Showing papers on "Sandwich panel published in 2022"

Investigation on the flexural properties of sandwich beams with auxetic core

Abstract: Availing cellular structures as the core of sandwich beams is an innovative approach to improve the efficiency of them. Nonetheless, the flexural characteristics of sandwich beams are affiliated to the core topology. Accordingly, choosing an appropriate core can have a significant efficacy on the performance of sandwich beams. The purpose of the present study is to assess the influence of using auxetic cores in flexural properties of sandwich beams. Specifically, experimental and finite element approaches were implemented to evaluate the flexural behavior, energy absorption and the stiffness of fully integrated 3D printed polymeric sandwich beams, made of square node anti-tetra chiral, arrowhead and re-entrant auxetic cores, compared with the conventional honeycomb core. Fabrication of specimens was performed using the FDM 3D printing method, and three-point bending tests were conducted on the printed specimens. Results indicated that selection of proper core topology has remarkable effect on the flexural properties of sandwich beams, and using auxetic core is potentially an efficient method to enhance mechanical properties of sandwich beams due to high load bearing capacity.

Three-point bending performance of sandwich panels with various types of cores

Abstract: In this paper, the bending performances of sandwich panels with corrugated triangular, honeycomb, aluminum foam, pyramidal truss, double sine corrugated (DSC), and 3D re-entrant auxetic cores are assessed and compared, both experimentally and numerically. Three-point bending experiments were performed on corrugated, honeycomb, aluminum foam, and truss core sandwich panels with identical face-sheets and core height. The experimental and numerical results compared well for panels with corrugated, honeycomb and truss cores. Parametric studies were subsequently performed, using ABAQUS, and three distinct modes of deformation were identified. The specific energy absorption (SEA) of the panels was found to increase with the core relative density; the one with a honeycomb core will be shown to have the greatest SEA, for the same core relative density, compared to the rests.

Experimental and numerical investigation on bending and compressive behavior of carbon-epoxy sandwich panel with novel M-shaped core

Abstract: Present paper has experimentally and numerically investigated the mechanical behavior of composite sandwich panel with novel M-shaped lattice core subjected to three-point bending and compressive loads. For this purpose, a composite sandwich panel with M-shaped core made of carbon fiber has been fabricated in this experiment. In order to fabricate the sandwich panels, the vacuum assisted resin transfer molding (VARTM) has been used to achieve a laminate without any fault. Afterward, polyurethane foam with density of 80 kg/m3 has been injected into the core of the sandwich panel. Then, a unique design was presented to sandwich panel cores. The study of force-displacement curves obtained from sandwich panel compression and three-point bending tests, showed that an optimum mechanical strength with a considerable lightweight. It should be noted that the experimental data was compared to numerical simulation in ABAQUS software. According to the results, polyurethane foam has improved the flexural strength of sandwich panels by 14% while this improvement for compressive strength is equal to 23%. As well as, it turned out that numerical results are in good agreement with experimental ones and make it possible to use simulation instead of time-consuming experimental procedures for design and analysis.

Sound Propagation of Three-Dimensional Sandwich Panels: Influence of Three-Dimensional Re-Entrant Auxetic Core

Abstract: Re-entrant auxetic cellular structures (RACSs) offer various mechanical properties. Specifically, their high acoustic absorption and dissipation properties turn them into proper candidates to effectively increase the sound insulation characteristics of sandwich plates. Accordingly, this approach proposes an analytical strategy to investigate the exact effect of using three-dimensional (3D)-RACS in order to determine the sound transmission loss (STL) coefficient of a sandwich panel. Therefore, the dynamic equations of fluid–structure interaction are extracted using 3D stress distribution, and then the obtained equations are solved analytically based on the state vector method. The reliability and precision of the outcomes are checked according to previous works. The results obtained are significant because the designed sandwich model seems to improve the sound characteristics of the system based on the STL comparisons between the current approach and the single-layer plates as well as sandwich panels with other core geometries. The achievements of this study can provide novel insights into the STL of 3D-RACS sandwich systems with a complex core model.

