Band 31, Heft 1

To investigate the damage evolution and failure mechanisms of fiber-reinforced composite materials under complex conditions, this study conducted in situ X-ray computed tomography (CT) compression and tensile tests on plain weave two-dimensional woven SiC/SiC composite materials. The obtained CT in situ image data captured the behavior of materials during loading and after failure. Using the image reconstruction of CT data, the actual microstructure and damage evolution of the material under six consecutive loading levels were accurately revealed. Three-dimensional visualization models of the composite material were established using image processing software to analyze the damage evolution under compression and tension, and the failure mechanisms were compared. The results showed that the compression and tension failure mechanisms of SiC/SiC composite materials were similar, with the transverse cracking of the matrix being the first mode of damage, followed by delamination between layers and longitudinal matrix cracking of fiber bundles. Specifically, in terms of compression failure, the strength of the fiber bundle itself has a greater influence, and fiber fracture is the main cause of ultimate material failure. On the other hand, the primary cause of tensile failure is the presence of porosity defects generated during material fabrication. Consequently, the tensile material fails earlier and can withstand lower loads.

Fiber reinforced polymer (FRP) have the advantages of high strength, corrosion resistance, and low density, which are widely used to serve as tray products in bolt support systems. As a key component, the low mechanical load-bearing capacity of trays significantly limits their widespread application. Besides, there is no corresponding theoretical calculations and strength analysis methods for the structural design. The aim of this study is to optimize the tray structure and improve its load-bearing capacity. Through theoretical calculations and finite element numerical analysis, the effect of inner surface taper and stiffener height on the load-bearing capacity of the tray under the application of constant axial force is investigated. The results show that first of all, the larger the inner surface taper is, the better the load capacity of the tray. Second, the special-shaped truncated cone type displayed better load capacity than the stiffener tray. Third, the higher the design height of the stiffener is, the smaller the deformation and shear stress on the top of the inner surface of the tray, and better load capacity is achieved. We believe that this study provides theoretical guidance for the structural design of high-performance FRP trays.

The interfacial transition zone (ITZ) percolation is an effective parameter reflecting the connectivity of ITZs in cementitious materials, and its emergence may accelerate the penetration of inimical ions. In the existing literature on ITZ percolation, aggregates are generally simplified as the identical-shaped particles and the thickness of the ITZ phase around them is set to be uniform, which differs greatly from the realities and may cause the large deviation. To determine the ITZ percolation with the response of different phases in a more realistic way, a more satisfying three-dimensional (3D) polyphase model of concrete is developed, in which the convex ovoids and polyhedrons are separately adopted to represent the sands and gravels. The realistic nonuniform ITZ is also assigned for these aggregates based on their specific sizes and the W/C for the cement matrix. By coupling these models with the continuum percolation theory in statistical physics, the influence of individual phases on the global percolation threshold ϕ agg,c of ITZs is further studied by the simulation. The results reveal that the models here provide a smaller percolation threshold ϕ agg,c than the previous prediction models containing the simplistic uniform ITZs. There is reason to believe that these results in the work would be closer to the actual threshold in the realistic circumstance.

To reveal the effects of void defects on the diffusivities of plain woven composites, a multiscale analysis framework considering the microscale and mesoscale voids is developed in this study. Different void modeling methods and analysis strategies are used to reveal the effects of void size, void shape, and void modeling assumptions on the equivalent diffusivities of the tows and plain woven composites. The analysis results show that the transverse or longitudinal diffusivities of tows predicted with an element-based modeling method are larger than those with void shapes considered. Considering void shape results in the variation of the predicted diffusivities. Based on the uniform assumption used for modeling the voids in the tows, the through-thickness and in-plane diffusivities are found to be dependent on the transverse and longitudinal diffusivities, respectively. Based on the element-based void modeling method for the tows, the predicted values are larger than those based on the uniform assumption. These tow void modeling methods cannot result in variation within predicted values. The effects of void shapes in the pure matrix on the diffusivities are also revealed, and the variation is observed.

The fabrication of robust and high-performance graphene-based electrodes on engineering plastics has garnered significant attention in recent years. In this study, we present a novel methodology to produce porous graphene structures derived from epoxy resin (EP) utilizing a straightforward laser direct-scribing process. Under the influence of a CO 2 laser in an ambient atmosphere, EP undergoes a transformation to yield laser-induced graphene (LIG-APP/EP). Furthermore, this LIG-APP/EP was employed to construct an electrode for lithium-ion batteries, which exhibited outstanding electrochemical performance. Notably, the initial charge and discharge capacities of the LIG-APP/EP electrode material were recorded at 976 and 1,452 mAh g −1 , respectively, with a coulombic efficiency of 67.2%. Such impressive performance can be ascribed to the hierarchical porous architecture of LIG-APP/EP and the concurrent doping with nitrogen (N) and phosphorus (P) atoms. Given these findings, LIG-APP/EP demonstrates significant potential for applications in advanced electrochemical systems. This innovative approach also offers profound implications for the sustainable recycling of discarded engineering plastics.

