Research Papers - Department of Civil Engineering
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Publication Open Access A Comparative Investigation of Infiltration and Channel Roughness of Ephemeral and Perennial Streams in a Mountainous Catchment(John Wiley, 2025-06) Khaniya, B; Gomes, P.I.A; Perera,M. D.D; Wai, O, W.HInfiltration and channel roughness, two major factors that govern stream discharge, were studied in similar-sized ephemeral and perennial streams in a mountainous tropical catchment. Seasons were defined based on two ephemeral flow conditions, i.e., with (wet season) and without (dry season) surface flow. A stream was divided transversely into low-flow areas (close to the thalweg) and high-flow areas (close to the channel margin). The highest average infiltration (~50 mm/h) was observed in the low flow areas around the thalweg of ephemeral streams in the dry season and was significantly higher than for any other spatial scale or temporal period. The infiltration in high-flow areas did not show a statistically significant difference between the two stream types, and surprisingly, perennial streams in the dry season showed higher infiltration than ephemeral streams. Since sediment moisture and organic content showed negative and positive correlations with infiltration, respectively, for both stream types and ephemeral streams showed statistically significant negative correlations between litter and infiltration during the dry season, the low infiltration in ephemeral high flow areas was attributed to stream-type dependent litter processing. The litter of ephemeral stream high-flow areas was subject to partial decomposition due to rapid drying and had residue of previously buried litter. Ephemeral channels were two to three times rougher than perennial channels. Standing crop biomass and mean particle size increased stream roughness in both stream types but were less prominent in ephemeral streams due to the presence of litter. The study demonstrated that litter has a special role in defining the infiltration pattern, channel roughness, and flood control potential of ephemeral streams.Publication Open Access Accelerated membrane durability testing of heavy duty fuel cells(IOP Publishing, 2014-11-19) Macauley, N; Alavijeh, A. S; Watson, M; Kolodziej, J; Lauritzen, M; Knights, S; Wang, G; Kjeang, ERegular durability testing of heavy duty fuel cell systems for transit bus application requires several thousand hours of operation, which is costly and time consuming. Alternatively, accelerated durability tests are able to generate failure modes observed in field operation in a compressed time period, by applying enhanced levels of stress. The objective of the present work is to design and validate an accelerated membrane durability test (AMDT) for heavy duty fuel cells under bus related conditions. The proposed AMDT generates bus relevant membrane failure modes in a few hundred hours, which is more than an order of magnitude faster than for regular duty cycle testing. Elevated voltage, temperature, and oxidant levels are used to accelerate membrane chemical stress, while relative humidity (RH) cycling is used to induce mechanical stress. RH cycling is found to significantly reduce membrane life-time compared to constant RH conditions. The role of a platinum band in the membrane is investigated and membranes with Pt bands demonstrate a considerable life-time extension under AMDT conditions, with minimal membrane degradation. Overall, this research serves to establish a benchmark AMDT that can rapidly and reliably evaluate membrane stability under simulated heavy duty fuel cell conditions.Publication Open Access Age-specific seasonal storage dynamics of Phragmites australis rhizomes: a preliminary study(Kluwer Academic Publishers, 2004-10) Karunaratne, S; Asaeda, T; Yutani, KAge-specific seasonal rhizome storage dynamics of a wetland stand of Phragmites australis (Cav.) Trin. ex Steud. in Japan, were investigated from April to October 2000. For each sampling date, above- and below-ground biomass and age-specific rhizome bulk density, ?rhiz were measured. Seven rhizome age classes were recognized, from <1 year to six years old, based on their position within the branching hierarchy as main criteria and rhizome color, condition of nodal sheaths and condition of the shoots attached to vertical rhizomes as secondary criteria. P. australis stand was moderately productive, having a net aerial and below-ground production of 1980 and 1240 g m−2, respectively, and a maximum mean shoot height of 2.33 ± 0.12 m. In spring, shoot growth started at the expense of rhizome reserves, decreasing the rhizome biomass as well as ?rhiz. Both parameters reached the seasonal minimum in May followed by a subsequent