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- Multi-objective optimization of pultruded composite sandwich panels for building floor rehabilitationPublication . Garrido, Mário; Madeira, JFA; Proença, M.; Correia, J. R.Composite sandwich panels are being increasingly considered for civil engineering structural applications, offering high versatility in constituent materials and their geometrical arrangement. This translates to a high number of design variables, in addition to a potentially large number of design requirements and objectives related to the panels' functions. This paper presents an optimization study of a composite sandwich panel system for building floor rehabilitation, using the Direct MultiSearch (DMS) method. Pultruded multicellular panels with a polyurethane (PUR) foam core and carbon- or glass-fibre reinforced polymer (C/GFRPF) faces and ribs/webs are considered. The panel architecture was defined using 3 geometrical variables and 14 material related variables. In addition, 8 competing objective functions were studied, related to aspects such as structural serviceability and resistance, thermal insulation, acoustic performance, cost minimization, and environmental performance. The results are presented in the form of Pareto optimal sets, from which several conclusions are drawn regarding common design-related options. The influence of core material density, of the number of ribs/webs, or of the type of fibre reinforcement and its respective layup on the different objective functions are addressed. Optimal solutions for meeting different design purposes are presented, providing useful insights for structural designers and sandwich panel manufacturers.
- Optimization of a composite impact attenuator for a formula student carPublication . Castro, J. M. P. B. C.; Fontana, M.; Araújo, Aurélio L.; Madeira, JFAThe current impact attenuator used by the Formula Student team of University of Lisbon is an out-of-shelf solution consisting in an aluminum honeycomb. The competition regulations defined for the impact attenuator’s design allow room for innovation, which can be used to build more efficient structures and explore new materials. The main objective of this work is to design and optimize a composite impact attenuator lighter than the solution currently used by the team. Experimental results and numerical models presented in previous works are considered in the development of a new approach. Several design parameters are studied and their influence on the behavior of the impact attenuators are taken into account. Direct Multisearch (DMS) algorithm directly coupled to Abaqus software is used to perform the optimizations. The lighter solutions’ mass is compared to the baseline aluminum structure’s and detailed descriptions are presented for chosen optimal designs, which constitute an improvement regarding the baseline’s mass.
- Multiobjective optimization of ceramic-metal functionally graded plates using a higher order modelPublication . Franco Correia, Victor; Madeira, JFA; Araújo, Aurélio L.; Mota Soares, Cristóvão ManuelA methodology of multiobjective design optimization of ceramic–metal composite plates with functionally graded materials, with properties varying through the thickness direction, obtained by an adequate variation of volume fractions of the constituent materials, is presented in this paper. Constrained optimization is conducted for different behavior objectives like the maximization of buckling load or fundamental natural frequency. Mass minimization and material cost minimization are also considered. The optimization problems are constrained by stress based failure criteria and other structural response constraints or manufacturing limitations. The design variables are the index of the power-law distribution in the metal-ceramic graded material and the thicknesses of the graded material and/or the metal and ceramic faces. An equivalent single layer finite element plate model having a displacement field based on a higher order shear deformation theory, accounting for the temperature dependency of the material properties, was developed and validated for the analysis of through-the-thickness ceramic-metal functionally graded plates. The optimization problems are solved with two direct search derivative-free algorithms: GLODS (Global and Local Optimization using Direct Search) and DMS (Direct MultiSearch). DMS, the multiobjective optimization solver, is started from a set of local minimizers which are initially determined by the global optimizer algorithm GLODS for each one of the objective functions.
- Optimization of a thin-walled composite crash absorberPublication . Fontana, Marco; Araújo, A. L.; Madeira, JFAThis work aims to improve upon the aluminium impact attenuator currently used by the University of Lisbon Formula Student team through a composite solution. The influence of geometrical variations, particularly the use of curved walls, and the number of objectives considered for the optimization are studied. To perform the optimizations, Abaqus is coupled with the Direct Multisearch (DMS) algorithm, the overall performance of the solutions is evaluated and the influence of the introduction of curved walls on the energy absorption capabilities discussed. Off-axis impacts are studied and the effect of curved walls in that situation analysed. An overview of the best configurations achieved is provided and one final configuration is selected.