Multilayer Sandwich Research Articles

Preparation of sunflower wax-based oleofoams and its application in inflatable reduced-fat mayonnaise

The present work aimed to prepare inflatable reduced-fat mayonnaise by using sunflower wax-based oleofoams (SWOF) as an oil phase. The effects of SW concentrations on the microstructure and the physical properties of oleofoams were investigated. Then the stable oleofoam formulations were chosen to prepare inflatable mayonnaise, and the functionality related to the physical (textural properties and thermal stability) and sensory attributes (appearance, color, and viscosity) of inflatable reduced-fat mayonnaise was compared with commercial low-fat mayonnaise (CLFM) & full-fat mayonnaise (CFFM). The microstructure study of SWOF indicated the presence of clearly visible SW crystals at the air-oil boundary and inside the continuous phase. This suggests that the stability of SWOF was accomplished through both Pickering and network crystallization. The SWOF exhibited a multi-layered sandwich structure, and the crystal layer thickness increased in oleofoams as the SW concentration rose. The oleofoams containing exceeded 6 wt% SW had better foamability and stability, a more elastic network, and a clear surface texture. Inflatable mayonnaise prepared by 10SWOF had comparable brightness, mouthfeel, and texture to CLFM, but sensitized to temperature. In general, the whipped mayonnaise prepared in this investigation had an acceptable appearance and textural properties and was suitable for foods that do not require heating.

Floating graphite felt-cellulose multilayer sandwich evaporator for solar salt-resistant seawater desalination: Mechanistic role of incorporated super water holding layer

Solar-to-steam generation (SSG) for seawater desalination is emerging process which faces several technology challenges for successful scaling up. Floating solar-to-steam generation (SSG) sandwich-based systems using hydrophilic water bridges have been proved to be fascinating technology for seawater desalination. However, the mechanistic pathways of heat dissipation, mass diffusion and convection are still the key bottlenecks for reliable scaling up. To solve the heat loss and surface salt deactivation, we demonstrate herein the performance of novel SSG structure for seawater desalination via the incorporation of cellulosic sponge as water holder to play a role of water transit between hydrophilic bridge and the top surface. Two systems using low-cost materials were compared, namely graphite felt/hydrophilic paper/polystyrene (GF-HP-PS) and Graphite felt/Water receiver/hydrophilic paper/polystyrene (GF-HP-WR-PS). The process of heat generation and localization was maximum in the GF-WR-HP-PS system, reaching 68.2 °C under 0.5 sun. The photothermal conversion efficiency was found to be 92 and 114 % under 0.5 sun for GF-HP-PS and GF-HP-WR-PS, respectively. On top of that, GF-HP-WR-PS shows effective steadily salt rejection during the desalination of seawater. The WR layer plays a crucial role to govern the confined water, which boosts the dissolution of salt and its convection without significant heat downward convection. As a practical consideration, the cost of used components to fabricate this SSG system is very acceptable and without major restrictions.

Vibroacoustic suppression of sandwich plates with imperfect acoustic black hole

Acoustic black holes (ABHs) have recently been revealed as an effective vibration-control technology. However, owing to their disadvantages such as low stiffness, structural discontinuity and manufacturing difficulties, ABHs are limited in terms of their practical application. Therefore, a multilayer composite sandwich plate with filled imperfect-ABH (F-IABH) is proposed in this study to attenuate the vibration and sound radiation of the multilayer sandwich plate, as well as to enhance its bearing capacity and maintain its topological continuity. The structural-damping characteristics and vibroacoustic response of F-IABH are determined using a semi-analytical wave propagation model developed based on symplectic and discrete radiation model methods. The accuracy and effectiveness of the analytical model are validated using the finite-element method. The results show that the F-IABH can achieve broadband vibration-attenuation and noise-reduction effects, and their vibration and noise reduction effects are significantly better than those of ABH structures. Additionally, the wave-damping characteristics of uniform, ABH, and F-IABH plates are analyzed. The results show that the wave damping of the F-IABH plate is much higher than that of the uniform plate, and that it generates more propagative waves to dissipate energy. Additionally, the damping-attenuation characteristics of each wave in the F-IABH and ABH plates exhibit similar variations. However, owing to the large variation range of the wave-mode damping characteristics of the F-IABH plate, the control effect of the latter on structural vibration and acoustic radiation is more significant than that of the ABH plate.