increase, indicating a translocation of reserves to rhizomes from shoots after they become self supporting. For each sampling date, ?rhiz increased with rhizome age. Given that the quantity of reserves remobilized by the rhizomes for spring shoot growth, as assessed by the drop in bulk density from April to May, were positively correlated (r = 0.97, P < 0.05) with rhizome age, it is proposed that for spring shoot formation older rhizomes remobilize stored reserves more actively than younger ones. Given that the accumulation of rhizome reserves (rise in bulk density) from May to August, May to September or May to November was negatively correlated (r = 0.97, 0.92 and 0.87, respectively, P < 0.05) with rhizome age, it seemed possible that younger rhizomes were ‘recharged’ at a higher rate than older ones. These resource allocation mechanisms pertaining seasonal rhizome storage dynamics are of paramount importance in formulating management and conservation strategies of wetlands and aquatic habitats. Our results indicate that a harvest of above-ground biomass from May to June would be more effective in reducing the growth than a harvest in July to August or later, when rhizome reserves have already been replenished. However, the latter may remove a larger shoot bound nutrient stock, still preserving a healthy stand for the subsequent years.Publication Open Access Analysis of Meandering River Morphodynamics Using Satellite Remote Sensing Data—An Application in the Lower Deduru Oya (River), Sri Lanka(MDPI, 2022-07-16) Basnayaka, V; Samarasinghe, J. T; Gunathilake, M. B; Muttil, N; Hettiarachchi, D. C; Abeynayaka, A; Rathnayake, URiver meandering and anabranching have become major problems in many large rivers that carry significant amounts of sediment worldwide. The morphodynamics of these rivers are complex due to the temporal variation of flows. However, the availability of remote sensing data and geographic information systems (GISs) provides the opportunity to analyze the morphological changes in river systems both quantitatively and qualitatively. The present study investigated the temporal changes in the river morphology of the Deduru Oya (river) in Sri Lanka, which is a meandering river. The study covered a period of 32 years (1989 to 2021), using Landsat satellite data and the QGIS platform. Cloud-free Landsat 5 and Landsat 8 satellite images were extracted and processed to extract the river mask. The centerline of the river was generated using the extracted river mask, with the support of semi-automated digitizing software (WebPlotDigitizer). Freely available QGIS was used to investigate the temporal variation of river migration. The results of the study demonstrated that, over the past three decades, both the bend curvatures and the river migration rates of the meandering bends have generally increased with time. In addition, it was found that a higher number of meandering bends could be observed in the lower (most downstream) and the middle parts of the selected river segment. The current analysis indicates that the Deduru Oya has undergone considerable changes in its curvature and migration rates.Publication Open Access Analysis of physical and chemical properties of alternative substrate material for sustainable green roofs(Research Square, 2022-07-14) Kader, S. AGreen roof is the roof of a building that is partially or completely enfolded with vegetation and its associated components. It promotes the sustainability of buildings and provides comfort for urban ecosystem. We have investigated the viability of using organic waste as a growing medium. This study determines the most suitable growing substrate by investigating organic wastes of Sawdust, Wood bark, Bio char, Coir, Compost and Base medium under the parameters of density, moisture content, drought resistance and thermal resistance, contribution for vegetation growth, pH, electric conductivity and nutrient constituents. Investigation of chemical parameters is a unique aspect of this study. New methodologies using mathematical concepts were used to find thermal conductivity and EC of specimens in our research. Preliminary study results shows that the most substrate composition will comprise 60% growing medium and 40% base medium (fertilizer + potting mix). During the experimental studies, we have compared the test results of each organic waste specimens under the mentioned physical and chemical parameters. Base medium (90:10) has highest bearing capacity to withstand 2 external loads including vegetation and other imposed loads. Sawdust (60:40) exhibited optimum attributes for lightweight substrate by having least saturated unit weight, dry unit weight and the highest moisture content. In terms of drought resistance and vegetation