Carbon fiber-reinforced polymer (CFRP) exhibits aging effects over time that can degrade its mechanical properties. In this study, a systematic investigation was carried out to investigate the effect of distilled water aging on the mechanical properties of CFRP composite patch bonded on Al 2024-T3 plates. We built a finite element model to analyze the effect of water absorption by the composite and the adhesive on the effectiveness of the composite patch repair. Using the experimentally evaluated mechanical properties of CFRP and Araldite adhesive subjected to distilled water immersion, finite element simulations were validated. The experimental observations deduce that there was a negligible effect of moisture absorption on the bulk mechanical properties of CFRP and adhesive over time. However, a significant effect of moisture absorption was observed on the elasto-plastic behavior of both CFRP and adhesive. Consequently, the numerical simulations suggest that the moisture absorption reduces the bonded composite patch repair efficiency attributed to an increase in the plasticity around the crack front and accordingly increases the damage in the adhesive layer. This study attempts to provide guidelines on the severity of damage caused by water absorption on the performance of structures repaired with composite patches.

Interfaces of cementitious layers have widely existed in construction projects, and they are the weakest part of the whole building. In this article, laser scanning and ultrasonic pulse, splitting tensile, and semi-disc fracture tests were carried out to study the bonding performance of cementitious layers. Different performance metrics, such as splitting tensile bond strength, ultrasonic pulse velocity, and attenuation of first arrival, were used to evaluate the bonding characteristics of the concrete layers. The results revealed that the parameters of the interface curve decreased, and the mechanical properties of the interface became weaker with an increase of the interval time. The amplitude of the first wave was more sensitive to the presence of the interface than the ultrasonic pulse velocity. Finally, the relationships between the performance metrics were analyzed. The fracture toughness of model I and mode II was highly correlated with the parameters of the micromorphology of the layered concrete, and the correlation coefficient is not less than 0.9511. The fracture toughness of mode I was strongly related to the splitting tensile strength, with a correlation coefficient of not less than 0.9744. This study was useful for the future study of the mode I and I fracture performance, the morphology, and other physical properties of cementitious layers.

This study investigated the influence of microbead dosages (0, 5, 10, 15, and 20%) on the frost resistance of expanded polystyrene (EPS) concrete. Five groups of EPS concrete specimens were prepared and subjected to rapid freeze–thaw tests. The freeze–thaw deterioration of EPS concrete was assessed using macroscopic indicators, including mass loss, strength loss, and dynamic elastic modulus loss. The underlying deterioration mechanism was revealed through the analysis of the EPS particle–matrix interface. A concrete damage plasticity model of EPS concrete based on damage mechanics theory was established. The results indicate that the addition of microbeads increased the strength of EPS concrete by 38–53%, reduced the strength attenuation after freeze–thaw damage by 8.1%, and improved the frost resistance level by 10–60 grades. The optimal dosage of microbeads is 15% of the cementitious material. The interfacial transition zone gaps in EPS concrete with added microbeads after freeze–thaw cycles are smaller, contributing to a more complete hydration reaction. The freeze–thaw damage model established in this study accurately reflects the freeze–thaw damage law of EPS concrete and provides a reference for studying the mechanical properties of EPS concrete under freeze–thaw cycles. The research findings of this study can enhance the strength and service life of EPS concrete, expanding its application scope as a structural material. The study provides valuable insights for future research and engineering applications related to the frost resistance of EPS concrete.

In this work, an Ag–Ti 2 SnC composite was fabricated by the hot-pressing sintering method, and the erosion behavior of Ag–Ti 2 SnC with volume percentages of 10–40% was studied at a load voltage of 10 kV. The arc life and breakdown current were observed at about 31–36 ms and 39 A, respectively. The cathode spot traveled the fastest on the surface of the Ag–40 vol% Ti 2 SnC composite. Due to emission center model, the temperature of the minor protrusions on the cathode surface increased, resulting in Ag ions, Ti ions, and Sn ions being generated. Combining with the ionized oxygen, Ag 2 O, AgO, TiO 2 , and SnO 2 were formed on the eroded Ag–Ti 2 SnC surface after arc erosion. The research results will broaden the application range of Ag–Ti 2 SnC electrical contact material and enrich the arc erosion mechanism.

