Research Papers - Department of Civil Engineering

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    Influence of ageing of graphene oxide on the properties and morphology of cement mortar
    (Nature Research, 2025-12-02) Suganthiny,G; Thambiliyagodage, C; Perera, S. V. T. J; Rajapakse, R. K. N. D
    Past studies show that Graphene Oxide (GO) enhances the structural properties of cement composites. However, GO reduces its chemical characteristics with ageing. This study determines the effects of the age of commercial and laboratory-produced GO on cementitious composites. The study considered GO of up to 35 weeks of age, and specimens were chemically characterised using various techniques. The ageing effects were evaluated using consistency, initial setting time, compressive strength, splitting tensile strength, and water absorption. The composite’s thermal resistance was also tested. GO was found to have a shelf life of 13 weeks from production to achieve favourable results. The morphology of the cement mortar was studied to determine the reason for the change in performance with GO age. This study confirms that the carbon-to-oxygen ratio (C/O) and the disorder of graphene oxide sheets (ID/IG ratio), along with the number of GO layers, govern the performance of GO-incorporated cement composites. Both ratios increase with GO age. Aged GOs in mortar increased the mean pore radius and reduced the surface area. Mortar samples with aged GOs have ettringite peaks, while early-age GO-containing samples lack ettringite peaks. Despite reduced mechanical performance with age, all mortar samples remained thermally stable at higher temperatures.
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    Influence of hydrogen functionalization on the fracture strength of graphene and the interfacial properties of graphene–polymer nanocomposite
    (Pergamon, 2015-11-01) Dewapriya, M. A. N; Rajapakse, R. K. N. D; Nigam, N
    Using molecular dynamics and classical continuum concepts, we investigated the effects of hydrogen functionalization on the fracture strength of graphene and also on the interfacial properties of graphene–polymer nanocomposite. Moreover, we developed an atomistic model to assess the temperature and strain rate dependent fracture strength of functionalized graphene along various chiral directions. Results indicate that hydrogen functionalization at elevated temperatures highly degrade the fracture strength of graphene. The functionalization also deteriorates the interfacial strength of graphene–polymer nanocomposite. Near-crack-tip stress distribution depicted by continuum mechanics can be successfully used to investigate the impact of hydrogen passivation of dangling carbon bonds on the strength of graphene. We further derived a continuum-based model to characterize the non-bonded interaction of graphene–polymer nanocomposite. These results indicate that classical continuum concepts are accurate even at a scale of several nanometers. Our work provides a remarkable insight into the fracture strength of graphene and graphene–polymer nanocomposites, which are critical in designing experimental and instrumental applications.
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    Influence of temperature and free edges on the mechanical properties of graphene
    (IOP Publishing, 2013-08-12) Dewapriya, M. A. N; Phani, A Srikantha; Rajapakse, R. K. N. D
    A systematic molecular dynamics simulation study is performed to assess the effects of temperature and free edges on the ultimate tensile strength and Young's modulus of a single-layer graphene sheet. It is observed that graphene sheets at higher temperatures fail at lower strains, due to the high kinetic energy of atoms. A numerical model, based on kinetic analysis, is used to predict the ultimate strength of the graphene under various temperatures and strain rates. As the width of a graphene reduces, the excess edge energy associated with free edge atoms induces an initial strain on the relaxed configuration of the sheets. This initial strain has a greater influence on the Young's modulus of the zigzag sheet compared with that of the armchair sheets. The simulations reveal that the carbon–carbon bond length and amplitude of intrinsic ripples of the graphene increases with temperature. The initial out-of-plane displacement of carbon atoms is necessary to simulate the physical behaviour of a graphene when the Nosé–Hoover or Berendsen thermostat is used.