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- A comprehensive review on analysis of nanocomposites: from manufacturing to properties characterizationPublication . M, Vinyas; Athul, S. J.; Harursampath, D.; Loja, Amélia; Trung, Nguyen ThoiThe study of nanocomposites in its diverse scientific fields has increased dramatically over the years with numerous theoretical and experimental techniques emerging and redefining the process of synthesis, analysis and cost control methodologies of nanocomposites. The present review is an attempt to identify the various methodologies, techniques, theories and formulations that are used in nanocomposite technology. As an overall qualitative appreciation it is possible to conclude that the diversity of processes involved in the manufacture and analysis of nanocomposites, impacts them differently, influencing their physical nature, chemical behaviour, biological interactions, optical properties and production costs which consequently may introduce some constraints to their application. Hence, a critical review on the best methodology would remain inconclusive. This work intends to collect and relate publications on different fields of the nanocomposites technology and application fields, aiming at contributing to achieve a wide perspective of different aspects of the nanocomposites processes and theories and with this, being an aid to ease and raise the production and analysis of nanocomposites to a higher level.
- Reconstruction and analysis of hybrid composite shells using meshless methodsPublication . Bernardo, G. M. S.; Loja, AméliaThe importance of focusing on the research of viable models to predict the behaviour of structures which may possess in some cases complex geometries is an issue that is growing in different scientific areas, ranging from the civil and mechanical engineering to the architecture or biomedical devices fields. In these cases, the research effort to find an efficient approach to fit laser scanning point clouds, to the desired surface, has been increasing, leading to the possibility of modelling as-built/as-is structures and components’ features. However, combining the task of surface reconstruction and the implementation of a structural analysis model is not a trivial task. Although there are works focusing those different phases in separate, there is still an effective need to find approaches able to interconnect them in an efficient way. Therefore, achieving a representative geometric model able to be subsequently submitted to a structural analysis in a similar based platform is a fundamental step to establish an effective expeditious processing workflow. With the present work, one presents an integrated methodology based on the use of meshless approaches, to reconstruct shells described by points’ clouds, and to subsequently predict their static behaviour. These methods are highly appropriate on dealing with unstructured points clouds, as they do not need to have any specific spatial or geometric requirement when implemented, depending only on the distance between the points. Details on the formulation, and a set of illustrative examples focusing the reconstruction of cylindrical and double-curvature shells, and its further analysis, are presented.
- An assessment of thick nanocomposite plates' behavior under the influence of carbon nanotubes agglomerationPublication . Craveiro, D.S.; Loja, AméliaThe influence assessment of carbon nanotubes (CNTs) agglomeration on CNT-reinforced composite (CNTRC) thick plates' behavior is the main aim of the present work. CNTs are known to agglomerate into clusters even for relatively low volume fractions, which imposes the need to characterize the effects this may introduce in structures behavior, also knowing that recent works have concluded that neglecting agglomeration phenomenon may lead to an overestimation of the mechanical properties of nanocomposites. Hence, it matters to understand how the arising of these clusters may affect the static and free vibrational behaviors of low side-to-thickness nanocomposite plates. To this purpose, the nanocomposite plate properties' estimation is performed by using the two-parameter model of agglomeration based on the Eshelby-Mori-Tanaka approach, while for behavioral analyses one considers a Higher-order Shear Deformation Theory (HSDT) based on the displacement field of Kant, implemented through the finite element method. The analyses developed consider a set of parametric studies involving the assessment of the influence of side-to-side ratios, side-to-thickness ratios, boundary conditions, and CNTs' distributions along the thickness. The results obtained allow concluding that the transverse deflections and fundamental frequencies of these structures are significantly influenced by the CNTs' agglomeration.
- Dynamic behaviour of soft core sandwich beam structures using kriging-based layerwise modelsPublication . Loja, Amélia; Barbosa, Joaquim; Mota Soares, Cristovão M.Sandwich structures with soft cores are widely used in applications where a high bending stiffness is required without compromising the global weight of the structure, as well as in situations where good thermal and damping properties are important parameters to observe. As equivalent single layer approaches are not the more adequate to describe realistically the kinematics and the stresses distributions as well as the dynamic behaviour of this type of sandwiches, where shear deformations and the extensibility of the core can be very significant, layerwise models may provide better solutions. Additionally and in connection with this multilayer approach, the selection of different shear deformation theories according to the nature of the material that constitutes the core and the outer skins can predict more accurately the sandwich behaviour. In the present work the authors consider the use of different shear deformation theories to formulate different layerwise models, implemented through kriging-based finite elements. The viscoelastic material behaviour, associated to the sandwich core, is modelled using the complex approach and the dynamic problem is solved in the frequency domain. The outer elastic layers considered in this work may also be made from different nanocomposites. The performance of the models developed is illustrated through a set of test cases. (C) 2015 Elsevier Ltd. All rights reserved.