Vibro-acoustic coupling in composite plate-cavity systems

2017 ◽  
Vol 24 (11) ◽  
pp. 2274-2283 ◽  
Author(s):  
A Saide Sarıgül ◽  
Erkan Karagözlü
Keyword(s):  
Composite Materials ◽  
Composite Plate ◽  
Natural Frequencies ◽  
Isotropic Plate ◽  
Coupled Systems ◽  
Coupling Analysis ◽  
Acoustic Characteristics ◽  
Acoustic Coupling ◽  
Number Of Layers

Composite materials are extensively utilized today as strategic products. Although this widespread use, their vibro-acoustics characteristics have not been examined extensively. Specifically, the interactive coupling between the vibration and acoustics of composite plate- cavity systems is an untapped field. In this paper, the results of a modal structural-acoustic coupling analysis for plates with different composite parameters are presented. Natural frequencies of the coupled systems are tabulated. The effects of material, ply angle and number of layers on the coupled vibro-acoustic characteristics of composite plate-cavity systems have been examined and compared with the behaviour of isotropic plate systems.

scholarly journals Experimental and Numerical Analyses on the Buckling Characteristics of Woven Flax/Epoxy Laminated Composite Plate under Axial Compression

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 995
Author(s):  
Venkatachalam Gopalan ◽  
Vimalanand Suthenthiraveerappa ◽  
Jefferson Stanley David ◽  
Jeyanthi Subramanian ◽  
A. Raja Annamalai ◽  
...  
Keyword(s):  
Environmental Sustainability ◽  
Composite Plate ◽  
Compressive Load ◽  
Laminated Composite ◽  
Green Composite ◽  
Laminated Composite Plate ◽  
Axial Compressive Load ◽  
Number Of Layers ◽  
Structural Applications ◽  
Ply Orientation

The evolution of a sustainable green composite in various loadbearing structural applications tends to reduce pollution, which in turn enhances environmental sustainability. This work is an attempt to promote a sustainable green composite in buckling loadbearing structural applications. In order to use the green composite in various structural applications, the knowledge on its structural stability is a must. As the structural instability leads to the buckling of the composite structure when it is under an axial compressive load, the work on its buckling characteristics is important. In this work, the buckling characteristics of a woven flax/bio epoxy (WFBE) laminated composite plate are investigated experimentally and numerically when subjected to an axial compressive load. In order to accomplish the optimization study on the buckling characteristics of the composite plate among various structural criterions such as number of layers, the width of the plate and the ply orientation, the optimization tool “response surface methodology” (RSM) is used in this work. The validation of the developed finite element model in Analysis System (ANSYS) version 16 is carried out by comparing the critical buckling loads obtained from the experimental test and numerical simulation for three out of twenty samples. A comparison is then made between the numerical results obtained through ANSYS16 and the results generated using the regression equation. It is concluded that the buckling strength of the composite escalates with the number of layers, the change in width and the ply orientation. It is also noted that the weaving model of the fabric powers the buckling behavior of the composite. This work explores the feasibility of the use of the developed green composite in various buckling loadbearing structural applications. Due to the compromised buckling characteristics of the green composite with the synthetic composite, it has the capability of replacing many synthetic composites, which in turn enhances the sustainability of the environment.

NUMERICAL AND EXPERIMENTAL STUDY ON FREE VIBRATION OF DELAMINATED WOVEN FIBER GLASS/EPOXY COMPOSITE PLATES

2012 ◽  
Vol 12 (02) ◽  
pp. 377-394 ◽  
Author(s):  
J. MOHANTY ◽  
S. K. SAHU ◽  
P. K. PARHI
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Numerical Study ◽  
Shear Deformation Theory ◽  
Composite Plates ◽  
Fiber Glass ◽  
Number Of Layers

This paper presents a combined experimental and numerical study of free vibration of industry-driven woven fiber glass/epoxy (G/E) composite plates with delamination. Using the first-order shear deformation theory, an eight-noded two-dimensional quadratic isoparametric element was developed, which has five degrees of freedom per node. In the experimental study, the influence of various parameters such as the delamination size, boundary conditions, fiber orientations, number of layers, and aspect ratio on the natural frequencies of delaminated composite plates are investigated. Comparison of the numerical results with experimental ones shows good agreement. Fundamental natural frequencies are found to decrease with the increase in the delamination size and fiber orientation and increases with the increase in the number of layers and aspect ratio of delaminated composite plates. The natural frequency of the delaminated composite plate varies significantly for different boundary conditions.

