Finite Element And Experimental VibrationAnalysis Of Viscoelastic Composite Structures (original) (raw)
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Advanced Composites Letters
Finite element analysis of sandwich and laminated composite structures with viscoelastic layers is performed. The present implementation gives the possibility to preserve the frequency dependence for the storage and loss moduli of viscoelastic materials exactly. Moreover, the storage and loss moduli in this case are defined directly in the frequency domain by an experimental technique for each material and can be used after curve fitting procedure in the numerical analysis. Damping characteristics of viscoelastic composite structures are evaluated by the energy method, the method of complex eigenvalues, from the resonant peaks of the frequency response function and using the steady state vibrations. Numerical examples are given to demonstrate the validity and application of the approaches developed for the free vibration, frequency and transient response analyses.
VIBRATION ANALYSIS OF VISCOELASTICALLY DAMPED COMPOSITE SANDWICH PLATES
19th International Congress on Sound and Vibration 2012 (ICSV 19), 2012
A numerical method based on a finite element approach to analyze the vibration and acoustic response of composite sandwich plates is presented. This method is an extension of the finite element formulation developed for the study of sandwich composites beams damped by means of viscoelastic materials. It is based on a layerwise displacement field through the plate thickness. The formulation assumes the classical lamination theory for the composite faces and Mindlin's theory for the core. The governing equations, obtained from Hamilton's principle, are discretized using a triangular plate finite element. The proposed approach uses very few unknown variables, and in the context of multilayered sandwich structures, the total number of the unknown variables is independent of the number of layers, which leads to a total number of DOFs much lower than in most zigzag theories, where the number of DOFs increases proportionally to the total number of discrete layers. The accuracy of the presented model is demonstrated by comparing predictions of free and forced vibration analyses of various sandwich composite plates with the results obtained by the PATRAN/NASTRAN finite element software package using a 3-D layered model.
Composite materials are used in many years ago and now days they are very use full. Since 4000 B.C straw was added soil to increase the resistance of the bricks. Although the benefits brought by the composite materials are known for thousands of years, just some years ago the right understanding of material behavior as well as the technology for designing composites war started to be developed. F111 airplane is the first model to incorporate this technology. Another example, of an airplane Boeing 767 has 2 tons in composite materials. The main possibility of material to combine with high strength and stiffness with low weight has also got the attention of the automobile industry. The Ford device or motor Company was developed a car in 1979 with some components made from composite materials. The type of modal was simply 570 kg lighter than the version in steel, only the transmission shaft had a reduction of 57% of its original weight. Since then Recently, Chrysler developed a car which was completely based on composite materials, and it " s known as CCV (Composite Concept Vehicle). Laminated composite materials are, generally lighter and stiffer than other structural materials. It consists of several layers of a composite mixture combination of matrix and fibers. Each and every layer can have similar (or) dissimilar material properties with having different fiber orientations under varying stacking sequence. Because of composite materials are produced in many several combinations and forms, the design engineer must consider many design alternatives. The structural components can made of composite materials such as different aircraft wings, helicopter blades, vehicle axles and turbine blades. This type of materials are used widely in structural applications where high strength-to weight and stiffness-to-weight ratios are required. In the composite " s fiber orientations by altering lay-up, composite beam material can be tailored to meet the particular requirements of stiffness and strength .The ability to manufacture a composite material are due to high strength of the material, low weight ratio, resistance in fatigue and low damping factor. The composite materials have wide range of applications in car and aircraft industries. Research work in the design of mechanical, aerospace and civil structure and development of composite materials has grown tremendously in few decades. The main thing is designing and modeling of industrial products for finding the free vibration characteristics of Laminated Composite Beam (LBC). Composites beam analysis is main important in mechanical and civil structural design such as railways, car suspension system and structural foundation. V. Tita, J. de Carvalho and J. Lirani [1] contributed for better understanding of the dynamic behavior of components made from fiber reinforced composite materials, specifically for the case of beams. In order to investigate the influence of the stacking sequence on the dynamic behavior of the components, using the Finite Element work has been carried out by experimental and numerical analysis and then results are presented and discussed. Subramanian [2] has investigated free vibration analysis of LCBs by using two higher order displacement primarily based on shear deformation theories and finite elements. Each theory is assumed as quantic and quartic variation of in-plane and