Relative Density Research Articles

Bio-Inspired Curved-Elliptical Lattice Structures for Enhanced Mechanical Performance and Deformation Stability.

Lattice structures, characterized by their lightweight nature, high specific mechanical properties, and high design flexibility, have found widespread applications in fields such as aerospace and automotive engineering. However, the lightweight design of lattice structures often presents a trade-off between strength and stiffness. To tackle this issue, a bio-inspired curved-elliptical (BCE) lattice is proposed to enhance the mechanical performance and deformation stability of three-dimensional lattice structures. BCE lattice specimens with different parameters were fabricated using selective laser melting (SLM) technology, followed by quasi-static compression tests. Finite element (FE) numerical simulations were also carried out for validation. The results demonstrate that the proposed BCE lattice structures exhibit stronger mechanical performance and more stable deformation modes that can be adjusted through parameter tuning. Specifically, by adjusting the design parameters, the BCE lattice structure can exhibit a bending-dominated delocalized deformation mode, avoiding catastrophic collapse during deformation. The specific energy absorption (SEA) can reach 24.6 J/g at a relative density of only 8%, with enhancements of 48.5% and 297.6% compared with the traditional energy-absorbing lattices Octet and body-center cubic (BCC), respectively. Moreover, the crushing force efficiency (CFE) of the BCE lattice structure surpasses those of Octet and BCC by 34.9% and 15.8%, respectively. Through a parametric study of the influence of the number of peaks N and the curve amplitude A on the compression performance of the BCE lattice structure, the compression deformation mechanism is further analyzed. The results indicate that the curve amplitude A and the number of peaks N have significant impacts on the deformation mode of the BCE lattice. By adjusting the parameters N and A, a structure with a combination of high energy absorption, high stiffness, and strong fracture resistance can be obtained, integrating the advantages of tensile-dominated and bending-dominated lattice structures.

Sustainable concrete production: Mechanical and durability behaviour of slag-based geopolymer containing recycled geopolymer aggregate

Geopolymer binders, synthesized by activating aluminous and silicate-rich materials with alkalis, are attracting great interest as an environmentally friendly building material to replace cement due to their low CO2 emissions and the possibility of disposing of industrial wastes. Intensive research on geopolymer binders and the prospect of their future widespread use have raised questions about end-of-life strategies for geopolymer concrete (GPC). In this study, the durability and mechanical properties of new geopolymer concrete (GRAC) produced from aggregate derived from one-part slag-based GPC subjected to ambient curing were investigated. In addition to the properties of recycled geopolymer aggregates (RGAs) such as ASR reactivity, water absorption rate, organic matter content, specific gravity, the effects of RGA size and amount on mechanical strength, SEM analysis, surface topography and length variation of new GRAC produced by adding different proportions of fine and coarse RGAs (30 %, 60 % and 100 %) were investigated. Consequently, it was observed that GRAC exhibited a mechanical strength comparable to that of GPC produced with natural aggregate, while the void content, water absorption rate, surface pores and microcracks of GRAC increased with the increase in RGA content. In addition, the resistance of GRAC to environmental degradation (acid, sulfate, salt and water effect) decreased with the increase in porosity. The high water absorption rate, porous structure and weak interface region (ITZ) of RGAs make GRAC produced with these aggregates more sensitive to external aggressive chemicals.

Fracture mechanics of bi-material lattice metamaterials

The advent of additive manufacturing technology empowers precise control of multi-material components or specific defects in lightweight lattice metamaterials, however, fracture mechanics and toughening design strategies in such metamaterials remain enigmatic. By incorporating theoretical analysis, numerical simulation, and experimental investigation, our study reveals that stretch-bend synergistic strut deformations caused by bi-material components or topology defects contribute notably tougher lattice structures surpassing its ideal single-material lattices. A peak fracture energy at a critical modulus ratio was found in a designed bi-material lattice composed of triangular soft struts and hexagonal stiff struts, which originates from the shift of fracture modes at crack tip from strut bending to stretching dominated failure modes as the modulus of soft struts increases, where the compromise in competition between bending-enhanced and stretching-weakened energy dissipations of struts deformations results in the maximized fracture energy. A parametric design protocol was proposed to optimize fracture energy of bi-material lattices through tuning the modulus ratio and relative density. Furthermore, the concept of stretch-bend synergistic toughening can also be applied to make tougher single-material lattices with specific topological defects. Our findings not only provide physical insights into directing crack propagation but also provide quantitative guidance to optimize fracture resistance within low-density tough lattice metamaterials.

