A new displacement-based higher order theory is presented here. The theory employs realistic displacement variations and is shown to be extremely accurate for even thick laminates and for any combination of mechanical and thermal loading. The importance of various higher-order terms in the proposed theory is discussed with reference to a specific numerical example.

K. Bhaskar

Department of Aerospace Engineering

T. K. Varadan

Mathematical models

Plates (structural components)

Stress analysis

Structural analysis

Thermal stress

Laminated Plates

Laminated composites

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

A new theory for accurate thermal/mechanical flexural analysis of symmetric laminated plates

Composite Structures

In this paper, the dynamic instability characteristics of sandwich panels with carbon nanotube (CNT) reinforced facesheets subjected to in-plane periodic load is investigated using a shear flexible QUAD-8 serendipity element. The formulation accounts for the realistic variation of the displacements through the thickness, possible discontinuity in slope at the interface and the thickness stretch affecting the transverse deflection. The influence of the aerodynamic force due to airflow over the plate, the in-plane and the rotary inertia effects are also included in the formulation. The accuracy of the present formulation is demonstrated considering the problems for which solutions are available. A detailed numerical study is carried out to bring out the efficacy of the present higher-order plate theory over the first-order plate theory. The present study examines the influence of the volume fraction of the CNT, core-to-facesheet thickness, the plate thickness and aspect ratio, damping and temperature on the dynamic instability boundaries and its associated origin of instability forcing frequencies. The effect of airflow over such sandwich plate is also investigated. The boundaries of the principal instability region are represented in the non-dimensional excitation frequency-load amplitude plane. © 2016 Elsevier Ltd

Dynamic instability analysis of sandwich plates with CNT reinforced facesheets

In this paper, the supersonic flutter characteristics of doubly curved sandwich shell panels, viz., cylindrical and spherical shells, with carbon nanotube (CNT) reinforced facesheets are investigated using QUAD-8 shear flexible shell element developed based on higher-order structural theory. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in slope of the in-plane displacement at the interface. The strain-displacement relation is accurately introduced in the formulation. The first-order high Mach number approximation to linear potential flow theory is employed for evaluating the aerodynamic pressure. The solutions of the complex eigenvalue problem, developed based on Lagrange's equation of motion, are obtained by QR algorithm. The accuracy of the present formulation is validated considering the problems for which solutions are available in the literature. A detailed numerical study is conducted to highlight the significance of the higher-order model over the first-order theory and also to examine the influence of the volume fraction of the CNT, core-to-face sheet thickness, the shell thickness and the aspect ratio, radius-to-thickness ratio, and temperature on the flutter boundaries. © 2015 Elsevier Ltd.

Investigation of supersonic flutter of thick doubly curved sandwich panels with CNT reinforced facesheets using higher-order structural theory

In this paper, the performance of different structural models based on global approach in evaluating the static response of curvilinear fibre composite laminates is analyzed. A Co shear flexible Quad-8 element developed based on higher-order structural theory is employed for the present study. The structural theory accounting for the realistic variation of displacements through the thickness and the possible discontinuity in the slope at the interface is considered. Four alternate discrete structural models, deduced from the generic structural model by retaining various terms in the displacement functions are examined for their applicability. The accuracy of the present formulation is demonstrated considering the problems for which analytical solutions are available. A systematic numerical study, assuming different ply-angle and lay-up, is conducted in bringing out the influence of various structural models on the static response of composite laminates with curvilinear fibres. © 2014 Elsevier Ltd.

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Assessment of certain higher-order structural models based on global approach for bending analysis of curvilinear composite laminates

Clamped cross-ply plates are analyzed here using a higher-order theory based on a realistic thickness-wise displacement field that accounts for a zig-zag variation of the in-plane displacements. Rigorous analytical solutions are obtained for this difficult problem using a methodology developed recently wherein simple Fourier series solutions of a corresponding simply-supported plate are superposed, each such component solution being summed without truncation using MATHEMATICA. Numerical results, for square homogeneous and three-layer plates under uniform and central point loads, are compared with those based on the classical and first-order theories. © 2005 Elsevier Ltd. All rights reserved.

Analytical solutions for flexure of clamped rectangular cross-ply plates using an accurate zig-zag type higher-order theory

A simple, semi-analytical model with mixed (stresses and displacements) fundamental variables starting from the exact three dimensional (3D) governing partial differential equations (PDEs) of laminated composite and sandwich plates for thermo-mechanical stress analysis has been presented in this paper. The plate is assumed simply supported on all four edges. Two different temperature variations through the thickness of plates are considered for numerical investigation. The accuracy and the effectiveness of the proposed model are assessed by comparing numerical results from the present investigation with the available elasticity solutions. Some new results for sandwich laminates are also presented for future reference.

Journal	Data powered by TypesetComposite Structures
Publisher	Data powered by TypesetElsevier BV
ISSN	02638223
Open Access	No