transverse displacements within the thickness coordinates of the beam respectively. Results are indicating that application of those theories and finite element model leads to natural frequencies with higher accuracy. Banerjee [3] has investigated the free vibration of axially laminated composite Timoshenko beams using dynamic stiffness matrix technique. L Santosh Sreekanth, and m kumaraswamy [4] used to two different fibers analyze the critical buckling loads at relative cracked and non-cracked beam including crack depth. In this present work the fabrication of E-glass fiber reinforced beam dimensions 200mmX40mmX9mm was carried out by hand lay-up technique. The natural frequencies of these beams ware evaluated for different boundary conditions like Cantilever, Simply supported, Fixed-Simply supported and Fixed-Ended. The evolution of the natural frequencies for above conditions was carried out using accelerometer, impact hammer and FFT analyser which been ABSTRACT: In the present work E-glass fiber reinforced composite beams were fabricated by hand lay-up method having three layers with orientations (0 0 , 30 0 ,-45 0). The first three natural frequencies of these beams ware evaluated experimentally using accelerometer, impact hammer and FFT analyzer, which is being operated by DEWESOFT software. The dimensions of the beams are 200mmX40mmX9mm. The first three natural frequencies were obtained for different boundary conditions like Cantilever, Simply supported, Fixed-Simply supported and Fixed-Ended conditions. The numerical analysis was also carried out to find the first three natural frequencies of the beam for the above boundary conditions using Euler beam equation. The process of find the first three natural frequencies was repeated by simulating the composite beam using ANSYS 16.2.The Results thus obtained in three methods were compared.
Frequency response analysis of laminated composite beams
Mechanics of Composite Materials, 1995
Fibre composite materials are widely used in structural applications requiring high stiffness-to-weight and strength-toweight ratios and a high damping. The significance of damping to the dynamic performance of structures is broadly recognized. Passive damping is an essential dynamic parameter for vibration and sound control, fatigue endurance, and impact resistance. Because of the increased need for highly damped structures, significant progress has been recently achieved in the analysis of damping of composites. Recent works on the damping mechanics of composite laminates [1-4] and structures [5][6][7][8] have shown that composite damping is anisotropic, highly tailorable, and depends on an array of micromechanical, laminate, and structural parameters, including constituent material properties, fibre volume ratios, ply angles, ply thicknesses, ply stacking sequence, temperature, moisture, and existing damage.
Finite Element Vibration Analysis of Damped Composite Sandwich Beams
The International Journal of Acoustics and Vibration
In this study, a finite element model for the vibration analysis of cross-ply laminated sandwich beams is presented. This formulation is an extension of our previous work on predicting the acoustic and vibration responses of sandwich beams and plates with homogeneous elastic faces and a viscoelastic core. The formulation is based on a layerwise linear axial displacement through the beam thickness. The formulation assumes the classical lamination theory for the faces and Timoshenko theory for the core. The governing equations of motion are obtained using Hamilton's principle. A finite element method and a beam element are further developed to predict the natural frequencies and modal loss factors. In order to validate the proposed model, several free vibration analyses of composite sandwich beams with different boundary conditions, length-to-thickness ratios and face laminations are presented. The results are then compared with solutions available in the literature and with those obtained by the PATRAN/NASTRAN finite element software package. These results show the validity of the present formulation. Finally, the effects of ply-stacking sequence, core-to-face stiffness ratio and core-to-face thickness ratio upon the natural frequencies and modal damping are investigated.
Vibration Analysis of Composite Plate
IJMER
Absrtact: Most of the structural components are generally subjected to dynamic loadings in their Working life. Very often these components may have to perform in severe dynamic environment where in the maximum damage results from the resonant vibrations. Susceptibility to fracture of materials due to vibration is determined from stress and frequency. Maximum amplitude of the vibration must be in the limited for the safety of the structure. Hence vibration analysis has become very important in designing a structure to know in advance its response and to take necessary steps to control the structural vibrations and its amplitudes. The present study involves extensive experimental works to investigate the free vibration of woven fiber Glass/Epoxy composite plates in free-free boundary conditions. The specimens of woven glass fiber and epoxy matrix composite plates are manufactured by the hand-layup technique. Elastic parameters of the plate are also determined experimentally by tensile testing of specimens. An experimental investigation is carried out using modal analysis technique, to obtain the Natural frequencies. Also, this experiment is used to validate the results obtained from the FEA using Ansys. The effects of different parameters including aspect ratio, and fiber orientation of woven fiber composite plates are studied in free-free boundary conditions in details. This study may provide valuable information for researchers and engineers in design applications.