Experimental and analytical investigations on single and repetitive impact failure responses of composite sandwich panels with orthogonal woven GFRP facesheets and PVC foam cores

Due to the unique design requirements for high load-bearing capacity of ship structures, composite materials used in the marine industry are gradually being developed with the characteristics of multi-layer sandwich structures with large thickness and cross-section, which are different from thin-walled composite materials widely applied in the aeronautical industry. However, sandwich composite materials used in marine structures have high susceptibility to impact event during in-service applications. The impact induced damage may seriously affect their mechanical performance and structural safety. Therefore, a comprehensive investigation in this paper on the failure mechanisms of composite sandwich panels with orthogonal woven GFRP facesheets and a PVC foam core layer is carried out with a series of single and repetitive low-velocity impact tests. The variations of impact force, dent depth, structural stiffness, failure modes, energy absorption and so on of composite sandwich panels against impact energy levels and impact numbers were explored. The results demonstrate that the delamination damage threshold at the first impact, the sudden drop of peak force and the slow descent process of impact force are the three typical characteristics of impact responses that corresponded to delamination initiation and fibre breakage of the upper panel, and compression damage of the core layer, respectively. The accumulated impact-induced damage has a significant negative effect on load-bearing and energy-absorption capabilities of composite sandwich panels. Moreover, an approximate theoretical analytical method is presented to solve the impact resistance of composite sandwich panels. The analytical results are compared well with experimental results. This research provides a detailed understanding of the damage mechanisms of composite sandwich panels under impact loadings and a guidance for impact resistant design of ship protective structures.

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.

Bending behavior of multi-layer sandwich composites reinforced with weft-knitted spacer fabrics

In this study, the bending properties of multi-layer sandwich composites (MLSCs) were investigated. For this purpose, first, 1 × 1- and 5 × 5-Rib gaiting weft-knitted spacer fabrics were produced using E-glass yarns. Then, glass/epoxy sandwich composites were prepared using produced fabrics as reinforcement and epoxy resin as matrix. Considering both the pattern of reinforcements and the arrangement of layers, different types of MLSCs were fabricated by the implementation of different stacking sequences. The prepared samples were subjected to the three-point bending test. Generally, the orientation of samples, structures of each sandwich’s layer, and stacking sequence of layers, as three impressive parameters affected the bending behavior of MLSCs. The results showed that in all samples, the maximum bending force (MBF) of MLSCs in the longitudinal direction is generally higher than that in the transverse direction. The MBF of MLSCs included both 5 × 5-Rib gaiting layers and 1 × 1-Rib gaiting layers increased with increasing the number of 5 × 5-Rib gaiting layers to 1 × 1-Rib gaiting layers. The MBF of MLSCs included of same number of 5 × 5-Rib gaiting and 1 × 1-Rib gaiting structures increases by placing the 5 × 5-Rib gaiting fabrics in the bottom layers, which shows the influence of stacking sequence on the bending behavior of MLSCs. According to the generated geometrical models, two-layer MLSCs are numerically simulated using the FEM. FE simulation and the experimental results brought about the same bending behavior of MLSCs.

Crashworthiness analysis and optimization of brain-coral-inspired multilayer sandwich structures under axial crushing

Inspired by brain corals and cuttlebone, this study employed 3D printing technology to fabricate a novel bio-inspired multilayer sandwich structure based on the Hilbert space-filling curve (named BHSS). The mechanical behavior and deformation process of the BHSS were compared through quasi-static axial crushing experiments and finite element (FE) simulations. The energy absorbing characteristics of the BHSS with different layers were compared through FE simulations, and the results indicated that the 4-layer BHSS displayed superior crashworthiness. Then, parametric studies were conducted to investigate the influence of layer-height gradient and wall-thickness gradient on the energy absorption performance and deformation modes of the BHSS. It was confirmed that the double gradient designs significantly reduced the initial peak force and improved the specific energy absorption of the BHSS. Finally, the multi-objectives optimization based on response surface method and the non-dominated sorting genetic algorithm (NSGA-II) was employed to optimize the geometric parameters of the BHSS, aiming at the optimal configuration for better crashworthiness. Compared to the original design structure, the SEA of the optimized knee point structure was increased by 21.8% and the IPF was reduced by 72.6%. These findings provided valuable guidelines for the brain-coral-inspired design of multilayer sandwich structures with superior energy-absorbing performance.

