Sandwich Structure Research Articles

Damage effect of composite sandwich structure under shock wave loading

Abstract To investigate the damage effect of composite sandwich structure under shock wave loading, the damage experiment of composite sandwich structure under blast loading was carried out systematically. By studying the response process of the maximum deformation value and plastic deformation value of different composite sandwich structures under blast loading with the change of relative distance, a characterization method that measures the overall deformation of composite sandwich structure is proposed. The damage law of composite sandwich structure under blast loading and the failure mode of front and rear panels and core layer are obtained. Additionally, the causes of overall deformation and local failure of the front and rear panels, as well as the failure mechanism of the core layer, are analyzed. By analysing the relationship between the relative distance and the deformation value, combined with the damage degree of the composite sandwich structure under different relative distance, the results show that the relationship between the maximum deformation value of the sandwich structure and the scaled distance is monotonous. It is reasonable to characterize the damage degree and overall deformation of sandwich structure. Finally, based on the maximum deformation value of the composite sandwich structure, the damage criterion of the composite sandwich structure under blast loading is proposed by using the shock wave overpressure criterion.

INVESTIGATION OF IMPACT PERFORMANCE OF CYLINDER CORRUGATED SANDWICH STRUCTURES WITH DIFFERENT GEOMETRIC CONFIGURATIONS

The aim of this study is to numerically investigate and compare the impact performance of CFRP composite cylinder sandwich structures with five different geometric configurations. The impact performances and damage types of composite cylinder structures for different core configurations were determined. The impact analyses were performed in LS DYNA finite element program using MAT-54 material model with Progressive damage analysis based on the combination of Hashin damage criterion, Cohesive zone model and Bilinear traction-separation law. Among the five different specimens in the study, the highest peak force (PF) value of 1.88 kN was obtained at impact point P2 of the Trapeozidal sandwich structure. The lowest value was obtained at P1 impact point in Triangular sandwich structure with 0.62 kN. The highest and lowest energy absorption efficiency occurred in the Triangular structure, 78% and 38% respectively. The PF value at P2 point is higher than P1. The effect of core support on PF is very important. Since point P1 is not supported by the core, it is determined that the deformation is larger than P2.

Compressive and Bending Properties of 3D-Printed Wood/PLA Composites with Re-Entrant Honeycomb Core

Compressive and Bending Properties of 3D-Printed Wood/PLA Composites with Re-Entrant Honeycomb Core

A parametric study on sandwich structures with star-shaped honeycomb core under blast loads

Abstract A finite element analysis of the blast resistance of the star-shaped honeycomb (SSH) core sandwich structure was carried out by using the CONWEP calculation model, with maximum deformation, energy absorption, and area specific energy absorption as the indicators of the explosion resistance. Based on the finite element method verified by experimental data, the influence of the structural parameters of each part of the SSH core sandwich panel on its anti-explosion performance was quantitatively investigated. The results show that the increase of the connecting ligament L and cell wall angle θ can improve the explosion resistance of the SSH core sandwich panel; the maximum deformation of the sandwich panel and the energy absorption capacity of the sandwich panel decreases with the increase of the three thickness coefficients (cell wall thickness t, the front panel thickness tf , and the back panel thickness tb ); the greater the TNT equivalent, the greater the maximum deformation of the sandwich panel, and the greater the energy dissipation; the use of SSH core sandwich panels as a protective structure in explosion protection systems significantly reduces the maximum deflection and enhances the energy absorption compared to solid panels of equal mass, respectively.

Study on Impact Load Mitigation for High-Speed Water Entry Projectiles Using Aluminum Foam Buffering Structure

Abstract This paper investigated the fluid-solid coupling nonlinear problem of water entry by a high-speed projectile, considering cavitation, air cushion effect, and water vapor generated by the high-speed relative motion between the projectile and the fluid. To this end, a sandwich structure containing aluminum foam attached piston was studied and designed. The numerical simulation of the entry process was analyzed by LS-DYNA. The results show that the sandwich structure reduces the peak impact load. 87.47% reduction in peak force during water entry and aluminum foam has good cushioning effect.

