Behavior Of Sandwich Plates Research Articles

Dynamic Analysis of Eccentrically Stiffened Sandwich Thick Plates with Auxetic Honeycomb Core and GPL-RC Face Layers under Blast Loading

The object of this study is eccentrically stiffened sandwich thick plates with the core layer made of negative poisson material. The analytical method base on the first order shear deformation theory (FSDT) is applied to analyse dynamic response and vibration of the plates. The numerical results of the study have been compared with other studies to evaluate the reliability of the calculation. The analysis results of the nonlinear dynamic response and the vibration show that the elastic foundation and the graphene volume ratio positively impact the behavior of the plates. On the other hand, imperfection and thermal environment have a negative effect on the behavior of sandwich plates. Research has also been performed to evaluate the effect of blast load, axial load and shape on the dynamic response of the plate.

Static and dynamic instability analysis of tapered CNTRC sandwich plates under uniform and non-uniform in-plane loadings using spline finite strip method

This paper presents the buckling analysis of rectangular sandwich plates with pure polymeric tapered cores and functionally graded carbon nanotube (FG-CNT) reinforced composite face sheets under static and harmonic dynamic loads. One uniform and four linearly-varying patterns are considered for the applied in-plane loads. The effective material properties of face sheets, in which the polymeric matrix is reinforced with aligned single-walled carbon nanotubes (SWCNT), are estimated using the extended rule of mixture. A higher-order zigzag shear deformation theory, which has the same number of dependent unknowns as the first-order theory, is employed to express the plate's displacement field. The governing equations are derived using Hamilton's principle and discretized by the spline finite strip method. The dynamic instability regions of plates with uniform and variable thickness are obtained by employing Bolotin's method. The accuracy of the present method is demonstrated by considering the problems for which solutions are available. A detailed numerical study is conducted to examine and compare the effects of different parameters, including the taper angle, type of the applied in-plane load, static and dynamic load factors, length-to-width ratios, the volume fraction of CNT, distribution pattern of CNTs along the thickness direction, temperature, and boundary conditions on the behavior of sandwich plate.

Thermal post-buckling behavior of imperfect temperature-dependent sandwich FGM plates resting on Pasternak elastic foundation

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and postbuckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.

Geometrical parameters influence on behavior of the sandwich plates with corrugated core

The influence of geometric parameters on behavior and stiffness of sandwich plates with corrugated core is considered in this paper. The following parameters were analyzed: ratio of core sheet and facing sheet thickness and the ratio of the core’s pitch to the core’s depth, as well as the corrugation angle. It is shown that changes of these parameters can contribute to increase or decrease of the corrugated sandwich plate stiffness.

Analysis of Buckling of Sandwich Plates with Viscoelastic Core Using Layerwise Theory

Sandwich plates are one of the important components in construction of engineering and especially aerospace structures. In this paper, buckling analysis of sandwich plates was investigated experimentally and analytically using layerwise theory. The sandwich plate was rectangular and made of two composite laminates as skins and a viscoelastic core. The formulation was based on the first order shear deformation theory and the Rayleigh-Ritz method was used for approximating and determining the displacement field. The behavior of viscoelastic material modeled using Zener three-element model. The results obtained from layerwise theory compared with experimental results and showed good agreement. This study demonstrated that, layerwise theory could describe buckling behavior of sandwich plates with high accuracy and represents more realistic and acceptable description of behavior of the plates with much less computational cost.