growth, Bio char (60:40) was exceptional. Wood bark (60:40) exhibited the most convincing thermal resistance. The best characteristics in terms of pH, EC and nutrient content were exhibited by Sawdust (60:40), Coir (60:40) and Compost (60:40) correspondingly. Based on final ratings by considering all the experimental results, Coir (60:40) have emerged as the optimum growing medium in terms of physical and chemical properties. The authors emphasize to utilize this experimental study results into large-scale construction industries to promote the urban ecosystems through sustainable green roof constructions.Publication Open Access Analysis of recent trends and variability of temperature and relative humidity over Sri Lanka(India Meteorological Department, 2022-07-01) Rathnayake, U; Gunathilake, M. B; Senatilleke, U; Alyousifi, YThe world is experiencing adverse consequences of climate change and shifts in climate regimes. Hence, studying the trends and patterns of meteorological variables is of major importance for many parties, including meteorologists, climatologists, agriculturists and hydrologists. Although several researchers have examined the trends and patterns in historical rainfall, only a few have examined the trends in atmospheric temperature. Noteworthy none of the previous studies have attempted to investigate trends in relative humidity over Sri Lanka. Therefore, identifying this existing research gap, this present paper presents a trends and variability analysis of atmospheric temperature and relative humidity of Sri Lanka. The long-term variations of minimum and maximum temperature and relative humidity records at 18 stations distributed in the three climatic zones namely, the dry zone, the intermediate zone and the wet zone in Sri Lanka were investigated for 30 years from 1990 to 2019. Annual and monthly trends were assessed using non-parametric statistical tests, including the Mann Kendall test (MK), Sen’s slope and Spearman’s rho test, while the changing points of temperature and humidity were determined using the Pettit test. In addition, the variability of climate parameters was estimated using the Coefficient of Variation (CoV). Interesting and encouraging results were obtained from the present analysis. Badulla in the intermediate climatic zone was identified with unexpected decreasing temperature trends, while several other areas were identified with expected increasing temperature and relative humidity trends. The adaptation practices based on these results would be interesting to incorporate in achieving sustainable development goals for the countryPublication Embargo An analysis of signalized intersections: Case of traffic light failure(IEEE, 2017-01-27) Mohamed Mafas, A. M; Amarasingha, NTraffic congestion due to failure of traffic lights is one of the problems in Colombo. To study traffic congestions due to failure of traffic lights, the traffic characteristics at intersections should be investigated. Capacity of the intersection is the main factor influenced for congestions. Data were collected at three intersections Malabe, Battaramulla and Rajagiriya and capacity of each identified. The capacity of each intersection was studied according to the Peak Hour Malabe and Rajagiriya had PHF of 0.95 and Battaramulla had the value of 0.91. Accordingly, the effective simple suggestions to manage these intersections may be introduction of telephone booth and police cabin to use the case of emergency.Publication Embargo An analysis of signalized intersections: Case of traffic light failure(Faculty of Graduate Studies and Research, 2017-01-26) Mohamed Mafas, A.M.; Amarasingha, N.Traffic congestion due to failure of traffic lights is one of the problems in Colombo. To study traffic congestions due to failure of traffic lights, the traffic characteristics at intersections should be investigated. Capacity of the intersection is the main factor influenced for congestions. Data were collected at three intersections Malabe, Battaramulla and Rajagiriya and capacity of each identified. The capacity of each intersection was studied according to the Peak Hour Malabe and Rajagiriya had PHF of 0.95 and Battaramulla had the value of 0.91. Accordingly, the effective simple suggestions to manage these intersections may be introduction of telephone booth and police cabin to use the case of emergency.Publication Embargo Analytical solution for size-dependent elastic field of a nanoscale circular inhomogeneity(ASME Digital Collection, 2007-05-01) Rajapakse, R. K. N. D; Tian, LianTwo-dimensional elastic field of a nanoscale circular hole/inhomogeneity in an infinite matrix under arbitrary remote loading and a uniform eigenstrain in the inhomogeneity is investigated. The Gurtin–Murdoch surface/interface