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1. . _." , t _z - * - 1 - -" *// ) // ( __.,. @ Thc 2ndInternational Conference on Composites: Characterization, l'abrication and Application (CCFA-2) Dec.27-30,2010, Kish Island, lran ICI IUST Analyzing elasticpropertiesof sandwichpanelswith cellular coresmade of composite laminates 24. sadeghian tA. A. Atai* and tAssistantProfessor, 2Graduate Student,Departntent of Mechanical Engineering, Islamic Azad University, Karai, Branch, Moaazen Blvd. Rajaee-Shahr,Karaj, Iran .(Tel : (261) 4 L8-2327, e-nall: atai@kiau.ac.ir) Abstract Sandwich panels are lightweight structureswith good bendirrg stiffiress and becauseof this, have found applications in auto and aerial industries and usually are made in the form of cellular cores. They can anisotropicrnedia to a very good extent. Up to now, the panels be-approximated a homogeneous by have teen rnade of isotropic materials but recently, FRP cores have been brought into attention. A lcrowledgeof the elasticpropertiesof the panel would be necessary. this work, the In comprehensive panel and the strain energy for that is obtained. Next, a homogenization stifgress matrix for each procedure based on energy is utilized to get the elastic properties. By applying certail remote slrain components, and solving the equations of equilibrium for the representativevolume element (RVE) along with consistency constraints, the deformation of each cell wall and from that the total strain anergy of the RVE is obtained.By equatingihis energyto that of the idealizedmaterial, the desired elasticity constantsfor the homogenizedpanel are obtained.By altering several parameterssuch as orientatiol of remote strain and geometryof the cell, the variation of elastic constantsis investigated. Somemunericalresultsof this tJpe are presented. sandwichstructure,cellularcore, compositepanel Keywords: stiffiness, 1. Introduction Sandwich struchues are lightweight hollow structues with considerable bending and other useful stiffnesses and reinforcing plate and shell construclions. which make them suitable for applicationssuch as aerospace these structuresare composedof periodic cellular configuration, of which the honeycomb strucfure is a Usually, famous one but other shapessuch as triangular, quadrilateral, circular, and scrambledpolygon are also common. Among olil investigations the stiftnessof honeycombstmcturesthe works of Kelsey et al. [1] and Chang and on Ebcioglu 12] can be mentioned. More recently Hohe invcstigated the stiffuess of cellular core structures rvith different cei geometry[3-5]. He consiclered core to be made of isotropic panelsmodeled as a Titnoshenko the bearn ald based on the concept of energy homogenization, he obtained the equivalent stiffrress of the homogenized medium. [n recent years, numerous investigations have been perforrned on sandwich structures with fiber reinforced compositecellular cores [6-8]. So, obtaining the elastic propertiesof such a structure would be important in order to investigateits behavior under different loading conditions. In this paper, the idea of homogenLation is useclto obtain the equivalent stiffiressesof triangular grid cell made of fiber reinforced symmetriccompositelaminate.The beam eletnentm.odel basedon the works of Kim et al.[9,10] who recently is piesented the eiact beam elementmodel rnade of compositelaminates.Sotne examples are presented. 2. Problem Formulation The notion used is also accordingto [3] is presented. homogenization In this section,the idea of energy-based f =fu *f , in basedon that reference.Consideraperiodic cellular body O bouncledby a smooth surface t|-,f and ' / represellts rest of the boundary on the is part of the boundarywith prescribeddisplacement which I