Corrugated Core Sandwich Panels Research Articles

Experimental and numerical investigation of damage in multilayer sandwich panels with square and trapezoidal corrugated cores under quasi-static three-point bending

Multilayer composite sandwich panels with corrugated cores have the potential for structural applications requiring high stiffness and strength-to-weight ratios. This study aims to experimentally and numerically investigate the bending response of sandwich panels with novel square and trapezoidal corrugated core configurations fabricated from E-glass fiber-reinforced epoxy composites, both with and without polyurethane foam filling. Quasi-static three-point bending tests were conducted to evaluate and compare the flexural stiffness and maximum load capacity of the panel designs. The cores were manufactured using vacuum-assisted resin transfer molding. Key results showed that changing the core geometry from square to trapezoidal improved the bending stiffness by up to 26 %. Incorporating polyurethane foam further increased the bending stiffness by up to 41 % and maximum load by up to 47 % compared to solid cores. Failure initiation and progression were governed by matrix cracking in the face sheets and cores, followed by core cell wall buckling and delamination. Finite element modeling using ABAQUS captured the progressive damage behavior, exhibiting good agreement with experimental force-displacement responses. Failure modes included matrix cracks, fiber fractures, core buckling and delamination. This study provides valuable insights into the mechanical performance of innovative corrugated core sandwich panel designs under quasi-static bending loads. The validated FE approach also enables virtual testing and optimization of composite sandwich structures.

Experimental crashworthiness analysis of corrugated-core sandwich panels under impact loading

ABSTRACT This research scrutinizes and contrasts the crashworthiness of single-core and two-core corrugated sandwich panels with varying configurations, influenced by crucial parameters like thickness, core angle, and foam filling. Experimental investigations encompass quasi-static compressive loads and low-velocity impact tests on these sandwich structures. Employing the design of the experiment (DOE) method, the study examines parameter impacts on initial peak crushing force (IPCF) and specific energy absorption (SEA) across three sequential steps. The fabrication phase involves creating square and trapezoidal aluminium sandwich panels bonded using specialized aluminium glue. The results notably highlight the pivotal role of corrugated sandwich panel thickness in enhancing crashworthiness, displaying a direct correlation between thickness and responses. Particularly, two-core configurations exhibit superior performance in reducing IPCF during low-velocity loading compared to other panels. These structures showcase exceptional capability in diminishing IPCF rates during low-velocity loading, surpassing even foam-filled panels and demonstrating superior crashworthiness among the tested configurations.

Analytical and numerical solution for multiple shape memory effect of smart corrugated-core sandwich panels with different patterns

Shape memory polymers (SMPS) are a class of smart materials used in various industries due to their unique properties. On the other hand, sandwich structures have attracted the attention of many researchers and industries due to their low weight and high strength. Therefore, this study it is aimed to present a semi-analytical solution to describe the behavior of a sandwich plate made of temperature-sensitive SMPs with a corrugated structure, based on the Reissner-Mindlin plate theory together with the viscoelastic theory. The solution is implemented for both dual shape memory (shape and force recovery) and triple shape memory scenarios. Three types of structure, including rectangular, triangular and trapezoidal, have been studied. In addition, in order to examine the impact of the support type, simply supported and clamped boundary conditions have also been investigated for three different geometries. Also, this work examines the impact of thermal stress caused by expansion. In addition to the semi-analytical solution, finite element modeling has also been carried out in all problems. Comparing the results in different geometries and supports shows the proposed semi-analytical solution's ability to predict the material's behavior with great accuracy. Moreover, by examining different cores and supports, one may observe a significant difference in the amount and distribution of the force and deformation, which are key to the design. Therefore, the semi-analytical solution can be considered reliable and accurate for various problems. In addition, compared to the finite element solution, the analytical solution enjoys a much higher speed; thus, it can be used for optimization and design problems that require a huge number of simulations.

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.

Wood-based corrugated core sandwich panels manufactured using a wooden mold

A wooden matched-die mold was manufactured to develop wood-based corrugated panels. Wood veneers brushed with resin were cold pressed between the mold halves and formed into a corrugated geometry. The corrugated panels were used as a core and bonded to flat veneer-based facesheets to develop sandwich panels. The whole manufacturing process involved a cold-forming technique that allowed panels to be produced with no heat. Specimens cut from both corrugated and sandwich panels were submitted to a four-point bending test to evaluate their structural performance. Adopting the same number of layers used to make the sandwich panels, flat panels were fabricated and tested to find the effect of this corrugated geometry and cold-forming process on the load-carrying capacity of the sandwich structures. A comparison with flat panels made with the same stacking of veneers showed an increase of 272% of the bending stiffness of the sandwich panels, which is known as the sandwich effect. Comparison between the bending results of the panels developed in this study with those manufactured using thermoset resin and hot-pressing technique indicated that the cold-forming process using the wooden mold is an effective and inexpensive method to develop wood-based corrugated sandwich panels.