Formaldehyde is one of the most common indoor air pollutants that seriously damage human health. It is of significant importance to effectively remove indoor formaldehyde. In this work, a novel cement-based composite with ZIF-8@TiO 2 -coated activated carbon fibers (TiO 2 -ACFs) was prepared and shown to remove the indoor formaldehyde effectively. TiO 2 was coated on ACFs via atomic layer deposition, and then ZIF-8 was grown on the surface of TiO 2 -ACFs. The ZIF-8@TiO 2 -ACFs were then mixed with cement slurry and thus formed a cement-based composite, which exhibited excellent formaldehyde removal performance. In particular, if assisted with UV light, the removal efficiency for formaldehyde by the cement-based composite showed an obvious increase.

River sand was consumed in large quantities, and alternatives to river sand were urgently needed. There are a large number of natural resources of aeolian sand in western China. Aeolian sand was prepared into aeolian sand concrete (ASC). It can greatly reduce the consumption of river sand and inhibit the process of desertification to protect the environment. ASC is a new type of concrete material prepared by using aeolian sand as fine aggregate. To clarify the chloride ion transport behaviour in the ASC under long-term natural immersion, the aeolian sand was 100% substituted for the river sand to prepare the full ASC with three water–binder ratios. The ASC was naturally immersed in 3 and 6% NaCl solutions for a long time, and nuclear magnetic resonance and microscopic scanning electron microscopy techniques were used. The change rule of chloride ion content at different depths of the ASC was studied, and its microstructure characteristics under different erosion times were analysed. The results showed that the free chloride ion concentration at different depths of the ASC increased with increasing water–binder ratio, immersion time, and chloride concentration. After soaking in the salt solution, the hydration products in the ASC reacted with chloride ions to form Friedel salt, which filled the internal pores and microcracks of the ASC, improved its interface transition zone structure, and increased the compactness of the test piece. The porosity of the three groups of ASC with different water–binder ratios decreased by 0.95, 1.03, and 1.15% after soaking in 6% salt solution for 12 m. To study the diffusion law of chloride ions in ASC, combined with influencing factors such as temperature, humidity, D value, deterioration effect and chloride ion combination, Fick’s second law was modified, and a chloride ion diffusion model of ASC with high accuracy was established, with a fitting correlation number above 0.93, which provided a reference for the research and application of ASC in saline areas.

In order to study the basic road performance and the mechanism of red mud modified asphalt, Marshall test, rut test, freeze-thaw splitting test, and immersion Marshall test were carried out for matrix asphalt mixture and red mud modified asphalt mixture, and molecular simulation technology was introduced to study the mechanism of red mud modified asphalt. The results showed that the penetration rate of red mud modified asphalt was lower than that of the matrix asphalt, and the softening point of asphalt was significantly improved after the addition of red mud, and the mixing of red mud reduced the asphalt ductility greatly. The intensity ratio (test strength ratio; TSR) of the freeze-thaw test of red mud modified asphalt under 3, 5, 7, 9, and 11% was increased by 13.18, 11.22, 13.54, 12.01, and 8.45%, respectively, compared with the matrix asphalt mixture, and the dynamic stability value increased by 127.23, 176.87, 200.99, 96.23, and 12.95%; the residual stability value of the immersion Marshall test increased obviously. Generally, the research of red mud modified asphalt is quite worthy, it can solve the problem of aluminum ore slag and reuse of resources, and provide a new way to extend the industrial chain.

Unsaturated polyester resin (UPR) is the most versatile liquid polymer with a wide range of applications in every aspect of the industry but it has low impact strength, low elongation at break, and low toughness. Its mechanical properties can be enhanced with the addition of an optimum percentage of nano-silica fillers by using ASTM polymer test standards, which have been followed by various research groups. For this research, enhanced mechanical properties of the resin have been tested for 0.5, 1, 2, 3, and 4% amount by weight fraction of the nano-silica as fiber nanomaterial. The sugar cane bagasse ash was collected from the Wenji Sugar Factory and extracted with the required size of the particle, which is 10 nm. The ability of extraction is used to manipulate the particle size as the researcher needs. The aim is to determine the enhanced mechanical properties of the UPR by the addition of optimum nano-silica particles. Nanoparticles have the effect of filling porous regions, crack path deflection, and crack bridging capability of the material, which provides good adhesion with the matrix to increase the mechanical properties of composite materials. Experimental result dictates that 0.5% nano-silica addition with 10 nm particle size performs best by enhancing the mechanical properties of composite material up to 30.45% for tensile, 33% for compression, 17.8% for flexural, a slightly 10% improvement for impact test and it shows an overall 27% better performance than the pure UPR. Thermal stability and glass transition temperature were not influenced by the addition of nano-silica.

