Performance Of Sandwich Structures Research Articles

Response of aluminium honeycomb sandwich panels under combined shock and impact loading: Experimental and numerical investigations

The performance of sandwich structures against individual shock loading and fragment impact loading has been extensively examined, but little is known about their performance in the presence of simultaneous shock and impact loading. Based on a recently developed composite projectile to simulate combined shock and single fragment impact loading, the performance of aluminum honeycomb core sandwich panels (HCSPs) against combined loading is methodically examined. The achieved results reveal that the combined loading exhibits a synergistic effect compared to the single loading, i.e., increased damage of the sandwich panel and enhanced perforation resistance of the sandwich panel. After that, a three-dimensional finite element simulation is performed to explore the underlying mechanism of the synergistic effect. Numerical analysis indicates that the increased damage is a result of perforation-induced reduction of load-carrying capacity of sandwich panel, while the enhanced perforation resistance is the result of deflecting-induced perforation time delay of the perforation process. Finally, the parametric investigation of sandwich geometries such as asymmetric face sheets, core density, and core height is comprehensively conducted. The gained results reveal that both performance and synergistic effect due to combined loading are sensitive to these parameters.

Performance of honeycomb sandwich structure under combined blast and impact of fragments

The response of sandwich structures under the synergistic effects of blast wave and fragments is a topic of interest for researchers and designers. Thus, the performance of a sandwich structure used for enhancing the protection of a target structure is numerically investigated because it may experience such complex loading conditions resulting from combined blast and fragment impact. A conventional sandwich structure modelled using aluminium alloy resists a bare blast load imposed on it. Analysis, however, reveals that fragments penetrate through the front facesheet of a conventional sandwich structure, indicating a lower resistance of the front facesheet to combined blast and fragment effects. Thus, the behaviour of conventional aluminium honeycomb sandwich structures is compared with enhanced sandwich configurations consisting of a front facesheet covered with multilayer lightweight composite Kevlar fabric material. The Kevlar fabric arrests the maximum number of fragments, and reduces their momentum, thereby reducing the damage level in the sandwich structure. The effect of the charge weight and shape of the fragments on the damage modes of the sandwich structure is also assessed. With the increase in charge weight, the momentum of the fragments is found to increase, and these penetrate the back facesheet of the sandwich structure.

Experimental investigation and simulation of 3D printed sandwich structures with novel core topologies under bending loads

Abstract In a range of applications, such as the automotive, aerospace, and shipbuilding sectors, where weight reduction is essential, sandwich structures are getting more popular. The performance of sandwich structures in bending can be enhanced by using lightweight core topologies. In this study, six different novel and new core topologies were designed with CATIA V5. Polylactic acid (PLA) sandwich structures with new core designs were produced using the fused deposition modeling (FDM) additive manufacturing method. In order to determine the mechanical characteristics of these six designed core topologies, three-point bending tests on sandwich structures were performed. The influence of core topology on the flexural characteristics of lightweight sandwich structures was investigated to appropriately choose and design the core topology of the sandwich structures to meet desired structural requirements. To evaluate the flexural behavior of sandwich structures, finite element simulation using ANSYS Workbench 2021 R2 was also performed. Both the experimental data and simulation were in good agreement and clearly showed that the sandwich structure with the triple bow core exhibited the highest mechanical properties. These results provide new perspectives on the investigation of the mechanical response of sandwich structures, which can be beneficial for many other industries and applications.

Dynamic response and failure mechanism characterization of composite‐metal sandwich structures under slamming impact utilizing CEL method

AbstractSlamming is a complicated fluid–structure coupling process accompanied with complex transfer of load and energy, which may pose a significant risk to the overall safety of structure. This paper aims to evaluate the dynamic response and elucidate the failure mechanism of composite‐metal sandwich structures under slamming impact. Firstly, a reliable numerical simulation process is established based on CEL method in ABAQUS/Explicit combining with a VUMAT subroutine, whose effectiveness is verified through the comparison with published experimental results. Subsequently, dynamic response of the sandwich structures is investigated considering the influence of slamming velocity and material constituent. Meanwhile, damage evolution and critical failure mechanism are assessed through progressive damage analysis. Results show that CF‐Al‐CF case owns the best mechanical performance and the latest ultimate failure moment. The overall performance of sandwich structure is mainly dependent on the mechanical properties of skin. Additionally, damage of Al‐CF‐Al case is more sensitive to the variation of velocity compared with that of CF‐Al‐CF and Al‐Al‐Al cases, which indicates that the ductility of core is responsible for ultimate damage. Moreover, extensively distributed matrix tension damage can be identified as the critical damage mode, which may further cause debonding damage and even fiber fracture.

