ABSTRACT Resin Transfer Molding (RTM) process is commonly used to produce high quality polymeric composites with simple or complex geometries in small to large sizes. In RTM process a preformed reinforcement is positioned inside the mold cavity. This dry reinforcement is actually a fibrous porous media whereby resin will flow. The mold is then closed and resin is injected. After complete impregnation of the reinforcement, resin cure process takes place. Numerical simulation is a very useful tool for mold design and process optimization, however resin and reinforced medium physical properties must be precisely determined. Medium permeability is probably the most important and most difficult parameter to be evaluated. In this work it is proposed a numerical/experimental methodology to determine transverse permeability in reinforcements used within RTM process. PAM-RTM software was chosen to simulate resin flow through the reinforced medium. Proposed methodology uses the inverse parameter estimation method to calculate the unknown permeability. Newton-Raphson method was used to solve the associated algebraic equation system, on which PAM-RTM software is used to calculate resin injection times. Results have shown that with previous knowledge (taken from literature or obtained experimentally) of the in-plane permeabilities ( Kxx and Kyy ), physical properties of the resin (ρ, µ), medium porosity (ε) and total filling time (t) it is possible to estimate transverse permeability in thick pieces. It was also performed a numerical study about the influence of transverse permeability in resin flow inside the mold. This study predicted several possible problems that may occur when transverse permeability is much smaller than in-plane permeabilities. Finally, it is possible to state that mold design and proper fibrous reinforcement choice can be optimized when numerical techniques are used.

Abstract Perforated steel thin plates are commonly used in structural engineering. Due to their geometric characteristics, these panels can suffer the undesired buckling phenomenon. In this context, the present work associates the computational modeling and the constructal design method to evaluate the influence of the geometric configuration in the plate buckling behavior, using the exhaustive search method to determine which geometries conduct to superior mechanical behavior. To do so, numerical models are employed to solve elastic and elasto-plastic buckling of plates having a centered perforation. Different hole types (longitudinal oblong, transversal oblong, elliptical, rectangular, diamond, longitudinal hexagonal, or transversal hexagonal) with different shapes (variation of characteristics dimensions of each hole type) are analyzed. Limit curves to avoid buckling were obtained, as well as the definition of the geometries that can improve up to 107% the plate performance.

Geometrically nonlinear static and dynamic behaviour of laminate composite shells are analyzed in this work using the Finite Element Method (FEM). Triangular elements with three nodes and six degrees of freedom per node (three displacement and three rotation components) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases with finite rotations and displacements an iterative-incremental scheme is employed. Numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes.

Um sistema combinado reator UASB-reator aeróbio foi utilizado para a remoção de nitrogênio total e DQO de efluente de parboilização de arroz. O experimento foi realizado em reatores de bancada, com volumes de 4 L (UASB) e 3,6 L (reator aeróbio). Os parâmetros de operação pH, temperatura, alcalinidade e concentração de ácidos voláteis foram monitorados durante o período experimental. Para o reator aeróbio de mistura completa, foi determinada, também, a concentração de oxigênio dissolvido. O sistema combinado reator UASB-reator aeróbio apresentou uma eficiência de remoção de carbono de 84% e uma eficiência de remoção de nitrogênio total Kjeldahl de 83%. O sistema proposto, nas condições experimentais, demonstrou ser adequado para remoção, simultânea, de DQO e de compostos oxidados de nitrogênio, em reator UASB.

An UASB-aerobic reactor system was used for the removal of total nitrogen and COD of effluent from industries of parboilized rice. The experiment was performed in reactors with volumes of 4 L (UASB reactor) and 3,6 L (aerobic reactor), respectevely. Temperature, pH, alkalinity and volatile acids concentration were monitored during the experiment. Dissolved oxygen concentration was determined for the aerobic reactor. The UASB-aerobic reactor system showed 84% carbon removal efficiency and 83% total Kjeldahl nitrogen removal efficiency. This system was able to remove, efficiently, COD and nitrogen in an UASB reactor.