This article aims to study the effects of corn starch and gellan gum (gellan glue) on the unconfined compressive strength of alluvial soft clay in Shanghai. Firstly, starch and gellan gum were evenly mixed into Shanghai cohesive soil in a certain proportion, and soil samples were prepared according to the optimal water content. Secondly, the unconfined compressive strength test was carried out according to the content of corn starch, gellan glue, and curing time. The strength characteristics of Shanghai soft clay under various test conditions were studied. Finally, the software for statistics and drawing was used to perform regression analysis and drawing on the experimental data. The results showed that in the unconfined compressive strength test, when the curing time was 28 days, the starch content was 3% mixed with 0.5% gellan gum, the unconfined compressive strength of the sample was the highest, and generally, it seems that the strength keep increasing with curing time.

Expansive soils pose major geotechnical challenges due to significant volume changes. This research investigates an innovative stabilization approach using sand, expanded polystyrene (EPS) beads, and jute fibres to enhance the properties of expansive soil. The purpose is to utilize the unique characteristics of these admixtures to restrict swelling potential and improve strength and load-bearing capacity. Experimental testing quantified improvements through parameters like unconfined compressive strength (UCS), swelling pressure, California bearing ratio (CBR), compaction characteristics, and Atterberg limits. Soil samples were prepared with individual and combined admixtures at optimum proportions and extensively tested after proper curing. Quantitative results indicated that including sand, EPS beads, and jute fibres increased the soil’s UCS by 41, 29, and 23%, respectively. The swelling pressure, on the other hand, decreased by 14, 18, and 11%, respectively. Maximum improvements were achieved with combined admixtures: UCS increased by 65%, swelling pressure reduced by 23%, and CBR improved from 5 to 6.5%. Regression analysis indicated a strong correlation ( R 2 = 0.96) between admixture proportions and resultant UCS. The key achievements are effective swelling control, a marked increase in shear strength parameters, and synergy between admixtures in enhancing expansive soil properties. This sustainable stabilization method using industrial by-products presents a promising solution for constructing stable civil structures even in problematic expansive soil regions.

This study discusses the experimental results of the ballistic impact on thick-layered carbon fibre-reinforced polymer (CFRP), glass-based FRP (GFRP), and Kevlar-based FRP (KFRP) composite plates. Ten 10 mm plates of each type were manufactured via the hand lay-up and vacuum bagging techniques to produce plates with a thickness of 2 mm each, which were bonded together using epoxy adhesive and hot pressed at 75°C to obtain thick layered plates with a total thickness of 20 mm each. The specimen plates were tested according to the NIJ 0108.01 standard in a special firing room using a 9 mm G2 Elite handgun with a full metal jacketed round nose 9 mm × 19 mm Mu1-TJ bullets moving at a velocity of approximately 358 m/s. The results indicated that no total penetration occurred on any of the plates. The bullets were destroyed by impact, and the penetration depths of the CFRP, GFRP, and KFRP plates were 11.10, 9.95, and 22.22%, respectively. The layered structures in these plates appear to have changed the penetration behaviour compared with previous studies. In this study, delamination was the primary failure mode.

In this study, solid waste titanium gypsum (TG) was used as raw material to design the basic mix ratio of aggregate, and TG artificial aggregate (TGA) was prepared based on alkali-activated cold bonding technology. The effects of different additives (slag, silica fume, and fly ash) on the properties of TGA were preliminarily investigated by using NaOH as activator in laboratory test, and the additives of TG aggregate were determined. Furthermore, the aggregate mix ratio was designed based on the additive, and the physical and mechanical properties, X-ray diffraction analysis, scanning electron microscopy analysis, and dry–wet cycle test of artificial aggregate were carried out. The results show that the artificial aggregate prepared by the same process and the aggregate prepared by silica fume as an additive has a high balling rate; it is technically feasible to use TG as the main raw material, silica fume as an additive, and NaOH as an activator to select a suitable mix ratio to prepare artificial aggregates. The microscopic test results reveal the internal products and structural degradation process of TG aggregate.

This study aims to develop composite plates using silkworm cocoon waste- and hybrid silkworm cocoon waste-reinforced polymer composite using epoxy resin as a matrix to replace synthetic fibers in bulletproof plates. The fabrication involved mixing 70 g of silkworm cocoon waste with 240 g of resin and 70 g of ultra-high molecular weight polyethylene, followed by cold compression molding. Tensile and impact tests on the resulting samples, using a standardized 9 mm projectile, showed a tensile strength of 107.4 MPa and an elastic modulus of 1240.3 MPa. With a back face signature (BFS) of 21.25 mm, the samples effectively intercepted the projectile, satisfying the stringent U.S. National Institute of Justice standard 0101.06, which specifies a maximum BFS of 44 mm. In comparison with hemp woven materials, silkworm cocoon waste has proven to be a promising substitute for both tensile and impact evaluations, attracting considerable interest and underscoring its role as a reinforcing agent for national fiber. This research has significant implications for industries and applications requiring affordable, lightweight, and efficient safeguards against ballistic dangers. Ultimately, it contributes to the progress of ballistic protection methods by encouraging exploration into innovative, bio-inspired, and sustainable materials capable of achieving superior impact resistance.