Large Torsion Deformation: Centrosymmetric Reentrant Honeycomb

There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

On the mechanical performance of honeycomb-core sandwich L-joint under bending load: an experimental-numerical study

The mechanical properties of sandwich structures have drawn much attention from research and industrial application, while sandwich structures in the form of L-joint have been rarely addressed. In this paper, L-joint sandwich structures were experimentally tested under bending load to investigate the mechanical performance during structural deformation and damage evolution. The corresponding testing process was numerically simulated using finite element (FE) modeling. Nomex® honeycomb was selected as the core material of the sandwich structure, with the outer facesheets made of thermosetting Carbon Fiber Reinforced Polymer (CFRP) prepreg. Sandwich structures in the form of thin-walled beams and L-joint were then manufactured with specially-designed molds. Quasi-static three-point bending tests up to failure were conducted on the sandwich panels. Experimental results revealed that the main failure mode of the sandwich panel was the fracture in the honeycomb wall. The stiffness and strength properties of the sandwich structure were analyzed with FE modelling results, which showed good agreement with the experimental data. The adhesively bonded and hybrid rivet-bonded sandwich L-joints were investigated under vertical crushing load, showing the main failure region located in the corner area of the L-joint. The proposed experimental-numerical method on the mechanical performance of sandwich structures can provide reliable guidance on the connection of the caravan floor and side walls in automotive industries.

Bending behavior of 3D printed sandwich beams with different core topologies

Lightweight core topologies have been considered as an advanced alternative to improve the overall performance of sandwich structures in bending. Designed sandwich beams containing 3D printed cores as conventional honeycomb, re-entrant auxetic honeycomb with two positions of the cells, and chiral topologies were created with CATIA V5. The sandwich beams were manufactured from polylactic acid polymer (PLA) by fused deposition modeling (FDM) using the Ultimaker 3 Extended printer. Three-point bending testing was conducted on sandwich beams using an Instron 8872 testing machine and following ASTM C393-20, as to obtain the strength, bending stiffness, and energy absorption of the sandwich beams for these three designed core topologies. Comments on the cores' performance and sandwich beams response are done together with observations concerning their failure.

Experimental and numerical investigation of sandwich structures with balsa core and hybrid corrugated composite/balsa core under three-point bending using digital image correlation

Sandwich structures are commonly used in automotive, aerospace, and civil infrastructure applications due to their high strength-to-weight and stiffness-to-weight ratios. In the present work, the performance of sandwich structures with aluminum facings and two different types of core, including balsa wood core and hybrid corrugated composite/balsa core subjected to three-point bending, is investigated, both experimentally and numerically. The face sheets are 6061-T6 aluminum alloy and the hybrid core has been made of balsa wood with average density of 125 kg m−3 and E-glass woven fabric, bonded together using epoxy resin. For data acquisition during the tests, a linear variable differential transformer has been placed under the mid-span of the specimens and a digital image correlation technique has been used for monitoring the full-field strain distributions and deflection pattern as well. Continuum damage mechanics has been employed for the finite element model analysis of the three-point bending tests. In order to predict the maximum load-bearing capacity and failure modes, a wood material behavior model for balsa and a combination of Hashin and Puck failure criterion for corrugated composite were imported into ABAQUS/Explicit via VUMAT subroutines. It was found that combining balsa core with corrugated composite results in prevention of catastrophic failure and consequently gradual decrease of load-bearing capacity. Furthermore, the results demonstrate that the hybrid core increases the strength-to-mass density and stiffness-to-mass density ratios by 34.7% and 28.2%, respectively. Numerical findings have been successfully compared to experimental data, which reveals its suitability for parametric analysis of the proposed hybrid core sandwich structure.

3D printed architected polymeric sandwich panels: Energy absorption and structural performance

Lightweight architected cellular cores have been introduced as an advanced alternative to improve the overall performance of sandwich structures. In this study, we implement semi-analytical and finite element approaches and conduct experimental impact tests to evaluate the performance of 3D printed lightweight sandwich panels with architected cellular cores of programmable six-sided cells. Changing the geometrical parameters of the cells leads to cellular cores of hexagonal, rectangular and auxetic topologies. A semi-analytical methodology is developed for conducting structural and low-velocity impact analyses based on a modified higher-order shear deformation theory. The standard mechanics homogenization is implemented through finite element modelling to accurately predict the effective mechanical properties of architected cellular cores. We apply explicit large deformation finite element analysis using ANSYS to analyze the elasto-plastic behavior of architected sandwich panels under a low-velocity impact. To experimentally corroborate the developed theoretical and computational models and to evaluate the manufacturability of the architected sandwich panels, we use the fused deposition modeling to 3D print samples of polylactic acid biopolymers. Uniaxial tensile test is first used to characterize the polymer. We then conduct low-velocity impact tests to investigate the energy absorption capability of architected sandwich panels. X-ray micro-tomography is finally employed to study the microstructural features of panels before and after the impact. The experimental and numerical results show that the auxetic sandwich panel is potentially an appropriate candidate for energy absorption applications due to its high-energy absorption capability and a minimum response force transferred from the 3D printed panel.

