Browsing by Author "Soares, C. M. Mota"
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- Analysis of functionally graded sandwich plate structures with piezoelectric skins, using B-spline finite strip methodPublication . Loja, Amélia; Soares, C. M. Mota; Barbosa, JoaquimFunctionally graded materials are composite materials wherein the composition of the constituent phases can vary in a smooth continuous way with a gradation which is function of its spatial coordinates. This characteristic proves to be an important issue as it can minimize abrupt variations of the material properties which are usually responsible for localized high values of stresses, and simultaneously providing an effective thermal barrier in specific applications. In the present work, it is studied the static and free vibration behaviour of functionally graded sandwich plate type structures, using B-spline finite strip element models based on different shear deformation theories. The effective properties of functionally graded materials are estimated according to Mori-Tanaka homogenization scheme. These sandwich structures can also consider the existence of outer skins of piezoelectric materials, thus achieving them adaptive characteristics. The performance of the models, are illustrated through a set of test cases. (C) 2012 Elsevier Ltd. All rights reserved.
- Benchmark exact solutions for the static analysis of multi-layered piezoelectric composite using PVDFPublication . Moleiro, Filipa Andreia de Matos; Soares, C. M. Mota; Soares, C. A. Mota; Reddy, J. N.The three-dimensional (3D) exact solutions developed in the early 1970s by Pagano for simply supported multilayered orthotropic composite plates and later in the 1990s extended to piezoelectric plates by Heyliger have been extremely useful in the assessment and development of advanced laminated plate theories and related finite element models. In fact, the well-known test cases provided by Pagano and by Heyliger in those earlier works are still used today as benchmark solutions. However, the limited number of test cases whose 3D exact solutions have been published has somewhat restricted the assessment of recent advanced models to the same few test cases. This work aims to provide additional test cases to serve as benchmark exact solutions for the static analysis of multilayered piezoelectric composite plates. The method introduced by Heyliger to derive the 3D exact solutions has been successfully implemented using symbolic computing and a number of new test cases are here presented thoroughly. Specifically, two multilayered plates using PVDF piezoelectric material are selected as test cases under two different loading conditions and considering three plate aspect ratios for thick, moderately thick and thin plate, in a total of 12 distinct test cases. (C) 2013 Elsevier Ltd. All rights reserved.
- Damping optimization of viscoelastic laminated sandwich structures using the direct multisearch methodPublication . J.F.A. Madeira; Araújo, A. L.; Soares, C. M. Mota; Soares, C. A. MotaA multiobjective approach for optimization of passive damping for vibration reduction in sandwich structures is presented in this paper. A layerwise finite element model for sandwich plates with viscoelastic core and anisotropic laminated face layers is used along with the complex modulus approach and the dynamic problem is solved in the frequency domain. Constrained optimization is conducted for maximisation of modal loss factors and minimisation of weight of sandwich beams and plates with elastic laminated constraining layers and a viscoelastic core, with layer thickness and laminate layer ply orientation angles as design variables. The problem is solved using the Direct MultiSearch (DMS) solver for derivative-free multiobjective optimization and solutions are compared with alternative ones obtained using genetic algorithms. DMS is a solver for multiobjective optimization problems which does not use any derivatives of the objective functions. It is based on a novel technique called direct multisearch, developed by extending direct search from single to multiobjective optimisation.
- EditorialPublication . Madeira, JFA; Pina, H.; Camotim, D.; Basaglia, C.; Poroseva, S. V.; Soares, C. M. Mota; Araújo, A. L.; Duarte, F. Moleiro; Sarrate, J.; Ledoux, F.; Kruis, J.; Dumont, S.; Lebon, F.; Santos, J. V. Araújo; Lopes, H. M. R.; Topping, B. H. V.This special issue includes fifteen extended, reviewed and revised papers originally presented at the Eleventh International Conference on Computational Structures Technology (CST2012) and the Eighth International Conference on Engineering Computational Technology (ECT2012) held concurrently in Dubrovnik, Croatia, 4–7 September 2012. The invited lectures presented at CST2012 and ECT2012 were published in: “Computational Methods for Engineering Science”, edited by B.H.V. Topping; and the invited review lectures in “Computational Technology Reviews” vols. 5 & 6, published by Saxe-Coburg Publications. Other contributed papers presented at the conferences were published in: “Proceedings of the Eleventh International Conference on Computational Structures Technology”, edited by B.H.V. Topping and “Proceedings of the Eighth International Conference on Engineering Computational Technology”, edited by B.H.V. Topping; both published by Civil-Comp Press. A further selection of papers from these conferences will be published in a Special Issue of “Computers & Structures” (Elsevier).
- Multiobjective optimization for vibration reduction in composite plate structures using constrained layer dampingPublication . Madeira, JFA; Araújo, Aurélio L.; Soares, C. M. Mota; Soares, C. A. MotaThis paper presents a multiobjective optimization approach to minimize weight and maximize modal damping in laminated composite panels with Constrained Layer Damping (CLD) treatments. The design variables are the number and position of the CLD patch treatments on the surface of the laminated plate. The Direct MultiSearch (DMS) solver for multiobjective optimization problems is used in this work. DMS is a solver which does not use any derivatives of the objective functions. A previously developed finite element model for sandwich plates with viscoelastic core and anisotropic laminated face layers is adapted to model the plate with the CLD treatments. Applications for L-shaped and T-shaped plates are presented and both trade-off Pareto optimal fronts and the respective treatment configurations are obtained and the results are analyzed and discussed.
- Optimization of magneto-electro-elastic composite structures using differential evolutionPublication . Loja, Amélia; Soares, C. M. Mota; Barbosa, JoaquimMagneto-electro-elastic structures are built from materials that provide them the ability to convert in an interchangeable way, magnetic, electric and mechanical forms of energy. This characteristic can therefore provide an adaptive behaviour to a general configuration elastic structure, being commonly used in association with any type of composite material in an embedded or surface mounted mode, or by considering the usage of multiphase materials that enable achieving different magneto-electro-elastic properties. In a first stage of this work, a few cases studies will be considered to enable the validation of the model considered and the influence of the coupling characteristics of this type of adaptive structures. After that we consider the application of a recent computational intelligence technique, the differential evolution, in a deflection profile minimization problem. Studies on the influence of optimization parameters associated to the problem considered will be performed as well as the adoption of an adaptive scheme for the perturbation factor. Results are also compared with those obtained using an enhanced particle swarm optimization technique. (C) 2013 Elsevier Ltd. All rights reserved.
- A study on the modeling of sandwich functionally graded particulate compositesPublication . Loja, Amélia; Barbosa, Joaquim; Soares, C. M. MotaDual-phase functionally graded materials are a particular type of composite materials whose properties are tailored to vary continuously, depending on its two constituent's composition distribution, and which use is increasing on the most diverse application fields. These materials are known to provide superior thermal and mechanical performances when compared to the traditional laminated composites, exactly because of this continuous properties variation characteristic, which enables among other advantages smoother stresses distribution profile. In this paper we study the influence of different homogenization schemes, namely the schemes due to Voigt, Hashin-Shtrikman and Mod-Tanaka, which can be used to obtain bounds estimates for the material properties of particulate composite structures. To achieve this goal we also use a set of finite element models based on higher order shear deformation theories and also on first order theory. From the studies carried out, on linear static analyses and on free vibration analyses, it is shown that the bounds estimates are as important as the deformation kinematics basis assumed to analyse these types of multifunctional structures. Concerning to the homogenization schemes studied, it is shown that Mori-Tanaka and Hashin-Shtrikman estimates lead to less conservative results when compared to Voigt rule of mixtures.