Finite element analysis of damping the vibrations of laminated composites
Computers & Structures, 1993
Ahstrati-There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures with desired eigen-frequencies and excitation frequencies, using materials that have damping properties, etc. Special damping layers made of various viscoelastic materials are widely applied in structures subjected to dynamic loading, especially those used in ship building and aerospace technology. A typical structure is that whose basic layer is covered with a damping layer and a thin constraining layer. Such classical sandwich structures have been widely investigated, especially with reference to the analysis of elastic vibrations.
An Extended Higher-Order Free Vibration Analysis of Composite Sandwich Beam With Viscoelastic Core
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
Free vibration analysis of sandwich beam with a viscoelastic core based on the extended high-order sandwich panel theory approach is presented. The effects of transverse shear and core compressibility are of high importance in sandwich structures, having an influence on the entire structural behavior especially in vibrations. For applications involving stiffer cores, the high-order sandwich panel theory (HSAPT) cannot accurately predict the shear and axial stress distributions in the core. Thus, by using the "Extended High-Order Sandwich Panel Theory" (EHSAPT), the in-plane rigidity of the core is considered in addition to the compressibility of the core in the transverse direction. The novelty of this theory is that it allows for three generalized coordinates in the core (the axial and transverse displacements at the centroid of the core, and the rotation at the centroid of the core) instead of just one (mid-point transverse displacement) commonly adopted in other available theories. The mathematical formulation uses the Hamilton principle and includes derivation of the governing equations along with the appropriate boundary conditions. The formulation uses the classical thin plate theory for the face sheets and a twodimensional elasticity theory or equivalent one for the core. In addition, Young modulus, rotational inertia, and kinetic energy of the core are considered and core is assumed as an orthotropic viscoelastic material. The analysis is applicable for any types of loading scheme, localized as well as distributed, and distinguish between loads applied at the upper or the lower face. The obtained results are compared with recent research published by the present authors which was done numerically by using FEM on viscoelastic sandwich beam and the corresponding results of other previous researches. The influence of material properties, face layup and geometry effect on natural frequencies of composite sandwich beams are investigated.
Journal of Mechanical Science and Technology, 2019
In order to investigate both static and dynamic characteristics of composite plates and validate a contemporary, non-invasive experimental technique a comparative experimental and numerical analysis was performed. Three, geometrically the same but different in ply orientation, carbon-epoxy laminates were tested in both healthy and damaged conditions. Damages were inflicted in a shape of horizontal crack. Experiments and numerical simulations were performed by digital image correlation (DIC) and finite element method (FEM), respectively. Obtained time-responses of the tested structures were fast Fourier transformed (FFT) to frequency domain for a clearer understanding of natural frequencies and oscillation modes. Results are presented in tabular and graphical form. The overall correspondence of two sets of structural displacements is satisfactory. Some discrepancies might be contributed to the idealized geometry and restraint consideration. Also, due to the fast damping of higher tones, the errors in determining higher natural frequencies increase but still remain in 5 % range.
Vibration Analysis of Laminated Composites Using Experimental
In this paper, damage detection for different types of defects (delamination, crack and hole) in the composite laminate plate and cylindrical shell be used to characterize the vibration behavior experimentally which used two types of load (plus and sine load) to find the frequency response. To this end, some plates and cylindrical shells are made using hand-lay-up process. Glass fiber is used as a reinforcement in the form of bidirectional fabric and general purpose polyester resin as matrix for the composite material of plates and cylindrical shells. From the results, the damage detection by using the Genetic algorithms is investigated. Also, these experiments are used to validate the results of free vibration obtained from the finite elements program.