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COB18 MODELAGEM DA EVOLUÇÃO DO DANO EM JUNTAS ALUMÍNIO-EPOXI SUBMETIDAS A SOLICITAÇÕES TRATIVAS / MODELING THE DAMAGE EVOLUTION IN AXIALLY LOADED ALUMINIUM-EPOXY BUTT JOINTS
E. M. Sampaio, F. L. Bastian
COPPE - Programa de Engenharia Metalúrgica e de Materiais, Universidade Federal do Rio de Janeiro
UFRJ, 21945-970, Rio de Janeiro, RJ Brasil
M. J. Q. Pinheiro, H. S. Costa Mattos
LMTA - Laboratório de Mecânica Teórica e Aplicada, Departamento de Engenharia
Mecânica, Universidade Federal Fluminense - UFF, 24210-240, Niterói, RJ Brasil
This work is concerned with the analysis of the damage behavior of adhesive joints consisting of an epoxy adhesive layer bonding aluminium alloy substrates. A model for butt joints, developed within the framework of Continuum Damage Mechanics, that accounts for the effect of the thickness of the adhesive layer on the strength of the system is proposed and analysed. Analytical examples are presented in order to illustrate the main features and possibilities of the model. To check the accuracy of the proposed model, the predicted values of the rupture stress for different values of the thickness of the adhesive layer are compared to experimental data, showing a good agreement.
Keywords: Aluminium-epoxy adhesive joints, adhesion, fracture, continuum damage mechanics.
COB83 THE HOMOGENISATION THEORY APPLIED TO NET FACESHEETS OF SANDWICH PLATES
Mário Kataoka-Filho 1 , Jorn S. Hansen 2 and Walter Kenkiti Takahashi 1
1 National Institute for Space Research - INPE - MCT - P.O. Box 510 12.227-010 - S. J. dos Campos - SP - BRAZIL
E-mail: kataoka@patroa.dem.inpe.br
2 Institute for Aerospace Studies - University of Toronto - 4925 Dufferin Street Downsview, Ontario - M3H-5T6 - CANADA
E-mail: hansen@bach.utias.utoronto.ca
In order to further increase the efficiency of composite sandwich structures, designers have been using composite facesheets manufactured from a uniform carbon fibre/epoxy net. In the present study, a procedure to approximate this net as a smoothed orthotropic continuum is presented. The smoothing process was accomplished using the theory of homogenisation and the resulting material coefficients are calculated using the Finite Element Method. To validate the procedure, a free-free modal test was completed and its results compared with numerical prediction.
Keywords: Homogenisation, Optimization and Sandwich Plate.
COB102 An Integrated Micro/Macro Stress Analysis of Laminate Composites: The Control Volume Finite Element Formulation
Antonio Ferreira Ávila
Departamento de Engenharia Mec"anica, Escola de Engenharia da UFMG
CEP 31270--901 Belo Horizonte, Brasil -- E--mail: avila@vesper.demec.ufmg.br
The control volume finite element formulation (CVFE) is described for solving solid mechanics equations for laminate composites. The CVFE is detailed based on the weighted residual method, and comparisons are drawn with the conventional Galerkin Finite Element method (GFEM) to be able to clearly establish the differences between the two methods. An integrated micro/macro mechanical formulation is proposed. First, a micromechanical analysis is performed to obtain the effective properties. The micromechanical model used is the Composite Cylinder Assemblage model (CCA). The macroscopic analysis is based on a variation of the Vanishing Fiber Diameter Theory (VFD). The integrated micro/macro analysis is performed for laminate composites using the concept of ``smeared'' elements. Punctual, uniform, and linear distributed loadings are considered in the stress analysis of unidirectional metal matrix composite structures. The results are compared to analytical solutions available in the literature. The CPU solution time between the CVFE and FEM are also compared.
Keywords: Control Volume Finite Element, integrated micro/macro mechanical model, metal matrix composites
COB138 ANÁLISE DA RESISTÊNCIA DE UM COMPÓSITO EM TRAÇÃO TRANSVERSAL E LONGITUDINAL / ANALISYS OF COMPOSITE STRENGTH IN TRANSVERSAL AND LONGITUDINAL TENSILE TESTS
Edson Vander Pimentel, Kátia Celina Da Silva Richetto & Herman Jacobus Cornelis Voorwald
Departamento de Materiais e Tecnologia, Faculdade de Engenharia - UNESP - Guaratinguetá
CEP: 12.500-000 Guaratinguetá - E-mail: pimentel@feg.unesp.br
The excellent mechanical behavior, regarding strength and stifness, makes of the composite material, a choice in structural application. The main objective of this work is the strength data analysis of a unidirectional laminate composite (carbon fiber/epoxy resin), in longitudinal and transversal directions. Several conditions of composite were tested, providing a large amount of experimental results that were studied using statistical considerations, such as media and standard deviation.The Weibull distribution that provides informations about scattering in strength data was also used.