Ballistic impact response of elastomer-retrofitted corrugated core sandwich panels

The ballistic impact resistance of metallic corrugated sandwich panels retrofitted with elastomeric coating (polyurea) is investigated through combined experimental and numerical efforts. Dynamic penetration process, failure mechanisms, ballistic limit velocity, and perforation energy threshold of polyurea-coated sandwich panels are firstly elucidated via experiments and then compared with those of non-coated sandwich panels. Subsequently, based upon a user-defined compressible model of polyurea, three-dimensional finite element (FE) simulations of both non-coated and coated sandwich panels are carried out to analyze the ballistic impact response, interrogate the energy absorption mechanisms, and assess the influence of coating position/thickness and projectile rigidity on ballistic performance. Excellent agreement between experimental measurements and numerical predictions is achieved. It is demonstrated that the presence of a sufficiently thick (e.g., ∼15 mm) impact-side elastomeric coating helps to curtail the kinetic energy of flat-ended projectiles, thus enhancing the penetration resistance considerably. The use of a thicker and impact-side coating is favored owing to its superior energy absorption capability. It is also ascertained that the effectiveness of polyurea coating in resisting rigid, flat-ended projectiles is much more remarkable relative to deformable, conical ones. Further, retrofitting an all-metallic sandwich panel with elastomeric coating broadens its multifunctionality significantly, enabling it to simultaneously carry structural loads, mitigate impact and blast loadings, and resist projectile penetration, at a minimal increase in fabrication cost and structural mass. The insights of this study provide a potential new avenue for enhancing the ballistic impact resistance as well as multifunctional attributes of all-metallic sandwich construction.

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.

Experimental investigation into the synergetic damage of foam-filled and unfilled corrugated core hybrid sandwich panels under combined blast and fragment loading

Foam filling strategy has been demonstrated to owing the ability to improve the blast resistance of sandwich panels under bare blast loading. But it is unclear that the effect of foam filling for performance improvement of sandwich panels in response to combined blast and fragments loading. In this paper, the corrugated core sandwich panels with and without aluminum foam fillers were designed, fabricated and finally tested under combined blast loading. Main attention focused on the influence of stand-off distance, foam filler density and core configuration on the dynamic responses in terms of deformation modes and failure mechanisms. The perforation failure of target panels could be alleviated with the increase of stand-off distance. The increase of foam filler density hardly affected the deformation/failure modes of panels, but it could reduce the permanent deformation of core webs and front face sheet. Relative to unfilled sandwich panels, foam filling behavior is an effective way to relieve the debonding failure between face sheet and core webs. Overall, the performance of foam-filled sandwich panels under combined blast loading is mediocre. The failure mode of foam-filled sandwich panels would transform from localized plastic deformation mode under bare blast loading to catastrophic failure under combined blast loading.

Energy absorption of foam-filled corrugated core sandwich panels under quasi-static loading

The present paper tries to introduce the effect of foam-filled on a type of trapezoidal corrugated core and their structures derived from the related previous studies. The main purpose of this work is to present a novel geometry of trapezoidal cores, and their configurations are inspired by the earlier works. These absorbers have been proposed to raise the specific energy absorption (SEA) while declining the initial peak crushing force. Therefore, five corrugated core sandwich panels have been tested under quasi-static axial compressive load experimentally and then simulated by ABAQUS software. The accuracy of the numerical simulations is validated by comparing the numerical results with the corresponding experimental data. Besides, some other simulations have been carried out to investigate the effect of foam density, core type, and thickness in more detail. The comparison results show that the SEA rate of bi-core sandwich panels which has not been filled by foam is better than the single trapezoidal core sandwich panels, and this rate is roughly around 70%. The best performance is relevant to the pure foam core without any trapezoidal core structure and the next item is the single foam-filled corrugated core and the lowest performance among them is related to the bi-core corrugated core foam-filled.