Effects of (Cd1/3Sb2/3)4+ co-substitution on the crystal structure, chemical bond characteristics, and microwave dielectric properties of CeO2-ZrO2-MoO3 ceramics

In this paper, Ce2[Zr1−x(Cd1/3Sb2/3)x]3(MoO4)9 (CZ1−x(CS)xM, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ1−x(CS)xM solid solution with a space group of R-3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ0.98(CS)0.02M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ1−x(CS)xM ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ0.98(CS)0.02M ceramics demonstrated superior performance at 675 °C, with εr = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τf = −17.73 ppm/°C.

Analysis of Alcohol Content in Fruit Vinegars as a Halal Testing Method for Fermented Products

The significance of halal certification has experienced notable growth over time as a result of the escalating demand for halal food products. One of the critical points of halal certification for food and beverages is the alcohol content contained within them. Fermented products represent a category of food and beverages with a pivotal consideration in ensuring compliance with halal dietary restrictions, particularly in relation to alcohol content. This study aimed to determine the alcohol content in persimmon vinegar, soursop vinegar, and combined (mix of persimmon and soursop) vinegar. The study conducted experimental analyses to assess the alcohol concentration in fruit vinegars employing a specific gravity calculation method using a pycnometer. The study found that the combined fruit vinegar had the highest alcohol content at 0.195%, while persimmon vinegar had the lowest alcohol content at 0.15%. The results showed that persimmon vinegar, soursop fruit vinegar, and combined fruit vinegar contained alcohol content below 0.5%, aligning with the halal standards outlined in the MUI Fatwa No. 10 of 2018.

High-Fidelity Simulation of the Light-to-Dense Stratification Transient in the HiRJET Facility

Density stratification in a large enclosure is a crucial phenomenon to heat transfer and sustainable passive heat removal of a sodium fast reactor during reactivity transients. However, engineering turbulence models were identified to have unsatisfactory performance in predicting propagation of a stratified front. Yet, the scarcity of high-resolution data for stratification hampers the development of models. To explor e applications of leveraging direct numerical simulation (DNS) data to support turbulence model development, this work conducted DNS using NekRS to study a long stratification transient in the High-Resolution Jet (HiRJET) experimental facility. This work considers an experiment run where light fluid is injected into a tank containing a denser fluid with a relative density difference of 1.5%. Formation of the stratified layer is identified as impingement of the buoyant jet promoting mixing of the two fluids. Based on the transient statistics, transport of the concentration can be characterized by regions with dominating effects of turbulent mixing, buoyant dissipation, and molecular diffusion, respectively, as moving away from the elevation of jet impingement. Concentration near the stratified front also exhibits oscillation at Brunt-Väisälä frequency. Preliminary validation of the simulation showed encouraging agreement of the concentration distribution with the reference experiment.

Forced convection heat transfer in AlSi7Mg lattice structures fabricated by additive manufacturing

The thermal-hydraulic performance of lattice structures with different topologies and relative densities was investigated. AlSi7Mg sandwich panels cored with vertical fin, pyramidal, and tetrahedral lattices were fabricated using additive manufacturing. Four different relative densities (7.5 %, 10 %, 12.5 %, and 15 %) were considered for each lattice core. The experiment was conducted under constant heat flux and steady-state forced convection. Results showed that increasing relative density led to an increase in the average Nusselt number by 3.2–12.5 % in the vertical fin, 23.8–56.4 % in the pyramidal lattice, and 38.8–46.9 % in the tetrahedral lattice. To evaluate the efficiency of different topologies, the average Nusselt number was compared at a fixed pumping power. The pyramidal lattice exhibited the best performance among the test samples, followed by the tetrahedral lattice. The numerical analysis was performed to gain further insights into the heat transfer mechanisms involved. As the relative density increased, an increase in both the maximum fluid velocity and turbulent kinetic energy was observed in all test samples. The numerical results demonstrate that the observed improvement in thermal-hydraulic performance with increasing relative densities in experiments is attributable to the enhanced momentum of the fluid and turbulent mixing.

