Sandwich panel

Abstract: Periodic cellular metals with honeycomb and corrugated topologies are widely used for the cores of light weight sandwich panel structures. Honeycombs have closed cell pores and are well suited for thermal protection while also providing efficient load support. Corrugated core structures provide less efficient and highly anisotropic load support, but enable cross flow heat exchange opportunities because their pores are continuous in one direction. Recent advances in topology design and fabrication have led to the emergence of lattice truss structures with open cell structures. These three classes of periodic cellular metals can now be fabricated from a wide variety of structural alloys. Many topologies are found to provide adequate stiffness and strength for structural load support when configured as the cores of sandwich panels. Sandwich panels with core relative densities of 2-10% and cell sizes in the millimetre range are being assessed for use as multifunctional structures. The open, three-dimensional interconnected pore networks of lattice truss topologies provide opportunities for simultaneously supporting high stresses while also enabling cross flow heat exchange. These highly compressible structures also provide opportunities for the mitigation of high intensity dynamic loads created by impacts and shock waves in air or water. By filling the voids with polymers and hard ceramics, these structures have also been found to offer significant resistance to penetration by projectiles.

Abstract: SANDWICH STRUCTURES: ORIGINS, ADVANTAGES, AND USES Description of Various Sandwich Constructions Advantages of Sandwich Construction over Construction Monocoque Thin Walled Construction Origins of Sandwich Construction Uses of Sandwich Construction Present Approach to Analysis Problems References ANISTROPIC ELASTICITY AND COMPOSITE LAMINATE THEORY Introduction Derivation of the Anisotropic Elastic Stiffness and Compliance Matrices The Physical Meaning of the Components of the Orthotropic Elasticity Tensor Methods to Obtain Composite Elastic Properties from Fiber and Matrix Properties Thermal and Hygrothermal Considerations Time-Temperature Effects on Composite Materials High Strain Rate Effects on Material Properties Laminae of Composite Materials Laminate Analysis [A], [B], and [D] Stiffness Matrices for a Mid-Plane Symmetric Sandwich Structure Piezoelectric Effects Problems References DERIVATION OF THE GOVERNING EQUATIONS FOR SANDWICH PLATES (PANELS) Introduction Plate Equilibrium Equations The Bending of Composite Material Laminated and/or Sandwich Plates: Classical Theory Classical Plate Theory Boundary Conditions Analysis of Composite Materials Laminated and/or Sandwich Panels Including Transverse Shear Deformation Effects Boundary Conditions for a Plate Using the Refined Plate Theory Laminated or Sandwich Plate on an Elastic Foundation Laminated or Sandwich Plates Subjected to Dynamic Loads Problems References BEAMS, COLUMNS, AND RODS OF COMPOSITE MATERIALS Development of Classical Beam Theory Some Simplified Sandwich-Beam Solutions Eigenvalue Problems of Sandwich Beams: Natural Vibrations and Elastic Stability Other Considerations Problems References ENERGY METHODS FOR SANDWICH STRUCTURES Introduction Theorem of Minimum Potential Energy Analysis of a Beam in Bending Using the Theorem of Minimum Potential Energy Reissner's Variational Theorem and Its Applications Static Deformation of Moderately Thick Beams Flexural Vibrations of Moderately Thick Beams Flexural Natural Frequencies of a Simply Supported Beam Including Transverse Shear Deformation and Rotatory Inertia Effects Minimum Potential Energy for Rectangular Plates A Rectangular Composite Material Plate Subjected to Lateral and Hygrothermal Loads In-Plane Shear Strength Determination of Composite Materials in Laminated and Sandwich Panels Problems References SOLUTIONS FOR RECTANGULAR SANDWICH PLATES Introduction Navier Solutions for Rectangular Sandwich Plates Levy Solutions for Plates of Composite Materials Perturbation Solutions for the Bending of a Composite Material Sandwich Plate, with Mid-Plane Symmetry and No Bending-Twisting Coupling Isotropic Sandwich Panels Subjected to a Uniform Lateral Load Minimum Weight Optimization for a Sandwich Panel Subjected to a Distributed Lateral Load Analysis of an Isotropic Sandwich Plate on an Elastic Foundation Subjected to a Uniform Lateral Load Static Analysis of Sandwich Plates of Composite Materials Including Transverse Shear Deformation Effects Exact Solution Other Considerations Problems References DYNAMIC EFFECTS ON SANDWICH PANELS Introduction Natural Flexural