Surface and honeycomb core damage in adhesively bonded aluminum sandwich panels subjected to low-velocity impact

Abstract: The effect of the adhesive geometry on the impact damage of adhesively bonded aluminum sandwich panels was studied experimentally and numerically. Both the physical testing and the finite element results show that the core damage depth is dependent on the adhesive fillet height and can be linearly correlated with the dent depth . The focus of the finite element simulation is on representing the adhesive fillet height and the constraint that it provides for the cell walls at the interface with the face-sheet. A hybrid method combining the numerical study and the Bayesian method was proposed to predict the range of core damage depths from the numerical simulations based on the variability of the adhesive fillets. The variation of the adhesive fillet height between different cell walls significantly influences the core damage depth and cannot be ignored when predicting the range of the core damage depth. The non-uniform distribution of the adhesive fillets causes the core damage depth to vary within a range of up to 20% of the core thickness for the panel configurations considered in this study.

Failure of carbon fiber composite sandwich cylinders with a lattice core under axial compressive loading

Abstract: Sandwich cylinders with a low-density pyramid-like truss core made of plain-woven carbon fiber fabrics are manufactured using a sequential hot press method. Then, the structural compressive strengths corresponding to four possible failure modes (Euler buckling, axisymmetric buckling, local buckling and face panel crushing of the sandwich cylinders) are obtained by theoretical analysis. The 3D failure mechanism map is accordingly generated to guide the design and preparation of the cylinder specimens. Thereafter, axial compressive tests are performed on the specimens to investigate the failure mechanisms of these structures and to validate the theoretical predictions. The errors between theoretical and experimental results, including both the axial compressive ultimate loads and failure modes, are acceptable. The developed 3D failure mechanism map provides an intuitive guide for the design of sandwich cylinders with a pyramid-like lattice truss core against buckling failure.

Vibro-acoustic analysis of the sound transmission through aerospace composite structures

Abstract: Abstract An in-plane honeycomb sandwich structure used in aerospace applications has been modeled, in order to study the structural-acoustic performances of the sandwich panel using a finite element analysis software. A modal and steady state analysis were conducted to investigate the vibro-acoustic and sound transmission characteristics of the sandwich panel. Several materials used in aerospace composite structures were tested to compare their acoustic performances and to deduce which material have a good acoustic insulation property. Two different cases of structural acoustic design, were performed in this research taking into account the effect of changing material, thickness of skins and the total mass on the sound transmission characteristics of the sandwich panel through varying the effective properties without compromising the mass of the panel in case of the first design. In case of the second design, we consider the thickness of skins as constant. The results reveals that the glass fiber reinforced polymer (GFRP) cores with fiber-reinforced plastic (FRP) facing materials have a better vibro-acoustic and sound transmission characteristics comparing to all other design cases presented in this article. GFRP cores with an FRP facing can replace the aluminum materials without affecting the acoustic performances of the panel with a mass reduction of the panel.

Static response of synclastic sandwich panel with auxetic wood-based honeycomb cores subject to compression

Abstract: Only a few research works show a method for creating doubly curved surfaces using single-layer auxetic structures. There are no studies regarding sandwich wood-based synclastic panels with the auxetic core. The main goal of this work was to determine the effect of the thin facings on the stiffness, strength, amount of absorbed energy, and damage of the synclastic panels with an auxetic core subjected to static compression. The facings of sandwich panels were manufactured out of cardboard and a copolyester of polyethylene terephthalate glycol (PETG). WoodEpox® composite was used as a material of the core structure. Synclastic panels were tested experimentally and analyzed using the finite element method. In addition, the damage process of the core and facings was described. The results of studies have shown a significant impact of the facing type of sandwich panel on its overall stiffness and ability to absorb energy. Cardboard panels are significantly more rigid than those made of PETG. Also, cardboard panels show a high ability to absorb energy. • Wood-based synclastic sandwich panels with an auxetic core were manufactured. • The effect of facings was analyzed. • The strength, stiffness, energy absorption, and damage were analyzed. • The numerical calculations were adopted. • A positive correlation between the type of facings and the mechanical properties was confirmed.