Study on flexural resilience of composite foam sandwich structures under hygrothermal environment

Under hygrothermal environments, the structural stability and strength of all-fiber composite aircraft are significantly affected during long-term flight use. The wing skin, as a critical structural component, plays a vital role in bearing and transmitting aerodynamic loads. Therefore, it is crucial to investigate the structural compressive stability and strength of the wing skin throughout the aircraft's entire life cycle under these conditions. This study employs a real wing carbon fiber foam sandwich structure to investigate the compressive stability and strength of the wing skin structure of a new energy aircraft under actual flight conditions, specifically during the entire process of the room temperature dry state (RTD) and elevated temperature wet state (ETW). Initially, three-point bending tests were conducted on carbon fiber reinforced polymer (CFRP) laminates, foam cores, and CFRP reinforced foam sandwich structures. The CFRP laminates fully rebounded after bending damage in both the RTD and ETW environments. While CFRP reinforced foam sandwich structures also rebounded fully in the RTD environment, their rebound performance diminished in hygrothermal conditions due to the thermoplastic mobility of the foam cores, resulting in only weak rebound capabilities. In hygrothermal environments, the thermoplastic mobility of the foam core leads to diminished resilience after bending damage, resulting in only weak rebound capabilities. Subsequently, compressive instability tests were conducted on the wing skin foam sandwich structure. The results indicated that the basic test study effectively predicted the structural test outcomes. Structural components in the RTD environment exhibited overall flexural instability under compressive load, with damage morphology resembling a circular curve; the damaged specimens fully rebounded after unloading. Conversely, specimens in the ETW environment displayed localized instability, characterized by a wrinkled damage profile, resulting in only weak rebound capabilities after unloading.

Anti-migration of DOS by Using HTPB/GO liner and GO film

Abstract The enhancement of anti-migration performance in insulation materials is critical for the stability and reliability of solid rocket motors (SRMs). This study explores two innovative methods to improve the barrier properties of Ethylene Propylene Diene Monomer (EPDM) insulation layers. Firstly, a composite liner combining Hydroxyl-Terminated Polybutadiene (HTPB) and Graphene Oxide (GO) was synthesized through a solution blending method. Additionally, a GO film was fabricated and integrated with the HTPB liner and EPDM to create a multilayer sandwich structure. The incorporation of these materials was found to significantly enhance the anti-migration performance, with the composite samples showing a 16.89% improvement over standard samples. The layered structure of GO effectively impedes the migration of dioctyl sebacate (DOS), enhancing the anti-plasticizer migration properties of the EPDM. While the multilayer sandwich samples also demonstrated improved performance, issues with adhesion between the GO film and EPDM lead to reduce its effectiveness. Future research will focus on improving the adhesion between the GO film and EPDM to further enhance anti-migration performance. This study provides valuable insights for developing high-performance EPDM insulation materials with enhanced anti-migration properties for aerospace applications.

Investigating SERS performance of controllable fabricated Ag periodic nanostructures with morphologies of nanoclaws and nanocones in detecting SARS-CoV-2 S protein

Investigating SERS performance of controllable fabricated Ag periodic nanostructures with morphologies of nanoclaws and nanocones in detecting SARS-CoV-2 S protein

Sandwich structure engineering for constructing proton exchange membranes with excellent stability and proton conductivity

Sandwich structure engineering for constructing proton exchange membranes with excellent stability and proton conductivity

Shock Response of Sandwich Panels with Additively Manufactured Polymer Gyroid Lattice Cores

Shock Response of Sandwich Panels with Additively Manufactured Polymer Gyroid Lattice Cores

Compressive response and failure mode of glass fiber reinforced polyimide composite honeycomb with cell wall defects

Obtaining some functions for honeycombs can be normally realized by perforating holes on the cell walls. However, excessive perforations, which are always identified as defects, have been shown to reduce the mechanical properties of the honeycomb. Continuous glass fiber reinforced polyimide composite(GF/PI) honeycombs are prepared in this work to investigate their compression processes by finite element analysis and 3D-DIC assisted quasi-static compression tests in order to further reveal the influence mechanism of perforation-induced cell wall defects on their out-of-plane compressive responses and failure modes. The results show that the failure mode of defect-free GF/PI honeycomb is progressive crushing mode, while the GF/PI honeycombs with certain configurations of cell wall defects fail in a fracture mode and fracture/progressive crushing mixed mode. These failure modes ultimately lead to the degradation of the energy absorption performance of the GF/PI honeycombs with cell wall defects. Subsequently, by increasing the matrix content, the failure modes of GF/PI honeycombs with cell wall defects are altered to progressive crushing owing to the reduction of the average maximum damage strain of the cell wall. In addition, the energy absorption performance of GF/PI honeycomb with the same defects configuration is effectively enhanced by 14.24%. This method significantly improves the compressive response and provides theoretical guidance for the structural-functional integrated design of honeycomb sandwich structures in high-performance radomes.