Vibrations of Sandwich Plates: Classical Theory Natural Flexural Vibrations of Sandwich Plates Including Transverse Shear Deformation Effects Forced-Vibration Response of a Sandwich Plate Subjected to a Dynamic Lateral Load Dynamic Response of Sandwich Plates to Localized Loads Large Amplitude Nonlinear Oscillations of Sandwich Plates Simply Supported on All Edges Linear and Nonlinear Oscillations of Specially Orthotropic Sandwich Panels with Various Boundary Conditions Vibration Damping Problems References THERMAL AND MOISTURE EFFECTS ON SANDWICH STRUCTURES General Considerations Derivation of the Governing Equations for a Thermoplastic Isotropic Plate Boundary Conditions General Treatment of Plate Nonhomogeneous Boundary Conditions Thermoelastic Effects on Beams Self-Equilibrium of Thermal Stress Rectangular Composite Material Plate Subjected to Lateral and Hygrothermal Loads References ELASTIC INSTABILITY (BUCKLING) OF SANDWICH PANELS General Considerations The Buckling of an Orthotropic Sandwich Plate Subjected to In-Plane Loads Classical Theory Elastic Stability of a Composite Sandwich Panel Including Transverse Shear Deformation and Hygrothermal Effects The Buckling of an Isotropic Plate on an Elastic Foundation Subjected to Biaxial In-Plane Compressive Loads The Buckling of Honeycomb Core Sandwich Panels Subjected to In-Plane Compressive Loads The Buckling of Solid- or Foam-Core Sandwich Panels Subjected to In-Plane Compressive Loads Buckling of a Truss-Core Sandwich Panel Subjected to Uniaxial Compression Elastic Stability of a Web-Core Sandwich Panel Subjected to a Uniaxial Compressive In-Plane Load Buckling of Honeycomb-Core Sandwich Panels Subjected to In-Plane Shear Loads Buckling of Solid-Core or Foam-Sandwich Panel Subjected to In-Plane Shear Loads Buckling of a Truss-Core Sandwich Panel Subjected to In-Plane Shear Loads Buckling of a Web-Core Sandwich Panel Subjected to an In-Plane Shear Load Other Considerations Problems References STRUCTURAL OPTIMIZATION TO OBTAIN MINIMUM-WEIGHT SANDWICH PANELS Introduction Minimum Weight Optimization of Honeycomb-Core Sandwich Panels Subjected to a Unidirectional Compressive Load Minimum Weight Optimization of Foam-Core Sandwich Panels Subjected to a Unidirectional Compressive Load Minimum Weight Optimization of Truss-Core Sandwich Panels Subjected to a Unidirectional Compressive Load Minimum Weight Optimization of Web-Core Sandwich Panels Subjected to a Unidirectional Compressive Load Minimum Weight Optimization of Honeycomb-Core Sandwich Panels Subjected to In-Plane Shear Loads Minimum Weight Optimization of Solid- and Foam-Core Sandwich Panels Subjected to In-Plane Shear Loads Minimum Weight Optimization of Truss-Core Sandwich Panels Subjected to In-Plane Shear Loads Minimum Weight Optimization of Web-Core Sandwich Panels Subjected to In-Plane Shear Loads Optimal Stacking Sequences for Composite Material Laminate Faces for Various Sandwich Panels Subjected to Various Loads Problems References SANDWICH SHELLS Introduction Analysis of Sandwich Cylindrical Shells under Axially Symmetric Loads A General Solution for Orthotropic-Sandwich Cylindrical Shells under Axially Symmetric Loads Shells with Mid-Plane Asymmetry Other Considerations Problems References BUCKLING OF SANDWICH CYLINDRICAL SHELLS Buckling of a Solid- or Foam-Core Sandwich Cylindrical Shell with Isotropic Faces Subjected to an Axially Symmetric Compressive End Load Buckling of a Solid- or Foam-Core Sandwich Cylindrical Shell with Orthotropic Composite Faces Subjected to an Axially Symmetric Compressive Load Buckling of a Honeycomb-Core Sandwich Cylindrical Shell with Composite Faces Subjected to an Axially Symmetric Compressive End Load Overall Buckling of Sandwich Cylindrical Shells Subjected to an Overall Bending Moment Buckling of a Sandwich Cylindrical Shell Due to External Pressure Buckling of a Sandwich Cylindrical Shell Due to Torsion Dynamic Buckling Problems References MINIMUM WEIGHT OPTIMIZATION OF SANDWICH CYLINDRICAL SHELLS General Discussion Minimum Weight Optimization of a Solid Foam-Core Sandwich Cylindrical Shell with Isotropic Faces Subjected to an Axially Compressive Load Minimum Weight Optimization of a Solid- or Foam-Core Sandwich Cylindrical Shell with Orthotropic Composite Material Faces Subjected to an Axially Compressive Load Minimum Weight Optimization of a Honeycomb-Core Sandwich Cylindrical Shell with Composite Material Faces Subjected to an Axially Symmetric Compressive Load Problems References APPENDIX 1: Core Materials APPENDIX 2: Face Materials APPENDIX 3: American Society for Testing Materials (ASTM) Standards for Sandwich Structures and Materials INDEX

