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Modal characterization of sandwich skew plates

Pavan-Kumar Dhotre, Srinivasa Chikkol V.

Acta Mechanica et Automatica

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2021

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Vol. 15, no. 3

143--153

EN

The current work focuses on the experimental and finite element free vibration studies of laminated composite sandwich skew plates. The comparison was made between the experimental values obtained by the Fast Fourier transform (FFT) analyzer and a finite el-ement solution obtained from CQUAD8 finite element of The MacNeal-Schwendler Corporation (MSC) / NASA STRucture Analysis (NAS-TRAN) software. The influence of parameters such as aspect ratio (AR) (a/b), skew angle (α), edge condition, laminate stacking sequence, and fiber orientation angle (θ°) on the natural frequencies of sandwich skew plates was studied. The values obtained by both the finite el-ement and experiment approaches are in good agreement. The natural frequencies increase with an increase in the skew angle for all giv-en ARs.

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Free vibration studies on skew sandwich plates

Kumar Dhotre Pavan, Venkateshappa Chikko Srinivasa

Composites Theory and Practice

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2020

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R. 20, nr 3-4

118--127

EN

The present work focuses on determining the fundamental frequencies of skew sandwich plates with face sheets considered to be classical thin plates, which are made of a graphite-epoxy material and an orthotropic core made of glass reinforced- epoxy using different boundary conditions. The fundamental frequencies were obtained using finite elements, which are validated with available literature results. The effects of the skew angle, ratio of the length to total thickness of the sandwich plate, and ratio of the thickness of the core to the face sheet on the fundamental frequency of skew sandwich plates were obtained. In addition, the effect of parameters such as the number of layers in the face sheet, the laminate stacking sequence and the fiber orientation angle on the fundamental frequencies of laminated skew sandwich plates was also ascertained. It was found that the CQUAD8 element yields better results than the CQUAD4 element in the present study. The fundamental frequencies were found to increase with an increasing skew angle. The variation in the fundamental frequency is negligible when there are a large number of layers in the face sheet.

3

English Temperature and moisture effect on laminated rhombic hyperbolic paraboloid

Chaubey Abhay, Kumar Ajay, Grzegorczyk-Frańczak Małgorzata, Szafraniec Małgorzata

Budownictwo i Architektura

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2019

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Vol. 18, nr 4

23--40

EN

The current work presents a hygrothermal analysis of laminated composite rhombic hyperbolic paraboloids. The cubic variation in displacement field together with cross curvature effects of the shell were used to solve the hygrothermal problem. Because of the parabolic variation of the transverse shear deformation, the shear correction factor was not necessary in this paper. In the mathematical model, the zero conditions of the transverse shear stress at the bottom and top of the shell were applied. The nine-noded curved isoparametric element with seven unknowns in each node was used to implement the present realistic mathematical model. The implementation of the finite element C0 (FE) of the present mathematical model was coded and performed in FORTRAN. The skew hyperbolic paraboloid on which the hygrothermal analysis was conducted had various temperatures, ply orientation, curvatures, moisture concentration, boundary conditions and thickness ratio. The paper shows that with the increase of the skew angle, the non-dimensional deflection decreases, and with the increase of moisture concentration, hygrothermal load and curvature ratio, the deflection increases. The results of the model presented in the paper were compared with other results published in the literature and were found to be consistent with them.

4

Finite element studies on free vibration of laminated composite cylindrical skew panels

Srinivasa C. V., Suresh Y. J., Prema Kumar W. P.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 1

165--180

EN

This paper presents the finite element studies on free vibration of isotropic and laminated composite cylindrical skew panels. The analysis is performed using CQUAD4 and CQUAD8 elements of MSC/NASTRAN. The effects of the panel angle, skew angle, aspect ratio and length-to-thickness-ratio on fundamental frequency of isotropic cylindrical skew panels are studied. The effects of additional parameters such as the fiber orientation angle, numbers of layers and stacking sequence on the fundamental frequency of antisymmetric composite laminates are also studied. It is found that the CQUAD8 element yields better results than the CQUAD4 element in the validation and convergence studies. The CQUAD8 element is employed for the remaining part of the studies. The fundamental frequencies are found to increase with the panel angle and skew angle. When the number of layers in the laminate is large, the variation of the fundamental frequency with the number of layers is not appreciable. The boundary conditions are found to have a significant influence on the fundamental frequency.

5

Vibration of thick/thin skewed taper cylindrical shell panel

Haldar S., Majumder A.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 3

649-660

EN

In this paper, a nine node isoparametric plate bending element is used for free vibration analysis of isotropic skewed taper cylindrical shell panels. The thickness of panels varies linearly in one direction only. In the present analysis first order shear deformation theory is incorporated. Two types of mass lumping schemes are recommended. In one of the mass lumping schemes the effect of rotary inertia is incorporated. Free vibration of skewed taper cylindrical shell panels having different shell thickness to radius (h/R) ratios, length to radius ratios (L/R), skew angles and different boundary conditions are analyzed following the shallow shell theory.