Split Vibration Modes in Acoustically-Coupled Disk Stacks

1995 ◽  
Author(s):  
Jung-Ge Tseng ◽  
Jonathan Wickert
Keyword(s):  
Natural Frequencies ◽  
Three Dimensional ◽  
System Level ◽  
Thin Plates ◽  
Mode Shapes ◽  
Design Parameters ◽  
Phase System ◽  
Acoustic Coupling ◽  
Annular Plates ◽  
Vibration Model

Abstract Vibration of an array of stacked annular plates, in which adjacent plates couple weakly through an acoustic layer, is investigated through experimental and theoretical methods. Such acoustic coupling manifests itself through split natural frequencies, beating in the time responses of adjacent or separated plates, and system-level modes in which plates in the array vibrate in- or out-of-phase at closely-spaced frequencies. Laboratory measurements, including a technique in which the frequency response function of all in-phase modes but no out-of-phase modes, or visa versa, is measured, demonstrate the contribution of coupling to the natural frequency spectrum, and identify the combinations of design parameters for which it is important. For the lower modes of primary interest here, the natural frequencies of the out-of-phase system modes decrease as the air layer becomes thinner, while those of the in-phase mode remain sensibly constant at the in vacuo values. A vibration model comprising N classical thin plates that couple through the three-dimensional acoustic fields established in the annular cavities between plates is developed, and its results are compared with measurements of the natural frequencies and mode shapes.

Analysis of free vibration of an isotropic plate with surface or internal long crack using generalized differential quadrature method

2019 ◽  
Vol 55 (1-2) ◽  
pp. 42-52
Author(s):  
Milad Ranjbaran ◽  
Rahman Seifi
Keyword(s):  
Differential Equations ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Isotropic Plate ◽  
Differential Quadrature Method ◽  
Differential Quadrature ◽  
Quadrature Method ◽  
Generalized Differential Quadrature Method ◽  
Generalized Differential

This article proposes a new method for the analysis of free vibration of a cracked isotropic plate with various boundary conditions based on Kirchhoff’s theory. The isotropic plate is assumed to have a part-through surface or internal crack. The crack is considered parallel to one of the plate edges. Existence of the crack modified the governing differential equations which were formulated based on the line-spring model. Generalized differential quadrature method discretizes the obtained governing differential equations and converts them into an algebraic system of equations. Then, an eigenvalue analysis was used to determine the natural frequencies of the cracked plates. Some numerical results are given to demonstrate the accuracy and convergence of the obtained results. To demonstrate the efficiency of the method, the results were compared with finite element solutions and available literature. Also, effects of the crack depth, its location along the thickness, the length of the crack and different boundary conditions on the natural frequencies were investigated.

PHASE SYNCHRONIZATION OF LINEARLY AND NONLINEARLY COUPLED OSCILLATORS WITH INTERNAL RESONANCE

2009 ◽  
Vol 23 (30) ◽  
pp. 5715-5726
Author(s):  
YONG LIU
Keyword(s):  
Coupling Strength ◽  
Coupled Oscillators ◽  
Internal Resonance ◽  
Natural Frequencies ◽  
Phase Synchronization ◽  
Coupled Systems ◽  
Nonlinear Coupling ◽  
Linear Coupling ◽  
Phase Dynamics ◽  
Diffuse Clouds

Phase synchronization between linearly and nonlinearly coupled systems with internal resonance is investigated in this paper. By introducing the conception of phase for a chaotic motion, it demonstrates that the detuning parameter σ between the two natural frequencies ω1and ω2affects phase dynamics, and with the increase in the linear coupling strength, the effect of phase synchronization between two sub-systems was enhanced, while increased firstly, and then decayed as nonlinear coupling strength increases. Further investigation reveals that the transition of phase states between the two oscillators are related to the critical changes of the Lyapunov exponents, which can also be explained by the diffuse clouds.

scholarly journals Simulation and Test of Discrete Mobile Surfaces for a RC-Aircraft

Aerospace ◽  
2019 ◽  
Vol 6 (11) ◽  
pp. 122
Author(s):  
Francesco Nicassio ◽  
Gennaro Scarselli
Keyword(s):  
Composite Materials ◽  
Unmanned Aerial Vehicles ◽  
Composite Plate ◽  
Stacking Sequence ◽  
Total Thickness ◽  
Aerodynamic Efficiency ◽  
Aerodynamic Pressure ◽  
Aerial Vehicles ◽  
Discrete Surface ◽  
Lever Effect