New Accomplishments on the Equivalence of the First-Order Displacement-Based Zigzag Theories through a Unified Formulation

The paper presents a critical review and new accomplishments on the equivalence of the first-order displacement-based zigzag theories for laminated composite and sandwich structures. Zigzag theories (ZZTs) have widely spread among researchers over the last few decades thanks to their accuracy in predicting the response of multilayered composite and sandwich structures while retaining the simplicity of their underlying equivalent single-layer (ESL) theory. The displacement field consists of two main contributions: the global one, able to describe the overall structural behaviour, and the local layer-wise one that considers the transverse shear continuity at the layer interfaces that describe the “zigzag” displacement pattern typical of multilayered structures. In the framework of displacement-based linear ZZTs, various assumptions have been made on the local contribution, and different theories have been deduced. This paper aims to provide a unified formulation for first-order ZZTs, highlighting some common aspects and underlying equivalencies with existing formulations. The mathematical demonstrations and the numerical examples prove the equivalence of the approaches to characterising local zigzag enrichment. Finally, it is demonstrated that the kinematic assumptions are the discriminants of the ZZTs’ accuracy.

Design, modelling, and manufacturing of sandwich radome structure with out-of-band absorption and in-band transmission performances

Muti-functional composite structures with customizable electromagnetic (EM) responses have attracted much interest in the radome field. In this study, a multi-layered foam-cored sandwich rasorber structure (FSRS) with absorption-transmission-absorption-type (A-T-A-type) of EM response was proposed. Silver-based frequency selective surface (FSS) screen and carbon-based film as alternatives for traditional metallized FSS and lumped resistors were integrated into the FSRS and prepared using a low-cost screen-printing method. Considering specific geometric and EM parameters, full-wave simulations were conducted to predict the EM characteristics of FSRS. Experimental findings demonstrated that under normal incidence, the absorption rate of the FSRS specimen in the frequency ranges of 3.2–6.4 GHz and 13.2–18 GHz is greater than 80 %, and the transmission rate in 9–11.3 GHz is greater than 80 %. Moreover, the absorption and transmission performances of the FRSR specimen remained stable under different polarization directions. The proposal may provide promising materials for future developments in low-observable radome technology.

A Sustainable Solution with Improved Chemical Resilience Using Repurposed Glass Fibers for Sewage Rehabilitation Pipes

This paper introduces a sustainable sewage rehabilitation solution, utilizing repurposed glass fibers for enhanced chemical resilience and environmental conservation. The approach involves dividing a unitary pipe into segments, assembled during commissioning, aiming to reduce installation and transportation costs, particularly in less accessible areas. Each pipe segment comprises a multi-layered glass fiber composite sandwich, joined by an adhesive reinforced with recycled glass fibers. The glass fiber-reinforced plastic (GFRP) pipe features a core of blended sand impregnated with resin, an outer layer for impact resistance, and an inner layer to prevent corrosion. Chemical resilience is assessed through a 10,000 h strain corrosion study exposing both unitary and two-piece circular GFRP pipes to sulfuric acid in a deflected condition. An apparent hoop tensile test evaluates mechanical integrity before and after exposure. The experimental results reveal that the two-piece pipe with a tongue and groove joint (TGJ) with recycled glass fiber adhesive exhibits superior long-term bending stress and failure strain % compared to unitary pipes. This enhancement is attributed to the TGJ’s improved load-bearing capability and chemical resistance. The failure strain % of the two-piece pipe (1.697%) is higher compared to the unitary pipe (1.2613%). The long-term bending stress of the two-piece pipe obtained is 119.94 MPa whereas the unitary pipe reaches 93.48 MPa at the 50-year mark. The cost analysis supports the adoption of the two-piece pipe over unitary pipes due to a 40% reduction in carbon emissions and transportation cost. The novelty lies in the utilization of multi-piece pipes with enhanced chemical resilience, achieved through the incorporation of milled fiberglass reinforcements in the TGJ. Strain corrosion tests take a long time to perform; hence, an accelerated test is needed to improve the current recommended testing standard.

