Behavior Of Sandwich Panels Research Articles

Edgewise Compression and Three-Point Bending Analyses of Repaired Composite Sandwich Panels.

In this work, the fracture behaviour of repaired honeycomb/carbon-epoxy sandwich panels under edgewise compression and three-point bending loading was analysed. Assuming the occurrence of damage resulting from a complete perforation leading to an open hole, the followed repair strategy consists of plug filling the core hole and considering two scarf patches with an angle of 10° in order to repair the damaged skins. Experimental tests were performed on undamaged and repaired situations in order to address the alteration in the failure modes and assess the repair efficiency. It was observed that repair recovers a large part of the mechanical properties of the corresponding undamaged case. Additionally, a three-dimensional finite element analysis incorporating a mixed-mode I + II + III cohesive zone model was performed for the repaired cases. Cohesive elements were considered in the several critical regions prone to damage development. The failure modes and the resultant load-displacement curves obtained numerically were compared with the experimental ones. It was concluded that the numerical model is suitable for estimating the fracture behaviour of sandwich panel repairs.

Flexural Characterisation of Sandwich Panel with Corrugated Glass Reinforced Polymer

The corrugated foam core sandwich construction is used in variety of structural applications. These structures are subjected to flexural, impact, edgewise compression and shear loads. Traditional process for manufacturing of sandwich panel is not suitable for making corrugated core sandwich panel. In this work a novel methodology has been developed for construction of corrugated foam core sandwich panel. The present study focuses on the flexural behaviour of sandwich panel by varying the foam densities and corrugated cell. Two types of densities with one cell and two cells are used. The sandwich employs a Glass Reinforced Polymer (GRP) orthotropic material for both the two outer skins and the inner core web. In particular, the core is designed to have uneven topology to cooperate with GRP skins in membrane and flexural properties by adding a corrugated foam core. At first, a comparison has been performed between different density foams. Initially, 40 kg/m3 with 1 unit cell and 32 kg/m3 with 1 unit cell are compared, and then the same densities are compared with 2 cells. Among all, 40 kg/m3 with two cells shows highest flexural strength compared to the other specimens. Also, the sandwich panel with an empty core has been tested to understand the strength of the face sheet and corrugated core.

Flexural behaviors of sandwich panels with AR-glass textile reinforced concrete under low-velocity impact

Textile reinforced concrete（TRC）can be used as the face-sheet for sandwich panels due to its lightweight, excellent tensile strength, high energy absorption, and ductility. This study investigates the flexural behavior of alkali-resistant glass-textile reinforced concrete (ARG-TRC) sandwich panels with different textile layers, core thicknesses, and interface forms under various impact velocities. A new manufacturing technique for ARG-TRC sandwich panels is proposed. The sandwich panels with four textile layers have superior load-carrying capability and impact resistance than those with two layers. The impact load can be transferred more effectively for panels with a core thickness of 40mm, allowing the top and bottom face-sheets to bear the load simultaneously for better impact resistance. Ribbed panels can reduce the possibility of side core tensile fracture and core crushing while improving flexural stiffness. It was also found that TRC sandwich panels typically exhibit four failure modes under the impact load, including face-sheet fracture, core shear fracture, side core tensile fracture, and core crushing fracture. The findings of this study can provide some insights into promoting the design and application of TRC sandwich panels in residential and industrial structures.

Experimental analysis of the impact behaviour of sandwich panels with sustainable cores

Experimental analysis of the impact behaviour of sandwich panels with sustainable cores

Crushable polymer foam behavior at cold temperatures

Experiments were conducted to characterize and develop predictive constitutive equations for the elastic-plastic, post-yield hysteresis behavior of Divinycell H100 foam at temperatures as low as −40°C. The initial elastic modulus and yield strength of the foam increased almost linearly by about 50% as temperatures decreased from 23 to−40°C. Post-yield hysteresis, which was described by strain hardening, viscoelasticity and damage also increased as the temperature fell to −40°C, but this behavior was curtailed by a sharp reduction in tensile and shear ductility as the foam approached its ductile-to-brittle transition temperature near −50°C. An anisotropic elastic-plastic, viscoelastic damage constitutive model was extended to predict cold temperature behavior. Good agreement was found between analytical predictions and the experimental results. The temperature-dependent constitutive equation can be used in conjunction with appropriate failure criteria to predict foam-core sandwich panel behavior in cold regions.

