• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.29-32
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• 2005

Based on the full layerwise displacement shell theory, vibration and damping characteristics of cylindrical sandwich panels are investigated. The transverse shear deformation and the normal strain are fully taken into account for structural damping modelling. Modal damping factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich beams. Present results shows that full layerwise theory can accurately predict vibration and damping characteristics of cylindrical composite panels with surface damping treatments and constrained layer damping. The viscoelastic materials depending on elevated temperature environment and exciting frequencies can be fully considered.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1994.10a
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• pp.121-128
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• 1994

A layerwise theory for the dynamic response of a laminated composite plate with integrated piezoelectric actuators and sensors subjected to both mechanical and electrical loadings is proposed. The formulation is derived form the variational principle with consideration for both total potential energy of the structures and the electrical potential energy of the piezoceramics. The governing equations of the present theory account for direct and converse effects of piezoelectrics, and layerwise variation of displacement field through the thickness of a laminate.

• Advances in nano research
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• v.6 no.4
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• pp.299-321
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• 2018

A layerwise shear deformation theory is applied in this paper for buckling analysis of piezoelectric truncated conical shell. The core is a multiphase nanocomposite reinforced by carbon nanotubes (CNTs) and carbon fibers. The top and bottom face sheets are piezoelectric subjected to 3D electric field and external voltage. The Halpin-Tsai model is used for obtaining the effective moisture and temperature dependent material properties of the core. The proposed layerwise theory is based on Mindlin's first-order shear deformation theory in each layer and results for a laminated truncated conical shell with three layers considering the continuity boundary condition. Applying energy method, the coupled motion equations are derived and analyzed using differential quadrature method (DQM) for different boundary conditions. The influences of some parameters such as boundary conditions, CNTs weight percent, cone semi vertex angle, geometrical parameters, moisture and temperature changes and external voltage are investigated on the buckling load of the smart structure. The results show that enhancing the CNTs weight percent, the buckling load increases. Furthermore, increasing the moisture and temperature changes decreases the buckling load.

• Steel and Composite Structures
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• v.12 no.6
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• pp.541-548
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• 2012

This paper deals with the applicability of extended layerwise optimization method (ELOM) for frequency optimization of laminated composite plates. The design objective is the maximization of the fundamental frequency of the laminated plates. The fibre orientations in the layers are considered as design variables. The first order shear deformation theory (FSDT) is used for the finite element solution of the laminates. Finally, the numerical analysis is carried out to show the applicability of extended layerwise optimization algorithm of laminated plates for different parameters such as plate aspect ratios and boundary conditions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1361-1369
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• 2005

Based on a full layerwise displacement shell theory, the nitration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modelling. The present finite element model Is formulated by using Hamilton's virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.772-778
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• 2005

Based on a full layerwise displacement shell theory, the vibration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modelling. The present finite element model is formulated by using Hamilton's virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

• Steel and Composite Structures
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• v.14 no.3
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• pp.283-293
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• 2013

This paper deals with the applicability of a new extended layerwise optimization method for thermal buckling load optimization of laminated composite plates. The design objective is the maximization of the critical thermal buckling of the laminated plates. The fibre orientations in the layers are considered as design variables. The first order shear deformation theory (FSDT) is used for the finite element solution of the laminates. Finally, the numerical analysis is carried out to show the applicability of extended layerwise optimization algorithm of laminated plates for different parameters such as plate aspect ratios and boundary conditions.

• Steel and Composite Structures
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• v.22 no.5
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• pp.1193-1214
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• 2016

In this paper, the 3D stress state and inter-laminar stresses in a rotating thin laminated cylinder shell are studied. The thickness of the cylinder is supposed to be thin and it is made of laminated composite material and can have general layer stacking. The governing equations of the cylindrical shell are obtained by employing the Layerwise theory (LWT). The effect of rotation is considered as rotational body force which is induced due to the rotation of the cylinder about its axis. The Layerwise theory (LWT), is used to discrete the partial differential equations of the problem to ordinary ones, in terms of the displacements of the mathematical layers. By applying the Free boundary conditions the solution of the governing equations is completed and the stress state, the inter-laminar stresses, and the edge effect in the rotating cylindrical shells are investigated in the numerical results. To verify the results, LWT solution is compared with the results of the FEM solution and good agreements are achieved. The inter-laminar normal and shear stresses in rotating cylinder are studied and effects of layer stacking and angular velocity is investigated in the numerical results.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.445-459
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• 2023

The current investigation is the first endeavor to apply the full layerwise finite element method (FEM) in free vibration analysis of functionally graded (FG) composite plates reinforced with graphene nanoplatelets (GPLs) in thermal environment. Unlike the equivalent single-layer (ESL) theories, the layerwise FEM focuses on all three-dimensional (3D) effects. The GPLs weight fraction is presumed invariable in each layer but varies through the plate thickness in a layerwise model. The modified Halpin-Tsai model is employed to acquire the effective Young's modulus. The rule of mixtures is applied to specify the effective Poisson's ratio and mass density. First, the current method is validated by comparing the numerical results with those stated in the available works. Next, a thorough numerical study is performed to examine the influence of various factors involving the pattern of distribution, weight fraction, geometry, and size of GPLs, together with the thickness-to-span ratio, thermal environment, and boundary conditions of the plate, on its free vibration behaviors. Numerical results demonstrate that employing a small percentage of GPL as reinforcement considerably grows the natural frequencies of the pure epoxy. Also, distributing more square-shaped GPLs, involving a smaller amount of graphene layers, and vicinity to the upper and lower surfaces make it the most efficient method to enhance the free vibration behaviors of the plate.

• Composites Research
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• v.15 no.3
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• pp.52-61
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• 2002

For the aerothermoelastic analysis of cylindrical piezolaminated shells, geometrically nonlinear finite elements based on the multi-field layerwise theory hale been developed. Applying a Han Krumhaar's supersonic piston theory, supersonic flutter analyses are performed for the cylindrical piezolaminted shells subject to thermal stresses and deformations. The possibility to increase flutter boundary and reduce thermoelastic deformations of piezolaminated panels is examined using piezoelectric actuations. Results show that active piezoelectric actuations can effectively increase the critical aerodynamic pressure by retarding the coalescence of flutter modes and compensating thermal stresses.