Implication of Nonclassical Effects on Dynamic Response of Sandwich Structures Exposed to Underwater and In-Air Explosions

2007 ◽  
Vol 51 (02) ◽  
pp. 83-93
Author(s):  
Liviu Librescu ◽  
Sang-Yong Oh ◽  
Jorg Hohe
Keyword(s):  
Dynamic Response ◽  
Structural Model ◽  
Sandwich Structures ◽  
Damping Ratio ◽  
Sandwich Panels ◽  
Geometric Imperfection ◽  
The Core ◽  
The Face ◽  
Time Histories ◽  
Global And Local

A study devoted to the dynamic response of sandwich panels to underwater and in-air explosions is presented. The study is carried out in the context of a geometrically nonlinear model of sandwich structures featuring anisotropic laminated face sheets and a transversely compressible orthotropic core. The unsteady pressure generated by the explosion and acting on the face of the sandwich panel includes the effect of the pressure wave transmission through the core. Its implications on the structural time-histories as corresponding to the underwater and in-air explosions are put into evidence. The effects of the transverse core compressibility on dynamic response are highlighted. In this sense, one of its major implications is the possibility to capture interactively the global and local (wrinkling) dynamic response of the panel. It is shown that implementation of the structural tailoring technique in the face sheets can constitute an important mechanism for enhancing the dynamic load-carrying capacity of sandwich panels when exposed to blast pulses. Effects of the core, the composite architecture of face sheets, orthotropy of the material of the core, geometrical non-linearities, initial geometric imperfection, and the damping ratio are investigated, and their implications for the dynamic response are highlighted. The comprehensive structural model considered in conjunction with the time-dependent loads generated by the underwater and in-air explosions, and the results obtained in this context, are expected to contribute to a better understanding of the response behavior and to be instrumental toward a better design of these structures.

Dynamic Response of Sandwich Anisotropic Flat Panels to Explosive Pressure Pulses

2001 ◽  
Author(s):  
Terry Hause ◽  
Liviu Librescu
Keyword(s):  
Dynamic Response ◽  
Detailed Analysis ◽  
Fiber Orientation ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Core Layer ◽  
Time Dependent ◽  
Pressure Pulses ◽  
The Face ◽  
Advanced Model

Abstract This paper addresses the problem of the dynamic response in bending of flat sandwich panels exposed to time-dependent external pulses. The study is carried out in the context of an advanced model of sandwich structures that is characterized by anisotropic laminated face sheets and an orthotropic core layer. A detailed analysis of the influence of a large number of parameters associated with the particular type of pressure pulses, panel geometry, fiber orientation in the face sheets and, presence of tensile uni/biaxial edge loads is accomplished, and pertinent conclusions are outlined.

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.

scholarly journals Research on the Weld Position Detection Method for Sandwich Structures from Face-Panel Side Based on Backscattered X-ray

Sensors ◽  
2019 ◽  
Vol 19 (14) ◽  
pp. 3198 ◽  
Author(s):  
Angang Wei ◽  
Baohua Chang ◽  
Boce Xue ◽  
Guodong Peng ◽  
Dong Du ◽  
...  
Keyword(s):  
Detection Method ◽  
Sandwich Structures ◽  
Detection System ◽  
High Reliability ◽  
Sandwich Panels ◽  
Experimental System ◽  
Maximum Absolute Error ◽  
X Ray ◽  
Position Detection ◽  
The Face

Web-core sandwich panels are a typical lightweight structure utilized in a variety of fields, such as naval, aviation, aerospace, etc. Welding is considered as an effective process to join the face panel to the core panel from the face panel side. However, it is difficult to locate the joint position (i.e., the position of core panel) due to the shielding of the face panel. This paper studies a weld position detection method based on X-ray from the face panel side for aluminum web-core sandwich panels used in aviation and naval structures. First, an experimental system was designed for weld position detection, able to quickly acquire the X-ray intensity signal backscattered by the specimen. An effective signal processing method was developed to accurately extract the characteristic value of X-ray intensity signals representing the center of the joint. Secondly, an analytical model was established to calculate and optimize the detection parameters required for detection of the weld position of a given specimen by analyzing the relationship between the backscattered X-ray intensity signal detected by the detector and the parameters of the detection system and specimen during the detection process. Finally, several experiments were carried out on a 6061 aluminum alloy specimen with a thickness of 3 mm. The experimental results demonstrate that the maximum absolute error of the detection was 0.340 mm, which is sufficiently accurate for locating the position of the joint. This paper aims to provide the technical basis for the automatic tracking of weld joints from the face panel side, required for the high-reliability manufacturing of curved sandwich structures.