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance (20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the finite element model. The numerically obtained test results were compared with the experimental to check the accuracy of the modelling. The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus. Furthermore, the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation, deformation and failure mode was examined. The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading. Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance. Also, increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption. However, inscribe circle diameter had a negative influence on the ballistic resistance. Also, the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions. The energy dissipation in plastic work was highest for circumferential direction, regardless of impact condition followed by tangential, radial and axial directions.

An improved predictive model for local deformational behavior of sandwich panels with gradient metallic foam cores

An improved predictive model for local deformational behavior of sandwich panels with gradient metallic foam cores

Investigation of Adhesive Debonding in Paper Honeycomb Sandwich Panel under Blast Load

Blast mitigation of structures have become a focus of many research works due to the rising threat imposed by explosive based terrorism. Sacrificial sandwich panels are one of such blast mitigation technique, which has proven to be effective in reducing the blast-induced damage on structures. Researchers are studying new materials like honeycomb to mitigate blast load as these materials have high strength to weight ratio, high stiffness and lightweight. The failures in sandwich structures subjected to blast load are core crushing, face-sheet bending and delamination of face-sheet from core. In present investigation, authors studied delamination behaviour of sandwich panel with paper honeycomb core using ABAQUS/Explicit®. The face-sheet and back-sheet of the sandwich panels considered here are made of stainless steel and core of paper honeycomb. The adhesive layer of Araldite(R) 2015 is modelled in ABAQUS/Explicit® using cohesive zone model (CZM). The authors studied effect of variation of thickness of adhesive layer. The investigation is compared based on internal energy and central point displacement time histories of back-sheet.

Numerical Investigation on the Effect of Composite Corrugated Cores in Lightweight Sandwich Panels under Planar Impact Loading

Lightweight sandwich structural components have been widely used in different industries as highly effective energy absorbers. This research aims to provide a comparative study on the role of the composite corrugated sheet as a core in sandwich panels under low velocity impact loading. To reach this goal, the crashworthiness characteristics of three sandwich panels with different corrugated cores, which consist of identical mass and mechanical properties, are evaluated under vertical and transverse loading. The finite element computation is done using LS-DYNA under planar loading conditions. To validate the numerical process, first, the dynamic compression behavior of the square corrugated core sandwich panel made of aluminum alloys in comparison to existing experimental data is analyzed and the appropriate compliance has been observed. Then the effect of composite material and core shape on the crashworthy behavior of sandwich panels is explored. The research results reveal that the material type and geometric configuration of corrugated core have a considerable effect on the mean crushing load and the energy absorption of sandwich panels. It is found that the triangular configuration has a higher capability in load carrying and energy absorption than the square and/or the sinusoidal configuration. The failure modes of the crushed corrugated sandwich panels also significantly influenced by the type of corrugation cores. The present results supply valuable information on low velocity impact response that can be helpful for increasing crashworthy performance and development of such lightweight structures.

Nonlinear vibration characteristic of a sandwich cylindrical panel with auxetic core and GPLRC facing sheets embedded with piezoelectric layers

This paper deals with the nonlinear vibration behavior of sandwich panels composed of Graphene platelet reinforced composite (GPLRC) skins and auxetic core embedded with piezoelectric layers subjected to the thermo-magneto-electric loading. The nonlinear equations are obtained by applying Hamilton’s principles in the framework of higher-order shear deformation theory (HSDT) and von Karman’s nonlinear theory. Linear and nonlinear equations of motion are solved by applying the differential quadrature method (DQM) and homotopy perturbation technique, respectively. In the numerical illustration, at first validation of the present formulation is carried out by comparing the numerical results with those available in the open literature. Then the effects of several parameters such as geometric parameters of auxetic core, applied voltage, magnetic potential, GPL volume fraction, different boundary conditions, and temperature rise on the nonlinear frequency response of sandwich panel are studied. From numerical results, it was concluded that the sandwich panel incorporating auxetic core and piezoelectric layers could increase the magneto-electrical power output.