elasticity model is applied to take into account the surface/interface stress effects. A closed-form analytical solution is obtained by using the complex potential function method of Muskhelishvili. Selected numerical results are presented to investigate the size dependency of the elastic field and the effects of surface elastic moduli and residual surface stress. Stress state is found to depend on the radius of the inhomogeneity/hole, surface elastic constants, surface residual stress, and magnitude of far-field loading.Publication Embargo Analytical solutions for a surface-loaded isotropic elastic layer with surface energy effects(Pergamon, 2009-11-01) Rajapakse, R. K. N. D; Zhao, XJConsideration of surface (interface) energy effects on the elastic field of a solid material has applications in several modern problems in solid mechanics. The Gurtin–Murdoch continuum model [M.E. Gurtin, A.I. Murdoch, Arch. Ration. Mech. Anal. 57 (1975) 291–323; M.E. Gurtin, J. Weissmuller, F. Larché, Philos. Mag. A 78 (1998) 1093–1109] accounting for surface energy effects is applied to analyze the elastic field of an isotropic elastic layer bonded to a rigid base. The surface properties are characterized by the residual surface tension and surface Lame constants. The general solutions of the bulk medium expressed in terms of Fourier integral transforms and Hankel integral transforms are used to formulate the two-dimensional and axisymmetric three-dimensional problems, respectively. The generalized Young–Laplace equation for a surface yields a set of non-classical boundary conditions for the current class of problems. An explicit analytical solution is presented for the elastic field of a layer. The layer solution is specialized to obtain closed-form solutions for semi-infinite domains. Selected numerical results are presented to show the influence of surface elastic constants and layer thickness on stresses and displacements.Publication Embargo Applicability of smartphone-based roughness data for rural road pavement condition evaluation(Taylor & Francis, 2022-02-23) Sandamal, R. M. K; Pasindu, H. RRural roads play a pivotal role in facilitating connectivity for the rural communities by providing access for their economic and social needs. Due to lack of funding and other resources, maintenance decision making is often done in an ad-hoc and subjective manner. Moreover, the inability to collect extensive data as needed to run most pavement management systems and technical expertise required has resulted in the low usage of such systems by local road agencies. Therefore, there is a need to develop a cost-effective, simplified approach for network-level pavement condition evaluation to assist in pavement maintenance management. The study explores the applicability of smartphone-based roughness data to assess the pavement condition of rural roads, and it is compared with the results from a Class III type roughness measurement equipment. Result show it has good correlation, which suggests it has sufficient accuracy when compared to the conventional roughness measurement methods. Furthermore, it is established that roughness results accurately represent the presence of pavement distresses and the overall pavement condition in the rural roads that are considered in maintenance decision making. The findings from the study would provide a cost-effective pavement condition data collection method that can be adopted for network-level condition evaluation in low volume roads.Publication Open Access Artificial Neural Network based PERSIANN data sets in evaluation of hydrologic utility of precipitation estimations in a tropical watershed of Sri Lanka(AIMS Geosciences, 2021-09) Gunathilake, M; Senarath, T; Rathnayake, U. SThe developments of satellite technologies and remote sensing (RS) have provided a way forward with potential for tremendous progress in estimating precipitation in many regions of the world. These products are especially useful in developing countries and regions, where ground-based rain gauge (RG) networks are either sparse or do not exist. In the present study the hydrologic utility of three satellite-based precipitation products (SbPPs) namely, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), PERSIANN-Cloud Classification System (PERSIANN-CCS) and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Dynamic Infrared Rain Rate near real-time (PDIR-NOW) were examined by using them to drive the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) hydrologic model for the Seethawaka watershed, a sub-basin of the Kelani River Basin of Sri Lanka. The hydrologic utility of SbPPs was examined by comparing the outputs of this modelling exercise against observed discharge records at the Deraniyagala