Stress analysis of homogenized web-core sandwich beams

EPJ Web of Conferences, 2010

International Journal of Fatigue, 2007

Sandwich beams have been manufactured from AISI type 304 stainless steel faces and AL6XN pyramidal core, and subjected to both monotonic and cyclic three-point bending in order to assess their monotonic and cyclic strengths. Collapse mechanisms maps for monotonic loading, and fatigue maps for cyclic loading are constructed with the aid of simple analytical models for the competing failure modes. These maps serve as useful design guides, and take the sandwich beam geometry as axes. The construction of the maps takes as input independent measured values for the monotonic and cyclic strengths of the faces and of the pyramidal core. Good agreement is found between the predicted and observed failure modes and strengths for both the static and fatigue tests. In particular, S-N fatigue curves for core shear are obtained from single-lap shear tests and from three-point bending tests, and are in close agreement.

Research Journal of Applied Sciences, Engineering and Technology, 2019

Mechanical behaviors comparison of sandwich beams with diversified core material among epoxy, polyamide and wood, as well as, a solid steel beam was executed under a shear force, a concentrated load and a distributed load, with the attention that, the last two load types producing combined shear and bending stresses. Another mechanical behavior was considered where the static deflections from the specimens, especially the sandwich ones, have two contributor values provided from both bending and shear rigidities. A theoretical analysis and a numerical simulation were utilized for validation and comprehension purposes of the output results and conclusions. With taking into consideration, the comparison parameters that must be constant were the core thickness 10 mm, face thickness 3 mm, total thickness 16 mm, length 300 mm, width 20 mm and steel for faces material. The results conclude that employment of sandwich beam over a solid one with the same dimensions and vice versa, lead to a significant fluctuation in the object's mechanical behavior and weight, where the targeted result is high rigidity to weight ratio which provided by the sandwich beam. In other words, the specimen's flexural rigidity has a significant impact on its un-similar stresses' categories of shear stress, bending stress and these two stresses combined, as well as, its static deflection.

19th AIAA Applied Aerodynamics Conference, 2001

An elasticity solution is obtained for a sandwich beam with a functionally graded core subjected to transverse loads. The sandwich is subdivided into four elements, the top and bottom face-sheets, and top and bottom halves of the sandwich core. Euler-Bernoulli beam theory is used to model the face-sheets and plane elasticity equations are used to analyze the core. The

Composite Structures, 2001

A modi®ed zig-zag technical theory suitable for the accurate analysis of multi-layered composite beams accounting for the full 3D stress state has been recently developed by one of the authors [U. Icardi, A three-dimensional zig zag theory for analysis of thick laminated beams. In: Modern Trends in the Theory and Behavior of Structures Symposium ASME 1999 Summer Conference, Blacksburg, Virginia, USA, 27± 30 June 1999]. In order to satisfy the transverse shear and the transverse normal stress and stress gradient continuity requirements at the laminae interfaces through appropriate jumps in the strains, the theory features a piecewise third-order approximation for the in-plane displacement and a fourth-order approximation for the transverse displacement across the thickness. In the present paper, the capability of such a theory to predict the displacement and stress distribution across the thickness of sandwich beams is numerically assessed. This is done by comparing present estimates with the Pagano's elasticity solution [N.J. Pagano, J. Compos. Mater. 3 (1969) 398±411] for simply-supported, sandwich beams with cross-ply faces, loaded by a sinusoidally distributed transverse load. Additional results are presented that evidence the eects played by an enhanced core's deformability, or by stiening the faces. It is seen from the numerical results presented the need for including non-classical complicating eects, to accurately predict the stress and displacement distributions across the thickness, and even for the estimation of the overall response. These comprise modeling of the transverse normal strain and transverse shear deformation; ful®llment of the transverse shear stress and transverse normal stress and stress gradient continuity conditions at interfaces; modeling of the crosssection warping. The numerical results show a good predictive capability of the present model with using one sublaminate for each layer and for the core, except for the case of faces with drastically dierent elastic moduli, which require use of more sublaminates. Ó