To investigate the impact of curing environments on the mechanical properties of coal gangue cementation (CGC), various curing methods were established, including standard bag curing, standard curing, natural sealing curing, natural curing, water curing, and varying curing ages. By examining the uniaxial compressive strength (UCS) and stress–strain relationship of CGC by applying axial loads, the influence mechanism was analyzed in terms of both physical and chemical reactions. Furthermore, a mechanistic structural model was established to illustrate the impact of the curing environment on the mechanical properties of CGC. The primary substances and reasons affecting the mechanical properties of CGC were analyzed through the use of scanning electron microscopy and X-ray diffraction techniques. Evaluation of influence factors on CGC mechanical properties by grey correlation degree. The findings indicate that curing temperature, humidity, and carbonization are the principal factors influencing the UCS. Maintaining constant temperature and humidity while isolating CO 2 is conducive to improving the UCS. The hydration products, such as needle-like ettringite and white fibrous calcium silicate hydrogel, fill the internal voids of CGC and are the primary substances affecting UCS. The hydration products formed during standard curing and natural curing of CGC can undergo carbonation with CO 2 to form CaCO 3 , which interacts with ettringite and hydrated calcium silicate to provide strength support for CGC. However, beyond a certain age, CO 2 will progressively diminish the UCS; the larger the contact area and the longer the exposure time to the gel materials in CGC, the faster the UCS decreases.

With the enhancement in science and technology, necessity of complex shapes in manufacturing industries have become essential for more versatile applications. This leads to the demand for lightweight and durable materials for applications in aerospace, defense, automotive, as well as sports and thermal management. Wire electric discharge machining (WEDM) is an extensively utilized process that is used for the exact and indented shaped components of all materials that are electrically conductive. This technique is suitable in practically all industrial sectors owing to its widespread application. The present investigation explores WEDM for LM6/fly ash composites to optimize different process variables for attaining performance measures in terms of maximum material removal rate (MRR) and minimum surface roughness (SR). Taguchi’s L 27 OA design of experiments, grey relational analysis, and analysis of variance (ANOVA) were employed to optimize SR and MRR. It has been noted from ANOVA that reinforcement ( R ) percentage and pulse on time are the most influential aspects for Grey Relational Grade (GRG) with their contributions of 28.22 and 18.18%, respectively. It is found that the best process variables for achieving the highest MRR and lowest SR simultaneously during the machining of the composite are gap voltage of 30 V, pulse on time of 10 µs, pulse off time of 2 µs, wire feed of 8 m/min, and R of 9%. The predicted GRG is 0.84, and the experimental GRG value is 0.86. The validation experiments at the optimized setting show close agreement between predicted and experimental values. The morphological study by optical microscopy revealed a homogenous distribution of reinforcement in the matrix which enhances the composite’s hardness and decreases the density.

We report here a convenient, rapid one-pot synthesis of new metal–metal core–shell nanocomposites comprising silver nanowires (AgNWs) coated with nickel. The resulting AgNWs and nickel-coated silver nanocables average 60–80 nm in diameter were prepared by the polyol synthetic route. This method employed ethylene glycol as a reducing agent and polyvinylpyrrolidone as a capping agent. These nanomaterials are designated as AgNWs (0.1 M) and Ag@Ni (0.2 M), Ag@Ni (0.3 M), Ag@Ni (0.4 M), and Ag@Ni (0.5 M) nanocables based on the nickel content and were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), UV–Visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. The morphology of each nanowire and nanocable was clarified using SEM, while EDX quantified the presence of Ni. XRD patterns confirmed the face-centered cubic structure of the nanomaterials. The Debye–Scherrer formula was applied to establish different characteristics such as crystallite size and lattice constant. Surface plasmon resonance was measured using UV−Vis spectroscopy and fluorescence of each product was determined by PL spectroscopy, respectively. Both the AgNWs and Ag@Ni nanocables catalyze the reduction of p -nitrophenol to p -aminophenol by sodium borohydride. Graphical abstract