Revealing multi-level shortrange migration of electrons on full-spectrum response e-LDH/t-BiOCl/Bi2S3 and their essential role in the detoxification of Cr(VI) and refractory organic pollutants

The toxic dyeing wastewater containing both carcinogenic Cr(VI) and refractory dyes poses serious threats to ecological safety and human health. Herein, a novel composite photocatalytic material e-LDH/t-BiOCl/Bi2S3 with an ultrathin sandwich structure constructed achieves removal rate constants of 0.044 and 0.019 min-1 for Cr(VI) and reactive red 2 by adsorption-photocatalysis synergistic mechanism in full-spectrum illumination. This structure employs the interface conditions and built-in electric field to form multilevel short-range charge migration channel, achieving the targeted reduction and oxidation of Cr(VI) and azoxy dyes by electrons (e-) and holes (h+). Besides facilitating the reduction of Cr(VI), e- can also enhance the effective utilization of h+ and mediate the formation of other reactive oxygen species that target RR2 degradation. The degradation mechanism, pathway, and biological toxicity of RR2 single and Cr(VI)/RR2 coexistence reaction system were discussed by DFT calculation, LC-MS characterization, and T.E.S.T. evaluation. Moreover, we further investigated the photocatalytic activity and cost-effectiveness of the e-LDH/t-BiOCl/Bi2S3 system under continuous flow and real water settings, and determined the primary water quality parameters that influence photocatalytic performance. This work establishes a new concept for the rational design of robust ternary heterostructure photocatalysts with desirable morphology and competitive performance for photocatalytic applications.

Assessment of Impact Resistance in Composite Sandwich Structures: An Experimental and Numerical Approach

Abstract: This paper presents an evaluation of the impact resistance of composite sandwich structures with regard to the type, design, and characteristics of impact in three parts. Structure consisting of lightweight core and reinforced face layers are widely used in all fields where high strength to weight ratios is desirable. It has established that carbon and glass fiber face sheets make quite different properties in impact absorption and structural resilience as foam or honeycomb cores. Both experimental and numerical formulations offer valuable results with few limitations toward the analysis of damage mechanisms within composite materials. A few suggestions for future work are related to further investigations of the constituent materials, improvements in numerical simulations, and the creation of purpose-oriented design recommendations for broader utilization of these structures in critical-end use applications

Impact behavior of natural material-based sandwich composites

Abstract Sandwich structures may be exposed to different impact loads depending on their areas of use. In this study, low-speed impact tests were implemented on balsa core sandwich composite materials and impact behaviors were examined. Balsa woods of 4, 6, 8, and 10 mm in thickness were used as core elements. Eight- and 12-layered glass fiber-reinforced composite materials with different orientation arrangements were used for the sandwich structures’ top and bottom surfaces. The fiber orientation angles of the glass fiber materials were determined as [0°]2s and [0°/90°]s. The balsa core sandwich composite materials were produced using the vacuum infusion method. The prepared samples were tested at impact energy of 15, 30, 45, and 60 J. At the end of these tests, the effects of impact energy, core thickness, increase in number of outer surface layers, and change in orientation angle on contact force, displacement, and absorbed energy values were analyzed. The outer surfaces of the damaged samples and the damage patterns that occurred in the balsa wood were examined after the tests.

Fabrication and mechanical behaviors of recoverable thermoplastic sandwich structures with circular honeycomb cores based on the continuous approach

Recyclable, lightweight materials using advanced processing techniques are essential for the sustainable development of future wind turbine blades. Thermoplastic composite sandwich structures were developed to satisfy this need. This study presents a novel continuous approach for fabricating recoverable fully thermoplastic composite honeycomb sandwich structures. Finite element models of the honeycomb and sandwich plate, accounting for surface-to-surface contact between cells, were developed. Uniaxial compression analysis was performed on honeycombs to investigate their failure modes and energy absorption characteristics. Furthermore, the deformation mode and load-bearing capacity of thermoplastic composite honeycomb sandwich panels were examined under out-of-plane compression and shear loads. Our comprehensive finite element model, incorporating the intricate contact behavior of individual cells, demonstrated a remarkable concordance with experimental outcomes. Insightful predictions were given regarding the correlation between contact areas and load-bearing capacities.