Morphing structures suitable for unmanned aerial vehicles (UAVs) have been investigated for several years. This paper presents a novel lightweight, morphing concept based on the exploitation of the “lever effect” of a bistable composite plate that can be integrated in an UAV horizontal tail. Flight dynamics equations are solved in Simulink environment, thus being able to simulate and compare different flight conditions with conventional and bistable command surfaces. Subsequently, bistable plates are built by using composite materials, paying particular attention to dimensions, asymmetric stacking sequence and total thickness needed to achieve bistability. NACA0011 airfoil is chosen for proving this concept. Wind tunnel tests demonstrate that the discrete surface is capable of withstanding the aerodynamic pressure. A remotely piloted vehicle is employed to test the discrete horizontal tail command during the take-off. The results show that, choosing a proper configuration of constraints, stacking sequence and aspect ratio for the bistable laminate, it is possible to tailor the snap-through mechanism. The proposed concept appears lighter and increases aerodynamic efficiency when compared to conventional UAV command surfaces.

Modal Properties of Hybrid Carbon/Kevlar Composite Thin Plate and Hollow Wing Model

2013 ◽  
Vol 446-447 ◽  
pp. 597-601
Author(s):  
H. Haidzir ◽  
Dayang Laila Majid ◽  
A.S.M. Rafie ◽  
M.Y. Harmin
Keyword(s):  
Mechanical Properties ◽  
Thin Plate ◽  
Composite Plate ◽  
Natural Frequencies ◽  
Computational Procedure ◽  
Modal Testing ◽  
Wing Model ◽  
Natural Modes ◽  
Superior Mechanical Properties ◽  
Hybrid Carbon

In any flutter prediction analysis, modal testing is necessary because flutter, a resonant like vibration occurs at a flutter frequency and adopts a mode shape akin to its structural natural modes. Modal testing can be performed computationally with knowledge of the mechanical properties of the structure. In the present work, computational modal analysis is first performed on a cantilevered hybrid composite thin plate and validated experimentally. Then, the computational procedure is demonstrated on a composite hollow wing model of same material. The concept of hollow wing is explored due to the superior mechanical properties of carbon/kevlar composite plate. It is observed that the natural frequencies of the hollow wing model are higher than thin plate due to stiffer configuration. A breathing mode was also observed at mode 4 for the hollow wing.

Fatigue Life of Hybrid Composites (DGEBA)

2020 ◽  
Vol 398 ◽  
pp. 54-59
Author(s):  
Nisreen Mizher Rahma ◽  
Lubna Ghalib ◽  
Khalid Mershed Eweed
Keyword(s):  
Composite Materials ◽  
Tensile Test ◽  
Glass Fiber ◽  
Fatigue Limit ◽  
Fatigue Test ◽  
Hybrid Composite ◽  
Fiber Type ◽  
Second Stage ◽  
Number Of Layers ◽  
Two Stages

This study presents the experimental results of the influence of mechanical fatigue and tensile on hybrid composite materials. Epoxy with Novolac resin are used as matrix for the reinforced materials that consist of glass fiber type E. The slates made of hybrid composite materials for two proportions (80% epoxy, 20% Novolac) and (60% epoxy, 40% Novolac) were reinforced by three volume fractions (10%, 20% and 30%) of glass fiber type (E), where been manufacturing (6) panels of hybrid composite materials, all these panels cutting into two groups samples with dimension (70x 10) mm in order to execute the fatigue test and (150x20) mm for tensile test, according to the specifications of the device used.The process took place in two stages: The two stages include executing the fatigue and tensile test specimens with a ratio (80% epoxy, 20% Novolac) in the first stage and (60% epoxy, 40% Novolac) in the second stage for the volume fractions (10%, 20% and 30%) of glass fiber type (E) and comparison the results between them for each stage. The results obtained from fatigue test in the first stage showed that the number cycle for fatigue limit decreased when the load and the number of layers of reinforcing are increased. But in the tensile test for the samples the results showed that the value of the elongation increasing to the point of failure when the load increased for the same layers of reinforcement, as well as the value of elongation decreasing to a failure when increased the number of layers of reinforcing glass fibers type (E) for the same load. The results of tensile and fatigue test obtained from the second stage showed similar to the results in the first stage, but the cycle number of fatigue limit less value from the first stage and the stress was higher in the fatigue test. For tensile test the elongation values ​​less and the stress values higher for the same volume fraction of the reinforcement due to increase in the proportion of Novolac.

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