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    Using super element and p-approximation for free vibration analysis of composite plates

    , Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 255 , 2004 , Pages 81-84 ; 01608835 (ISSN) Sharafaty Zangeneh, M ; Ahmadian, M. T ; Ghoreishi, S. R ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2004
    Abstract
    Effective and efficient methods in computational mechanics have been of interest for the designers and engineers in the last decade. A 3D super elements is developed and implemented for the free vibration analysis of the composite plates. These new elements have been constructed by a 2D super elements in the plane direction and p-version finite element in the thickness direction. Results of 2D super elements are comparable to SHELL 63 and results of 3D super elements with cubic polynomial are comparable to SHELL 93. In the thin plates, 2D super element (or SHELL 63) and 3D super elements (or SHELL 93) have same results, but in the thick plates results change drastically. Natural frequencies... 

    Modeling of Delamination Buckling of Composite Laminates

    , M.Sc. Thesis Sharif University of Technology Tavakoly, Ashkan (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    The fiber-reinforced composite materials are used widely because of their high strength-to-density and stiffness-to-density ratios. The laminated composites are susceptible to delamination. When a delaminated composite plate is subjected to in-plane compression, buckling in the delaminated region may occur. In this thesis, after verification and validation of the models, the effect of the length of the longest and near surface delamination and beneath delaminations on critical buckling load of composite laminates are investigated. Numerical study is carried out to determine the buckling load of clamped composite plates with different symmetric and anti symmetric stacking sequences. The... 

    Dynamic analysis of laminated composite plates traversed by a moving mass based on a first-order theory

    , Article Composite Structures ; Volume 92, Issue 8 , 2010 , Pages 1865-1876 ; 02638223 (ISSN) Ghafoori, E ; Asghari, M ; Sharif University of Technology
    2010
    Abstract
    The dynamic response of angle-ply laminated composite plates traversed by a moving mass or a moving force is investigated. For this purpose, a finite element method based on the first-order shear deformation theory is used. Stationary and adaptive mesh techniques have been applied as two different meshing schemes. The adaptive mesh strategy is then used to avoid off-nodal position of moving mass. In this manner, the finite element mesh is continuously adapted to follow and comply with the path of moving mass. A Newmark direct integration method is employed to solve the equations of motion. Parametric study is directed to find out how different parameters like mass of the moving object as... 

    Dynamic analysis of orthotropic laminated composite plates under axial load on elastic foundation

    , Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) Ahmadian, M. T ; Pirbodaghi, T ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2006
    Abstract
    In this paper, free vibration analysis of laminated composite plates is carried out using first shear deformation theory and finite element method. Effect of axial tension and compression forces on the natural frequencies of the structure is investigated. Applying elastic foundation under the laminated composite plates has enabled us to achieve desired frequencies. The displacements are based C0 - nine plate bending element and each node has three degree of freedom. The equations of motion are derived using Hamilton's principle. Results indicate the tension forces will increase the natural frequency while the compression force reduces the natural frequency. The buckling force of plate is... 

    Wavelet-based active sensing for quantitative assessment of through-thickness crack size and angle in composite plates

    , Article 28th Congress of the International Council of the Aeronautical Sciences 2012, ICAS 2012 ; Volume 3 , 2012 , Pages 2417-2424 ; 9781622767540 (ISBN) Soltani, Z ; Ekhtiari, M ; Abedian, A ; Sharif University of Technology
    2012
    Abstract
    Cost-effective and reliable damage detection is critical for utilization of composite materials. This paper utilizes PZT piezoelectric disks to excite the first symmetric Lamb wave (S0 mode). The interaction of Lamb wave mode with a through-thickness crack of different lengths and angles in [0/45/-45/90]s CF/EP laminate plates is analyzed in terms of finite element method. This study contributes to the damage detection by developing an improved wavelet-based signal processing technique that enhances the visibility and interpretation of the Lamb wave signals related to defects. Based on the amount of energy dissipated by the damage, a damage index is defined as the function of an electric... 

