Damping in Sandwich Beams With Shear-Flexible Cores

1967 ◽  
Vol 89 (4) ◽  
pp. 662-670 ◽  
Author(s):  
C. W. Bert ◽  
D. J. Wilkins ◽  
W. C. Crisman
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Material Properties ◽  
Sandwich Beam ◽  
Flexural Vibration ◽  
Logarithmic Decrement ◽  
Sandwich Beams ◽  
Hexagonal Cell ◽  
Modal Shape ◽  
Beam Geometry

This paper is a theoretical and experimental study of the effect of core shear flexibility on the lowest natural frequency, node locations, and damping in sandwich beams with cores of high shear flexibility as exemplified by honeycomb-type cores. A new method of analysis is presented for predicting the logarithmic decrement for damping in sandwich beams undergoing free vibration, provided that the beam geometry and constitutent material properties are known. Natural frequency, modal shape, and logarithmic decrement are all dependent upon the dynamic shear coefficient. Two new simplified derivations for this coefficient are presented in this paper. Flexural vibration experiments were conducted on free-free sandwich beam strips at frequencies from 300 to 700 cps. Facings were glass-epoxy laminates and cores were hexagonal-cell honeycomb of either aluminum or glass-phenolic. For each beam, lowest natural frequency, associated node locations, and logarithmic decrement in free vibration were measured and compared with those predicted by applying four different theories.

Flexural Vibration of Segmented Elastic-Viscoelastic Sandwich Beams

1975 ◽  
Vol 42 (4) ◽  
pp. 897-900
Author(s):  
B. E. Sandman
Keyword(s):  
Steady State ◽  
Numerical Study ◽  
Sandwich Beam ◽  
Flexural Vibration ◽  
Middle Layer ◽  
Resonant Mode ◽  
Sandwich Beams ◽  
Simply Supported ◽  
Viscoelastic Core ◽  
Longitudinal Nonuniformity

A pair of governing differential equations form the basis for the study of steady-state forced vibration of a sandwich beam with longitudinal nonuniformity in the stiffness and mass of the middle layer. The spatial solution for simply supported boundary conditions is obtained by a Fourier analysis of both material and kinematic variations. The solution is utilized in the numerical study of a sandwich beam with a segmented configuration of elastic and viscoelastic core materials. The results exemplify a tuned configuration of core segments for optimum damping of the first resonant mode.

The Effect of Reinforcement Structure on the Modal Parameters for Sandwich Structure Composite Plate

2011 ◽  
Vol 194-196 ◽  
pp. 2420-2424
Author(s):  
Guo Li Zhang ◽  
Ya Nan Wang ◽  
Jia Lu Li ◽  
Guang Wei Chen ◽  
Li Chen ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Composite Plate ◽  
High Speed ◽  
Sandwich Structure ◽  
Flexural Vibration ◽  
Sandwich Composite ◽  
Reciprocating Motion ◽  
Modal Shape ◽  
Reinforcement Structure ◽  
Plate Specimen

In order to investigate the effect of different reinforcement structure on the dynamic characteristics of sandwich structure composite plates used for manufacturing the high speed reciprocating motion composite components, four kinds of paulownia wood sandwich composite test specimens with dimensions of 350×83.5×9.5mm was designed and made by hand lay-up performing and press molding technology. The woven and 2D braiding fabric prepreg were both selected as top face and inner face materials , respectively, and the carbon fiber woven fabric prepreg was chosen as inner part materials. According to the impulse response modal test method, a modal test system was established. It was found that this kind of sandwich structure composite plate has bigger natural frequency value, it’s minimum natural frequency was about 609.77Hz that could meet the requirement for high speed reciprocating motion parts. The dynamic test results shown that the natural frequency of F2BAF-IUC-CPW sample is higher t about 11.17% at least, selecting 2D integral braiding pipe fabric as top face and inner face reinforced materials could effectively improve the dynamic properties of sandwich composite rectangular plates. The modal experiments indicated that the modal shapes of sandwich composite plate specimen with four kind reinforcement structures were identical, it’s 1st modal shape, 2nd modal shape and 3rd modal shape presented torsional vibration shape, flexural vibration shape and torsional flexural vibration shape, separately, the modal shapes of sandwich composite plate specimen were not obviously affected by reinforcement structure.

