مطالعه، مدل سازي و تحليل صفحات كامپوزيتي دو پايداره ﴿داراي دو حالت پايدار﴾

چكيده انگليسي :

Modeling and Analysis of Bi Stable Composite Plates Masih Moore Email m moore@me iut ac ir Date of submission February 19 2012 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language Farsi Supervisor Saeed Ziaei Rad Email szrad@cc iut ac irAbstractMorphing or a shape adaptable structure can be described as a structural system whose shape and structuralcharacteristics can be changed in order to satisfy the operational characteristics alteration A main type ofmorphing structures is so called the bi stable structures The interest in bi stable structures comes from theirability that these structures can have two different stable equilibrium configurations to define a discrete set ofstable shapes The geometrical changes occur with no need to continuously consume power and mechanicalhinges to preserve the structure in each stable shape It is well known that in the asymmetric compositelaminate bi stability occurs due to residual stresses resulting from differences in coefficients of thermalexpansion and elastic properties in each lamina within the laminate Consequently when these structures aresubjected to a thermal load one can observe out of plane large deflection and cylindrical configurations thatcontradict with the classical lamination theory CLT prediction In this research the thermal response andstability characteristics of a bi stable composite plate with different asymmetric composition are considered Attention was focused on the temperature dependency of laminate mechanical properties especially on thethermal expansion coefficients of the composite graphite epoxy plate and the effect of including resin layerson the stability characteristics of the laminate To this end Hyer s theory was used to study the relationshipbetween temperature and curvature of asymmetric cured graphite epoxy laminates in the temperature range The strain fields were approximated and then used in the expression for the total potential energy based onthe Rayleigh Ritz technique The set of the obtained equations were solved by a specifically writtenMATLAB program in order to predict the curvatures variation versus temperature Optical microscopy wasused to characterize the laminate composition The effect of temperature dependency of laminate mechanicalproperties resin layers and lay up thickness variations were also investigated by Hyer s theory The resultsobtained from the theory were compared with the finite element simulations implemented in ABAQUSsoftware and experimental results and a good correlation was obtained In order to study the stabilitycharacteristics of asymmetric laminates a nonlinear finite element methodology using ABAQUS softwarewas developed to predict the critical loads that responsible for snap through and snap back behaviors Theeffects of the mentioned factors such as including resin layers and temperature dependency of laminatemechanical properties on the critical loads were also investigated The results obtained from the finiteelement simulations were compared with experimental results and a good agreement was obtained Thecurrent research also explores the potential for implementing bi stable structures for Uninhabited AerialVehicle UAV wing configuration To this end the stability characteristics of a bi stable tapered compositepanel were studied in the ABAQUS software The morphing of NACA 23012 airfoil flappers with bi stablestructures was also studied The flappers were modeled by graphite epoxy asymmetric laminates in theABAQUS software and the magnitude of loads required to actuate the airfoil section between the stableshapes was evaluated Keywords Bi stable structures Graphite epoxy plate Finite element method Snapbehavior Thermal response Rayleigh Ritz method Morphing airfoil

مر، مسيح

مطالعه، مدل سازي و تحليل صفحات كامپوزيتي دو پايداره ﴿داراي دو حالت پايدار﴾

پديده پرش ناگهاني , پاسخ حرارتي , روش ريلي-رتيز , روش اجزاء محدود , بال مورفينگ