    Structural Health Monitoring of composite Plates with Piezoelectric WaferActive Sensors

    , M.Sc. Thesis Sharif University of Technology Soltani, Zahra (Author) ; Abedian, Ali (Supervisor)
    Abstract
    Cost-effective and reliable damage detection is critical for utilization of composite materials. This research investigates a wavelet-based approach for SHM and detection of through-thickness crack in different lengths and angles in [0/45/-45/90]s CF/EP composite plate utilizing ANSYS finite element method (FEM) software and digital signal processing technique utilizing MATLAB software. To this end, a dual-PZT actuation scheme is applied, aimed at generating the S0 mode at a square composite plate. This study contributes to the damage detection by developing an improved wavelet-based signal processing technique that enhances the visibility and interpretation of the Lamb wave signals related... 

    New approach for fatigue life prediction of composite plates using micromechanical bridging model

    , Article Journal of Composite Materials ; Volume 49, Issue 3 , February , 2015 , Pages 309-319 ; 00219983 (ISSN) Adibnazari, S ; Farsadi, M ; Koochi, A ; Khorashadizadeh, S. N ; Sharif University of Technology
    SAGE Publications Ltd  2015
    Abstract
    The use of micromechanical models to study composite material's behavior leads to save time and cost. In this paper, bridging micromechanical models have been used in order to observe the behavior of unidirectional laminate composite under fatigue loading. In order to study the fatigue behavior, stiffness degradation has been studied as well as the strength degradation and a driftnet model has been proposed for each of them. The strength degradation has only been studied for the unidirectional fiber, while the stiffness degradation has been studied for the fibers with different fiber angle. The results are compared with macro-mechanical models and other methods in literature  

    Buckling of laminated composite plates with elastically restrained boundary conditions

    , Article Structural Engineering and Mechanics ; Volume 74, Issue 5 , June , 2020 , Pages 577-588 Kouchakzadeh, M. A ; Rahgozar, M ; Bohlooly, M ; Sharif University of Technology
    Techno-Press  2020
    Abstract
    A unified solution is presented for the buckling analysis of rectangular laminated composite plates with elastically restrained edges. The plate is subjected to biaxial in-plane compression, and the boundary conditions are simulated by employing uniform distribution of linear and rotational springs at all edges. The critical values of buckling loads and corresponding modes are calculated based on classical lamination theory and using the Ritz method. The deflection function is defined based on simple polynomials without any auxiliary function. The verifications of the current study are carried out with available combinations of classic boundary conditions in the literature. Through... 

    Using the hybrid DAS-SR method for damage localization in composite plates

    , Article Composite Structures ; Volume 247 , 2020 Nokhbatolfoghahai, A ; Navazi, H. M ; Groves, R. M ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In this paper, the hybrid Delay-And-Sum (DAS) with Sparse Reconstruction (SR) method was further developed for damage location in composite plates. In composite materials, anisotropy leads to some challenges in using conventional damage location methods, which are developed for isotropic materials. In the hybrid DAS-SR method, the DAS and SR methods were combined as a complement of each other. To investigate the DAS-SR method for composite structures, the group velocity of the travelling wave for different directions was first measured experimentally via PZTs. The DAS and SR formulations were then modified to be compatible with the direction-dependent group velocities. The results show that... 

    Probabilistic thermal stability of laminated composite plates with temperature-dependent properties under a stochastic thermal field

    , Article Acta Mechanica ; Volume 233, Issue 4 , 2022 , Pages 1351-1370 ; 00015970 (ISSN) Parviz, H ; Fakoor, M ; Hosseini, F ; Sharif University of Technology
    Springer  2022
    Abstract
    Probabilistic thermal buckling analysis of composite plates with temperature-dependent properties under stochastic thermal fields is performed by developing a new temperature increment-based algorithm for solving the stochastic nonlinear equation. The temperature distribution is assumed to be a stochastic Gaussian field which leads to spatially varying stochastic mechanical properties. The stochastic thermal field is decomposed by applying the Karhunen–Loeve theorem. The combination of stochastic assumed mode method and polynomial chaos is proposed as an alternative solution for the time-consuming stochastic finite element method. The uncertainty of the critical temperature is studied by... 