streamflow gauging station during two extreme rainfall events from 2016 and 2017. The observed discharges were simulated considerably better by the model when RG data was used to drive it than when these SbPPs. The results demonstrated that PERSIANN family of precipitation products are not capable of producing peak discharges and timing of peaks essential for near-real time flood-forecasting applications in the Seethawaka watershed. The difference in performance is quantified using the Nash-Sutcliffe Efficiency, which was >0.80 for the model when driven by RGs, and <0.08 when driven by the SbPPs. Amongst the SbPPs, PERSIANN performed best. The outcomes of this study will provide useful insights and recommendations for future research expected to be carried out in the Seethawaka watershed using SbPPs. The results of this 479 AIMS Geosciences Volume 7, Issue 3, 478–489. study calls for the refinement of retrieval algorithms in rainfall estimation techniques of PERSIANN family of rainfall products for the tropical region.Publication Open Access Artificial neural network to estimate the paddy yield prediction using climatic data(Hindawi, 2020-07) Amaratunga, V; Wickramasinghe, L; Perera, A; Jayasinghe, J; Rathnayake, U. SPaddy harvest is extremely vulnerable to climate change and climate variations. It is a well-known fact that climate change has been accelerated over the past decades due to various human induced activities. In addition, demand for the food is increasing day-by-day due to the rapid growth of population. Therefore, understanding the relationships between climatic factors and paddy production has become crucial for the sustainability of the agriculture sector. However, these relationships are usually complex nonlinear relationships. Artificial Neural Networks (ANNs) are extensively used in obtaining these complex, nonlinear relationships. However, these relationships are not yet obtained in the context of Sri Lanka; a country where its staple food is rice. Therefore, this research presents an attempt in obtaining the relationships between the paddy yield and climatic parameters for several paddy grown areas (Ampara, Batticaloa, Badulla, Bandarawela, Hambantota, Trincomalee, Kurunegala, and Puttalam) with available data. Three training algorithms (Levenberg–Marquardt (LM), Bayesian Regularization (BR), and Scaled Conjugated Gradient (SCG)) are used to train the developed neural network model, and they are compared against each other to find the better training algorithm. Correlation coefficient (R) and Mean Squared Error (MSE) were used as the performance indicators to evaluate the performance of the developed ANN models. The results obtained from this study reveal that LM training algorithm has outperformed the other two algorithms in determining the relationships between climatic factors and paddy yield with less computational time. In addition, in the absence of seasonal climate data, annual prediction process is understood as an efficient prediction process. However, the results reveal that there is an error threshold in the prediction. Nevertheless, the obtained results are stable and acceptable under the highly unpredicted climate scenarios. The ANN relationships developed can be used to predict the future paddy yields in corresponding areas with the future climate data from various climate models.Publication Open Access Assessment of pollution sources, fate of pollutants, and potential instream interventions to mitigate pollution of earthen canals of urban to rural-urban fringe(Springer International Publishing, 2019-11) Gomes, P. I. A; Fernando, B. A. V. W; Dehini, G. KThree representative earthen canals from urban, peri-urban, and rural-urban fringe of Sri Lanka were studied for a 2-year period against different seasons to capture insights important in ecological rehabilitation. Only the canal from rural-urban fringe showed a better water quality in wet season; elucidating, the impact of contaminated catchment runoff in the other canals. At a given sampling session, one or two peaks (relative maxima) were observed in urban and peri-urban canals for pollution representative parameters such as nitrate nitrogen and soluble reactive phosphorus. Those peaks were highly localised, an indication of poor advection. In general, two-dimensional variations of electrical conductivity and turbidity in dry season were uniform in urban and peri-urban canals, an indication of dominant molecular diffusion. This was further evidenced via physical models for different flow stages (low, high, and bankfull). Therefore, fate of contaminants had to be mainly governed by assimilation via sediments. However, grey water footprint analyses showed urban and peri-urban canals have over utilised the natural