Analysis of sandwich structures with corrugated and spiderweb-inspired cores for aerospace applications

The bending response of laminated composite sandwich structures developed for aircraft flaps is analyzed, in two parts. In the first part, the carbon fiber reinforced plastic (CFRP) and Aluminium 6061 based single-sided trapezoidal corrugated core sandwich panels are considered. The developed design is observed to withstand higher loads and exhibits higher flexural stiffness as compared to the similar corrugated geometries in the literature. The core design is iteratively modified to maximize the contact points between the core and panel in contact with the lift forces. The structure is treated as a cantilever, thus, representing the boundary conditions of aircraft flaps. The influence of ply-orientation, stacking sequences of face sheets, and panel thickness on the bending response are studied. As a result, an optimized sandwich composite structure with two times more stiffness and 40% lower stress levels as compared to the initial design is arrived. Furthermore, dynamic analysis is performed considering sinusoidally varying load along the space and time. In the second part, a novel bio-inspired spiderweb core design for the aircraft flap is developed. The stiffness of the bio-mimicked sandwich composite structures is observed to be better than the optimized corrugated core structures proposed in the first part. The influence of scaling and patterning the geometry is also investigated. The simulations are further extended to study the influence of hail impact on the sandwich structures with optimized corrugated and spiderweb cores to estimate the maximum induced stresses and peak forces. Finally, the corrugated design is replaced with the proposed spiderweb-based core design while preserving the optimal fiber orientation and ply-thickness developed in the first part.

Shock resistance of elastomer-strengthened metallic corrugated core sandwich panels

How polyurea coating affects the shock resistance of fully-clamped metallic corrugated core sandwich panels against high-velocity aluminum foam projectile impact is systematically elucidated via a mixed experimental and numerical investigation. Dynamic deformation process, deformation/failure modes, and permanent deflections of polyurea-coated sandwich panels are testified at various projectile momentum and compared with those of non-coated sandwich panels. A high-fidelity finite element (FE) model considering both rate-dependent compressive and tensile behaviors of polyurea elastomer is established and employed to simulate the dynamic response of polyurea-coated sandwich panels, interrogate the underlying enhancement mechanisms, and estimate the effects of projectile momentum and coating thickness/area/position upon permanent mid-span deflection and energy absorption. Reasonable agreement is realized between FE predictions and measurements. The presence of polyurea coating helps curtail permanent deflection in the central region and avoid shear failure around the clamping area. The benefit of polyurea coating on mitigating impact deformation remains stable as the projectile momentum is varied over a broad range, and the use of thicker, larger, and impact-side coating is preferred. The observed performance improvement is attributed mainly to enhanced plastic bending moment and membrane force in the polyurea-coated sandwich panel. The results of this study open up a new avenue to enhance the shock resistance of metallic sandwich structures subjected to impulsive loading.

Experimental analysis of corrugated core sandwich panel with smart composite face-sheets under high-velocity impact

The present research work investigated on the behavior of corrugated core composite sandwich panel (CCCS) with composite face-sheets reinforced by pseudo-elastic NiTi shape memory alloy (SMA) wires subjected to high-velocity impact experimentally. The number of SMA wires, their location, and their pre-strain percentage are the parameters studied in this investigation. The sandwich specimens were made by woven glass fibers/epoxy composite face-sheets strengthened by the SMA wires and Aluminum corrugated core and prepared using the wet hand lay-up method. Their behavior is evaluated under high-velocity impact test by a gas gun impactor testing machine. According to the results obtained, a significant change in the amount of energy absorption of the specimens containing SMA wires is observed. By increasing the number of the SMA wires, the energy absorption by the specimen is increased, but by pre-straining the SMA wires, the effect in energy absorption is significant. Also, when the projectile hits the SMA wire in CCCS, better properties in energy absorption can be observed. The results show that the energy absorption increased from 117.247 J for the specimen without the SMA wire to 128.749 J for the six SMA wires specimen. On the other hand, by applying the pre-strain to the SMA wires, the residual stresses in the specimens and hence the energy absorption in the specimen with six SMA wires with 3% pre-strain increased to 142.57 J.

