Browsing by Author "Moleiro, F."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- Deformation prediction of composite specimens subjected to three-point bending testsPublication . Monte, Sara M. C.; Infante, Vírginia; Moleiro, F.; Madeira, J. F. A.A computational and experimental study was carried out in order to determine the deformations of specimens made in laminated composite material when subjected to three - point bending test. The specimens were produced using unidirectional carbon fiber prepreg with different aspect ratios and different lamination schemes. The experimental deformations of the bending tests were obtained using an innovative method called digital image correlation. At the computational level, two models were compared: the first developed in ANSYS and the second, not available in any commercial program, developed by MOLEIRO, 2010.The latter presents a mixed Layerwise formulation that assumes displacements and transverse stresses as independent variables, and therefore is able to a priori fulfill the interlaminar continuity C^0 of tranverse stresses and displacements. ANSYS model uses a solid element, in the laminated structural version, and assumes a displacement formulation. It was concluded that the ANSYS model results are more similar to the experimental results of longer specimens and the Layerwise mixed model results are more similar to the experimental results of shorter specimens.
- Deformations and stresses of multilayered plates with embedded functionally graded material layers using a layerwise mixed modelPublication . Moleiro, F.; M. Franco Correia, V.; Araújo, A.L.; Mota Soares, C.M.; Ferreira, A.J.M.; Reddy, J.N.This work presents a new layerwise mixed model for the static analysis of multilayered plates with embedded functionally graded material (FGM) layers subjected to transverse mechanical loads. This model is capable to fully describe a two-constituent metal-ceramic FGM layer continuous variation of material properties in the thickness direction, using any given homogenization method to estimate its effective properties. The present model is based on a mixed least-squares formulation with a layerwise variable description for displacements, transverse stresses and in-plane strains, chosen as independent variables. This mixed formulation ensures that the interlaminar continuity requirements at the layers interfaces, where the material properties actually change, are fully fulfilled a priori for all independent variables. The order of the in-plane two-dimensional finite element approximations and the order of the z-expansion through each layer thickness, as well as the number of layers, whether FGM layers or not, are considered free parameters. The full description of the FGM effective properties is achieved by applying to the z-continuous elastic coefficients a z-expansion through the layer thickness of a given order, set as an added free parameter, in a similar approach to finite element approximations. The numerical results consider both single-layer and multilayered functionally graded plates with different side-to-thickness ratios, using either Mori-Tanaka or the rule of mixtures estimates for the FGM effective properties with different material gradation profiles. The present model results are assessed by comparison with three-dimensional (3D) exact solutions and closed form solutions, which demonstrate its capability to predict a highly accurate quasi-3D description of the displacements and stresses distributions altogether.
- Fully coupled thermomechanical analysis of multilayered plates with embedded FGM skins or core layers using a layerwise mixed modelPublication . Moleiro, F.; M.Franco Correia, V.; Ferreira, A.J.M.; Reddy, J.N.This work presents a new layerwise mixed model for the fully coupled thermo-mechanical static analysis of multilayered plates with embedded functionally graded material (FGM) layers, either skins or core layers, under thermal and/or mechanical loads. This model is able to fully describe a two-constituent metal-ceramic FGM layer z-continuous effective properties through-thickness, using any given homogenization method, and is here extended to the fully coupled thermo-mechanical analysis. It is based on a mixed least-squares formulation with a layerwise variable description for displacements, transverse stresses and in-plane strains, along with temperature, transverse heat flux and in-plane components of the thermal gradient, taken as independent variables. This mixed formulation ensures that the interlaminar continuity requirements, where the material properties may actually change, are fully fulfilled a priori by all chosen independent variables. The numerical results consider single-layer and multilayered plates with different side-to-thickness ratios, under thermal or mechanical loads, using mainly Mori-Tanaka estimate for the FGM effective properties with different material gradation profiles. The results are assessed by comparison with three-dimensional (3D) exact solutions, and demonstrate the model capability to predict a highly accurate quasi-3D thermo-mechanical description of the through-thickness distributions of displacements and stresses, as well as temperature and heat flux.
- Layerwise mixed models for analysis of multilayered piezoelectric composite plates using least-squares formulationPublication . Moleiro, F.; Mota Soares, C.M.; Mota Soares, C.A.; Reddy, J.N.This work provides an assessment of layerwise mixed models using least-squares formulation for the coupled electromechanical static analysis of multilayered plates. In agreement with three-dimensional (3D) exact solutions, due to compatibility and equilibrium conditions at the layers interfaces, certain mechanical and electrical variables must fulfill interlaminar C0 continuity, namely: displacements, in-plane strains, transverse stresses, electric potential, in-plane electric field components and transverse electric displacement (if no potential is imposed between layers). Hence, two layerwise mixed least-squares models are here investigated, with two different sets of chosen independent variables: Model A, developed earlier, fulfills a priori the interlaminar C0 continuity of all those aforementioned variables, taken as independent variables; Model B, here newly developed, rather reduces the number of independent variables, but also fulfills a priori the interlaminar C0 continuity of displacements, transverse stresses, electric potential and transverse electric displacement, taken as independent variables. The predictive capabilities of both models are assessed by comparison with 3D exact solutions, considering multilayered piezoelectric composite plates of different aspect ratios, under an applied transverse load or surface potential. It is shown that both models are able to predict an accurate quasi-3D description of the static electromechanical analysis of multilayered plates for all aspect ratios.
- Optimization of fibers orientation in a composite specimenPublication . Monte, S. M. C.; Infante, V.; Madeira, J. F. A.; Moleiro, F.This article is devoted to the study of the optimal design of fibers orientation in a composite specimen with the objective to minimize the displacement. The composite specimen considered is within the scope of aerospace and mechanical applications. The objective function associated with the composite design is computed based on a static analysis of a finite element solid model, which allows one to define (or control) the fibers orientation. The recent global and local optimization using direct search methods (GLODS) is used for the optimization process. To validate and compare the numerical and optimized results, the specimens were manufactured and tested experimentally. The orientation of the layers that minimize the maximum displacement is achieved through the computational interaction of the optimization program, GLODS, in loop with the finite element program, ANSYS. It is shown that the optimized lamination schemes found by GLODS minimized about 60% of the displacement compared to the nonoptimized specimens.
- Optimization of Metal–Ceramic Functionally Graded Plates Using the Simulated Annealing Algorithm.Publication . Franco Correia, Victor; S. Moita, J.; Moleiro, F.; M. Mota Soares, C.This work involves the design optimization of metal–ceramic through the thickness of functionally graded material (FGM) plates subjected to thermomechanical loadings. Constrained optimization was performed for minimum mass and minimum material cost of the FGM plates. The design process of FGM plate structures requires a good choice of metal and ceramic materials and the adequate definition of the components volume fractions through the thickness direction in order to accomplish a certain structural behavior, while optimizing the material costs and/or the plate mass. Here, the optimization problems are solved with the simulated annealing (SA) algorithm, not requiring the calculation of the derivatives of the objective or constraint functions. Constrained single objective optimization cases are studied, and validated with alternative solutions, considering the p-index and the FGM plate thickness as design variables. New optimization cases, involving additionally the metal and ceramic materials as design variables, are presented both for benchmark purposes and to demonstrate the suitability of the SA algorithm to solve those optimization problems.