assimilation capacity of many water quality parameters by several folds. This study proved the importance of inducing attenuation by instream physical heterogeneity similar to natural streams or naturalised canals such as the canal from the rural-urban fringe of this study.Publication Open Access Atomic-scale finite element modelling of mechanical behaviour of graphene nanoribbons(Springer Netherlands, 2019-03) Damasceno, D. A; Mesquita, E; Rajapakse, R. K. N. D; Pavanello, RExperimental characterization of Graphene NanoRibbons (GNRs) is still an expensive task and computational simulations are therefore seen as a practical option to study the properties and mechanical response of GNRs. Design of GNR elements in various nanotechnology devices can be approached through molecular dynamics simulations. This study demonstrates that the atomic-scale finite element method (AFEM) based on the second generation REBO potential is an efficient and accurate alternative to the molecular dynamics simulation of GNRs. Special atomic finite elements are proposed to model graphene edges. Extensive comparisons are presented with MD solutions to establish the accuracy of AFEM. It is also shown that the Tersoff potential is not accurate for GNR modeling. The study demonstrates the influence of chirality and size on design parameters such as tensile strength and stiffness. Graphene is stronger and stiffer in the zigzag direction compared to the armchair direction. Armchair GNRs shows a minor dependence of tensile strength and elastic modulus on size whereas in the case of zigzag GNRs both modulus and strength show a significant size dependency. The size-dependency trend noted in the present study is different from the previously reported MD solutions for GNRs but qualitatively agrees with experimental results. Based on the present study, AFEM can be considered a highly efficient computational tool for analysis and design of GNRs.Publication Embargo Atomistic and continuum modelling of stress field at an inhomogeneity in graphene(Elsevier, 2018-12-15) Dewapriya, M. A. N; Rajapakse, R. K. N. DThe influence of an atomic inhomogeneity on the resulting stress field of a nanoscopic matrix material can be remarkably different from the corresponding continuum descriptions due to the significance of surface energy and the discrete nature of matter at the nanoscale. In this work, we conducted a comprehensive molecular dynamics study to investigate the stress field at an atomic inhomogeneity, in the form of an elliptical hole or a circular hexagonal boron-nitride inclusion, in graphene. The results show that stress concentration factor at an inhomogeneity is higher than the corresponding classical continuum solution. We estimated the surface elastic constants for a modified continuum framework using the molecular dynamics results. Comparison between the atomic simulations and the modified continuum model reveals the limitations of such continuum-based models for the two-dimensional materials. Molecular dynamics results imply that the underlying atomic structure softens the effect of inhomogeneity compared to a continuum description thus causing an amplification of the stress filed. The molecular dynamics and modified continuum solutions for stress concentration are presented in simplified forms and design charts to facilitate preliminary design of graphene-based hybrid materials.Publication Embargo Atomistic and continuum modelling of temperature-dependent fracture of graphene(springer, 2014-06-01) Dewapriya, M. A. N; Rajapakse, R. K. N. D; Phani, A.SThis paper presents a comprehensive molecular dynamics study on the effects of nanocracks (a row of vacancies) on the fracture strength of graphene sheets at various temperatures. Comparison of the strength given by molecular dynamics simulations with Griffith’s criterion and quantized fracture mechanics theory demonstrates that quantized fracture mechanics is more accurate compared to Griffith’s criterion. A numerical model based on kinetic analysis and quantized fracture mechanics theory is proposed. The model is computationally very efficient and it quite accurately predicts the fracture strength of graphene with defects at various temperatures. Critical stress intensity factors in mode I fracture reduce as temperature increases. Molecular dynamics simulations are used to calculate the critical values of J integral (JIC) of armchair graphene at various crack lengths. Results show that JIC depends on the crack length. This length dependency of JIC can be used to explain the deviation of the strength from Griffith’s criterion. The paper provides an in-depth understanding of fracture of graphene, and the findings are important in the design of graphene based nanomechanical systems and