Dynamic Bending Behaviour of Sandwich Structures for Marine Applications

This paper examines the mechanical performance of fibre-reinforced composite sandwich structures (FRPSSs) for maritime applications, focusing on the impact bending and damage sequence after seawater exposure. Glass-fibre/epoxy facesheets with various PVC foam core configurations underwent low-velocity single and multiple impacts. An in situ moisture-uptake methodology monitored moisture ingress until saturation. Results showed moisture uptake reduced impact bending capacity and bending stiffness to varying degrees. While energy-absorption performance remained largely unchanged under single impacts, significant differences were noted for multiple impacts. Failure analysis confirmed the reductions in some damage modes such as facesheet fracture, indentation, and core shear failures, while core shearing, delamination, core/facesheet debonding, and fibre breakage were identified as the main failure modes. These insights enhance understanding and optimisation of FRPSSs for improved out-of-plane damage resistance in marine applications.

Crashworthiness of multi-layer gradient corrugated sandwich circular tube structures

A novel multi-layer gradient sandwich tube design, which combines corrugated and circular structures, was developed in this study. The results of quasi-static compression tests and ABAQUS numerical simulations demonstrate that the energy absorption of the multi-layer corrugated sandwich (A333N666) is 147% greater than that of a traditional corrugated sandwich (A3N6). The crushing force efficiency (CFE) increased by 29.3%, and the specific energy absorption (SEA) improved by 36%. For single-layer corrugated sandwich structures, the crashworthiness index increases with the wave number. However, this rate of increase diminishes over time. The crashworthiness index also increases with the wave number for multi-layer sandwich structures, and the magnitude of this increase becomes increasingly pronounced. Notably, experiments and numerical simulations show that the effect of the amplitude gradient arrangement on the crashworthiness index is more significant than that of the wave number gradient. The amplitude gradient arrangement (A432N666) demonstrates the best performance, exhibiting a 42.4% increase in SEA and a 33% increase in CFE compared to the single-layer corrugated sandwich structure (A3N6). Overall, the multi-layer amplitude gradient design exhibits exceptional crashworthiness. The findings of this study may provide valuable insights for the design of thin-walled structures.

Structural Optimization of a High-Performance Green Sandwich Made of Sisal Reinforced Epoxy Facings and Balsa Core.

Within the range of composite laminates for structural applications, sandwich laminates are a special category intended for applications characterized by high flexural stresses. As it is well known from the technical literature, structural sandwich laminates have a simple configuration consisting of two skins of very strong material, to which the flexural strength is delegated, between which an inner layer (core) of light material with sufficient shear strength is interposed. As an example, a sandwich configuration widely used in civil, naval, and mechanical engineering is that obtained with fiberglass skins and a core of various materials, such as polyurethane foam or another lightweight material, depending on the application. Increasingly stringent regulations aimed at protecting the environment by reducing harmful emissions of carbon dioxide and carbon monoxide have directed recent research towards the development of new composites and new sandwiches characterized by low environmental impact. Among the various green composite solutions proposed in the literature, a very promising category is that of high-performance biocomposites, which use bio-based matrices reinforced by fiber reinforcements. This approach can also be used to develop green sandwiches for structural applications, consisting of biocomposite skins and cores made by low-environmental impact or renewable materials. In order to make a contribution to this field, a structural sandwich consisting of high-performance sisal-epoxy biocomposite skins and an innovative renewable core made of balsa wood laminates with appropriate lay-ups has been developed and then properly characterized in this work. Through a systematic theoretical-experimental analysis of three distinct core configurations, the unidirectional natural core, the cross-ply type, and the angle-ply type, it has been shown how the use of natural balsa gives rise to inefficient sandwiches, whereas performance optimization is fully achieved by considering the angle-ply core type [±45/90]. Finally, the subsequent comparison with literature data of similar sandwiches has shown how the optimal configuration proposed can be advantageously used to replace synthetic glass-resin sandwiches widely used in various industrial sectors (mechanical engineering, shipbuilding, etc.) and in civil engineering.

3D-Printed lightweight sandwich structures with carbon-fibre-reinforced polymer skins and glass-fibre-reinforced polymer core: a comparative study

3D-Printed lightweight sandwich structures with carbon-fibre-reinforced polymer skins and glass-fibre-reinforced polymer core: a comparative study

Research on flow structure and heat transfer mechanism of windward bend lattice frame

Research on flow structure and heat transfer mechanism of windward bend lattice frame