Keywords: Compósito laminado unidirecional, Compósito fibra de carbono/resina epoxi, Análise estatística, Distribuição de Weibull / Unidirectional laminate composite, Carbon fibre /epoxy resin composite, Statistical analisys, Weibull distribution
COB217 A FINITE ELEMENT ANALYSIS OF STRESS AND DELAMINATION IN SANDWICH ORTHOTROPIC LAMINATED PLATES
Alves Brandão, L.O.C., Levy Neto, F. and Mamiya, E. N.
Departamento de Engenharia Mecânica, FT - Universidade de Brasília, 70910-900 Brasília, DF - E-mail: levy@orion.enm.unb.br
This work presents a finite element displacement analysis of a laminated composite plate under static bending. The laminate is a symmetric sandwich constituted of three layers with orthotropic mechanical properties. The present theory assumes a piecewise linear distribution of the inplane displacements through the thickness, and as a consequence describes distinct measures of shear for the inner and the outer layers. The numerical results obtained from the finite element simulations were compared with analytical as well as numerical solutions. Fiber failure and delamination criteria were implemented for the analysis of integrity of the laminated plate.
Keywords: Laminated plates, finite elements, delamination, layerwise theory.
COB370 HYBRID COMPOSITE PLATES WITH SHAPE MEMORY ALLOY FIBERS
Marcelo Amorim Savi
Departamento de Engenharia Mecânica e de Materiais, Instituto Militar de Engenharia
22.290.270, Rio de Janeiro, RJ - E-Mail: d4savi@epq.ime.eb.br
Pedro Manuel Calas Lopes Pacheco
Departamento de Engenharia Mecânica, CEFET/RJ, 20.271.110, Rio de Janeiro, RJ - E-Mail: calas@cefet-rj.br
Intelligent materials can be used on intelligent structures as actuators that may be embedded in structural material (matrix), forming what is called hybrid composites. Actuators made of shape memory alloys (SMAs) have shown a great potential in situations where high force, large strain, and low frequency structural control are needed. This contribution discusses the bending modeling of hybrid composite plates using shape memory alloy fibers. A numerical method is developed and some numerical simulations show the pseudoelastic behavior of these composites.
Keywords: Composite Materials, Shape Memory Alloys, Intelligent Structures.
COB830 NOTCHED STRENGTH OF COMPOSITE LAMINATES WITH UNIDIRECTIONAL TAPE LAYERS
Eugênio de Azevedo Soriano & Sérgio Frascino M. de Almeida
Instituto Tecnológico de Aeronáutica - Div. Enga Mecânica-Aeronáutica
12228-900 São José dos Campos - SP - E-mail: frascino@mec.ita.cta.br
The strength of notched composite laminates with unidirectional tape layers is investigated under the assumption that the failure of the 0° plies governs laminate failure. The failure criterion proposed by Mar and Lin is utilized to define the fracture parameter of a 0° ply. Experimental results obtained from different laminates indicated that under certain conditions the fracture parameter of a 0° ply is essentially constant, regardless of the orientation of the neighboring plies. The 0° -ply fracture parameter is used to compute the laminate fracture parameter, which is subsequently used in the failure criterion to predict the laminate notched strength. The use of this technique significantly reduces the number of tests required to characterize a family of laminates. Correlation between predicted and experimental notched strength showed excellent agreement.
Keywords: composite materials, notched strength, fracture, laminates, carbon/epoxy
COB947 TÉCNICAS DE FABRICAÇÃO PARA LAMINADOS COM BORDAS MOLDADAS RESISTENTES À DELAMINAÇÃO / DELAMINATION RESISTANT MANUFACTURING TECHNIQUES FOR LAMINATES WITH MOLDED EDGES
Geraldo M. Cândido, Sérgio Frascino M. de Almeida & Fabiano Mazza
Divisão de Enga Mecânica-Aeronáutica - Instituto Tecnológico de Aeronáutica
12228-900 São José dos Campos - SP Brasil E-mail: frascino@mec.ita.cta.br
The strength of composite laminates may be reduced because of delaminations emanating from the free edges. The laminate strength depends on the stacking sequence and the finishing of the free edges. The use of laminates with molded edges leads to a gain in productivity but may have adverse effects on the strength. In this work, fabrication procedures are proposed to reinforce the molded edges producing laminates with high edge delamination strength.