Thermal characteristics of multilayer sandwich Nomex honeycomb core composite with heating elements for railways wall panels

The composite material has been widely used in vehicle interiors, particularly in applications such as the wall-side panels of railways. The sandwich honeycomb composite, which combines two composite skins with a metal honeycomb, is the preferred structure in aerospace and railway applications due to its rigidity at minimal weight. As a functional composite material that provides heat flux to passengers, a multilayer sandwich Nomex honeycomb core composite with heating elements has been developed. In this design, the heating element is inserted into the inner composite material as a heat generation component, producing heat transferred to the other side of the panel. The thermal and structural behaviors of the sandwich composite with heating elements are orthotropic and require careful assessment to understand the material characteristics of the developed composite parts. In this study, conduction heat transfer in the functional honeycomb composite is simulated using the Finite Element Method (FEM) and validated with experimental results. The study proposes three steps to solve the problem: determining the heat-transfer parameters, simplifying the Nomex honeycomb core, and conducting a full-scale heat-transfer simulation. This research aids operating systems in controlling the heat generator input to prevent dangerous conditions. The results indicate that the simulation trends closely align with the experimental results.

Experimental and numerical investigation of multi-layered honeycomb sandwich composites for impact mechanics applications

This project aims to investigate the design of a multi-layered sandwich composite and its performance under impact loading conditions. An experimental and numerical assessment was performed to conclude the effect of increasing the layers of sandwich panels. Three specimens of four different sandwich panel configurations were manufactured to be tested. The skin of the sandwich panels comprises a twill carbon-reinforced epoxy resin, whereas the core consists of a 2D Nomex honeycomb core. The panels are then subjected to transverse impact loading to investigate their impact behaviour. These experimental results are then used to verify numerical models constructed in LS-Dyna. The models of the honeycomb-reinforced sandwich panels are investigated using MAT-054 and MAT-142 material cards in LS-Dyna to find the most economical computational approach. Finally, the energy absorption characteristics calculated during the experimental and numerical work are used to conclude the multi-layered sandwich composite's performance and provide design recommendations. The findings suggest that by increasing the core and shell numbers through the thickness of the panel, the specific energy absorption capability will increase.

Self-similar chiral organic molecular cages

The endeavor to enhance utility of organic molecular cages involves the evolution of them into higher-level chiral superstructures with self-similar, presenting a meaningful yet challenging. In this work, 2D tri-bladed propeller-shaped triphenylbenzene serves as building blocks to synthesize a racemic 3D tri-bladed propeller-shaped helical molecular cage. This cage, in turn, acts as a building block for a pair of higher-level 3D tri-bladed chiral helical molecular cages, featuring multilayer sandwich structures and displaying elegant characteristics with self-similarity in discrete superstructures at different levels. The evolutionary procession of higher-level cages reveals intramolecular self-shielding effects and exclusive chiral narcissistic self-sorting behaviors. Enantiomers higher-level cages can be interconverted by introducing an excess of corresponding chiral cyclohexanediamine. In the solid state, higher-level cages self-assemble into supramolecular architectures of L-helical or D-helical nanofibers, achieving the scale transformation of chiral characteristics from chiral atoms to microscopic and then to mesoscopic levels.

Mechanical and energy absorption properties of multilayered ultra-light sandwich panels produced by 3D-printing and electroforming

This investigation aims to assess the mechanical and energy absorption properties of the light sandwich panel portions made of open-cell polymer and metal/polymer foam cores. These multi-layered sandwich panels were produced by additive manufacturing of polymeric resin and electrodeposition of three layers of metals, Ni/Ni−Cu/Ni, with 4,5, and 6 pores per inch (PPI). The yield strength, energy absorption density, complementary energy, and specific energy absorption (SEA)were measured during uniaxial compression deformation. The results indicate that compared with pure Ni and Cu sandwich panel portions with the same thickness, the abovementioned properties of the sandwich panels had a noteworthy improvement. Mechanical and energy absorption properties were improved by increasing the PPI and the presence of metallic layers. In a sandwich panel with 6 PPI, the yield strength (energy absorption density)wasimproved from 0.12 MPa (0.12 MJ/m3) for the polymeric sandwich panel to 1.83 MPa (0.67 MJ/m3)for the metallic sandwich panel. Investigations on normalized energies of these structures show a predictable behavior for these sandwich panels during plastic deformations. The results show that the multi metallic layers improved the mechanical behavior of these novel sandwich panels. Noticeable enhancement of the calculated properties of these advanced materials guarantees their unique application in variable industries.

