Effects of Normal Strain in Core Material on Modal Property of Sandwich Plates

1997 ◽  
Vol 119 (4) ◽  
pp. 493-503 ◽  
Author(s):  
Byung-Chan Lee ◽  
Kwang-Joon Kim
Keyword(s):  
Elastic Modulus ◽  
Shear Modulus ◽  
Layer Thickness ◽  
Dynamic Modeling ◽  
Core Layer ◽  
Base Layer ◽  
Core Material ◽  
Sandwich Plates ◽  
The Core ◽  
Plate Length

In vibration analysis of sandwich beam/plates, it is often assumed that there is shear deformation only, without extension or compression in the viscoelastic layer. Certainly, this assumption may have limitations, for example, with increase of the core thickness or frequency range of vibration. The purpose of this paper is to consider the normal, as well as shear strain of the core material for modal parameter estimation of the sandwich plates and to investigate how much error will be caused by neglecting the extension or compression in the core material. Natural frequencies and modal loss factors are estimated for a simply supported square plate by taking the normal as well as shear deformation into account for dynamic modeling. Nondimensional characteristic equations are formulated and solved numerically for various ratios of the base layer thickness to plate length, core layer thickness to base layer, constraining layer thickness to base layer, and shear modulus of core material to elastic modulus of base layer. The effects of the various parameters on the modal properties are shown to be intercorrelated to each other and hence difficult to summarize in one phrase. Normal deformation of the core material plays an important role when the thickness ratio of constraining layer to base layer is 0.5 and its Poisson’s ratio is smaller than 0.49, and hence need to be included in the dynamic modeling especially for estimation of modal damping when one of the following conditions are met; 1) the ratio of base layer thickness to plate length is greater than 0.02, 2) the thickness ratio of core layer to base layer is greater than 0.01, 3) the wavelength of a mode is less than one third of the plate length, 4) the ratio of shear modulus of core material to elastic modulus of base material is less than 10−5.

Consideration of Both Extensional and Shear Strain of Core Material in Modal Property Estimation of Sandwich Plates

1995 ◽  
Author(s):  
Byung-Chan Lee ◽  
Kwang-Joon Kim
Keyword(s):  
Shear Strain ◽  
Layer Thickness ◽  
Sandwich Beam ◽  
Base Layer ◽  
Core Material ◽  
Viscoelastic Layer ◽  
Sandwich Plates ◽  
Modal Parameter ◽  
The Core ◽  
Plate Length

Abstract In vibration analysis of sandwich beam/plates, it is often assumed that there occurs shear deformation only, i.e. no extension or compression, in the core viscoelastic layer. Certainly, this assumption may have limitations, for example, with increase of the core thickness or frequency range of vibration. The purpose of this paper is to consider the extentional as well as shear strain of the core for modal parameter estimation of the sandwich plates and to investigate how much error will be caused by neglecting the extension or compression in the core material. Natural frequencies and modal loss factors are estimated for a simply supported square plates under each of the above two assumptions. Nondimensional characteristic equations are formulated and solved for various ratios of the base layer thickness to plate length, core to base layer thickness, and constraining layer to base layer thickness.

Modal Loss Factors of Thick Three-Layer Cylinders With Viscoelastic Core

1995 ◽  
Author(s):  
Hamid R. Hamidzadeh ◽  
Yanfei Jiang
Keyword(s):  
Shear Modulus ◽  
Natural Frequencies ◽  
Core Material ◽  
Constrained Layer Damping ◽  
Material Damping ◽  
The Core ◽  
Linear Viscoelastic Material ◽  
Wide Range ◽  
Elastic Cylinders ◽  
Loss Factors

Abstract An analytical solution to the free vibration of a damped three-layer thick sandwiched cylinder of infinite extend is presented. The constrained layer damping is accomplished by sandwiching a linear viscoelastic material between two isotropic elastic cylinders with the same properties. The governing equation is derived based on elasto-dynamic theory utilizing complex elastic moduli. Dimensionless natural frequencies and modal loss-factors are extracted. Special case for a three-layer sandwiched cylinder with similar elastic properties is considered. The computed dimensionless frequencies are compared with previously established results. The comparison indicates the validity of the proposed mathematical procedures. In addition, the effects of various values of material damping for the core layer and ratio of the core shear modulus to the shear modulus of the elastic cylinders on natural frequencies and modal loss-factors are studied. For a given configuration, modal information for the first two modes for n = 0, 1, 2, 3 and 4 are presented for a wide range of core material damping and G2/G1 ratio.