2009

The thesis presents a theory for the bending of laser-welded web-core sandwich plates. The sandwich plate theory and homogenization are utilised, enabling a similar, fairly coarse, FE mesh to be used for design alternatives with different cross-sectional dimensions. This is considered to be beneficial during the design, when different alternatives should be evaluated. The thesis also studies the main factors that contribute to the total bending response of laser-welded webcore sandwich plates. The actual periodic structure is homogenized, giving equivalent stiffness properties for the sandwich plate. The differential equations for this homogenous sandwich plate, with thick face plates, consist of those for displacements of the well-known Reissner-Mindlin and Kirchoff plate theories. Therefore, the solution of these differential equations can be carried out using commercial Finite Element software. The periodic structure is reconsidered when the stress formulations are derived. The approach is validated with Finite Element calculations based on actual 3D topology. The rotation stiffness of the laser stake welded T-joint between the web and face plate is derived experimentally. This is considered to be important since the rotation stiffness affects the shear stiffness in the opposite direction to that of the web plate. An experimental procedure for the determination of the T-joint rotation stiffness is developed and validated. The mechanics of the T-joint are investigated with Finite Element analyses. The moment introduced by the web plate to the face plate is very important when deflections and normal stresses are considered. This moment is affected by the stiffnesses of the web plate and the T-joint. The deflections are significantly increased by a decrease in the web plate or T-joint rotation stiffness. The influence is greatest with cross-sections where the face plate thickness is large and the web plate spacing is small. Plates with a low aspect ratio under a uniform pressure load have the same maximum deflection, regardless of the T-joint rotation stiffness. Contrary to this, plates with a high aspect ratio or a patch load on a small area are very sensitive to rotation stiffness. The periodicity of the structure is found to have a significant influence on normal stresses in the face and web plates. Because of homogenization shear-induced, periodic, normal stresses vanish. In actual structures these stresses can be an order of magnitude higher than those induced by the bending moments of the sandwich plate. Therefore, the periodic structure as presented in this thesis should be taken into consideration when the normal stresses are calculated. Patch loads on a very small area can cause normal stresses even higher than those induced by shear. The web plate thickness is found to have a significant influence on stresses, but in the measured range of T-joint rotation stiffness values, the stresses are found to be unaffected.

Thin-walled Structures, 2015

This paper deals with the analytical and numerical studies of elastic buckling of a three-layered beam with metal foam core. Mechanical properties of the core are variable along the z-axis. There are two schemes of displacement of the faces and core of the beam: a broken line hypothesis and a non-linear hypothesis. The mathematical models for both types of displacements are presented. The governing differential equations of the sandwich beam are derived. Numerical analysis of sandwich beams is conducted in ANSYS environment. The finite elements analysis has been performed using a linear elastic buckling model. The analysis with constant and variable Young's modulus of the core of the beam is carried out. The values of the critical load obtained by the analytical and numerical (FEM) methods are compared.

Composite Structures, 1990

Sandwich beams containing cracks in the mid-plane of the core are investigated. The cracked part is subjected to a constant remote shear stress field. Beams with different cross-section geometries and materials were analyzed by the finite element method (FEM) in order to compute the stress intensity factors at the crack tips. An analytical approach for estimation of the energy release rate, based on a potential energy calculation, is presented that agrees well with results from the FE analyses. Results from four-point bending tests with cracked beams show that the fracture load can be accurately predicted. The simplicity of the analytical model makes it possible to compute critical crack lengths and safety factors for various types of sandwich beams. G = -a U/n. aa per unit width

AIP Conference Proceedings, 2015

The sandwich structure is known by inner and outer faces which acted compositely with relatively low strength core. Sandwich panel consisted of two thin and stiff skins and separated by a thick and lightweight core. The objective of this study to predict the behaviour of the laser-welded sandwich panel under three-point bending test. Numerical modelling of laserwelded was studied and run under bending loading. The sandwich panels were studied on a different number of the unit cell; 1-core, 2-core and 3-core. The role of a number of web-core to determine overall deformation and local failure response of the sandwich panel was studied. Faceplate and web plate were connected by using diode laser welding. The plates were cut by using sheet metal cutter machine for precise dimension. The sandwich panel modelled by using Abaqus 6.13 version to predict the response of the sandwich panel under bending loading. Cell wall buckling was found as an initial failure in the corrugated core system. The prediction result showed good agreement with experimental measurements.

2017

Sandwich structures are mainly used due to its low weight and high strength supporting compressive and flexural strengths, also showing excellent thermal insulation characteristics. Nowadays, sandwich beams are requested in many applications like aviation, missiles, boats and civil construction which demands an analytical method to predict its properties. It consists in a core rounded by a lamina or a laminate in both of your sides. Core's main function is to guarantee a high moment of inertia. The kinematic behavior of sandwich structures has been described based on formulations of laminated plate theories. This paper brings an analytical model for sandwich beams assisted by software, computed through Python algorithms. The software uses a database with properties and other pertinent information that serve as the basis for calculations. The user interface is user-friendly and allows calculations to be done more quickly and improves your experience. The analysis are based on classical laminate theory and Timoshenko plain beams deflection, since it attempts for the transversal shear displacement. As inputs, the program needs to be entered the core and laminate types, provided in its database, dimensions like height, breadth and length. As outputs, user obtains flexural rigidity of sandwich beam, core and face stresses, shear stresses, deflection and mass.