Nonlinear geometric fluid-structure interaction model of multilayered sandwich plates in contact with unbounded or bounded fluid flow

Based on the Kirchhoff-Love theory and von Kármán's geometric nonlinearity, the nonlinear vibration analysis of multilayered sandwich plates under ideal flow is presented. Rectangular plates are considered to be laminated of orthotropic composite layers as upper and lower face sheets as well as a central lightweight core made of functionally graded (FG), anisogrid lattice or metal foam materials. Three coupled equations of motion are reformulated into one decoupled governing equation in terms of transverse deflection (w) using the method of inverse differential operator. For the first time, an impermeability condition is developed that considers the moderately large deflection of the contact surface in order to correct the pressure distribution of fluid flow. Based on the potential flow theory, closed-form expressions of hydrodynamic pressure are obtained for different fluid boundary conditions including infinite depth of fluid, flow bounded by a rigid wall and flow between two identical elastic plates. Then, the Galerkin and multiple-scale perturbation methods are used to obtain closed-form solution of nonlinear natural frequency in terms of maximum vibration amplitude. Finally, case studies are presented to investigate the effects of geometric ratios, boundary condition, material distribution, layup, characteristics of flow and geometric nonlinearity on the response quantities. Findings indicate that the large deformation term in the developed impermeability condition has significant effect on the pressure distribution and its effect is more pronounced for thicker plates with larger mode number in the flow direction. Therefore, the novel nonlinear fluid-structure interaction model should be considered to study flow-induced dynamic behavior of sandwich plates with different boundary conditions. In addition, the snap-through behavior is seen in the nonlinear frequency-upstream speed curves and the incipient points of dynamic instability can vary remarkably with the fluid boundary conditions.

Parametric studies and compressive performance of GH4169/K465 Kagome lattice structure prepared by selective laser melting

This paper is proposed a sufficient strategy to enhance the Kagome lattice structure by introducing sphere connections at the joints of the rods. Three types of lattice structures, namely single-cell Kagome, sandwich monocyte, and multi-layer sandwich GH4169/K465, were fabricated through the selective laser melting method. Experimental results demonstrated that the load peak value of the lattice structure increased gradually with variations in rod diameter and angle. When the rod diameter is 2 mm and the angle is 50°, the comprehensive performance is relatively excellent. Both the single-cell Kagome and sandwich monocyte structures exhibited a secondary load peak curve for the load versus displacement curve.The primary failure mode of the spherical connections Kagome structure is member fracture. For sandwich cell structures, when the rod diameter is 1.1 mm, the elastic modulus, yield strength and energy absorption of SRK are 412 MPa, 17.02 MPa and 8.05 MJ/mm3, respectively. When the rod diameter is increased to 1.7 mm, the properties of SRK are 561 MPa, 84.32 MPa and 35.49 MJ/mm3, respectively. The properties of SRK gradually increase with the increase of rod diameter. the elastic modulus, yield strength, and energy absorption of strut-reinforced Kagome with varying rod diameters surpass those of both the Kagome and spherical connections Kagome structures. The failure mode in strut-reinforced Kagome structures is primarily due to rod buckling. In the compressive stress-strain curve of the multi-layer sandwich structure,when the deformation amount is 0.2, SRK has a higher compressive strength than Kagome and SCK structure, which can reach about 350 MPa, while Kagome and SCK are lower than 200 MPa. demonstrated a gradual increasing trend in stress with increasing strain. In addition, the mechanical properties of the Kagome lattice structure are enhanced due to partial structural failure, with fracture occurring in certain members.

Underwater impulsive response of sandwich structure with multilayer foam core

Abstract The coupling between fluid-solid interaction and structural response is a crucial factor in understanding the resistance of sandwich structures to underwater blasts. In this study, we present a theoretical model that predicts the dynamic response of multilayer foam core sandwich beams subjected to underwater impulses. We carried out a time-scale intercoupling analysis by considering the compressible core in both incident impulse and structural response. In the incident impulse coupling phase, the one-dimensional fluid-structure interaction in terms of cavitation evolution is conducted to obtain the incident pressure profile. A four inter-stages response model is proposed for further analyze the structural response coupling phase and its coupling with core strength. Explicit finite element calculations are performed to verify the theoretical results in terms of the velocity profile, transverse deflection, and core compression. The results suggest that the interaction between the four stages of the dynamic response is significantly influenced by the impulsive intensity and core strength, and the sandwich beam does not undergo all the four stages. The equivalent core strength used in the theoretical analysis is confirmed accurate to predicts impact resistance of the corresponding graded core sandwich beam, which is inferior to the sandwich beam with uniform cores, despite having the same areal mass.

