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.

Structural-Acoustic Optimization of Sandwich Panels

2006 ◽  
Vol 129 (3) ◽  
pp. 330-340 ◽  
Author(s):  
Francesco Franco ◽  
Kenneth A. Cunefare ◽  
Massimo Ruzzene
Keyword(s):  
Composite Structures ◽  
Sandwich Panels ◽  
Structural Elements ◽  
Acoustic Response ◽  
Truss Core ◽  
Design Flexibility ◽  
Radiated Sound ◽  
Optimal Configurations ◽  
Selection Of ◽  
Radiated Sound Power

Sandwich panels comprising face sheets enclosing a core are increasingly common structural elements in a variety of applications, including aircraft fuselages, flight surfaces, vehicle panels, lightweight enclosures, and bulkheads. This paper presents the optimization of various innovative sandwich configurations for minimization of their structural-acoustic response. Laminated face sheets and core geometries comprising honeycomb and trusslike structures are considered. The design flexibility associated with the class of considered composite structures and with truss-core configurations provides the opportunity of tailoring the structure to the load and dynamic response requirements of a particular application. The results demonstrate how the proper selection of selected key parameters can achieve effective reduction of the radiated sound power and how the identified optimal configurations can achieve noise reduction over different frequency ranges and for various source configurations.

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.

scholarly journals Honeycomb Composite Structures of Aluminum: Aerospace Applications

2019 ◽  
Author(s):  
D.L. Majid ◽  
Nor Hafizah Manan ◽  
Yee Ling Chok
Keyword(s):  
Composite Structure ◽  
Composite Structures ◽  
Sandwich Structure ◽  
Design Criterion ◽  
Specific Strength ◽  
The Core ◽  
Aerospace Applications ◽  
The Face ◽  
Aluminum Honeycomb ◽  
Strength And Stiffness

A honeycomb composite structure is usually composed of a lightweight hexagonal core sandwiched between two thin face sheets that are adhesively joined. Both the core and the face sheets can be combinations of many types of materials depending on the application. In this article, an overview of the design and manufacturing process of aluminum honeycomb composite structures particularly for aerospace application is presented. Aluminum honeycomb composite structures are lightweight constructions with high specific strength and stiffness that are applied mainly in the aerospace industry. An aluminum honeycomb panel is typically made up of the secondary structural components and interiors of an aircraft such as the wing skin, trailing edge, control surface, flooring, partitions, aircraft galleys, and overhead bins, to name a few. Other applications are in the spacecraft, helicopter, missile, and satellite. Owing to its honeycomb design peculiar to the hexagonal beehives, it can reach more than 30 times higher in stiffness and 10 times higher in flexural strength compared to its solid counterpart of the same weight. The mechanical properties of the honeycomb composite structure hinge on the materials of the core and face sheets, the core geometries, and the thickness of the face sheets. Designed for superior flexural and shear loading, the selection of the optimal honeycomb design will depend on the application requirements. The principal design criterion of a sandwich structure in aerospace applications is weight saving, and there is a trade-off between performance and cost. In terms of manufacturing of the honeycomb composite sandwich structure, the two main processes are the expansion process commonly used for low-density cores and the corrugation process for higher density cores.

Finite element buckling analysis of laminated composite sandwich panels with transversely flexible core carrying attached elastic strip

2012 ◽  
Vol 14 (6) ◽  
pp. 715-733
Author(s):  
Karamat Malekzadeh Fard ◽  
Alireza Sayyidmousavi ◽  
Zouheir Fawaz ◽  
Habiba Bougherara
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Sandwich Panels ◽  
Element Model ◽  
Attached Mass ◽  
Element Analysis ◽  
The Core ◽  
The Face

In this article, a three-dimensional finite element model is proposed to study the effect of distributed attached mass with thickness and stiffness on the buckling instability of sandwich panels with transversely flexible cores. Unlike the previous works in the literature which have made use of unified displacement theories, the present model uses different types of finite elements to model the core and the face sheets. It utilizes shell elements for the face sheets and three-dimensional solid elements for the core which enables the model to account for the transverse flexibility of the structure. The motions of the face sheets and the core as well as the attached mass are related through defining constraint equations between the nodes of their respective finite elements based on the concept of master and slave nodes which is incorporated into the finite element analysis program ANSYS through a user-defined subroutine. The validated finite element model is then used to study the effects of size, thickness, material property, aspect ratio, and the position of the attached mass on the buckling load of a sandwich panel under different combinations of boundary conditions. The results presented in this study have hitherto not been reported in the literature.