Analytical and numerical investigation of the free vibration of functionally graded materials sandwich beams

2021 ◽  
Vol 2 (110) ◽  
pp. 72-85
Author(s):  
S.H. Bakhy ◽  
M. Al-Waily ◽  
M.A. Al-Shammari
Keyword(s):  
Analytical Solution ◽  
Free Vibration ◽  
Functionally Graded Materials ◽  
Sandwich Beam ◽  
Beam Theory ◽  
Functionally Graded ◽  
Gradient Index ◽  
Sandwich Beams ◽  
Graded Materials ◽  
The Impact

Purpose: In this study, the free vibration analysis of functionally graded materials (FGMs) sandwich beams having different core metals and thicknesses is considered. The variation of material through the thickness of functionally graded beams follows the power-law distribution. The displacement field is based on the classical beam theory. The wide applications of functionally graded materials (FGMs) sandwich structures in automotive, marine construction, transportation, and aerospace industries have attracted much attention, because of its excellent bending rigidity, low specific weight, and distinguished vibration characteristics. Design/methodology/approach: A mathematical formulation for a sandwich beam comprised of FG core with two layers of ceramic and metal, while the face sheets are made of homogenous material has been derived based on the Euler–Bernoulli beam theory. Findings: The main objective of this work is to obtain the natural frequencies of the FG sandwich beam considering different parameters. Research limitations/implications: The important parameters are the gradient index, slenderness ratio, core metal type, and end support conditions. The finite element analysis (FEA), combined with commercial Ansys software 2021 R1, is used to verify the accuracy of the obtained analytical solution results. Practical implications: It was found that the natural frequency parameters, the mode shapes, and the dynamic response are considerably affected by the index of volume fraction, the ratio as well as face FGM core constituents. Finally, the beam thickness was dividing into frequent numbers of layers to examine the impact of many layers' effect on the obtained results. Originality/value: It is concluded, that the increase in the number of layers prompts an increment within the frequency parameter results' accuracy for the selected models. Numerical results are compared to those obtained from the analytical solution. It is found that the dimensionless fundamental frequency decreases as the material gradient index increases, and there is a good agreement between two solutions with a maximum error percentage of no more than 5%.

Effect of Distributed Attached Mass on the Vibration of Sandwich Panel Using Higher Order ESL Theory

2012 ◽  
Vol 488-489 ◽  
pp. 35-39 ◽  
Author(s):  
Shahab Tafazoli ◽  
S.M.R. Khalili
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Material Properties ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Single Layer ◽  
Higher Order ◽  
Design Parameters ◽  
Attached Mass ◽  
The Face

In this paper, effects of adding a distributed attached mass added to the face sheets of sandwich panels on free vibration of the system are investigated. Higher order equivalent single layer (ESL) theory is expanded and used. Mass Inertias of the distributed attached mass are taking into account. Various design parameters including geometrical and material properties, such as density, thickness of the attached mass and the panel are investigated to show the decreasing effect on the fundamental natural frequency of the system due to the adding of the distributed attached mass.

Free Vibration and Buckling Analysis of Sandwich Beams with Functionally Graded Carbon Nanotube-Reinforced Composite Face Sheets

2015 ◽  
Vol 15 (07) ◽  
pp. 1540011 ◽  
Author(s):  
Helong Wu ◽  
Sritawat Kitipornchai ◽  
Jie Yang
Keyword(s):  
Carbon Nanotube ◽  
Free Vibration ◽  
Volume Fraction ◽  
Slenderness Ratio ◽  
Micromechanical Model ◽  
Sandwich Beam ◽  
Sheet Thickness ◽  
Functionally Graded ◽  
Sandwich Beams ◽  
Reinforced Composite

This paper investigates the free vibration and elastic buckling of sandwich beams with a stiff core and functionally graded carbon nanotube reinforced composite (FG-CNTRC) face sheets within the framework of Timoshenko beam theory. The material properties of FG-CNTRCs are assumed to vary in the thickness direction, and are estimated through a micromechanical model. The governing equations and boundary conditions are derived by using Hamilton's principle and discretized by employing the differential quadrature (DQ) method to obtain the natural frequency and critical buckling load of the sandwich beam. A detailed parametric study is conducted to study the effects of carbon nanotube volume fraction, core-to-face sheet thickness ratio, slenderness ratio, and end supports on the free vibration characteristics and buckling behavior of sandwich beams with FG-CNTRC face sheets. The vibration behavior of the sandwich beam under an initial axial force is also discussed. Numerical results for sandwich beams with uniformly distributed carbon nanotube-reinforced composite (UD-CNTRC) face sheets are also provided for comparison.

The Theoretical Prediction and Experimental Verification of Modal Parameters for Carbon Fiber Reinforced Composites with Sandwich Structure

2011 ◽  
Vol 194-196 ◽  
pp. 2415-2419
Author(s):  
Guo Li Zhang ◽  
Ya Nan Wang ◽  
Jia Lu Li ◽  
Guang Wei Chen ◽  
Li Chen ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Carbon Fibre ◽  
Rectangular Plate ◽  
Natural Frequency ◽  
Flexural Vibration ◽  
Woven Fabric ◽  
Core Material ◽  
Sandwich Composite ◽  
Modal Shape ◽  
Modal Test