scholarly journals Cavity Formation Modeling of Fiber Fuse in Single-Mode Optical Fibers

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Yoshito Shuto
Keyword(s):  
Optical Fibers ◽  
Nonlinear Oscillation ◽  
Relaxation Oscillation ◽  
Core Layer ◽  
Single Mode ◽  
Core Material ◽  
Cavity Formation ◽  
Van Der Pol Equation ◽  
Van Der Pol ◽  
The Core

The evolution of a fiber-fuse phenomenon in a single-mode optical fiber was studied theoretically. To clarify both the silica-glass densification and cavity formation, which have been observed in fiber fuse propagation, we investigated a nonlinear oscillation model using the Van Der Pol equation. This model was able to phenomenologically explain both the densification of the core material and the formation of periodic cavities in the core layer as a result of a relaxation oscillation.

scholarly journals Sound Transmission Loss of a Sandwich Plate with Adjustable Core Layer Thickness

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4160
Author(s):  
Tom Ehrig ◽  
Martin Dannemann ◽  
Ron Luft ◽  
Christian Adams ◽  
Niels Modler ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Core Layer ◽  
Constrained Layer Damping ◽  
Sound Transmission Loss ◽  
Frequency Range ◽  
The Core ◽  
Set Up ◽  
Stiffness And Damping

Compressible Constrained Layer Damping (CCLD) is a novel, semi-active, lightweight-compatible solution for vibration mitigation based on the well-known constrained layer damping principle. The sandwich-like CCLD set-up consists of a base structure, a constraining plate, and a compressible open-cell foam core in between, enabling the adjustment of the structure’s vibration behaviour by changing the core compression using different actuation pressures. The aim of the contribution is to show to what degree, and in which frequency range the acoustic behaviour can be tuned using CCLD. Therefore, the sound transmission loss (TL), as an important vibro-acoustic index, is determined in an acoustic window test stand at different actuation pressures covering a frequency range from 0.5 to 5 kHz. The different actuation pressures applied cause a variation of the core layer thickness (from 0.9 d0 to 0.3 d0), but the resulting changes of the stiffness and damping of the overall structure have no significant influence on the TL up to approximately 1 kHz for the analysed CCLD design. Between 1 kHz and 5 kHz, however, the TL can be influenced considerably well by the actuation pressure applied, due to a damping-dominated behaviour around the critical frequency.

scholarly journals Nonlinear Vibration Behavior of Sandwich Beams With Entangled Fiber Core Material

2013 ◽  
Author(s):  
Elsa Piollet ◽  
Guilhem Michon ◽  
Dominique Poquillon
Keyword(s):  
Shear Modulus ◽  
Shear Strain ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Sandwich Beam ◽  
Experimental Tests ◽  
Core Material ◽  
Sandwich Beams ◽  
Fiber Core ◽  
The Core

In this paper, the use of entangled cross-linked fibers as core material in vibrating sandwich beams is investigated. The aim is to analyze the effect of this specific core material in terms of damping. The dynamic shear properties of the material are first studied experimentally. The shear modulus is shown to decrease with increasing shear strain amplitude at low shear strains. To include an amplitude dependency of the core material properties in the sandwich beam behavior, an analytical model is proposed. The equations of motion are derived using Lagrange’s equations. The shearing of the core is introduced in the equations through the use of virtual work to allow any relationship between shear stress and shear strain, including damping and nonlinearities. Experimental tests are carried out on sandwich beams with entangled fiber core material. The Frequency Response Function obtained exhibits decreasing resonant frequency and peak amplitude with increasing load amplitude. This softening behavior is consistent with the decreasing shear modulus. The proposed model is used take into account the softening nonlinearity. The FRF is reproduced with a linearly decreasing shear modulus and linearly increasing loss factor.