    Hygrothermal Stress Analysis in Composite Laminatesby Perturbation Method

    , M.Sc. Thesis Sharif University of Technology Jenabi, Farhad (Author) ; Nosier, Asghar (Supervisor)
    Abstract
    For studying the hygrothermal deformation of generally laminated composite platesunder uniform temperature change and uniform moisture absorption change, by starting from the reduced form of elasticity displacement field for a long flat laminate, an analytical method is developed in order to accurately calculate the interlaminar stresses near the free edges of the laminate. The constant parameters appearing in the reduced displacement field, describe the global deformation of the laminate and appropriately obtained by employing an improved first-order shear deformation theory.For solving the coupled equilibrium equations of agenerally laminated composite plate, some of the stiffness... 

    Influence of material and geometrical parameters on stress field of composite plates with insert

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 226, Issue 12 , 2012 , Pages 1573-1582 ; 09544100 (ISSN) Mazraehshahi, H. T ; Zakeri, A. A ; Sharif University of Technology
    2012
    Abstract
    Reduction of stress concentrations in the area of pin-loaded holes is one of the greatest challenges in the design of multilayered fibre-reinforced composite structures. Among many approaches to decrease concentration effects, putting metallic inserts in the holes is a convenient method. In this research, finite element analysis is applied to assess the effects of manufacturing parameters on stress concentration in the vicinity of the holes in composite plates with inserts. Edge and pitch distance, thickness and materials of insert, clearance between insert and composite part, and stiffness of the adhesive filling the gap are studied in this article. Investigations show that the optimum... 

    Free-edge stress analysis of general composite laminates under extension, torsion and bending

    , Article Applied Mathematical Modelling ; Volume 36, Issue 4 , 2012 , Pages 1570-1588 ; 0307904X (ISSN) Sarvestani, H. Y ; Sarvestani, M. Y ; Sharif University of Technology
    2012
    Abstract
    In this study, based on the reduced form of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates subjects to extension, torsion, and bending. The constant parameters being in the displacement field, which describe the global deformation of a laminate, are appropriately calculated by using the improved first-order shear deformation theory. Reddy's layerwise theory is subsequently employed for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. Various numerical results are developed for the... 

    Interlaminar stress analysis of general composite laminates

    , Article International Journal of Mechanical Sciences ; Volume 53, Issue 11 , 2011 , Pages 958-967 ; 00207403 (ISSN) Yazdani Sarvestani, H ; Yazdani Sarvestani, M ; Sharif University of Technology
    Abstract
    In this study, based on the reduced from of elasticity displacement field for a long laminate, an analytical method is established to exactly obtain the interlaminar stresses near the free edges of generally laminated composite plates under the extension and bending. The constant parameters, which describe the global deformation of a laminate, are properly computed by means of the improved first-order shear deformation theory. Reddys layerwise theory is subsequently utilized for analytical and numerical examinations of the boundary layer stresses within arbitrary laminated composite plates. A variety of numerical results are obtained for the interlaminar normal and shear stresses along the... 

    Free vibration analysis of symmetrically laminated fully clamped skew plates using extended Kantorovich method

    , Article Key Engineering Materials, 22 March 2011 through 24 March 2011, Kuala Lumpur ; Volume 471-472 , 2011 , Pages 739-744 ; 10139826 (ISSN) ; 9783037850596 (ISBN) Fallah, A ; Kargarnovin, M. H ; Aghdam, M. M ; Sharif University of Technology
    2011
    Abstract
    In this paper, free vibration analysis of thin symmetrically laminated skew plates with fully clamped edges is investigated. The governing differential equation for skew plate which is a fourth order partial differential equation (PDE) is obtained by transforming the differential equation in Cartesian coordinates into skew coordinates. Based on the multi-term extended Kantorovich method (MTEKM) an efficient and accurate approximate closed-form solution is presented for the governing PDE. Application of the MTEKM reduces the governing PDE to a dual set of ordinary differential equations. These sets of equations are then solved with infinite power series solution, in an iterative manner until... 

