Ravi Prakash Khandelwal

VIBRATION AND BUCKLING ANALYSIS OF LAMINATED SANDWICH PLATE HAVING SOFT CORE

Free vibration and buckling of laminated sandwich plate having soft core is studied by using an efficient C0 continuous finite element (FE) model based on higher-order zigzag theory (HOZT). In this theory, the in-plane displacement field for both the face sheets and the core is obtained by superposing a global cubically varying displacement field on a zigzag linearly varying displacement field with a different slope in each layer. The transverse displacement is assumed to be quadratic within the core while it remains constant in the faces beyond the core. The proposed model satisfies the condition of transverse shear stress continuity at the layer interfaces and the zero transverse shear stress condition at the top and bottom of the plate. The nodal field variables are chosen in an efficient manner to overcome the problem of C1 continuity requirement of the transverse displacement. Numerical examples on free vibration and buckling covering different geometric and material features of laminated composite and sandwich plates are presented. Many new results are also presented which should be useful for future research.

Static and Dynamic Control of Smart Composite Laminates

An efficient C0 continuous two-dimensional finite-element model has been presented in this paper for the control of laminated composite and sandwich plates embedded/surface-bonded with piezoelectric layers and subjected to mechanical loading as well as electric potential. The problem of modeling of smart laminates involves the coupling between mechanical and electrical fields. The structural component is modeled by an efficient equivalent single-layer plate theory, which ensures interlaminar shear-stress continuity and zero transverse shear-stress conditions at the top and bottom of the plate surfaces. Moreover, this theory contains unknowns defined at the reference plane (i.e., midplane) only. The electric field is modeled using layerwise theory, which contains the unknowns at each layer interfaces. The proposed combine model, which may be called a refined hybrid plate model, is implemented to analyze the coupled problem of piezoelectricity in laminated composites and sandwich plates.

An efficient hybrid plate model for accurate analysis of smart composite laminates

An efficient C0 continuous two-dimensional finite element model for the accurate analysis of laminated composite plates embedded and/or surface bonded with piezoelectric layers and subjected to mechanical loading and/or electrical potential has been presented in this article. The problem of smart laminates involves the coupling between mechanical and electrical fields. The mechanical/structural component is modeled by an efficient equivalent single-layer plate theory, which ensures interlaminar shear stress continuity and zero transverse shear stress conditions at the top and bottom of the plate surfaces. Moreover, this theory contains unknowns at the reference plane (i.e. the mid-plane) only. The electrical field is modeled using layer-wise theory, which contains the unknowns at each layer interfaces. In order to calculate the accurate through-the-thickness transverse shear stress variations, a simple approach based on least square error method is applied to the three-dimensional equilibrium equations of the plate problem at the postprocessing stage, after in-plane stresses are calculated using the finite element model based on the above-mentioned refined plate theory and layer-wise theory. The proposed combine model, which may be called as a refined hybrid plate model, is implemented to analyze the coupled problem of piezoelectricity in laminated composites and sandwich plate bending.

A new heat flux continuity model for thermal analysis of laminated plates

A new analytical model has been proposed in this paper for the accurate analysis of through-the-thickness temperature variation in composites and sandwich laminates based on piecewise linear zig-zag thermal lamination theory. This theory assumes a piecewise linear through-the-thickness temperature distribution in terms of temperature at the reference plane and temperature slopes at the layer interfaces. The continuity of temperature at different layers is ensured by choosing a suitable temperature profile. The unknown slopes at different interfaces are subsequently expressed in terms of the reference plane slopes through satisfaction of heat flux continuity conditions at the layer interfaces. The thermal conduction properties of different layers in the thickness direction are utilized for this purpose. This helps to maintain lesser number of computational unknowns and the resulting formulation for the thermal analysis can be very conveniently combined with the 2D refined layer-wise theories used for the mechanical analysis of laminated plates. Numerical examples are solved to show the accuracy of the proposed model by comparing the present results with 3D solutions.

Efficient 2D thermo-mechanical analysis of composites and sandwich laminates

ABSTRACT The static behavior of composites and sandwich plates in thermo-mechanical environment is investigated by a two dimensional (2D) FE model. An efficient higher-order zig-zag theory (HOZT) considering actual through-thickness temperature profile and a least square error (LSE) method to accurately predict the inter-laminar stresses is implemented in this model. The in-plane displacement field is obtained by superposing a cubically varying global displacement field on a zig-zag displacement field having different slopes at each layer. This plate theory represents parabolic through thickness variation of transverse shear stresses, which satisfy the inter-laminar continuity at the layer interfaces and zero transverse shear stress conditions at the top and bottom of the plate. In the present 2D finite element (FE) model, the first derivatives of transverse displacement have been treated as independent variables to circumvent the problem of C1 continuity associated with the above plate theory (HOZT). The accurate through-thickness distribution of temperature is obtained by using a linear zig-zag thermal lamination theory proposed by the authors by using the thermal conduction properties of different constituent layers in the thickness direction. The LSE method is applied at the postprocessing stage to accurately calculate the inter-laminar stresses by the 3D equilibrium equations of the plate problem, after in-plane stresses are calculated. The proposed combined FE model (HOZT+LSE) is implemented to analyze the static behavior of laminated composites and sandwich plates subjected to thermo-mechanical loadings. Many new results are also presented that should be useful for the future reference.