Keywords: Composites, manufacturing, free edge, tensile strength
COB1000 IDENTIFICAÇÃO DE PROPRIEDADES ELÁSTICAS DE MATERIAIS COMPOSTOS A PARTIR DE ENSAIOS DINÂMICOS / Identification of elastic properties of composite materials from dynamic tests
Jesiel Cunha
Departamento de Ciências Físicas-Universidade Federal de Uberlândia
Campus Santa Mônica-Uberlândia-MG-Brasil-E-mail : jecunha@ufu.br
This work consists in the identification of the stiffness properties of composite materials from dynamic tests. Unknown coefficients are identified by a technique of model updating. The used formulation (modal approach) is based on the minimization of the eigensolution residuals (sensitivity method). Errors of generalized masses are considered. This technique allows the simultaneous identification of several properties from a single test. Stiffness properties of extension, bending, twisting and transverse shear are identified. A discussion of the differents identification approaches of elastic constants of composite materials from dynamic tests is presented. Results obtained by numerical simulations show the efficiency of the method.
Keywords: Materiais compostos - Identificação - Vibração - Rigidez - Ajuste de modelos
Composite materials - Identification - Vibration - Stiffness - Model updating
COB1001 APLICAÇÃO DOS ALGORITMOS GENÉTICOS NA IDENTIFICAÇÃO DE CONSTANTES ELÁSTICAS DE MATERIAIS COMPOSTOS A PARTIR DO COMPORTAMENTO VIBRATÓRIO / APPLICATION OF GENETIC ALGORITHMS FOR THE IDENTIFICATION OF ELASTIC CONSTANTS OF COMPOSITE MATERIALS FROM DYNAMIC TESTS
Jesiel Cunha
Departamento de Ciências Físicas-Universidade Federal de Uberlândia
Campus Santa Mônica-Uberlândia-MG-Brasil-E-mail : jecunha@ufu.br
This work is placed within the framework of the identification of stiffness properties of composite materials from dynamic tests. More precisely, the used approach is inserted in the general context of model updating. The genetic algorithms method is used as a complementary technique allowing a first estimation of the elastic coefficients, in other words, the initial finite element model is estimated. The refinement of solutions can thus be made by a classic updating method, as for example the sensitivity method. The procedure allows the simultaneous estimation of several properties, from a single test. Properties of extension, bending, twisting and transverse shear effects can be identified. Results obtained by numerical simulation show the efficiency and robustness of the genetic algorithms.
Keywords: Algoritmos genéticos - Materiais compostos - Identificação - Vibração - Rigidez
Genetic algorithms - Composite materials - Identification -Vibration - Stiffness
COB1178 Buckling and post-buckling BEHAVIOR of laminated composite cylindrical shells
Román A. A. Aléman & Paulo B. Gonçalves
Departamento de Engenharia Civil, PUC/Rio - Rua Marquês de São Vicente, 225 - Gávea, CEP: 22435-900 - Rio de Janeiro - RJ
Tel. (021)529-9325-Fax (021)511-1546- E-mail: paulo@civ.puc-rio.br
In the present work an analysis of the stability of layered composite cylindrical shells under axial compression or lateral pressure is carried out using a non-linear shear deformable shell theory. Using general computer algebra routines written in MAPLE, an analytical solution is obtained for the critical load and corresponding critical mode. A modal solution based on the seminal ideas of Koiter’s post-buckling theory is employed together with the Rayleigh-Ritz method to obtain the non-linear equilibrium equations governing the post-critical behavior of the shell and the fundamental solution of an imperfect shell. Again these equations are obtained and solved by the use of symbolic algebra. A detailed parametric analysis is presented and the effects of fiber orientation, material properties, number of layers and shell geometry on the critical and post-critical behavior are discussed. It is observed that the shell stability is highly dependent on the laminate characteristics and, from these observations, it is concluded that, in order to exploit efficiently the composite material, an specific laminate should be designed for each application.
Keywords: laminated shell, composite material, stability, post-critical behavior, limit point and bifurcation point (cascas laminadas, materiais compósitos, estabilidade, comportamento pós-crítico e bifurcações).