Structural response of the U-type corrugated core sandwich panel used in ship structures under the lateral quasi-static compression load

This paper addresses a study on the structural deformation mechanism of the U-type corrugated core sandwich panel used in ship structures under the lateral quasi-static compression load through the experimental, numerical and analytical methods. Based on the results from quasi-static experiment and the finite element simulation, the deformation characteristics of the U-type corrugated core sandwich panel under the lateral quasi-static compression load are analyzed. The results show that the deformation of the U-type corrugated core sandwich panel can be divided into two processes according to whether the core is in contact during the compression process. And the deformation process has little influence on the variation trend of the structural resistance curve. Based on this, the deformation mode of the U-type corrugated sandwich panel is summarized, and the analytical formula of the deformation resistance of the U-type corrugated core sandwich panel is developed. It is shown that the proposed theoretical deformation model can reflect the main deformation process, and the analytical results match well with the experimental and numerical results.

Flexural Properties of 3D-printed hierarchical-sinusoidal corrugated core sandwich panels with natural fiber reinforced skins

The main aim of this study is to investigate the effect of printed hierarchical-sinusoidal corrugated core patterns and the load direction on the flexural properties of the cotton/epoxy composites sandwich panels. For the cores, six sinusoidal corrugated structures were considered. Besides, possible arrangements (transvers or longitudinal wave, arch downward or upward) of the sinusoidal corrugated cores with respect to the loading direction were considered. Totally, 72 cores were fabricated using a 3D printer and poly lactic acid material. It was observed that for the transverse arrangement, the flexural strength of sandwich panels is significantly improved by changing the pattern from the simple form to the hierarchical patterns. In contrast, for the longitudinal pattern, improvement in the flexural properties was not obtained by changing the core pattern. It was also manifested that corrugated core arrangement has remarkable effect on the mechanical properties of the sandwich panels. For the transverse pattern core panel, the maximum values of normalized face-sheet bending strength (FBS), core shear ultimate strength (CSUS) and energy absorption were obtained as 7.17 MPa/kg, 223.91 MPa/kg and 114.56 J/kg, respectively. Besides, for the longitudinal pattern core panel, the maximum values of FBS, CSUS and energy absorption were obtained as 7.86 MPa/kg, 245.78 MPa/kg and 330.75 J/kg, respectively. Comparing the obtained results with the available data in the literature manifested that the flexural properties of the corrugated core sandwich structures are significantly improved by changing its core system from the other materials to the printed material.

Sound Insulation of Corrugated-Core Sandwich Panels: Modeling, Optimization and Experiment.

With the extension of the applications of sandwich panels with corrugated core, sound insulation performance has been a great concern for acoustic comfort design in many industrial fields. This paper presents a numerical and experimental study on the vibro-acoustic optimization of a finite size sandwich panel with corrugated core for maximizing the sound transmission loss. The numerical model is established by using the wave-based method, which shows a great improvement in the computational efficiency comparing to the finite element method. Constrained by the fundamental frequency and total mass, the optimization is performed by using a genetic algorithm in three different frequency bands. According to the optimization results, the frequency averaged sound transmission of the optimized models in the low, middle, and high-frequency ranges has increased, respectively, by 7.6 dB, 7.9 dB, and 11.7 dB compared to the baseline model. Benefiting from the vast number of the evolution samples, the correlation between the structural design parameters and the sound transmission characteristics is analyzed by introducing the coefficient of determination, which gives the variation of the importance of each design parameter in different frequency ranges. Finally, for validation purposes, a sound insulation test is conducted to validate the optimization results in the high-frequency range, which proves the feasibility of the optimization method in the practical engineering design of the sandwich panel.

각종 주름판 코어 샌드위치 패널의 강성 및 진동 해석

Corrugated core sandwich panels are relatively lightweight structure components compared to their large flexural rigidity, and are widely used in automotive, aerospace, ship, and plant industries. However, research on rigidity and vibration for these sandwich panels remains fairly poor. In this study, the optimal sandwich panel is determined by presenting the rigidities of corrugated core sandwich panels with sinusoidal, triangular, trapezoidal, and rectangular waves. Furthermore, by analyzing the vibration of the sandwich panels for arbitrary boundary conditions, a basic visual program for practical and efficient static and dynamic design data extraction of the sandwich panels is completed.