Experimental investigation on the perforation behaviour of sandwich panels with hybrid composite face sheets and cellular aluminium core using quasi-static and instrumented inverse impact methods

With the rising demand for lightweight and high-performance shielding systems, sandwich panels made of thin rigid face sheets and cellular material cores have recently received much attention. The present study aims to investigate the perforation behaviour of lightweight sandwich panels made of fibre reinforced composite face sheets and aluminium foam core under quasi-static and dynamic testing conditions. A particular focus is made on the fibre hybridization effect on the overall panel behaviour. Impact perforation tests were conducted using an inverse perforation technique. Instead of conventional free-flying projectile impact tests, studied samples are fixed in a hollow projectile. Then, this assembly is accelerated toward an instrumented steel perforator replacing the incident bar of a split Hopkinson pressure bar. Consequently, this modified split Hopkinson pressure bar system can be used as both a perforator and a measuring device. Therefore, the piercing force-displacement curves, the energy absorption capability as well as the penetration and damage mechanisms of the tested panels was analysed and compared to quasi-static perforating tests. To better assess the testing results, quasi-static tensile and bending tests were carried out on the face sheets materials. Moreover, quasi-static and dynamic compression tests were performed on the aluminium foam core using conventional test methods and direct split Hopkinson pressure bar. Unlike the aluminium alloy face sheets, the experimental findings revealed that the sandwich panels with composite face sheets demonstrated higher rate sensitivity, better perforation resistance and specific energy absorption capability. Results have also shown that the hybridization of carbon and glass fabrics combined their best tension and bending properties as well as their higher dynamic strength, which has increased the sandwich panel's perforation resistance.

Flexural behavior of sandwich panels with 3D printed cellular cores and aluminum face sheets under quasi-static loading

In this study, sandwich panels are presented with polylactic acid (PLA) core made through the FDM method. The face sheets of the panels are made out of aluminum 3105 alloy. The mechanical properties of the proposed samples were investigated under flexural quasi-static load. Different panels were tested by a three-point flexural test to determine their collapse properties; moreover, cubic specimens were exposed to quasi-static compression load. The results confirmed the effective role of layering type in the FDM method on the collapse properties of the sandwich panel. Results showed that type of the main pattern extension can affect the collapse properties. A comparison of the cubic samples under three different quasi-static compressive loading indicated that the collapse properties and absorbed energy of the samples depend on the loading direction. The proposed lightweight structures absorb high energy in comparison with ordinary one which was investigated in this paper; thus they can be an ideal structure for industries. Numerical modeling was another part of the study which was done by LS-DYNA and good agreement between numerical and experimental results was observed.

The effect of core materials on flexural behaviour of sandwich panels with basalt FRP facesheets

The flexural behaviour of sandwich panels with basalt fiber-reinforced polymer (BFRP) facesheets was investigated. A total of 10 sandwich panels were subjected to six-point flexural tests to simulate uniformly distributed loading conditions. The variable parameters were the core thickness (30, 50, 60 and 100 mm), core category (polyurethane [PU], extruded polystyrene [XPS], rock-mineral wool [RW]), and hybrid core (PU+RW and XPS+RW). Finally, the shear distribution coefficient of core material for sandwich panels with BFRP facesheets was modified depending on the experimental data. The experimental results showed that an increase in the PU core thickness significantly increased the flexural strength and rigidity of the sandwich panels. For different core materials, the maximum loads of the panels were positive with the shear strength of the core materials. Whereas, XPS+RW hybrid core not only can significantly decreases the costs, but also exhibits the highest bearing capacity and stiffness as compared with the PU+RW hybrid and PU cores.

Bending behaviour of sandwich panels of vegetal fabric reinforced cementitious matrix: Experimental test and numerical simulation

Sandwich panels represent a lightweight solution with additional properties as insulation compared to traditional solutions used for building enclosures. In this study, a technology based on vegetal FRCM (fabric reinforced cementitious matrix) provides an economical, sustainable and competitive solution. The research introduces a composite design made of different vegetal fabrics (hemp and sisal) and mortar as skins of the sandwich and a core of extruded polystyrene. Both composite skins were connected with different types of connectors including vegetal designs. An experimental campaign of sandwich panels included four-point bending tests and a later development of numerical models capable of reproducing the experimental results. The results obtained show that the use of vegetal fabrics and connectors were as competitive for the development of effective composite action as synthetic fabrics (glass fiber).