Structural stability and electrochemical response of 3D printed and reactively sintered Ga-doped Li7La3Zr2O12 electrolytes

Cubic Ga-doped Li7La3Zr2O12 (LLZO) tubes with one closed end were produced by a 3D printing-reactive sintering process. For the first time, the structural stability of Ga-doped LLZO tubes (relative density: ∼88 %, cubic LLZO fraction > 90 %) was evaluated after immersion in eutectic PbLi, a candidate molten breeder, at 350 and 450 °C. The high ionic conductivity cubic LLZO phase was maintained after immersion at 350 °C for 100 h, while secondary phase formation and conversion of cubic LLZO to the tetragonal polymorph was observed after 6 h at 450 °C. Li was successfully pumped through the tubes during linear voltage sweeps at 350 °C, indicating that Ga-doped LLZO is a possible candidate for hydrogen isotope extraction in PbLi via direct electrolysis.

Hybrid artificial neural network models for bearing capacity evaluation of a strip footing on sand based on Bolton failure criterion

This paper employs the Bolton failure criterion, incorporating strength-dilatancy relationships, to analyze the bearing capacity factor of a strip footing on dense sand. Utilizing finite element limit analysis (FELA) based on the lower and upper bound theorems, the study presents the results as average bound solutions. By using the Bolton model, the b parameter is first calibrated and found that it should be about 3.50 to align the ultimate bearing capacity (qu) from FELA to have a good agreement with that from experimental test results from previous studies. The influence of parameters relevant to the Bolton failure criterion is analysed, showing that an increase in relative density (DR) significantly affects the variation in the bearing capacity factor (Nγ) at higher Q values, while lower Q values inhibit dilatancy due to soil crushing. The width of the strip footing (B) has a decreasing effect on Nγ at higher Q values, and the unit weight (γ) changes minimally impact Nγ within the range of 16–22 kN/m3. Additionally, an increase in the critical state friction angle (ϕcv) consistently increases Nγ, highlighting its direct correlation with soil shear strength. A hybrid artificial neural network (ANN) model integrates machine learning with four optimization algorithms: Imperialist Competitive Algorithm (ICA), Ant Lion Optimization (ALO), Teaching Learning Based Optimization (TLBO), and New Self-Organizing Hierarchical Particle Swarm Optimizer with Jumping Time-Varying Acceleration Coefficients (NHPSO-JTVAC). Comparative rank analysis of hybrid ANN models based on the selection of the optimal number of hidden neurons demonstrates that the ANN-TLBO model excels in predicting the bearing capacity factor, achieving a score of 48. This conclusion is corroborated by an error heatmap matrix, which indicates a minimized percentage of error relative to other hybrid ANN models. Importance analysis identifies particle crushing strength (Q) as the most significant factor influencing the bearing capacity factor (Nγ).

A novel Li3Mg4(Nb1-xVx)O8 ceramic with high Q×f value and good temperature stability with low sintering temperature

A series of low-loss Li3Mg4(Nb1-xVx)O8 (0.02 ≤ x ≤ 0.08) ceramics has been synthesized in this work, with the optimal sintering temperature lowered to 950°C due to the incorporation of V5+ ions. Moreover, the effects of substituting V5+ for Nb5+ on the sintering, composition, structure and properties of the ceramics have been systematically analyzed. It has been discovered that the permittivity (εr) and quality factor (Q×f) of Li3Mg4(Nb1-xVx)O8 ceramics exhibit a correlation with the relative density, which is influenced by the variation in grain size distribution resulting from the substitution of V5+ ions. Additionally, the total lattice energy of Li3Mg4(Nb1-xVx)O8 ceramics is also affected by the bond characteristics within the Nb-O octahedra, thus influencing the Q×f value. The resonant frequency temperature coefficient (τf) fluctuates within a small range. The Li3Mg4(Nb0.98V0.02)O8 ceramics exhibit excellent microwave dielectric properties at 950°C: εr∼14.03, Q×f∼93,425 GHz, τf∼-6.12 ppm/°C, with a relative density reaching 98.3 %. Compared to unsubstituted Li3Mg4NbO8 ceramics, the sintering temperature is reduced by 200°C without forming impurity phases. While adjusting the τf value to nearly zero, it maintains a high Q×f value, indicating promising applications in Low-Temperature Co-fired Ceramics (LTCC).

