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- Optimization of fibers orientation in a composite specimenPublication . Monte, Sara M. C.; Infante, Virginia; Madeira, JFA; Moleiro, FilipaThis 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.
- Design optimization of functionally graded plates under thermo-mechanical loadings to minimize stress, deformation and massPublication . Moleiro, Filipa; Madeira, Jose Firmino Aguilar; Carrera, Erasmo; Reddy, J. N.This work addresses the multiobjective design optimization of metal-ceramic functionally graded (FG) plates, which are composed of a main functionally graded material (FGM) layer and may include metal and/or ceramic faces, under thermo-mechanical loadings. The design variables are the thickness of the FGM layer, the index of its power-law distribution of metal-ceramic volume fractions, and if included, the thickness of the metal and/or ceramic faces. The three objectives focus on mass, maximum transverse displacement and maximum value of the Tsai-Hill failure criteria to measure the stress field, aiming to minimize all together. Both thermal and mechanical problems are solved simultaneously using a layerwise mixed model based on least-squares formulation with multi-field independent variables, namely, displacements, temperature, transverse stresses, transverse heat flux, in-plane strains and in-plane components of the thermal gradient. The FGM layer z-continuous effective properties are fully described via high-order z-expansions, similarly to finite element approximations. The multiobjective optimization problem is solved by Direct MultiSearch (DMS) derivative-free method, which uses the notion of Pareto dominance to retain a list of feasible non-dominated solutions. Numerical results provide optimal designs of FG plates under thermo-mechanical loadings, exploring distinct metal-ceramic constituent materials and different side-to-thickness ratios, including three-dimensional approximate solutions for validation.
- Thermo-mechanical design optimization of symmetric and non-symmetric sandwich plates with ceramic-metal-ceramic functionally graded core to minimize stress, deformation and massPublication . Moleiro, Filipa; Madeira, Jose Firmino Aguilar; Carrera, E.; Ferreira, A. J. M.This work explores the multiobjective design optimization of symmetric and non-symmetric sandwich plates with ceramic-metal-ceramic functionally graded (FG) core, along with ceramic faces (if included), under thermo-mechanical loadings. The FG core is made of two functionally graded material (FGM) layers, each with the volume fractions of the constituent phases defined by a power-law function through-thickness, with the interface between them metal-rich and the core outer surfaces ceramic-rich. In line with symmetric or nonsymmetric sandwich plates, the design variables involve the thickness of each FGM layer of the core and the index of its power-law function, along with the thickness of each ceramic face. The thermal and mechanical problems are fully coupled using a layerwise mixed least-squares model with multi-field independent variables, including, most importantly, displacements, temperature and transverse stresses. The FG core z-continuous effective properties are also fully described by high-order z-expansions, as demonstrated adopting the rule of mixtures. The multiobjective optimization problem is solved by Direct MultiSearch derivative-free method, minimizing mass, transverse displacement and the stress field, measured by Tsai-Hill failure criteria, all together. Numerical results provide optimal symmetric and non-symmetric sandwich plates with ceramicmetal-ceramic FG core, considering distinct constituent materials and including three-dimensional approximate solutions for validation.
- Characterization and optimization of hybrid carbon-glass epoxy composites under combined loadingPublication . Infante, Virginia; Madeira, JFA; Rui B. Ruben; Moleiro, Filipa; Teixeira De Freitas, SofiaThis work is intended to characterize the mechanical behavior of hybrid carbon-glass composite plates under combined loading of bending and torsion, and to determine the optimal ply fiber orientations to minimize the maximum out-of-plane displacement under such loading conditions. Hybrid composite plates were manufactured with 10 plies each and different stacking sequences using hand lay-up, with carbon fiber and glass fiber reinforcements in an epoxy matrix. Two experimental setups (involving two distinct boundary conditions) are here considered to test the composite plates, both simulating combined loading of bending and torsion. Numerical simulations of the experimental tests were performed in ABAQUS (R) and validated with the experimental data. Using the ply fiber orientations as design variables, the hybrid composite plates were then optimized using global and local optimization using direct search (GLODS). The objective function of minimization of the maximum out-of-plane displacement is carried out through an interactive cycle between GLODS and ABAQUS (R). Specimens of three optimized laminates were also manufactured for experimental validation. The optimization process contributed to improve the performance of the hybrid composite plates in more than 30% when compared to some non-optimized plates.