The recent study reports the fabrication and corrosion behavior of two Ti alloys, 88% Ti–12% Zr and 84% Ti–12% Zr–4% Ta, in 3.5% NaCl electrolyte. These alloys were manufactured using powder metallurgy, where the powders were mixed, ball milled, and sintered. The corrosion behavior of these alloys was examined using various electrochemical and spectroscopic tests. Cyclic polarization experiments indicated that adding 4% Ta reduces corrosion of the TiZr alloy by suppressing anodic dissolution, resulting in a lower corrosion rate. The Nyquist and Bode impedance spectra for the tested alloys revealed that the presence of 4% Ta within TiZr alloy highly decreases the corrosion by increasing the impedance of the interface, the maximum degree of phase angle, and polarization resistance. The chronoamperometric current measured at −0.10 V (Ag/AgCl) proved that the presence of 4% Ta powerfully alleviates both uniform and pitting corrosion for TiZr alloy by lowering the obtained absolute currents. The surface investigation using scanning electron microscopy confirmed the homogeneity of the surfaces. The elemental analysis performed on the surface using energy dispersive spectroscopy revealed that the surface of TiZr alloy forms a top film including different oxides such as TiO 2 and ZrO 2 , and for TiZrTa alloy, the surface has TiO 2 + ZrO 2 plus TaO 2 . Experiments demonstrated that Ta has the ability to increase the corrosion passivation of TiZr alloy.

This study explains the conductive mechanism of C12A7:C from the perspective of crystal structure. C12A7:C is a carbon derivative of C12A7 and prepared by CaCO 3 and Al 2 O 3 in sealed graphite crucible through high-temperature sintering experiments. The main component was confirmed to be C12A7:C through X-ray diffraction inversion analysis. The four-probe method revealed that it is a semiconductor with conductivity of 4,339 S/m. A conductive model of C12A7:C crystal was established to study its conductive mechanism. Through theoretical calculations of the conductive structure model, the density of states and transfer function are important factors determining the conductivity of C12A7:C crystals. Based on the analysis of these two factors, C is the key to electron transfer in the C12A7:C crystal. Further research indicates that the C–C bond is the main form of C in C12A7:C crystals. These C–C bonds satisfy the formation conditions of conjugated systems and are key to the conductivity of C12A7:C crystals. Through simulation calculations, the volt ampere characteristic curve of C12A7:C exhibits Ohmic conductor characteristics. The conductivity of C12A7:C obtained through theoretical calculation is consistent with the experimental results. In conclusion, the conductivity of C12A7:C crystal is mainly due to the C–C conjugated system formed by carbon atoms in the crystal.

To evaluate the mechanical property of concrete materials rapidly, a fast prediction model of the concrete equivalent modulus is proposed based on the random aggregate model and scaled boundary finite element method (SBFEM). First, a random aggregate model of meso-concrete is employed to construct the representative volume element (RVE) according to the aggregate content, gradation, shape, etc. Second, the RVE model is transformed to be a grayscale image and stored as a digital matrix. The quadtree mesh is partitioned automatically for simulation by SBFEM. There are only six types of unique subdomains, and the hanging node does not affect the simulation accuracy. The global stiffness matrix can be assembled directly according to the six subdomain stiffness matrices. Finally, the equivalent modulus is predicted by using the numerical homogenization method. Several numerical examples are employed to verify this model, and the results are compared with that of other methods. The result indicates that the proposed model can efficiently determine the equivalent modulus. Furthermore, the effect of the aggregate gradation, shape, porosity, and pore water are studied and analysed in this work. The proposed model is potential and helpful in predicting the mechanical properties of concrete or other composite materials.

This study examines the impact of the recycled brick powder (RBP) replacement rate, especially at elevated temperatures on RBP-ultra-high-performance concrete (UHPC) properties such as the stress–strain curve, Poisson’s ratio, elastic modulus, and axial compressive strength through uniaxial compression experiments. The results show that with the increase of heating temperature, the axial compressive strength of the specimen increases first and then decreases under natural cooling (NC). In contrast, Poisson’s ratio shows opposite values. The peak strain continues to increase, and the initial elastic modulus and peak secant modulus continue to decrease. Compared with NC, the axial compressive strength of the specimens under water cooling has been reduced, the peak strain is generally larger, the initial elastic modulus and the peak secant modulus are smaller, and the incorporation of RBP also has a certain effect on the mechanical properties. Through regression analysis, an equation is established to calculate the axial compressive strength of RBP-UHPC with temperature, accounting for variables such as temperature, RBP replacement rate, and cooling method. Furthermore, based on the results of axial compression experiments, a constitutive equation for axial compression in RBP-UHPC after exposure to high temperatures is proposed. Overall, the theoretical curve closely aligns with the experimental curve, verifying its accuracy.