Out-of-plane compression of a novel hybrid corrugated core sandwich panel

Lightweight sandwich panels with fluid-through cellular cores are promising for applications requiring simultaneous load-bearing and heat dissipation such as the combustion chamber of scramjet. While existing core topologies have exhibited good designability for specific thermal or mechanical requirements, the increasing demand for multifunctional attributes usually points to different core topology designs. Finding a single core topology that possesses excellent mechanical and thermal properties simultaneously remains challenging. To address the issue, the concept of a hybrid core (termed herein as the N core) that combines the conventional corrugated core with the web core was proposed to mitigate confliction between thermal and mechanical designs. Out-of-plane compressive characteristics of the hybrid cored sandwich panel was investigated theoretically, numerically and experimentally. An elastic–plastic analytical model was developed to predict the out-of-plane compressive behavior, with connection strength between facesheets and core as well as non-uniform strut thickness accounted for. For validation, test sample was fabricated using 3D-printing technology and tested under quasi-static out-of-plane compression. The validated model was then employed to exploit optimal configuration of the N core and maximum load capacity of the panel at minimal weight. It was demonstrated that, due to non-uniform strut thickness, the hybrid structure exhibited stepwise deformation, i.e., initial, subsequent and ultimate failures. Under the constraint of equal mass, the load capacity of either the hybrid or corrugated core is superior to the web core, while both the hybrid and web cores outperform the corrugated core in terms of active cooling capacity. For multifunctional applications, the proposed hybrid corrugated core possesses comprehensive thermal and mechanical advantages over conventional corrugated and web topologies.

Heat transfer efficiency of hierarchical corrugated sandwich panels

As a kind of biomimetic materials, ultralight hierarchical porous structures possessing excellent mechanical properties such as load bearing, impact energy absorption, vibration reduction and noise attenuation have been exploited. Often, these porous structures exhibit continuous flow passages that allow for cooling fluids to pass through, thus enabling simultaneous load-bearing and active heat dissipation. This study investigated the convective cooling efficiency of a sandwich panel with hierarchical corrugated core subjected to heating from the face sheets and active cooling through the core. Built upon the classical fin approach, a theoretical model coupling wall heat conduction and fluid convection in the core was established for the hierarchical corrugated-core sandwich panel, covering the full range of fluid flow (from laminar, transition to turbulent). The theoretical model predictions were validated against full numerical simulations. Based on the theoretical model, an artificial intelligence optimization method (i.e., the ant colony algorithm) was adopted to find the optimal combination of key independent geometric parameters of the sandwich panel for maximized heat transfer performance. For the problem of multi-variables optimization, it was demonstrated that the ant colony algorithm is superior in terms of computational time to the traditional exhaustive search method. For a given pressure drop, a set of optimum geometric parameters corresponding to maximum cooling efficiency was found for the proposed hierarchical corrugated-core sandwich panel.

Modeling the high temperature behavior of all-composite, corrugated-core sandwich panels undergoing ablation

Owing to their structural efficiency, the development of structurally integrated thermal protection systems (SITPS) for the next generation aerospace vehicles is currently of interest. Herein, an all-composite sandwich structure with corrugated core is devised and fabricated. After homogenization of the corrugated core, a one-dimensional (1-D) analytical model is developed. The surface ablation is described by considering thermal decomposition, phase transition and thermochemical ablation. With the thermal loading and moving boundary conditions determined by the surface ablation calculation, a heat transfer analysis is performed. To provide insight into the effect of lateral heat transfer and thermal short through the sandwich structures, a two-dimensional (2-D) finite element model is also presented. In addition, a thermal exposure experimental test with oxyacetylene flame is carried out to validate the proposed models. The 1-D analytical model is found to be of satisfactory accuracy, which is useful for rapid preliminary SITPS design.

Inertial amplification induced band gaps in corrugated-core sandwich panels

Corrugated-core sandwich panels (CSPs) have numerous applications but suffer from poor vibration performance in low-frequency range. To address this issue, a type of four-bar inertial amplification (IA) mechanism, whose inertia is increased by amplifying the movement of small masses, is proposed here to enhance the low-frequency vibration reduction capability of CSPs. The proposed structure is modelled by using finite element method (FEM) with considering the in-plane and out-of-plane degrees of freedom of IA mechanisms simultaneously. After validating the proposed model by the commercial software from the perspective of the band-structure, the vibration characteristics of the IA-CSP are investigated numerically. The results show that the attachment of the IA mechanisms can obtain wide bandgaps in low-frequency range, which hence greatly enhancing the vibration suppression performance of typical CSPs. Compared with the local resonators attached CSP, the proposed IA-CSP achieves broader band attenuation in low-frequency range with the same additional mass. Considering spatial constraints, the parametric studies are performed, which reveals that the spans and local stiffness of the IA attached locations determine the degree of nonlocality and hence influence the edge frequencies of bandgaps. The concept of tunable bandgap knob is finally presented to realize the dynamic manipulation of bandgaps under the spatial constraints.