Structural-Acoustic Optimization of Sandwich Panels

2005 ◽  
Author(s):  
Francesco Franco ◽  
Kenneth A. Cunefare ◽  
Massimo Ruzzene
Keyword(s):  
Numerical Optimization ◽  
Composite Structures ◽  
Gradient Methods ◽  
Sandwich Panels ◽  
Relative Importance ◽  
Structural Elements ◽  
Acoustic Response ◽  
The Core ◽  
Design Flexibility ◽  
The Face

Sandwich panels, comprising face sheets enclosing a core, are increasingly common structural elements in a variety of applications, including aircraft fuselages and flight surfaces, vehicle panels, lightweight enclosures, and bulkheads. The design flexibility associated with such composite structures provides significant opportunities for tailoring the structure to the load and dynamic response requirements for the particular application. Design flexibility encompasses the details of the face sheets and the core. This paper deals with the numerical optimization of different sandwich configurations for the purposes of achieving reduced structural acoustic response. Laminated face sheets and core geometries, comprising honeycomb and truss-like structures, are considered. The relative importance of the mass and stiffening properties of the core and face sheets are discussed. The optimization work is carried out using commercial codes. Benefits and limits of using an optimization algorithm based on gradient methods are highlighted.

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.

Dynamic Response and Damage Mechanism of Two-Core Composite Sandwich Panels under Low-Velocity Impact

2013 ◽  
Vol 405-408 ◽  
pp. 2810-2814
Author(s):  
Chang Liang Li ◽  
Da Zhi Jiang ◽  
Jing Cheng Zeng ◽  
Su Li Xing
Keyword(s):  
Dynamic Response ◽  
Contact Force ◽  
Impact Energy ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Damage Mechanism ◽  
The Other ◽  
Foam Core ◽  
Transverse Impact ◽  
Low Velocity

Dynamic response and damage mechanism of two-core sandwich panels with foam and honeycomb cores and glass fiber/epoxy composite sheets under low-velocity transverse impact are investigated. The emphasis is focused on the contact force response and crash mechanism of the two-core sandwich panels. Effects of configurations, impact energy levels and types of the cores on the dynamic response are investigated. A modified drop-test experiment is carried out to obtain contact force history of the two-core sandwich structures under different impact energies. The experimental results show that the 10:10 configurations for both honeycomb and foam core sandwich structures under lower impact energy absorb more impact energy than the other two structures. However, under higher impact energy, the honeycomb core sandwich structures of 15:5 configuration absorbs a little more impact energy than the other two, while for the foam core sandwich structures the 5:15 configuration shows a little better impact resistance. Results also show that when impact energy is low foam core sandwich structures do better in absorbing impact energy than the honeycomb ones.

Dynamic Response of Sandwich Panels With a Flexible Core Under Simultaneous Low-Velocity Impacts of Multiple Small Masses

2006 ◽  
Author(s):  
K. Malekzadeh ◽  
M. R. Khalili
Keyword(s):  
Dynamic Response ◽  
Plate Theory ◽  
Sandwich Panels ◽  
Shear Deformation Theory ◽  
Core Layer ◽  
Contact Forces ◽  
Low Velocity ◽  
The Face ◽  
The Impact ◽  
Flexible Core

Dynamic response of sandwich panels with a flexible core under simultaneous low-velocity impacts of multiple small masses has investigated in this paper. The contact forces between the panel and the impactors are treated as the internal forces of the system. Shear deformation theory is used for the face sheets while three dimensional elasticity is used for the soft core. The fully dynamic effects of the core layer and the face-sheets are considered in this study. The results in multiple mass impacts over sandwich panels are presented based on proposed improved higher-order sandwich plate theory (IHSAPT). As no literature could be found on the impact of multiple impactors over sandwich panels, the present formulation is validated indirectly by comparing the response of two cases of double small masses and single small mass impacts based on Olsson’s wave control principle.