    Non-linear vibration analysis of laminated composite plates resting on non-linear elastic foundations

    , Article Journal of the Franklin Institute ; Volume 348, Issue 2 , March , 2011 , Pages 353-368 ; 00160032 (ISSN) Pirbodaghi, T ; Fesanghary, M ; Ahmadian, M. T ; Sharif University of Technology
    2011
    Abstract
    In this study, the homotopy analysis method (HAM) is used to obtain an approximate analytical solution for geometrically non-linear vibrations of thin laminated composite plates resting on non-linear elastic foundations. Geometric non-linearity is considered using von Karman's straindisplacement relations. Then, the effects of the initial deflection, ply properties, aspect ratio of the plate and foundation parameters on the non-linear free vibration is studied. Comparison between the obtained results and those available in the literature demonstrates the potential of HAM for the analysis of such vibration problems, whose governing differential equations include the quadratic and cubic... 

    A layerwise finite element for geometrically nonlinear analysis of composite shells

    , Article Composite Structures ; Volume 186 , 2018 , Pages 355-364 ; 02638223 (ISSN) Hosseini Kordkheili, S. A ; Soltani, Z ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    This work aims to develop a nonlinear layerwise shell element formulation for shear-deformable laminated composite plate and shell structures. The element is formulated based on a zigzag theory in presence of individual local coordinates in the thickness direction for separate layers. In order to properly employ the zigzag theory, the considered local coordinates have different ranges of variation for middle, upper and lower layers. Using Mindlin-Reissner theory a convenient displacement field is derived for each layer and an ordered algorithm is adapted to calculate increments in the director vector of each layer due to relative finite rotations of its adjacent layers. Employing this shear... 

    Boundary control of a vibrating FGM rectangular plate

    , Article 12th International Conference on Intelligent Engineering Systems, INES 2008, Miami, FL, 25 February 2008 through 29 February 2008 ; 2008 , Pages 13-18 ; 9781424420834 (ISBN) Rastgoftar, H ; Eghtesad, M ; Khayatian, A ; Rastgoftar, H ; Sharif University of Technology
    2008
    Abstract
    This paper presents a solution to the boundary stabilization of a FGM plate in free transverse vibration. The composite laminated plate dynamics is presented by a linear forth order partial differential equation (PDE). A linear control law is constructed to stabilize the plate. The control force consists of feedback of the velocity at the boundaries of plate. The novelty of this article is that it is possible to stabilize asymptotically a free transversely vibrating composite plate with simply supported or clamped boundary condition via boundary control without resorting to truncation of the model. © 2008 IEEE  

    Natural frequencies of stiffened and unstiffened laminated composite plates

    , Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 7 , 2007 , Pages 593-600 ; 0791843017 (ISBN) Ahmadian, M. T ; Pirbodaghi, T ; Pak, M ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2007
    Abstract
    In this study the free vibration of laminated composite plates with and without stiffeners subjected to axial loads is carried out using finite element method. The plates are stiffened by laminated composite strip and Timoshenko beam. The plates and the strips are modeled with rectangular 9 noded isoparametric quadratic elements with three degrees of freedom per node and the Timoshenko beam is modeled with linear 2 noded isoparametric quadratic elements with 2 degrees of freedom per node. The effects of both shear deformation and rotary inertia are implemented in the modeling of plate and stiffener. The governing differential equations are obtained in terms of the mid-plane displacement... 

    Damage behavior of fiber reinforced composite plates subjected to drop weight impacts

    , Article Composites Science and Technology ; Volume 66, Issue 1 , 2006 , Pages 61-68 ; 02663538 (ISSN) Hosseinzadeh, R ; Shokrieh, M. M ; Lessard, L ; Sharif University of Technology
    2006
    Abstract
    Fiber reinforced materials are widely used in many industrial structures including automotive, aviation, and civil due to their lower weights compared to metal structures. Full-composite body structures, especially in automotive and aviation applications, are becoming a proper replacement for current metal ones. For this reason, damage of such structures subjected to impact is a crucial case study in current research. The typical types of damages are mainly caused during production, repair, maintenance, or by particle crashes during function, and collisions between different structures. In this paper, four different fiber reinforced composite plates are studied after being impacted by a...