Dynamic response and failure mechanism of S-shaped CFRP foldcore sandwich structure under low-velocity impact

Abstract: To study the impact resistance of the S-shaped carbon-fiber foldcore sandwich structure, the S-shaped foldcore was prepared by the hot press molding process, and then the S-shaped carbon-fiber foldcore sandwich structure was designed by face-to-core bonding and curing through a secondary bonding process. Two hemispherical impactors with different diameters were used to preload different energies to impact the node position and base position of the sandwich panel, respectively, revealing the failure mechanism, response characteristics of the sandwich panel, and the influence of various variables on the impact resistance of the structure. The research shows that the panel of S-shaped foldcore sandwich structure has tensile fracture failure. The core is affected by the structural characteristics and load-bearing forms, and there are mainly two failure modes of brittle crushing fracture and tensile fracture. The load–displacement curve shows that the relative size of the impactor and the unit cell of the core has a significant influence on the impact damage behavior. The sandwich panel has better impact resistance for the impactor with diameter greater than the cell span, and the difference between different impact positions is reduced. In application, the span of the core cell can be reduced to further improve the protective effect of the structure. The sandwich structure studied in this paper is lightweight and has good impact resistance, which can be used in the field of lightweight protection in the future. • A new type of S-shaped foldcore was prepared by hot pressing. • The dynamic response and damage mode of the structure under low-velocity impact are studied. • The core damage mode is determined by the structural characteristics and load-bearing form. • The sandwich panel has better impact resistance for impactors whose size is larger than the unit cell span.

Double-layer woven lattice truss sandwich composite for multifunctional application: Design, manufacture and characterization

Abstract: Woven lattice truss sandwich (WLTS) structures have excellent debonding resistance with integral textile construction. As the WLTS has limited thickness, a double-layer WLTS (DWLTS) composite was designed and fabricated to improve the blast resistance of the sandwich panel, as well as keep its electromagnetic (EM) wave transmission properties. The panel was placed by two layers of WLTSs and plain fabrics, and co-cured using vacuum bag molding process to ensure the interfacial shear resistance. In-field explosion experiments reveal that the DWLTS has excellent blast-resistance and EM wave transmission characteristics. The transmission exceeds 80% in 4.5–8.5 GHz and 16–17.2 GHz, and the maximum transmittance is 98.27% at 4.9 GHz. The panel has little damage until the scaled distance is smaller than 1.026 kg/m1/3 with standoff distance of 0.6 m and TNT mass of 0.2 kg. No debonding was observed.

Nonlinear aeroelastic analysis of sandwich composite cylindrical panel with auxetic core subjected to the thermal environment

Abstract: In this study, nonlinear aeroelastic instability of a composite sandwich panel subjected to a supersonic airflow and thermal loading is investigated. The sandwich panel is composed of three-phase composites with polymer/Graphene platelet/fiber skins at the top and bottom surfaces and an auxetic honeycombs core layer with a negative Poisson’s ratio. The motion equations of the panel within the framework of higher-order shear deformation theory (HSDT) and von Kármán nonlinearity are driven. In addition to Krumhaar’s modified supersonic piston, unsteady aerodynamic pressure in the supersonic flow regime is considered. The governing equations of the sandwich panel are derived by implementing Hamilton’s principle and solved by the generalized differential quadrature method (GDQM). Validation of the present formulation is assessed by comparing the numerical results with those available in the open literature. Then, the effects of several parameters such as geometric parameters, volume fraction, Mach number, different boundary conditions, yaw angle, and different inclined angles on the nonlinear aeroelastic stability of sandwich panels are examined. Finally, it was found that the ratio of core thickness, inclined angle, and Mach number have significant effects on aerodynamic pressure.