Specific bending stiffness of in-mould-assembled hybrid sandwich structures with carbon fibre reinforced polymer face sheets and aluminium foam cores manufactured by a polyurethane-spraying process

2017 ◽  
Vol 21 (8) ◽  
pp. 2779-2800 ◽  
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay A Weidenmann
Keyword(s):  
Carbon Fibre ◽  
Sandwich Panels ◽  
Aluminium Foam ◽  
Face Sheet ◽  
The Core ◽  
Four Point Bending ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
The Face ◽  
Fibre Reinforced Polymer

In this paper, the bending stiffness-to-weight-ratio of novel hybrid sandwich structures is investigated. The build-up of the sandwich panels consisted of face sheets made from carbon fibre reinforced polymer, aluminium foam cores and an interface of foamed polyurethane. The sandwich panels were produced in a single step, infiltrating the face sheet fibres and connecting the face sheets to the core simultaneously. By means of mechanical characterization, specimens with several variations of face sheet architecture and thickness, core structure and interface properties were examined. Quasi-static four-point bending and flatwise compression tests of the sandwich composites were conducted, as well as tensile tests of the face sheets. The results of the tensile and compressive tests were integrated in analytical models, describing the sandwich stiffness depending on the load case and the face sheet volume fraction. The effective Young’s modulus of the composite, measured in the four-point bending test, correlates well to the modelled effective bending modulus calculated from the single components face sheet and core. The model underestimates the effective density of the bending specimens. It could be shown that this underestimation results from the polyurethane foam connecting the face sheets to the core, as the mass of this polyurethane is not included in the model.

Effective Design Analysis of Fixture Development for Stitching a Sandwich Panels in an Aerospace Application

2014 ◽  
Vol 592-594 ◽  
pp. 1055-1059 ◽  
Author(s):  
R. Santhanakrishnan ◽  
Darius Stanley ◽  
Thangavel Sanjeeviraja ◽  
A. Joseph Stanley
Keyword(s):  
Composite Structures ◽  
Sandwich Panels ◽  
Sheet Thickness ◽  
Shear Stiffness ◽  
Foam Structure ◽  
Aerospace Application ◽  
Low Weight ◽  
Structural Applications ◽  
The Face ◽  
Effective Design

In recent years, sandwich structures have been considered as viable engineering constructions. The use of composite structures in aerospace and civil structural applications have been increasing especially due to their extremely low weight that leads to reduction in the total weight , high flexural and corrosion resistance in addition to higher transverse shear stiffness. Various combinations of core and face sheet thickness have been evaluated by many researchers worldwide. This study evaluates the aspects of putting the face sheets and core together through stitching and studies the effects and effectiveness of stitching. This paper mainly deals with design of fixture used to stitching sandwich panels, which helps to stitch different file orientations such as 900, 450, 900/450/900and 900/450. Keywords: Sandwich Panels, Composite Materials, Design of Fixture, Stitching panels, and Stitched Foam Structure

Finite element modelling of sandwich panels with graded core under various boundary conditions

2012 ◽  
Vol 116 (1186) ◽  
pp. 1289-1314 ◽  
Author(s):  
M. Kashtalyan ◽  
B. Woodward
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Sandwich Panels ◽  
Stress Concentrations ◽  
Displacement Fields ◽  
Various Boundary Conditions ◽  
The Core ◽  
The Face ◽  
3D Elasticity ◽  
3D Finite Element Method

Abstract Sandwich panels are widely used in the aerospace industry instead of solid plates due to their high flexural stiffness-to-weight and flexural strength-to-weight ratios. However due to the mismatch of properties between the face sheets and the core, stress concentrations can occur at the face sheet/core interfaces, often leading to delamination. One possible solution to this problem is the introduction of a graded core — a core in which the properties vary gradually from the face sheets to the core centre, eliminating any abrupt changes in properties. In this paper a 3D finite element method, fully validated through comparison with results from the literature and a 3D elasticity solution, is applied to modelling of sandwich panels with graded core. The approach makes use of graded elements to study the effect of varying the boundary conditions on the elastic deformation of the panel subject to uniformly distributed loading. Comparative analysis of stress and displacement fields in sandwich panels with homogeneous and graded cores is carried out under various combinations of simply supported, clamped and free edges.

Nonlinear thermo-mechanical behaviour of soft core sandwich panels – Creep effects

2018 ◽  
Vol 22 (8) ◽  
pp. 2629-2654
Author(s):  
Ehab Hamed ◽  
Yeoshua Frostig
Keyword(s):  
Sandwich Panels ◽  
Maxwell Model ◽  
Core Material ◽  
Internal Stresses ◽  
Structural Behaviour ◽  
Principle Of Superposition ◽  
The Core ◽  
Generalized Maxwell Model ◽  
The Face ◽  
Incremental Step

Sandwich panels can be subjected to significant changes in ambient temperature, which develop and sustain over certain time periods and lead to creep of the core material, and consequently to changes in the internal stresses and deformations with time. This paper deals with this issue with focus on the geometrically nonlinear aspects of structural behaviour. A theoretical model is developed, which combines the concepts of the principle of superposition of viscoelasticity, with the high-order sandwich theory (HSAPT), and the temperature dependency of the viscoelastic material properties. The nonlinear HSAPT formulation accounts for the deformability of the core in shear and through its thickness and it is based on large displacement kinematics of the face sheets. The convolution integral of viscoelasticity is converted into a rheological generalized Maxwell model after the expansion of the relaxation moduli into Prony series with temperature-dependence terms, which enables the solution of the governing equations through an incremental step-by-step time analysis without the need to store the response history. The capabilities of the model are demonstrated through numerical examples. It is shown that the creep of the core material can lead to bifurcation buckling of the sandwich panel under sustained temperatures that are smaller than the critical temperature obtained under an instantaneous increase of temperature.

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