Trinitroglycerin-loaded chitosan nanogels accelerate angiogenesis in wound healing process

Trinitroglycerin (TNG) with remarkable angiogenic, antibacterial, and antioxidative activity is a promising candidate to govern wound healing capacity. However, its clinical administration is limited due to associated complications and NO short half-life. In the current study, TNG-loaded chitosan nanogels (TNG-Ngs) were examined in-vitro and in-vivo to gain insight into their clinical application. We prepared TNG-Ngs and characterized their physiochemical properties. The potential of TNG-Ngs was assessed using biocompatibility, scratch assay, and a full-thickness skin wounds model, followed by histopathological and immunohistochemistry examinations. TNG-Ngs particle size 96 ± 18 and definite size distribution histogram. The loading capacity (LC) and encapsulation efficiency (EE) of prepared TNG-Ngs were 70.2 % and 2.1 %, respectively. The TNG-Ngs samples showed enhanced migration of HUVECs with no apparent cytotoxicity. The topical use of TNG-Ngs200 on the wounds revealed a complete wound closure ratio, skin component formation, less scar width, remarkable granulation tissue, promoted collagen deposition, and enhanced the relative mean density of α-SMA and CD31. TNG-Ngs accelerated wound healing by promoting collagen deposition and angiogenic activity, as well as reducing inflammation. The findings indicated that TNG-Ngs is expected to be well vascularized in the wound area and to be more effective in topical therapy.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

One-step E-Jet printing of loofah-like ZnO nanostructures by real-time laser zone irradiation

Loofah-like nanostructures have been applied in many fields because of their high specific surface area, high porosity, and low density. Developing additive manufacturing methods for loofah-like nanostructures remains a challenge. This paper proposed a novel E-Jet nanoprinting method with real-time laser zone irradiation, for one-step fabricating of loofah-like ZnO nanostructures. The combination of laser irradiation and electrohydrodynamic effect had been proved in detail by adding laser irradiation to the traditional E-Jet printing process. Printable ZnO inks were prepared. The numerical model of the jetting under the combination of flow field and electric field; and the model of the interaction between laser and printing structure were established respectively. The laser beam irradiated the printing structure in real-time to rapidly absorb energy, resulting in thermal expansion and thermal decomposition. The shock wave generated by laser irradiation induced the physical fragmentation and redistribution of particles in the printed structure. Printing at different laser powers was investigated; and the loofah-like ZnO nanostructures, down to the scale of ∼90 nm, have been directly printed without post-processing. The characteristic morphology and hydrophilic characteristics of the printed structure were studied. This study provided a new way for green and efficient additive fabrication of loofah-like nanostructures, which was of significance for the development of nanofabrication and nanodevices.

A gel polymer electrolyte functionalized separator for high-performance lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries, featuring ultrahigh specific theoretical energy density with low-cost raw materials, have been deemed one of the most promising candidates for next-generation energy storage and conversion devices. However, the shuttle effect of soluble Li polysulfides (LiPSs) has seriously hindered their practical deployment. Herein, we report that tris(pentafluorophenyl)borane (TPFPB) is used to modify the separator (TPFPB/Al2O3) for suppressing the shuttle effect of LiPSs. In detail, the introduction of TPFPB induces 1,3-dioxolane solvent ring-opening polymerization to form a gel layer between the S cathode and separator for suppressing the shuttle effect of Li polysulfides, effectively improving the electrochemical performance of Li-S batteries. The Li-S batteries using the TPFPB/Al2O3 separator demonstrate outstanding cycling stability and high capacity retention rates. This work provides a useful guideline for separator modification using a functional interface layer to design high-performance Li-S batteries.

