analysis results showed 16% increase in storage modulus for 0.5 wt%, although the Tg did not show any significant increase. Single edge notch bending (SENB) fracture toughens (KIC) measurements were carried out for different weight percentage of the filler content. The toughening effect of GNP was most significant at 1.0 wt% loading, where a 43% increase in KIC was observed. Among the two different dispersion techniques, 3RM process gives the optimum dispersion where both electrical and mechanical properties are better.Publicationtype: Journal Article58