This study investigates the potential use of Yellow River sand (YRS) sourced from the lower reaches of the Yellow River in China as a sustainable and cost-effective substitute for quartz sand in engineered cementitious composites (ECCs). This region accumulates around 400 million tons of sand annually. The study evaluates the impact of different YRS replacement percentages (0, 25, 50, 75, and 100%) on mechanical and microstructure properties under freeze-thaw conditions, focusing on assessing the ECC durability during cooling cycles. The results show that YRS exhibits a smaller normal distribution of particle sizes compared to that of quartz sand and a 5.77 times greater specific surface area, affecting the ECC particle size distribution. After 300 cooling cycles, the R25 group maintains 97.5% of the initial mass and 79.4% of flexural strength, indicating superior durability. The R25 group also demonstrates a minimal decrease of 11.5% in equivalent bending strength, reaching a level of 104.4% compared to R0. The R25 group’s porosity is 30.80%, with an average pore size of 20.47 mm, showing 1.3% and 6.7% decreases compared to the R0 group. Additionally, this study establishes a failure progression equation using the Weibull probability distribution model, with calculated values closely aligning with measured values. Overall, this study recommends using YRS as a sustainable ECC material. Graphical abstract

In this study, the fabrication of Ti-12%Zr-4%Ta-2%Sn alloy, Ti-12%Zr-4%Ta-4%Sn alloy, and Ti-12%Zr-4%Ta-6%Sn alloy using powder metallurgy fabrication technique has been carried out. The influence of Sn addition on the corrosion of these alloys after 30 min and 3 days in 3.5% NaCl solution using various techniques has been reported. The Nyquist spectra revealed that boosting Sn content from 2 to 4% and further to 6% increases the corrosion resistance of the alloy through increasing the diameter of the obtained semicircle. Bode spectra also elucidated that the increased percentage of Sn increases the values of the impedance of the interface | Z | and the maximum degree of the phase angle ( Φ ). It was indicated from the cyclic polarization curves that the increased Sn content increases the passivation of the alloy through decreasing its rate of corrosion and increasing its corrosion resistance. The measured current over time at −0.10 V showed that the alloy with low Sn content, 2%, records the highest currents, which pronouncedly decreases when Sn content increases to 4% and further to 6%. Prolonging the time of exposure from 30 min to 3 days greatly enhances the passivation of the TiZrTaSn alloys due to the formation of mixed oxides of TiO 2 , ZrO 2 , TaO 2 , and SnO 2 . The results of these electrochemical measurements were confirmed by the surface investigations carried out by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results collectively proved that the uniform corrosion remarkably decreases with the increase in the Sn% and that the pitting corrosion is not likely to take place.

Mo 2 C layer was generated on the diamond surface via vacuum micro-evaporating, which was used as the reinforcement particles to fabricate diamond/Cu composites by spark plasma sintering (SPS). The effect of evaporation parameters on the forming of Mo 2 C, and the holding time on diamond/Cu composites fabrication is studied. Combined with the experiment and finite element analysis (FEA), the holding time on diamond/Cu composites influence on the thermal conductivity (TC) of composites is further discussed. The results show that the Mo 2 C area on the diamond surface would gradually enlarge and cover the diamond surface evenly with the increment in evaporation time and temperature, better vacuum micro-evaporating parameters were given as 1,000°C for 60 min. The fractures in the diamond/Cu composites are mainly ductile fractures on copper and diamond falling out from the Mo 2 C interface. It was found that sintering time would significantly influence the dissipation property of diamond/Cu composites. A comprehensive parameter for SPS was obtained at 900°C, 80 MPa for 10 min, the relative density (RD) and TC of the composites obtained under the parameter were 96.13% and 511 W/(m K). A longer sintering time would damage the Mo 2 C interlayer and further decrease the bonding between copper matrix and diamond particles, which would lower the RD and TC of composites. It can be obtained from the comparison of simulation results and experimental results that the FEA result is closer to the experimental results due to the gaps with low heat conduction, and the air in the gaps is added in the simulation process.

Composite sandwich structures are widely used in the aerospace field due to their advantages of high strength, lightweight, and fatigue resistance. However, these structures are prone to damage with very-low-energy impacts. In order to improve the impact resistance of aircraft skin structure, a low-velocity impact resistance of sandwich structure specimens was tested by means of drop hammer impact, and the impact damage area was scanned by ultrasonic C-scan, and obtains the impact damage of specimens with different impact energies and different ply sequences. Combined with the Hashin failure criterion, the finite element equivalent model of composite sandwich structure under low-velocity impact was established. The errors between the simulation results and the C-scan results of the test piece were less than 10%, in which the experimental measurements and numerical predictions were in close agreement. Finally, the finite element equivalent model was applied to optimize the application of model sandwich, which was used for fuselage skin of a certain electric aircraft. The total thickness of the laminate structure remains unchanged before and after optimization, but the impact resistance was significantly enhanced. The ±45° lay-up was beneficial for the structure to absorb the impact energy.

