Eventos Anais de eventos
DINAME 2017
XVII International Symposium on Dynamic Problems of Mechanics
DYNAMIC BEHAVIOR AND OPTIMIZATION OF COMPOSITE TOW STEERED PLATES
Submission Author:
Thiago Guimaraes , MG
Co-Authors:
Thiago Guimaraes, Daniel de Almeida Pereira, Domingos Rade
Presenter: Thiago Guimaraes
doi://10.26678/ABCM.DINAME2017.DIN17-0216
Abstract
In the last years, many techniques and procedures have been employed to optimize traditional constant stiffness composites laminates (CSCL). On the other hand, recent manufacturing methods enable to explore non conventional design approaches. The mechanism development of automatic fiber placement allows the design of variable stiffness composite laminates (VSCL), where the fibers are placed following a curvilinear trajectory. Differently from CSCL, the VSCL the stiffness is a function of the position on the laminate. VSCL can also be obtained considering variable fiber spacing, where the proportion of fiber and resign are not constant in the laminate. Some authors have explored the benefits of VSCL to improve buckling, to reduce stress concentrations around holes, to maximize the fundamental frequency in conical shells and even to optimize the aeroelastic behavior of composite wings. This work proposes a semi-analytical model to optimize a flat plate, controlling the angles in the interpolating positions in the laminate using Lagrange functions of different orders and for two different boundary conditions. A structural model based on Ritz method combined with the classical lamination theory to model the composite laminate is used. The plate is considered thin, modeled based on strain-displacement assumptions of Von-Karman, and the inertia terms are based on the hypotheses of Kirchhoff. The equations of motion are obtained from Lagranges equations. The modal properties (natural frequencies and mode shapes) are found by solving the associated eigenvalue problem. The proposed model is compared regarding fundamental frequencies and mode shapes are validated with a Nastran model. A convergence analysis is done to find the number of terms necessary in the Ritz series to converge the semi analytical model. The influence of the steering parameters on the fundamental frequency is examined. A differential evolution (DE) algorithm is used to optimize the fiber placement by controlling the interpolation points of Lagrange functions for different orders. The optimization aims to maximize the first natural frequency . In all the simulations, different configurations are tested: linear tow steered angle in one direction and steered plates interpolated by Lagrange functions of first order, second order and third order. Preliminary results show the maximization of the fundamental frequency by increasing the order of interpolation and also that as the polynomial order increases the fiber path become more complex and brings new challenges to manufacturing process. For all simulated conditions, one notices the benefits of VSCL in terms of the vibrational aspects, which leads to conclude that the design can be done properly for a specific purpose such as to avoid a specific range of excitation frequency, or to increase the aeroelastic stability margin.
Keywords
variable stiffness composite, Optimization, plate vibration
