Eduardo Lenz Cardoso

THE INFLUENCE OF MATRIX IMPREGNATION ON EFFECTIVE ELASTIC PROPERTIES OF A UNIDIRECTIONAL CARBON NANOTUBE BUNDLED COMPOSITE: A TOPOLOGY OPTIMIZATION APPROACH

The present work aims to find the optimum distribution of a certain amount of matrix around a pack of fibers, which is the representative volume element of a bundle of carbon nanotubes, in order to maximize a linear combination of the effective properties of the media. The homogenization by asymptotic expansion is used to find the effective properties and a topology optimization procedure is conducted to find the optimal material distribution. In the adopted Representative Volume Element (RVE), the fibers are fixed in the domain, and the optimization is performed only at matrix, whose properties are parameterized by the Solid Isotropic Material with Penalization (SIMP) method. Three distinct linear combinations of the components of the fourth order stiffness tensor are chosen, as well as three distinct admissible volume fractions for the matrix. The numerical results are presented by both the optimal material distributions in the RVEs and the convergence plots of the objective functions. The results show which regions of the RVE play a significant role for the effective properties of the composite, and may be used for a careful manufacturing process guide.

Topology Optimization of Piezoelectric Actuators Considering Geometric Nonlinearities

This work shows a methodology for the optimum design of piezelectric actuators undergoing large deformations. An equilibrium formulation for the finite movement of a piezoelectric body is introduced, as well as its finite element discretization. The solution of the nonlinear finite element equations is acomplishied through a new coupled-field arc-length algorithm. The optimization consists in the maximization of the output displacements subject to volume and displacement constraints. Sensitivities are derived with respect to mechanical displacements and electric potentials. The Generalized Method of Moving Asymptotes (GMMA) is used for the solution of the optimization problem. The results obtained with the proposed formulation are shown and the influence of the geometric nonlinearities is discussed.