Nonlinear Response of a Shallow Sandwich Shell With Compressible Core to Blast Loading

2008 ◽  
Vol 75 (6) ◽  
Author(s):  
Renfu Li ◽  
George A. Kardomateas ◽  
George J. Simitses
Keyword(s):  
Shallow Shell ◽  
Laminated Composite ◽  
Blast Loading ◽  
Geometrical Parameters ◽  
Sandwich Shell ◽  
Nonlinear Dynamic Response ◽  
The Core ◽  
The Laplace Transform ◽  
The Face ◽  
Shallow Sandwich Shell

This paper investigates the nonlinear dynamic response of a shallow sandwich shell subject to blast loading with consideration of core compressibility. The shallow shell consists of two laminated composite or metallic face sheets and an orthotropic compressible core. Experimental results and finite element simulations in literature have shown that the core exhibits considerable compressibility when a sandwich panel is subjected to impulse loading. To address this issue properly in the analysis, a new nonlinear compressible core model is proposed in the current work. The system of governing equations is derived by means of Hamilton’s principle in combination with the Reissner–Hellinger’s variational principle. The analytical solution for the simply supported shallow shell is formulated using an extended Galerkin procedure combined with the Laplace transform. Numerical results are presented. These results demonstrate that this advanced sandwich model can capture the transient responses such as the stress shock wave effect and the differences in the transient behaviors of the face sheets and the core when a sandwich shadow shell is subjected to a blast loading. However, in the steady state dynamic stage, all the displacements of the face sheets and the core tend to be identical. This model can be further used to study the energy absorption ability of the core and the effects of different material and geometrical parameters on the behaviors of sandwich structures subject to blast loading.

Geometrical Nonlinear Effects in the Dynamic Response of Sandwich Beams

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Itay Odessa ◽  
Oded Rabinovitch ◽  
Yeoshua Frostig
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
High Order ◽  
Theory Approach ◽  
Nonlinear Frequency ◽  
Sandwich Beams ◽  
Nonlinear Dynamic Response ◽  
The Core ◽  
Geometrical Nonlinear ◽  
The Face

Abstract The geometrical nonlinear dynamic response of sandwich beams is studied using a dynamic high-order nonlinear model. The model is derived using the variational principle of virtual work and uses the Extended High-Order Sandwich Panel Theory approach with consideration of two interfaces between the three layers. A first-order shear deformation theory is adopted for the face sheets, while the kinematic assumption of high-order small deformations that account for out-of-plane compressibility are considered for the core layer. The nonlinearity of the dynamic model is introduced by considering geometrically nonlinear kinematic relations in the face sheets. The nonlinear kinematic relations and the dynamic modeling aim to evaluate the effects of the two features and their coupling on the response. The nonlinear dynamic response of sandwich beams is studied through two numerical cases and comparison of the nonlinear results with their linear counterparts. The first case looks into the coupling of the global geometrical nonlinear behavior with the dynamic behavior. The second case focuses on the local instability of the face sheets and its interaction with the compressibility of the core in the dynamic response of soft core sandwich beams. The comparison of linear and nonlinear dynamic response in the two cases sheds light on the coupling of the geometrical nonlinear and dynamic behaviors. Among other features, the latter is expressed by nonlinear attractors, higher modes response, nonlinear frequency response, and significant wrinkling response.

Free Vibration of Sandwich Flat Panels With Laminated Anisotropic Face Sheets

2001 ◽  
Author(s):  
Terry Hause ◽  
Liviu Librescu
Keyword(s):  
Free Vibration ◽  
Detailed Analysis ◽  
Material Properties ◽  
Fiber Orientation ◽  
Structural Model ◽  
Geometrical Parameters ◽  
Stacking Sequence ◽  
The Core ◽  
The Face ◽  
Advanced Model

Abstract A study of the effect of anisotropy of face-sheets and of other physical/geometrical parameters on eigenfrequency characteristics of flat sandwich panels is presented. The study is carried out in the context of an advanced model of sandwich structures. A detailed analysis of the influence of a large number of parameters associated with the panel geometry, fiber orientation and stacking sequence in the face sheets, and material properties of the core is accomplished, and pertinent conclusions are outlined. Validations of frequency predictions obtained within the present structural model against the few ones available in the specialized literature are accomplished, and excellent agreements are reported.