Simulation study on deformation behavior of sandwich panels with corrugated cores

In this study, the deformation behaviour of sandwich panels structures with different configurations of corrugated cores under the effect of quasi-static bending loading is investigated numerically. The corrugated core is consists of cast polyamide (PA6) material with circular, sinusoidal, rectangular, trapezoid, and triangular geometries. An Aluminum 6063-T5 plate is used as the skin of the sandwich panel. According to the analysis results, the sandwich panel with a trapezoidal core provided the highest deformation resistance with 6363.6 N. The circular core sandwich panel showed the lowest deformation resistance with 4262.5 N. The sandwich panel with the highest specific carrying and specific energy capacity is the trapezoidal core panel.

Deflection behavior of sandwich panel with corrugated core of trapezoidal cross section

Deflection behavior of sandwich panel with corrugated core of trapezoidal cross section

A Novel Implementation of the LDEM in the Ansys LS-DYNA Finite Element Code.

In this paper, a novel implementation of the Lattice Discrete Element Method (LDEM) is proposed: in particular, the LDEM is implemented in the Ansys LS-DYNA finite element code. Such an implementation is employed to evaluate the fracture behaviour of sandwich panels under bending. First, the novel hybrid model proposed is validated by simulating some three-point bending experimental tests carried out at the University of Parma, and then it is used to model the fracture behaviour of sandwich panels under four-point bending. Failure mechanisms, damage locations, and load-deflection curves are numerically determined by employing such a novel model, and the results show a good agreement with the available experimental findings.

Optimizing the Aerothermomechanical Behavior of Sandwich Panels Using Genetic Algorithm

A multi-objective optimization of a sandwich structure is presented to maximize the fundamental frequency and the critical buckling temperature while minimizing the cost of the laminate, alongside with keeping the weight lower than a preset value. The sandwich structure was chosen to be made of a high-stiffness, relatively expensive material (carbon/epoxy), and a low-stiffness, relatively low- cost material for the core (glass/epoxy). The governing equations are derived using the principle of virtual work, based on the first-order shear deformation plate theory. MATLAB Genetic Algorithm toolbox is used to find the optimum stacking sequence and ply thicknesses to achieve the optimal solution. The ground structure was used to set the initial ply stacking sequence and then the algorithm assumes the existence or absence of each ply and their thicknesses. The optimum buckling temperature and natural frequency values are introduced for different aerodynamic pressure values and under simply supported boundary condition.

Impact behavior of natural rubber based syntactic foam core sandwich structures

Abstract In this study, the impact behavior of sandwich panels of natural rubber-based syntactic foam cores with aluminum face sheets was investigated experimentally and with the help of finite element analysis (FEA). Syntactic foam cores were produced byadding glass bubbles (GB) to the natural rubber (NR). Natural rubber was dissolved at room temperature with chemical solvents mixed with glass bubbles at 10, 20, and 30 weight percentages. Very low density (~0.8 g × cm-3) and high compressible foams were obtained depending on the GB weight percentages. Aluminum face sheets and the NR/GB syntactic foam core developed were joined by adhesive bonding to produce sandwich beam specimens. The sandwich beams manufactured in this way were subjected to impact loading under three-point bending boundary conditions experimentally. The experimental results were compared with finite element simulation results under the same loading and boundary conditions. The damage mechanism of the sandwich panels devised were analyzed. According to the results, natural rubber containing an additive of 20 wt.-% GBs showed better impact resistance than the others.

Experimental and Optimization Study of Compression Behavior of Sandwich Panels with New Symmetric Lattice Cores

The paper presents a novel core design for sandwich panels and conducts an experiment to determine whether the mechanical strength of symmetric aluminum lattice core sandwich panels can be improved. Both Design of Experiments (DOE) and Response Surface Methodology (Box-Behnken) were used to establish a quantitative relationship between the strength-to-weight ratio and the input parameters. The thickness of the sheet, the height of sandwich panels, and the width of the seat were all considered design variables to achieve the optimal state. The maximum Initial Peak Crushing Forces (IPCF) were then determined using quasi-static axial flatwise compression tests. This study found that the model's predicted values were consistent with the experimental results. As a result, the parameters were optimized using the Design-Expert software to maximize the initial peak force while minimizing the weight. The results were validated using the Genetic Algorithm, NSGA2, and LINGO. The results indicated that the height of the sandwich panel and the thickness of the sheet had the most significant impact on the maximum force and panel weight. To this end, it is concluded that introducing a novel core design for the sandwich panel, utilizing a suitable Snap-Fitting method for attaching lattice parts rather than using a paste, and finally optimizing the core were the primary reasons for achieving this level of strength.