composite materialsPublication Embargo Atomistic modelling of crack-inclusion interaction in graphene(Pergamon, 2018-05-15) Dewapriya, M. A. N; Meguid, S. A; Rajapakse, R. K. N. DIn continuum fracture mechanics, it is well established that the presence of crack near an inclusion leads to a significant change in the crack-tip stress field. However, it is unclear how atomistic crack-inclusion interaction manifests itself at the nanoscale where the continuum description of matter breaks down. In this work, we conducted molecular dynamics simulations to investigate the interactions of an atomic-scale boron nitride inclusion with an edge crack in a graphene sheet. Numerical simulations of nanoscale tensile tests were obtained for graphene samples containing an edge crack and a circular inclusion. Stress analysis of the samples show the complex nature of the stress state at the crack-tip due to the crack-inclusion interaction. Results reveal that the inclusion results in an increase (amplification) or a decrease (shielding) of the crack-tip stress field depending on the location of the inclusion relative to the crack-tip. Our numerical experiments unveil that inclusions of specific locations could lead to a reduction in the fracture resistance of graphene. Results of the crack-inclusion interaction study were compared with the corresponding results of crack-hole interaction problem. The study also provides an insight into the applicability of well-established continuum crack-microdefect interaction models for the corresponding atomic scale problems.Publication Open Access Atomistic modelling of size-dependent mechanical properties and fracture of pristine and defective cove-edged graphene nanoribbons(Multidisciplinary Digital Publishing Institute, 2020-07) Damasceno, D. A; Rajapakse, R. K. N. D; Mesquita, ECove-edged graphene nanoribbons (CGNR) are a class of nanoribbons with asymmetric edges composed of alternating hexagons and have remarkable electronic properties. Although CGNRs have attractive size-dependent electronic properties their mechanical properties have not been well understood. In practical applications, the mechanical properties such as tensile strength, ductility and fracture toughness play an important role, especially during device fabrication and operation. This work aims to fill a gap in the understanding of the mechanical behaviour of CGNRs by studying the edge and size effects on the mechanical response by using molecular dynamic simulations. Pristine graphene structures are rarely found in applications. Therefore, this study also examines the effects of topological defects on the mechanical behaviour of CGNR. Ductility and fracture patterns of CGNR with divacancy and topological defects are studied. The results reveal that the CGNR become stronger and slightly more ductile as the width increases in contrast to normal zigzag GNR. Furthermore, the mechanical response of defective CGNRs show complex dependency on the defect configuration and distribution, while the direction of the fracture propagation has a complex dependency on the defect configuration and position. The results also confirm the possibility of topological design of graphene to tailor properties through the manipulation of defect types, orientation, and density and defect networks.Publication Open Access Atomistic simulation of tensile strength properties of graphene with complex vacancy and topological defects(Springer Vienna, 2020-08) Damasceno, D. A; Rajapakse, R. K. N. D; Mesquita, E; Pavanello, RDefects including topological and vacancy defects have been observed in graphene during fabrication. Defects are also introduced to break the lattice symmetry of graphene and thereby obtain enhanced optoelectronic and other properties. It is important that gains in certain properties due to the presence defects are not at the expense of mechanical strength which is important in handling graphene and device fabrication. This paper presents a comprehensive study of the tensile strength and fracture strain of monolayer graphene with commonly observed topological defects and nanopores. Both molecular dynamics and the atomic-scale finite element method (AFEM) are used in this study, and the accuracy of AFEM in simulating complex topological and vacancy defects including line defects is established. It is found that the tensile strength properties have a complex dependency on the defect shape, size, and chirality. Certain defect geometries are found to be mechanically superior to other defect geometries thereby supporting the concept of topological design of graphene to optimize properties. The study also establishes AFEM as an efficient and potential tool for topological optimization of the mechanical behaviour of graphene.