Dynamic Response Analysis of Square Honeycomb Sandwich Plates Subjected to Blast Loading

2013 ◽  
Vol 477-478 ◽  
pp. 160-164
Author(s):  
Lei Deng ◽  
An Wen Wang ◽  
Liu Wei Mao
Keyword(s):  
Dynamic Response ◽  
Relative Density ◽  
Sheet Thickness ◽  
Blast Loading ◽  
Response Analysis ◽  
Geometrical Parameters ◽  
Sandwich Plates ◽  
Finite Element Software ◽  
Honeycomb Sandwich ◽  
The Face

The dynamic response of the square honeycomb sandwich plates subjected to blast loading was simulated and analyzed by using the finite element software ABAQUS.With the given mass per unit area,core sheet spacing and height,the optimal relative density of the core was obtained under blast loading of three levels.With this optimal relative density,the sandwich plates have the best shock resistance ability and the top and bottom face sheets have the smallest deflection subjected to impulsive load.The sandwich plates were compared with the solid plates having the same mass per unit area.The results show that the sandwich plates have higher strength and energy absorption capability.Furthermore,influence of geometrical parameters including core sheet spacing,thickness,height and face sheet thickness on the face sheetss maximum deflection were discussed.

Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process

2017 ◽  
Vol 742 ◽  
pp. 317-324
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Manufacturing Process ◽  
Sandwich Structures ◽  
Bending Stiffness ◽  
Effective Density ◽  
Sandwich Composites ◽  
Open Cell ◽  
The Core ◽  
Bending Modulus ◽  
The Face ◽  
Spraying Process

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.

Devolution processes and the theory of historical development by S. Sanderson

2021 ◽  
pp. 72-77
Author(s):  
A.V. Verkhoturov ◽  
◽  
A.A. Obukhov
Keyword(s):  
Historical Development ◽  
World System ◽  
Human Society ◽  
Evolutionary Trend ◽  
The Core ◽  
The World ◽  
The Face ◽  
American Historian ◽  
Immanuel Wallerstein ◽  
Main Ideas

Analyzed is one of the most comprehensive modern approaches to the problem of the existence of evolution of human society as such and of specific human communities, i.e. “General Theory of Historical Development” by American historian and sociologist Stephen Sanderson. While agreeing, in general, with its main ideas, we believe that it is important to note that the issue of existence of individual communities demonstrating devolution (regression to an earlier historical state), stagnation or degeneration at certain historical stages is practically ignored in the framework of the theory under consideration. This creates its vulnerability in the face of specific empirical data, indicating a deviation from the evolutionary trend. We believe that overcoming this theoretical difficulty is possible in the process of comprehending the theory of S. Sanderson in the context of ideas of the world-system approach of Immanuel Wallerstein. We want to show that examples of devolution, stagnation and degeneration of societies do not deny general progressive evolutionary tendencies, characteristic for the world-system as a whole, but only indicate the transition of a particular society to a lower level within the world-system (from the core to the semi-periphery, or from the semi-periphery to the periphery).

Nonlinear dynamic response and vibration of imperfect eccentrically stiffened sandwich third-order shear deformable FGM cylindrical panels in thermal environments

2017 ◽  
Vol 21 (8) ◽  
pp. 2816-2845 ◽  
Author(s):  
Nguyen D Duc ◽  
Ngo Duc Tuan ◽  
Phuong Tran ◽  
Tran Q Quan ◽  
Nguyen Van Thanh
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Geometrical Nonlinearity ◽  
Cylindrical Panel ◽  
Geometrical Parameters ◽  
Third Order ◽  
Nonlinear Dynamic Response ◽  
Elastic Foundations ◽  
Thermal Environments ◽  
Cylindrical Panels