Experimental Investigation of the Shear Cutting Behaviour of Sandwich Panels

2015 ◽  
Vol 825-826 ◽  
pp. 433-440 ◽  
Author(s):  
Philipp Stein ◽  
David Übelacker ◽  
Dirk Holke ◽  
Peter Groche
Keyword(s):  
Cutting Force ◽  
Sandwich Panels ◽  
Sheet Thickness ◽  
Cutting Parameters ◽  
Core Material ◽  
Burr Formation ◽  
Exhaust Emission ◽  
The Core ◽  
Design Engineers ◽  
The Face

Continually increasing exhaust emission standards for automobiles and an increasing environmental awareness push design engineers to develop new constructive and material concepts. So-called sandwich panels, consisting of stiff facings and light-weight cores, offer the possibility to combine properties of different materials synergistically. When processing large quantities, as is the case in the automotive industry commonly used manufacturing processes for cutting sandwich panels, like sawing or milling, are not applicable. A common manufacturing process to cut metal sheets in high quantities is shear cutting. However, pre-trials of shear cutting of sandwich panels have shown that it is not possible to achieve flawless cutting surfaces with current process layouts. Characteristic types of failure like high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material were ascertained. Thus, in this study, the influence of cutting parameters, such as the clearance and the punch diameter, on these types of failure is examined. Five different clearances between 0.025 mm and 0.4 mm with two punch diameters, 8 mm and 32 mm, were investigated. In order to compare the influence of different materials, three commercially available sandwich panels were studied. The chosen sandwich panels differ both in the face sheet thickness and the core material. Finally, the shear cutting force is measured to identify a possible correlation between the cutting force and the face bending. As a result, optimal clearances to minimize the face bending are derived. Additionally, the influence of the core stiffness on the cutting force is determined.

Implication of Anisotropy of Face-Sheets and Core Layer Materials on the Load Carrying Capacity of Advanced Sandwich Panels: Linear and Nonlinear Responses

2000 ◽  
Author(s):  
Liviu Librescu
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structure ◽  
Sandwich Panels ◽  
Core Layer ◽  
Anisotropic Materials ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying ◽  
The Face ◽  
Sandwich Shells

Abstract This paper deals with a comprehensive geometrically nonlinear theory of shallow sandwich shells that includes also the effect of the initial geometric imperfections. It is assumed that the face-sheets of the sandwich structure are built-up from anisotropic materials layers, whereas the core layer from an orthotropic material. As a result of its features the structural model can provide important information related to the load carrying capacity of sandwich structures in the pre- and postbuckling ranges. Moreover, by using the directionality properties of face-sheets materials, possibilities of enhancing the load carrying capacity of sandwich shells/plates are reached. Selected numerical illustrations emphasizing these features are presented and pertinent conclusions on the beneficial implications of anisotropy of face-sheets and core layer materials upon the load-carrying capacity of sandwich panels are emphasized. Under the present study, the sandwich structure consists of a thick core-layer bonded by the face-sheets that consist of composite anisotropic materials, symmetrically laminated with respect to the mid-surface of the core-layer. The initial geometric imperfection consisting of a stress free initial transversal deflection, will be also incorporated in the study. The loads under which the nonlinear response will be analyzed consist basically of uniaxial/biaxial compressive edge and lateral loads.

Failure mode maps for four-point-bending of hybrid sandwich structures with carbon fiber reinforced plastic face sheets and aluminum foam cores manufactured by a polyurethane spraying process

2017 ◽  
Vol 21 (8) ◽  
pp. 2654-2679 ◽  
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay A Weidenmann
Keyword(s):  
Carbon Fiber ◽  
Failure Mode ◽  
Aluminum Foam ◽  
Failure Modes ◽  
Sandwich Panels ◽  
Bending Tests ◽  
The Core ◽  
Four Point Bending ◽  
The Face ◽  
Spraying Process

This work focuses on failure mode maps of sandwich panels exposed to bending load, which were produced using a polyurethane spraying process. This process allows for an automated production of sandwich panels omitting a separate bonding step of the face sheets to the core. The investigated sandwich panels consisted of carbon fiber reinforced face sheets in various configurations, and four different core structures of aluminum foam or Nomex honeycomb. After production, measurements of the pores inside the core foam structures, the fiber package thickness inside the face sheets, and the density homogeneity of the core structure were made using X-ray computed tomography. The failure mode maps were based on the individual mechanical properties of the face sheets and the core, determined by mechanical testing. The critical forces determining the failure modes were partially modified to fit the application on foam core structures and face sheets with a porous matrix. The verification of the failure modes was performed with four-point bending tests. Since all tested configurations of sandwich specimens were produced using the same process route, the applied models for the creation of the failure mode maps could be verified for numerous parameter combinations. Except for two parameters with inconstant properties, the failure modes determined by the failure mode maps matched the observed failure modes determined by the bending tests.

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