Influence of Core Splice to the Mechanical Behavior of Sandwich Plate

The cores have to be spliced in the manufacturing process of sandwich plate due to the processing technology, the influence of core splice, compared with integrated core, on mechanical behavior of sandwich plate were investigated through two experiments. Two styles of specimens (B-style and C-style) were taken into experiments in sequence which included two kinds of plate with different cores.Firstly, it was found in stiffness experiment that stiffness and strength of sandwich plate with splicing core were obviously weaker than that with integrated core, which mean the former performed larger deformation under the same predetermined load with higher strain and behaved lower ultimate bearing capacity. Meanwhile the failure modes were mainly sheet crushing collapse and there was no evident difference in the failure mode of the two styles specimens with different cores. It concluded that the cores splice reduced the stiffness in location of two core splicing but the effect on the failure mode was slight.Secondly, it was found in stability experiment that the mechanical behaviour was approximately linear under the predetermined axial load and the predetermined out-of-plane load and similarly bulking strength of the sandwich plate with splicing core was about 10%~15% lower than that with integrated core. Basically, delamination between sheet and core kept accompany with bulking of the plate each time and two styles specimens with different cores didn’t show evident differences in failure mode as well. It demonstrated the conclusion and that core splice accounted to make the specimens produced geometric imperfections which resulted in stiffness reduction.Thirdly, based on experiments it was clear that the mechanical behaviour of sandwich plates with splicing cores suffered from more obvious discreteness compared with that with integrated cores, which indicated that manufacturing technology had greater influence on the former and core splice should be avoided in some important location of structure.Lastly, numerical simulation method based on progressive damage analysis was also studied and good correlation with experimental results was obtained, which could well predict the mechanical behaviour of the sandwich plates with splicing core and integrated core.

Load-carrying behaviour of web-core sandwich plates in compression

This paper investigates theoretically the compressive load-carrying behaviour of geometrically imperfect web-core sandwich plates. Slender plates, which first buckle globally, are considered. The study is carried out using two approaches, both solved with the finite element method. The first is the equivalent single-layer theory approach. First-order shear deformation theory is used. The second approach is a three-dimensional shell model of a sandwich plate. Plates are loaded in the web plate direction. Simply supported and clamped boundary conditions are considered with a different level of in-plane restraint on the unloaded edge. The results show that the behaviour of the sandwich plate is qualitatively equal to the isotropic plate of the same bending stiffness for deflections lower than the plate thickness. As the deflections increase, the lower in-plane stiffness of the sandwich plate results in lower post-buckling stiffness. Local buckling of face plates in the post-buckling range of the sandwich plate further reduces the structural stiffness.

Optimization Design of Heterogeneous Metal Sandwich Plate Using Response Surface Method

Heterogeneous metal sandwich plate is composed of high strength material face-sheets and low-density material core. In this paper, the crashworthiness property of the heterogeneous metal sandwich plate was investigated with combining the response surface method and finite element simulation. The specific absorption energy of sandwich plate is made as the crashworthiness performance index, and approximation written as a third-order function of the section parameters by means of the response surface method. According to the BB experiment design method, 29 groups of sandwich plate with different section structure parameters were selected and finite element numerical simulations were conducted to study on deformation behavior of sandwich plates during the collision process. Then, the coefficients of approximate specific absorption energy function were solved with regressive analysis. Consequently, the relationship between the crashworthiness performances of sandwich plate and the section parameters α, β, D, d was obtained.

Numerical Analysis on Failure Behavior of Composite Sandwich Plate

The Composite sandwich plate is made of two laminated face-sheets and one core material. Since such a kind of structure has many advantages, they have been widely used in structural manufacturing industry. However, when sandwich plates are impacted by transverse loadings, damages that are usually invisible would occur inside the sandwich plate and those damages would potentially reduce the structural safety. Therefore, it is necessary to elucidate the failure mechanism and how they affect the failure behaviors of sandwich structures for safety purpose. To this end, the present study is to investigate the impact failure behaviors of sandwich plates subjected to a rigid spherical impactor. Numerical simulation approach is carried out by finite element method. To predict the initial failure, several failure criteria to face-sheets and core material are proposed. In addition, to further simulate the progressive failure behaviors, a stiffness modification method is proposed and incorporated into the finite element software. The analytical results show that the local failure including fiber breakages, delamination, core cracking and plasticity is the main failure mechanism of cases studied. Furthermore, parametric study is also conducted and discussed in the paper.