This study follows an analytical approach to investigate the nonlinear dynamic response and vibration of eccentrically stiffened sandwich functionally graded material (FGM) cylindrical panels with metal–ceramic layers on elastic foundations in thermal environments. It is assumed that the FGM cylindrical panel is reinforced by the eccentrically longitudinal and transversal stiffeners and subjected to mechanical and thermal loads. The material properties are assumed to be temperature dependent and graded in the thickness direction according to a simple power law distribution. Based on the Reddy’s third-order shear deformation shell theory, the motion and compatibility equations are derived taking into account geometrical nonlinearity and Pasternak-type elastic foundations. The outstanding feature of this study is that both FGM cylindrical panel and stiffeners are assumed to be deformed in the presence of temperature. Explicit relation of deflection–time curves and frequencies of FGM cylindrical panel are determined by applying stress function, Galerkin method and fourth-order Runge-Kutta method. The influences of material and geometrical parameters, elastic foundations and stiffeners on the nonlinear dynamic and vibration of the sandwich FGM panels are discussed in detail. The obtained results are validated by comparing with other results in the literature.

scholarly journals Public Space as a Venue for Peacebuilding in Lebanon? The Role of Civic Movements in Reclaiming Public Space in Beirut and Tripoli

2021 ◽  
pp. 25-46
Author(s):  
Aseel Naamani ◽  
Ruth Simpson
Keyword(s):  
Public Space ◽  
Public Life ◽  
Public Spaces ◽  
Urban Spaces ◽  
Building Relationships ◽  
The Core ◽  
The Face ◽  
History Of ◽  
Post War

The issue of public spaces is increasingly at the core of civic movements and discourse of reform in Lebanon, coming to the fore most recently in the mass protests of October 2019. Yet, these most recent movements build on years of activism and contestation, seeking to reclaim rights to access and engage with public spaces in the face of encroachments, mainly by the private sector. Urban spaces, including the country’s two biggest cities – Beirut and Tripoli – have been largely privatised and the preserve of an elite few, and post-war development has been marred with criticism of corruption and exclusivity. This article explores the history of public spaces in Beirut and Tripoli and the successive civic movements, which have sought to realise rights to public space. The article argues that reclaiming public space is central to reform and re-building relationships across divides after years of conflict. First, the article describes the evolution of Lebanon’s two main urban centres. Second, it moves to discuss the role of the consociational system in the partition and regulation of public space. Then it describes the various civic movements related to public space and examines the opportunities created by the October 2019 movement. Penultimately it interrogates the limits imposed by COVID-19 and recent crises. Lastly, it explores how placemaking and public space can contribute to peacebuilding and concludes that public spaces are essential to citizen relationships and inclusive participation in public life and affairs.

Free Vibration Analysis of Symmetric Sandwich Beams

2017 ◽  
Vol 872 ◽  
pp. 399-404
Author(s):  
Zakaria Ibnorachid ◽  
Khalid El Bikri ◽  
Lhoucine Boutahar
Keyword(s):  
Sandwich Beam ◽  
Free Vibration Analysis ◽  
Core Layer ◽  
Equation Of Motion ◽  
Geometrical Parameters ◽  
Symmetric Vibration ◽  
Materials Properties ◽  
The Core ◽  
Validation Of Results ◽  
Good Agreement

The aim of the present work is to study the linear free symmetric vibration of three-layer sandwich beam using the energy method. The zigzag model is used to describe the displacement field. The theoretical model is based on the top and bottom layers behave as Euler-Bernoulli beams while the core layer as a Timoshenko beam. Based on Hamilton’s principle, the governing equation of motion sandwich beam is obtained in order to calculate the linear frequency parameters. Two types of boundary conditions simple supported-simple-supported (SS-SS) and clamped-clamped (C-C) under the influence of materials properties and geometrical parameters are studied. The validation of results is done by comparing with another studies, which available in the literature and found good agreement between the studies.

Sign in / Sign up

Export Citation Format

Share Document