Investigation of Structural Energy Absorption Performance in 3D-Printed Polymer (Tough 1500 Resin) Materials with Novel Multilayer Thin-Walled Sandwich Structures Inspired by Peano Space-Filling Curves.

Inspired by Peano space-filling curves (PSCs), this study introduced the space-filling structure design concept to novel thin-walled sandwich structures and fabricated polymer samples by 3D printing technology. The crushing behaviors and energy absorption performance of the PSC multilayer thin-walled sandwich structures and the traditional serpentine space-filling curve (SSC) multilayer thin-walled sandwich structures were investigated using quasi-static compression experiments and numerical analysis. Taking the initial peak crushing force (IPF), specific energy absorption (SEA), and crushing force efficiency (CFE) as evaluation criteria, the effects of geometric parameters, including the curve order, layer height, septa thickness, and wall thickness, on energy absorption performance were comprehensively examined. The results indicated that the energy absorption capacity of the PSC structure was significantly enhanced due to its complex hierarchy. Specifically, the second-order PSC structure demonstrated a 53.2% increase in energy absorption compared to the second-order SSC structure, while the third-order PSC structure showed more than a six-fold increase in energy absorption compared to the third-order SSC structure. Furthermore, a multi-objective optimization method based on the response surface method and the NSGA-II algorithm were employed to optimize the wall thickness and layer height of the proposed novel PSC structures. The optimal solutions suggested that a reasonable wall thickness and layer height were two important factors for designing PSC structures with better energy absorption performance. The findings of this study provide an effective guide for using the space-filling concept with Peano curves for the design of a novel polymer thin-walled energy absorber with high energy absorption efficiency.

Advanced Composite Materials for Structure Strengthening and Resilience Improvement

Advanced composite materials have excellent performance and broad engineering application prospects, and have received widespread attention in recent years. Advanced composite materials can mainly be divided into fiber-reinforced composite materials, laminated composite materials, matrix composite materials, and other composite materials. This article provides a comprehensive overview of the types and characteristics of advanced composite materials, and provides a comprehensive evaluation of the latest research on structural strengthening and resilience improvement in advanced composite materials from the perspectives of new methods, modeling optimization, and practical applications. In the field of fiber-reinforced composite materials, the hybrid technology of carbon fiber and glass fiber can achieve dual advantages in combining the two materials. The maximum increase in mechanical properties of multilayer sandwich RH plate by hybrid technology is 435.4% (tensile strength), 149.2% (flexural strength), and 110.7~114.2% (shear strength), respectively. In the field of laminated composite materials, different mechanical properties of laminated composite materials can be obtained by changing the deposition sequence. In the field of matrix composites, nano copper oxide particles prepared by nanotechnology can increase the hardness and tensile strength of the metal matrix material by 77% and 78%, respectively. In the field of other composite materials, viscoelastic materials and magnetorheological variants have received widespread attention. The development of composite materials benefits from the promotion of new methods and technologies, but there are still problems such as complex preparation, high cost, and unstable performance. Considering the characteristics, application requirements, cost, complexity, and performance of different types of composite materials, further improvements and innovations are needed in modeling and optimization to better meet practical engineering needs, such as the application of advanced composite materials in civil engineering, ships, automobiles, batteries, and other fields.

Flash joining of metal-ceramic multi-layered sandwich structure

The present study uses Flash joining technique to join sandwiched Titanium (Ti) metal with two pre-sintered Titanium dioxide (TiO2) pellets. This method employs Direct Current (DC) to enable rapid diffusion across stacked layers, due to Joule heating, resulting in reliable and continuous interface of the sandwich structure. Joining was found to be more uniform and continuous at lower current density, with respect to that at higher current densities. However, current direction has a detrimental effect on the anodic interface in comparison to the cathodic interface, resulting in superior mechanical properties at cathodic interface. This differential joining behaviour can be attributed to concentration of oxygen vacancies at the anodic interface. X-ray Photoelectron Spectroscopy and Raman, indicating higher concentration of oxygen vacancies at anodic interface, support this notion. The study reveals the directional effect of the current on joining ceramics to metals to attain superior structural integrity for complex multi-layered sandwich structures.