Bending Analysis of SMA Embedded Rectangular Laminated Sandwich Plates with Soft Core Using 3D Finite Element Method

Nowadays Shape Memory Alloys (SMAs) are used as actuators in many applications such as aerospace structures. In sandwich structures, the SMA wires or plates are used in the skins for shape control of the structure or vibration damping. In this paper, bending behavior of sandwich plates with embedded SMA wires in their skins is studied. 3D finite element method is used for construction and analysis of the sandwich plate with a flexible core and two stiff skins. Some important points such as continuity conditions of the displacements, satisfaction of interlaminar transverse shear stresses, the conditions of zero transverse shear stresses on the upper and lower surfaces and in-plane and transverse flexibility of soft core are considered for accurate modeling and analysis of sandwich structures. Solution for bending analysis of sandwich plates under various transverse loads are presented and the effect of many parameters such as plate dimensions, loading conditions, material properties of core, skins and SMA wires are studied. Comparison of the present results in special case with those of the three-dimensional theory of elasticity and some plate theories confirms the accuracy of the proposed model.

딤플형 내부구조 금속 샌드위치 판재의 제작 및 정적 굽힘 실험

Metallic sandwich plates with various inner cores have important new features with not only ultra-light material characteristics and load bearing function but also multifunctional characteristics. Because of production possibility on the large scale and a good geometric precision, sandwich plates with inner dimpled shell structure from a single material have advantages as compared with other solid sandwich plates. Inner dimpled shell structures can be fabricated with press or roll forming process, and then bonded with two face sheets by multi-point resistance welding or adhesive bonding. Elasto-plastic bending behavior of sandwich plates have been predicted analytically and measured. The measurements have shown that elastic perfectly plastic approximation can be conveniently employed with less than 10% error in elastic stiffness, collapse load, and energy absorption. The dominant collapse modes are face buckling and bonding failure after yielding. Sandwich plates with inner dimpled shell structure can absorb more energy than other types of sandwich plates during the bending behavior.

Static and Nonlinear Impact Analyses of Free–Free Sandwich Plates on a Solid Half-space

In this study, an elastic model for static and nonlinear impact responses of a composite sandwich plate on an elastic half-space including the anti-plane core effect is developed. The effects of the elastic half-space and the anti-plane core are studied, and the contact force history and maximal deflection are predicted. Compared to the available analytical static analysis of rigid plates on a solid half-space and the numerical finite element modeling using LS-DYNA, the proposed theoretical method shows its validity and advantages in predicting the static and impact behaviors of sandwich plates sitting on a solid half-space. The predicted non-uniform distribution of transferred force under static load sheds new light on the understanding of force action mechanism between the sandwich system and the solid half-space. The two important impact factors (i.e., the maximal deflection and the peak contact force) provided by this study can be used to determine the damage size and position. Further, the semi-analytical model developed can be served as a basis for optimal design of fully backed sandwich collision protection systems, of which both minimizing the rebounded residual velocity of the projectile and keeping the underneath protected structures intact are important.

A triangular v. Kármán type finite element for sandwich plates with transversely compressible core

The present study is concerned with a new higher-order finite element for sandwich plates with transversely compressible core. The underlying plate theory is of the multilayer type, where the standard Kirchhoff–Love hypothesis is adopted for the face sheets whereas a second order displacement expansion is used for the core. Geometrical nonlinearities are included in the v. Kármán sense. Based on this plate theory, a triangular finite element with three nodes on each face sheet is developed. The element uses a discrete Kirchhoff approach for the face sheets and a simplified three-dimensional formulation for the core. The discretized nonlinear problem is solved by the Newton–Raphson method. Subsequently, the model is applied to the postbuckling analysis of different sandwich panels. It is observed that the local face wrinkling instability which is enabled by the transverse compressibility of the core has a significant effect on the overall behavior of sandwich plates.