Abstract: Introduction. Honeycomb core. Sandwich design. Honeycomb processes. Sandwich fabrication. Structural applications. Other honeycomb applications. Honeycomb and sandwich testing. Sandwich panel repair. Appendix. Index.

Abstract: Explosive tests were performed in air to study the dynamic mechanical response of square honeycomb core sandwich panels made from a super-austenitic stainless steel alloy. Tests were conducted at three levels of impulse load on the sandwich panels and solid plates with the same areal density. Impulse was varied by changing the charge weight of the explosive at a constant standoff distance. At the lowest intensity load, significant front face bending and progressive cell wall buckling were observed at the center of the panel closest to the explosion source. Cell wall buckling and core densification increased as the impulse increased. An air blast simulation code was used to determine the blast loads at the front surfaces of the test panels, and these were used as inputs to finite element calculations of the dynamic response of the sandwich structure. Very good agreement was observed between the finite element model predictions of the sandwich panel front and back face displacements and the experimental observations. The model also captured many of the phenomenological details of the core deformation behavior. The honeycomb sandwich panels suffered significantly smaller back face deflections than solid plates of identical mass even though their design was far from optimal for such an application.

Abstract: A method is described by which the dispersion relations for a two-dimensional structural component can be predicted from a finite element (FE) model. The structure is homogeneous in two dimensions but the properties might vary through the thickness. This wave/finite element (WFE) method involves post-processing the mass and stiffness matrices, found using conventional FE methods, of a segment of the structure. This is typically a 4-noded, rectangular segment, although other elements can be used. Periodicity conditions are applied to relate the nodal degrees of freedom and forces. The wavenumbers—real, imaginary or complex—and the frequencies then follow from various resulting eigenproblems. The form of the eigenproblem depends on the nature of the solution sought and may be a linear, quadratic, polynomial or transcendental eigenproblem. Numerical issues are discussed. Examples of a thin plate, an asymmetric laminated plate and a laminated foam-cored sandwich panel are presented. For the last two examples, developing an analytical model is a formidable task at best. The method is seen to give accurate predictions at very little computational cost. Furthermore, since the element matrices are typically found using a commercial FE package, the meshing capabilities and the wealth of existing element libraries can be exploited.