A innovative structure of sandwich composite rectangular plate with dimensions of 350 ×83.5×9.5mm was designed, it was made of unidirectional prepreg of carbon fibre and woven fabric prepreg of carbon fiber as face materials and paulownia as core material by hand lay-up performing and press molding technology for investigating the dynamic performance such as natural frequency and modal shapes. Based on testing the in-plane and out-plane mechanical properties of composite samples reinforced by unidirectional carbon fibre and carbon fiber woven fabric, a ANSYS FEA dynamic modeling was developed. According to the impulse response modal test method, a modal test system was established. The natural frequency test results showed that the minimum natural frequency of sandwich composite rectangular plate is about 616.45Hz which is higher about 27.5% than that of aluminum rectangular plate reinforced by carbon. The modal experiment indicated that the 1st modal shape, 2nd modal shape, 3rd modal shape and 4th modal shape of the sandwich composite rectangular plate were torsional vibration, flexural vibration shape, torsional flexural vibration and double-flexural vibration separately. It was found the calculating precision of FEA dynamic predication was very high, the dynamic predicating results by FEA could provide fundamental data to the optimal design high speed reciprocating sandwich composite rectangular parts.

Free vibration characteristics of multi-core sandwich composite beams: Experimental and numerical investigation

2021 ◽  
pp. 096739112110576
Author(s):  
Rajeshkumar Selvaraj ◽  
Kamesh Gupta ◽  
Shubham Kumar Singh ◽  
Ankur Patel ◽  
Manoharan Ramamoorthy
Keyword(s):  
Free Vibration ◽  
Natural Frequencies ◽  
Sandwich Beam ◽  
Laminated Composite ◽  
Core Layer ◽  
Experimental Results ◽  
Sandwich Composite ◽  
Sandwich Beams ◽  
End Conditions ◽  
Vibration Responses

This study investigates the free vibration responses of laminated composite sandwich beam with multi-cores using experimental and numerical methods. The laminated composite face sheets are made by using hand layup method. An experimental modal test has been carried for different configurations of multi-core sandwich beams under different end conditions. The single-core and multi-core sandwich beams has been modeled and the natural frequencies of sandwich beams are determined using ANSYS software. The numerical model is verified by comparing the obtained natural frequencies with experimental results. The numerical and experimental results indicate that the multi-core sandwich beam greatly influences the structural stiffness compared with single-core sandwich beam under different end conditions. Furthermore, the influence of several parameters such as the end conditions, thickness of the core layer, and stacking sequence on the natural frequencies of the various configurations of the multi-core sandwich beams are presented.

Nonlinear Vibration of Sandwich Beams with Functionally Graded Negative Poisson’s Ratio Honeycomb Core

2019 ◽  
Vol 19 (03) ◽  
pp. 1950034 ◽  
Author(s):  
Chong Li ◽  
Hui-Shen Shen ◽  
Hai Wang
Keyword(s):  
Nonlinear Vibration ◽  
Poisson’S Ratio ◽  
Sandwich Beam ◽  
Flexural Vibration ◽  
Functionally Graded ◽  
Poisson's Ratio ◽  
Sandwich Beams ◽  
Negative Poisson’S Ratio ◽  
Honeycomb Core ◽  
Negative Poisson's Ratio

This paper investigates the nonlinear flexural vibration of sandwich beams with functionally graded (FG) negative Poisson’s ratio (NPR) honeycomb core in thermal environments. The novel constructions of sandwich beams with three FG configurations of re-entrant honeycomb cores through the beam thickness direction are proposed. The temperature-dependent material properties of both face sheets and core of the sandwich beams are considered. 3D full-scale finite element analyses are conducted to investigate the nonlinear vibration, and the variation of effective Poisson’s ratio (EPR) of the sandwich beams in the large deflection region. Numerical simulations are carried out for the sandwich beam with FG-NPR honeycomb core in different thermal environmental conditions, from which results for the same sandwich beam with uniform distributed NPR honeycomb core are obtained as a basis for comparison. The effects of FG configurations, temperature changes, boundary conditions, and facesheet-to-core thickness ratios on the nonlinear vibration ratio curves and EPR–deflection curves of sandwich beams are discussed in detail.

FREE ASYMMETRIC TRANSVERSE VIBRATION OF CIRCULAR MONOLAYER GRAPHENE

NANO ◽  
2014 ◽  
Vol 09 (07) ◽  
pp. 1450072
Author(s):  
WIN-JIN CHANG ◽  
HAW-LONG LEE
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Mode Shape ◽  
Transverse Vibration ◽  
Nonlocal Elasticity ◽  
Nonlocal Parameter ◽  
Flexural Vibration ◽  
Nonlocal Elasticity Theory ◽  
Monolayer Graphene ◽  
Nodal Lines

The free vibration equations of circular monolayer graphene are analytically derived based on nonlocal elasticity theory. The natural frequency and mode shape for the axisymmetric and asymmetric circular monolayer graphenes are analyzed using the equations. The results show that the natural frequency of the asymmetric graphene is larger than that of the axisymmetric one. The natural frequency decreases with increasing nonlocal parameter for the axisymmetric and asymmetric graphenes. In addition, the diametrical nodal lines and nodal circles for the flexural vibration of the circular monolayer graphene are investigated. To avoid vibration failure of the sensors, they can be placed at the diametrical nodal lines and nodal circles.

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