• 복합신소재구조학회 논문집
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• 제3권4호
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• pp.17-26
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• 2012

This study presents a governing equations of bending behavior of anisotropic sandwich plates with multi-layered laminated composite faces. Based on zig-zag models for through thickness deformations, the shear deformation of composite faces is included. All edges of plate are assumed to be simply supported. Results of the bending analysis under lateral loads are presented for the influence of various lay up sequences of antisymmetric angle-ply laminated faces. The accuracy of the approach is ascertained by comparing solutions from the sandwich plates theory with composite faces to the laminated plates theory. Since the present analysis considers the bending stiffness of the core and also the transverse shear deformations of the laminated faces, the proposed method showed higher than that calculated according to the general laminated plates theory. The information presented might be useful to design sandwich plates structure with polymer matrix composite faces.

• Steel and Composite Structures
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• 제21권3호
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• pp.461-477
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• 2016

Steel-concrete-steel (SCS) sandwich composite wall has been proposed for building and offshore constructions. An ultra-lightweight cement composite with density1380 kg/m3 and compressive strength up to 60 MPa is used as core material and inter-locking J-hook connectors are welded on the steel face plates to achieve the composite action. This paper presents the numerical models using nonlinear finite element analysis to investigate the load displacement behavior of SCS sandwich walls subjected to axial compression. The results obtained from finite element analysis are verified against the test results to establish its accuracy in predicting load-displacement curves, maximum resistance and failure modes of the sandwich walls. The studies show that the inter-locking J-hook connectors are subjected to tension force due to the lateral expansion of cement composite core under compression. This signifies the important role of the interlocking effect of J-hook connectors in preventing tensile separation of the steel face plates so that the local buckling of steel face plates is prevented.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.491-504
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• 2018

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton's principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

• Steel and Composite Structures
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• 제3권4호
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• pp.289-306
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• 2003

A series of tests was conducted to study the behaviour of steel-composite sandwich beams under low velocity hard impact. Damage characteristic and performance of sandwich beams with different spacing of shear connector were evaluated under impact loading. Thin steel plates were used as top and bottom skins of the sandwich beams and plain concrete was used as the core material. Shear connectors were provided by welding of angle sections on steel plates. The sandwich beams were impacted at their midpoint by a hemi-spherical nose shaped projectile dropped from various heights. Strains on steel plates were measured to study the effects of impact velocity or impact momentum on the performance of sandwich beams. Spacing of shear connectors is found to have significant effects on the impact response of the beams.

• Steel and Composite Structures
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• 제26권5호
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• pp.649-662
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• 2018

In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of two-dimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

• Structural Engineering and Mechanics
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• 제1권1호
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• pp.87-102
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• 1993

A $C^{\circ}$ continuous finite element formulation of a higher order displacement theory is presented for predicting linear and geometrically non-linear in the sense of von Karman transient responses of composite and sandwich plates. The displacement model accounts for non-linear cubic variation of tangential displacement components through the thickness of the laminate and the theory requires no shear correction coefficients. In the time domain, the explicit central difference integrator is used in conjunction with the special mass matrix diagonalization scheme which conserves the total mass of the element and included effects due to rotary inertia terms. The parametric effects of the time step, finite element mesh, lamination scheme and orthotropy on the linear and geometrically non-linear responses are investigated. Numerical results for central transverse deflection, stresses and stress resultants are presented for square/rectangular composite and sandwich plates under various boundary conditions and loadings and these are compared with the results from other sources. Some new results are also tabulated for future reference.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.224-227
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• 2001

Adaptive analysis of multilayered composite and sandwich plates is carried out. The adaptive analysis is based on a finite element error form, which measures the difference between the through-the-thickness distribution of finite element displacement and the actual displacement. The region where the error-measure exceeds the prescribed admitted error value, the finite element mesh locally refined in the thickness direction using the mesh superposition technique. Several numerical tests are conducted to validate the effectiveness of the current approach for adaptive analysis of laminated plates.

• 한국강구조학회 논문집
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• 제12권6호
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• pp.749-758
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• 2000

본 연구는 지그재그모델에 근거하여 두꺼운 금속, 폴리머 복합재료 면재의 전단변형 효과를 고려해서 샌드위치평판의 휨해석 지배방정식을 유도하였으며, 판의 네 변은 단순지지 되어 있다고 가정하였다. 역대칭 적층면재의 화이버 각도와 면재의 적층수를 변화시켜가며 휨해석의 결과를 나타내었다. 해석방법의 정확성을 위해 일반 적층판이론의 값과 비교를 하여 검증을 하였다. 그 결과 적층판이론으로 구한 값보다 처짐에 있어서 더 큰 값을 나타냄을 알 수 있었는데, 그 이유로는 본 해석방법이 면재, 심재 모두 휨강성과 전단변형을 고려하였기 때문이라 사료된다. 강재, 폴리머 복합면재를 갖는 샌드위치평판을 설계할 때 제시된 정보를 유용하게 이용될 수 있을 것이다.

• Steel and Composite Structures
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• 제45권5호
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• pp.767-774
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• 2022

A geometrically nonlinear stability analysis of sandwich annular plates with cellular core and particle-reinforced composite layers has been performed in the present research. The particles are powders of graphene oxide (GOP) which act as nanoscale filler of epoxy matrix. To this regard, Halpin-Tsai micromechanical scheme has been used to define the material properties of the layers. A square shaped core has been considered for which the material properties have been defined based on the relative density concept. Large deflection theory of thin shells has been selected to develop the complete formulation of sandwich plate. The geometrically nonlinear stability analysis of sandwich annular plates has been carried out by indicating that the buckling load is dependent on particle amount, thickness of layer and core relative density.

• Steel and Composite Structures
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• 제32권5호
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• pp.633-642
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• 2019

In this work, lightweight sandwich plates consisting of a functionally graded porous (FGP) core and two laminated composite face sheets resting on elastic foundation have been proposed. Three different profiles are considered for the distributions of porosities along core thickness. The main aim of this paper is the investigation of the buckling behavior of the proposed porous sandwich plates (PSPs) by reporting their critical mechanical loads and their corresponding mode shapes. A finite element method (FEM) based on first order shear deformation theories (FSDT) is developed to discretize governing equations for the buckling behavior of the proposed sandwich plates. The effects of porosity dispersion and volume, the numbers and angles of laminated layers, sandwich plate geometrical dimensions, elastic foundation coefficients, loading and boundary conditions are studied. The results show that the use of FGP core can offer a PSP with half weight core and only 5% reduction in critical buckling loads. Moreover, stacking sequences with only ${\pm}45$ orientation fibers offer the highest values of buckling loads.