Fabrication of Al-Ti intermetallic alloy via aluminothermic reduction process from TiO2 in molten salts

ABSTRACT A novel method based on the aluminothermic reduction of TiO2 in Na3AlF6-AlF3-CaF2 molten salts has been proposed to prepare Al-Ti intermetallic alloys in this research. The Al-Ti intermetallic alloy was obtained by reducing dissolved TiO2 in electrolyte molten salt using liquid Al as a reductant at the stirring rate of 200 r/min for 5 min under 960°C, and it was mainly enriched in the Al matrix which was dispersed in molten salts. The lower alloy layers in the melt pool were characterised by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), taking advantage of the specific gravity difference between the molten salt and the alloy. The TiAl3 was the major intermetallic alloys phase formed between Al and Ti according to XRD results. The Al2O3 by-product in the reduction process of TiO2 was dissolved in electrolyte molten salt.

On mechanical and tribological behaviour of microwave sintered TiN – 5 wt% Al2O3–5 wt% Y2O3 nanocomposite

Titanium nitride has potential applications in wide range of mechanical parts, cutting tools etc., primarily due to its high wear resistance. In the present study, a novel TiN-based nanocomposite was developed with nano additives alumina (Al2O3) and (Y2O3), 5 wt% each; using microwave irradiation at 900 W in ambient atmosphere. In-situ microwave sintering was carried out at a temperature of 1500 °C and 5 min holding time. The sintered nanocomposites achieved a relative density of ∼93%. XRD analyses showed that the major TiN phase was retained without any significant change in its peak positions after sintering. Minor phases of Y2Ti2O7 and Y3Al5O12 were formed during sintering due to chemical realignment of the constituent phases, were detected which acted as crack inhibitors. Microstructural studies indicated homogeneous distribution of the additives throughout the TiN matrix. The average Vickers microhardness of the TiN nanocomposites was ∼14 GPa, while indentation crack resistance was estimated within 3.9–4.0 MPa·m1/2. Wear and friction studies (ball-on-disc) of the microwave sintered TiN nanocomposite carried out with bearing steel ball under dry (unlubricated) and under deionised water (lubricated) sliding exhibited promising tribological behaviour. The friction coefficient (COF) between the contact pair was monitored within 0.5–0.6 after 45 min of dry sliding. Wear volume of the nanocomposite was obtained between 0.013 and 0.058 mm3 after 45 min of sliding (dry). Presence of iron oxides on worn surfaces confirmed mass transfer from the steel counterbody to the nanocomposite surface. Analyses of the worn surfaces showed that the wear mechanisms were predominantly abrasive and adhesive.

Mixing design and performance of porous asphalt mixtures containing solid waste

The process of urbanization generates substantial amounts of solid waste materials, including glass, red brick, concrete, and ceramic tile. Effective treatment methods for these waste materials are currently lacking, resulting in significant land wastage and environmental pollution. Utilizing these waste materials in the construction of asphalt pavements presents a viable solution for their high-quality and large-scale utilization. In this study, the properties of commonly produced urban solid waste materials, including glass, red brick, concrete, and ceramic tile, were investigated for their suitability as limestone porous asphalt mixtures. The physical and chemical properties of the coarse aggregate were examined using four groups of preliminary tests, including leakage analysis, scattering, rutting, and freeze-thaw splitting tests. The results revealed that the apparent relative density varied for different particle sizes within the range of 2.36–4.75 mm, 4.75–9.5 mm, 9.5–16 mm, and 13.2–16 mm. However, the dynamic stability of the glass specimen was only 740 times/mm, which falls significantly below the technical requirement of 1500 times/mm. Additionally, the high-temperature stability of the glass specimen was deemed unsatisfactory. The red brick test piece exhibited inadequate water stability due to its high-water absorption rate. Therefore, reducing the amount of waste glass and minimizing the incorporation of waste red brick are recommended. The findings of this study contribute to the expansion of application methods and techniques for urban solid waste, improving the utilization rate of solid waste resources. Furthermore, the study sheds light on the changes in the performance of solid waste aggregates mixed with porous asphalt mixtures, providing valuable insights for road engineering endeavors.