Axial crushing and transverse bending responses of sandwich structures with lattice core

The performance of sandwich structure with expanded metal sheets as the core was studied under axial crushing and transverse impact bending. Relationships between the force and displacement at the mid-span of the sandwich beams were obtained from the experiments. Numerical simulations were carried out using ABAQUS/EXPLICIT and the results were thoroughly compared with the experimental results. Then, the influence of the cell orientation and size of the cell were investigated. It was shown that the cell orientation was a critical parameter affecting the failure mode and energy absorption capability, leading to the increase in the peak load and specific energy absorption during the axial crushing tests. Specific energy absorption of the sandwich beams with lattice core under axial crushing ranges from 117 to 2934 J/kg, which is higher than that of beams under transverse bending. The results showed that the increase in cell angle up to ϴ = 90 increased the energy absorption by 624.4%. It was found that effects of the cell size and cell orientation on the energy absorption were dependent on each other governing the low-velocity impact response of the sandwich beams with lattice cores.

Research on Crushing Performance of Sandwich Panel with V-Type Corrugated Core under Shock Load

Sandwich panels with a V-type corrugated core are developed to investigate their crushing performance under lateral load based on the numerical method. The validity and feasibility of the calculation method is qualified by comparing numerical results with experiment results. Based on that, finite element software is applied to analyze the effects of structural parameters on the crushing performance of sandwich structure. Then inspecific energy increases as the core thickness and inclination angle are increased, but it will induce as the core height is raised. Additionally, the average crushing strength is increased with the increasing thickness, but it will decrease as the core height and inclination angle are raised. The results of this research may help the practical design and optimization of sandwich panel with corrugated core.

Influence of resin viscosity and vacuum level on mechanical performance of sandwich structures manufactured by vacuum bagging

AbstractThe choice of process parameters is critical in optimizing the mechanical properties of sandwich structures produced using the vacuum bagging technique. The aim of this paper is to analyze how the viscosity of the resin/curing agent system and the vacuum level influence the morphology and the mechanical behavior of sandwich beams with composite faces (epoxy resin and glass fiber fabric named COMBI 900) and a PVC foam core. Four different sandwich structures were produced by varying the viscosity of the epoxy resin/curing agent at constant maximum vacuum pressure. Three further structures were manufactured by varying the strength of the vacuum with the resin viscosity maintained constant at the minimum level. Three point bending tests were carried out on all seven sandwiches. The analysis shows that although both parameters affect the mechanical characteristics of the structure, the viscosity of the resin system is clearly the more influential of the two. The morphological structure of the sandwiches was analyzed both by scanning electron microscope (SEM) and by muffle furnace ignition to calculate the percentage of fibers, matrices, and voids present in the different samples © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:20–30, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20172

Evaluation of the Flexural Rigidity of Sandwich Structures Using Experimentally Obtained Mechanical Properties of the Constituents

Prediction of mechanical performance of sandwich constructions is a difficult task due to the complex nonlinear and inelastic behavior of the constituent materials. This study tries to utilize an analytical model to estimate the mechanical performance of sandwich structure based on the mechanical properties of the constituents. To this end, the mechanical properties of the core and skin materials were examined separately. The mechanical behavior and deformation mechanism of Ni alloy foam structures have been studied using uniaxial compression testing. The mechanical properties of alloy 625 coating were determined using tensile testing. The flexural rigidity of sandwich structures were calculated using experimentally obtained elastic moduli of the alloy 625 coating and Ni alloy foam. The model was also used to calculate the flexural rigidity of sandwich samples with different skin thicknesses. This study also investigates the effect of post fabrication heat treatment on the mechanical performance of the sandwich structures.

207 GFRP板-アルミハニカムのサンドイッチ構造体の衝撃吸収性能の評価(関東支部 茨城講演会)

207 GFRP板-アルミハニカムのサンドイッチ構造体の衝撃吸収性能の評価(関東支部 茨城講演会)

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.

Performance of Sandwich Structures with Composite Reinforced Core

Sandwich panels with a foam core reinforced with composite laminates were investigated. The effective material properties of the reinforced core were obtained by homogenization. The general equations of equilibrium for sandwich plates were derived and used for parametric studies of the behavior of the sandwich plates. Three Point Bending tests were performed to experimentally measure the bending stiffness along with the strength of sandwich beams. The test results were also used to verify the analytical solution obtained by using the sandwich plate theory. It was found that local indentation must be included in the theoretical model. Static punching tests (SPT) and low velocity impact (LVI) tests were performed to investigate the behavior of sandwich plates under static and dynamic point loads. The force-displacement relations were modeled based on indentation data. The damage modes, effects of the core reinforcement, and effects of the foam were investigated. A second manufacturing method for constructing the reinforced core was presented, and its properties were compared with those obtained using the original manufacturing method.