scholarly journals Experimental Study on Shear Property of Integrated Sandwich Panel of Aluminum Honeycomb and Epoxy Resin

2015 ◽  
Vol 9 (1) ◽  
pp. 1000-1006 ◽  
Author(s):  
Xin Yaju ◽  
Zhao Xuya ◽  
Liu Xiaoman ◽  
Tie Rui ◽  
Cheng Shuliang
Keyword(s):  
Elastic Modulus ◽  
Bearing Capacity ◽  
Epoxy Resin ◽  
Layer Thickness ◽  
Sandwich Panel ◽  
Composite Layer ◽  
Specimen Thickness ◽  
The Core ◽  
Additional Layer ◽  
Aluminum Honeycomb

In order to realize functional integration, a new kind of sandwich panel was made. By carrying out quasi-static shear experiments, its elastic modulus and ultimate bearing capacity with different resin immersing thickness, additional layer thickness of resin and specimen thickness were investigated. The load - displacement curves and failure models were obtained, which were compared with the traditional aluminum honeycomb sandwich panel. The experiments indicated that the integrated aluminum honeycomb and epoxy resin sandwich panel’s shearing process undergoes three phases: elasticity, yield and destruction. The specimen’s elastic modulus and ultimate bearing capacity increase with the increase of the resin thickness, additional layer thickness of resin and the specimen thickness, which greatly improve compared to the traditional sandwich structure. The composite layer and the core show good stability under shearing process, and there is no peeling-off or cracking between the composite layer and the core.

Cylindrical Buckling of Sandwich Plates

1946 ◽  
Vol 13 (4) ◽  
pp. A253-A260
Author(s):  
J. N. Goodier
Keyword(s):  
Plane Strain ◽  
Sandwich Plate ◽  
Core Material ◽  
Sandwich Plates ◽  
The Core

Abstract In the buckling of “sandwich plates” with a relatively easily deformed interior, or core, material, the core is not stiff enough to keep plane sections plane when the bending occurs. The core must then be analyzed according to the equations of plane strain, but the fact that the bending takes place in the presence of thrust means that terms representing the destabilizing tendency of the thrust must be included. The resulting problem is solved in the present paper for a sandwich plate in “cylindrical buckling”—that is in a mode analogous to that of the hinged column.

Tension and compression of sandwich composites with weft-knit fabric cores

2020 ◽  
Vol 34 (07n09) ◽  
pp. 2040004
Author(s):  
Jieng-Chiang Chen ◽  
Yi-Fang Zhuang
Keyword(s):  
Compressive Force ◽  
Core Layer ◽  
Longitudinal Force ◽  
Test System ◽  
Core Material ◽  
Sandwich Composite ◽  
Sandwich Composites ◽  
Carbon Fabric ◽  
The Core ◽  
Tension And Compression

The manufacturing techniques of sandwich composites containing core layers of weft-knit glass fabric (WG) and weft-knit carbon fabric (WC) with carbon fabric skin layers are discussed herein. The core layers of the sandwich composites were fabricated with WG-reinforced epoxy (E) resin, WC-reinforced epoxy resin, and polyurethane foam (F). The core layer was then stacked with two pieces of carbon fabric on the top and bottom surfaces to fabricate the sandwich composites. Three sandwich composites [plain carbon fabric sandwich composite with a WG core layer (C/E/WG), plain carbon fabric sandwich composite with a WC core layer (C/E/WC), and plain carbon fabric sandwich composite with an F core layer (C/E/F)] were developed in this study. A two-step manufacturing procedure was developed to achieve sufficient adhesiveness between the skin and core layers. The tensile, flatwise compressive, and longitudinal compressive properties of these sandwich composites were measured according to referred ASTM standards on a materials test system (MTS 810). Experimental results revealed that the WC core materials displayed excellent resistance to a flatwise compressive force and the foam core material show weak resistance. Under longitudinal compression, the skin and core layer of the C/E/F specimen separated, indicating that the C/E/F specimen could not withstand longitudinal force. Moreover, the C/E/WG and C/E/WC specimens both bend at the end of the same test.

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