Electrodeposition of calcareous cement from seawater in marine silica sands

The erosion of marine sediments is a pressing issue for coastal areas worldwide. Established methods to mitigate coastal erosion fail to provide lasting and sustainable solutions to protect marine ecosystems. Here we demonstrate the application of mild electrical stimulations to precipitate calcareous mineral binders from seawater in the pores of marine soils via electrodeposition, an alternative approach to mitigating coastal erosion. Results of electrochemical laboratory experiments unveil that the polymorphs, precipitation sites, intrusion mechanisms, and effects of electrodeposited minerals in marine sands vary as a function of the magnitude and duration of applied voltage, soil relative density, and electrolyte ionic concentration. Surprisingly, in addition to the precipitation of calcium carbonate and magnesium hydroxide, the formation of hydromagnesite is also observed due to electrically driven fluctuations in the local pH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${pH}$$\\end{document}. These electrodeposits lead to enhanced mechanical and hydraulic properties of the marine sands, indicating that electrodeposition routes could be developed to reinforce marine soils in coastal areas that more closely mimic natural systems.

Effects of Y3+ doping on the microstructure evolution, optical, dielectric, and non-Ohmic properties of Na1/3Cd1/3Bi1/3Cu3Ti4O12 ceramics

In this study, Na1/3Cd1/3(Bi1-xYx)1/3Cu3Ti4O12 (NCBYCTO, x = 0−0.20) ceramics were successfully prepared via solid state method. Their microstructure along with the optical, dielectric, and non-Ohmic properties were investigated systemically. It was shown that Y3+ doping caused the decrease in cation vacancy concentration and the increase in optical energy band. With the increase of Y3+ content, ceramics exhibited a more stable structure, while their average grain size increased from 6.80 μm to 9.12 μm and then decreased to 2.17 μm with the dopant amount. The relative density increased from 94.7 % for the undoped specimen to 95.6 % for the specimen with x = 0.20. The giant dielectric constant (ɛ′ = 44200) at a relatively low dielectric loss (tanδ = 0.048) at 10 kHz was obtained in the specimen with x = 0.08, being more than three times that of undoped sample and demonstrating the outstanding frequency stability in the range of 40−106 Hz. The giant dielectric constant below 106 Hz originated from Maxwell–Wagner relaxation related to the insulating grain boundaries (GBs) and followed the internal barrier layer capacitor model. Besides that, Y3+ doping improved the nonlinearity properties of NCBYCTO ceramics. The specimen with x = 0.20 had the largest nonlinearity coefficient α (∼9.60) and breakdown field strength Eb (∼7.15 kV/cm). At last, the nonlinear J-E characteristics were closely related to the GB conductivity activation energy.

Homogenization-based topology optimization for self-supporting additive-manufactured lattice-infilled structure

Lattice-infilled structures possess prominent properties at relatively low mass, which are of great significance in academic investigations and engineering fields such as aerospace science and biomedical applications. However, both the macro geometry and relative density distribution of the infilled microstructure exert considerable influence on performances of lattice-infilled structure and the structural manufacturability needs to be considered. In this work, an optimization design methodology for self-supporting additive-manufactured lattice-infilled structures is proposed, in which the macro geometry and relative density distribution of the microstructure are concurrently optimized. Microstructure is infilled after topology optimization and octree structure is introduced into the boundary layers of the lattice core to support the top shell during fabrication. The effectiveness of the proposed optimization design method for self-supporting additive-manufactured lattice-infilled structures was proved by both three-point-bending test and full-scale finite element simulation. Compared with the uniformly-infilled sample, mass-specific stiffness and strength of the topologyoptimized sample were improved by 41.2% and 112.1%, respectively. The proposed design method for lattice-infilled structures provides potential for designing additive-manufactured high-performance lightweight structures, which will broaden the boundaries of lattice structure in engineering applications.