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AbstractThe in-plane auxetic honeycomb sandwich panels (AHSPs) with polyurea-metal laminate (PML) as faceplates were proposed, and their vibration and acoustic properties were investigated. The natural frequency, damping loss factor, sound transmission loss (STL), and sound field pressure distribution were simulated by the finite element, which was then compared with the AHSP without a polyurea layer. The sound insulation properties of the AHSPs with PML faceplates were significantly enhanced due to the viscoelastic energy consumption of the polyurea layer. By changing the thickness of the polyurea layer and adopting different honeycomb geometries, the sound insulation ability of the sandwich plate could be further enhanced. The average STL rose by 2.3–4.7 dB when the polyurea layer thickness was increased, hence significantly improving the noise suppression ability of the AHSPs. When the geometric tilt angle θ of the honeycomb core is −45°, the sandwich panel exhibits superior sound insulation performance. [ABSTRACT FROM AUTHOR]

The research and development of novel protective structures with excellent mechanical load-bearing and energy-absorbing characteristics are one of the current interests in aerospace, marine, and automobile industries. In this research, we fabricate foam-filled multi-layered hybrid composite graded lattice sandwich panels (MHCGLSPs) with different configurations and investigate their dynamic response characteristics experimentally and numerically. The influences of strain rate, relative density, filled foam, and graded arrangement on the crushing behavior of the present panels are depicted, and three main failure modes including core buckling (CB), facesheet breakage (FB), and polyurethane foam breakage (PB) are revealed. Furthermore, the numerical results obtained by finite element models based on the Hashin failure criterion and Johnson–Cook model are in good agreement with the experimental results. It is shown that all the present MHCGLSPs possess excellent energy absorption performance, and the non-graded specimens and gradually weaker specimens possess better ultimate load-bearing capacity under the premise of equal relative density, which can provide guideline for further studies on the novel multi-layered protective structures. [ABSTRACT FROM AUTHOR]

An efficient finite element model based on conventional shell elements available in ABAQUS software has been developed for free vibration analysis of FGM monolayer and sandwich flat panels. Applications to sandwich plates with an FGM layer embedded as either a core or face sheets with different through-the-thickness material gradations in the form of power (P-FGM), sigmoid (S-FGM), and exponential (E-FGM) distributions are considered. A user-defined material subroutine UMAT was used to implement functionally graded properties of the constitutive FGM layer. Numerical studies are given for free vibrations of monolayer and sandwich plates subjected to various boundary conditions and with different structural parameters such as span-to-thickness, face sheet-core-face sheet thickness and aspect ratios, and volume fraction index. The studies showed very good agreement between the present results and those existing in the literature that confirmed the accuracy of the developed model at minimal computational costs. This emphasizes the efficiency of the shell-based modeling strategy proposed for the calculations. A series of numerical solutions obtained in the research extends the results of known testing examples and may serve as additional benchmark data for other analysts. [ABSTRACT FROM AUTHOR]

The dynamic response of clamped square sandwich panels with layered-gradient closed-cell aluminum foam cores under the impact of metallic foam projectiles is investigated. The present solutions are compared to those results of monolithic solid plates and non-graded monolithic core sandwich panels. The resistance performance of specimens to projectile impact is estimated by the maximum transient central-point deflection of back face-sheet. Results indicate that all the sandwich panels have a better shock resistance performance than the monolithic solid plate with the equivalent mass, and the resistance of sandwich panels to shock loading could be improved by utilizing the layered-gradient cores. The sandwich configuration is demonstrated to be able to effectively contribute to energy absorption and material efficiency, and the positive gradient-core configuration is the best choice in term of specific energy absorption. The strain-rate effect of face-sheet and core materials can mitigate the deformation of the back face-sheet of specimens due to its hardening effect. [ABSTRACT FROM AUTHOR]

In this study, metallic pyramidal lattice truss core sandwich structures, including single-layered as well as multi-layered ones, are fabricated from EOS Aluminium AlSi10 Mg, utilizing additive manufacturing method. Out-of-plane and in-plane compression as well as shear tests were carried out in order to measure the stiffness and strength properties of the structures. The out-of-plane compressive strength is determined by buckling of struts, and specimens fail in plastic yielding of face sheets for in-plane tests. And for the shear performance of the specimens, the strength is dominated by the node failure. In addition to experimental testing, finite element models have been developed for simulating the stiffness and strength properties and the numerical results agree well with experimental performance. [ABSTRACT FROM AUTHOR]

The main purpose of this work is to study the bending behavior and deformation mechanisms of sandwich panels with AlSi7-alloy foam cores obtained by the powder metallurgy method. For this purpose, quasi-static three-point bending tests were performed on samples of AlSi7-alloy foam sandwich panels at different cross-head displacement rates: 1, 10, 20, 40 and 80 [mm/min]. Load-deflection values were registered during the bending test and further transformed into bending moment-rotation data. Obtained results show that different failure collapse modes can be obtained for samples with identical nominal dimensions, depending on the cross-head displacement rate. [ABSTRACT FROM AUTHOR]