The aim of this study is to enhance the carbonation resistance of fully recycled aggregate concrete through diverse measures in an effort to enhance solid waste disposal, reduce the consumption of natural aggregates, and broaden the utilization of recycled aggregate concrete. Six sets of fully recycled aggregate concrete specimens were prepared and subjected to rapid carbonation tests. Carbonation depth and compressive strength measurements were taken at different ages (3, 7, 14, and 28 days). Subsequent calculations and analyses were conducted on both parameters for each set of specimens. Results indicate that the incorporation of microspheres and high-toughness polypropylene fibers (HTPP) substantially improves the carbonation resistance of fully recycled aggregate concrete, leading to a 48% reduction in carbonation depth by the 28th day. Furthermore, a relative compressive strength model for fully recycled aggregate concrete post-carbonation was established based on the strength data of each specimen group. This model accurately depicts the growth pattern of compressive strength after carbonation. Additionally, a carbonation depth prediction model was developed through fitting analysis of carbonation depth data, effectively foreseeing the depth of carbonation in fully recycled aggregate concrete. Based on the carbonation depth, the carbonation life of fully recycled aggregate concrete was predicted. The carbonation life of recycled aggregate concrete with added microspheres and HTPP fibers can be increased by up to 278%. Finally, scanning electron microscopy (SEM) was employed to examine the microstructure of fully recycled aggregate concrete, revealing the mechanisms by which various methods enhance its carbonation resistance. The carbonation resistance improvement technology of fully recycled aggregate concrete is selected through this study characteristics such as simplicity, convenience, and cost-effectiveness, which are crucial for the widespread application of recycled aggregate concrete in building structures.

To realize the recycling of iron tailings powder (IP) and desulfurization ash (DA) and reduce the high preparation cost of mine filling cementitious materials (MCs), this article adopts sodium carbonate (SC) as an activator to prepare iron tailings powder-desulfurization ash mine filling cementitious materials (IDMC). The effects of IP content, DA content, SC content, and mirabilite content on the mechanical properties and setting time are experimentally investigated. The micromorphology and phase compositions of the hydration products of IDMC are analyzed and characterized by scanning electron microscopy and X-ray diffraction. The results show that the initial setting time of the IDMC is reduced by 0.87 and 21.83% when the mirabilite content is increased from 0 to 1% and 2%, respectively, and the compressive and flexural strengths of the IDMC are increased by 24.01 and 86.25% when the IP content is increased from 0 to 20%, respectively. The IP not only participates in the hydration reaction but also plays an aggregate filling effect, significantly improving the mechanical properties of the IDMC. The pozzolanic effect is gradually enhanced with the increase of the DA content, and the hydration degree of the IDMC increases. The SC as an activator can moderately reduce the shrinkage rate of the IDMC. Based on the multi-index optimization analysis, the optimal mix proportion of the IDMC is obtained, which provides an effective reference for the preparation of the novel MC.

The 2.5D carbon glass hybrid woven composite (CGHWC) is currently being utilized as a protective material for the external cables of solid rockets due to its extensive advantages in terms of structural load-bearing and integrated thermal insulation. This study reveals that 2.5D hybrid woven composites, prepared using T300 and T800, exhibit improved compression and tensile properties, respectively. T300 and T800 carbon fibers are preferred for the preparation of 2.5D CGHWC, with a volume fraction of carbon fibers along the weft yarn ranging from 20 to 60%. As the proportion of carbon fibers increases, the weft tensile and compressive strength of the composite material progressively improve, resulting in a maximum increase of 67% in tensile strength and 52% in compressive strength. The optimal volume fraction of carbon fibers was found to be 40%. The performance retention of low-cost hybrid composite materials was investigated, and it was found that even when the cost of carbon fibers decreased by 87.5%, the mechanical properties could still be maintained at above 85%. This article has expanded the mechanical performance database of hybrid composite materials, providing data support and theoretical foundation for the large-scale engineering application of composite materials.

In order to achieve metallurgical bonding in the form of solid solution at the Cu/W interface and avoid the formation of intermetallic compounds, the novel high entropy alloys (HEAs) were designed on the basis of the mature high entropy alloy criteria. The CuCrCoFeNi x Ti high entropy alloys interlayers were applied to weld the CuW and CuCr bimetals by sintering–infiltration technology. Scanning electron microscope, energy dispersive spectrometry, and X-ray diffraction were used to explore the interfacial microstructure evolutions and strengthening mechanism of CuW/CuCr joints with applied HEA interlayers. The interfacial characterization results show that HEAs were diffused and dissolved into bimetallic materials, and a diffusion solution layer of 2–3 μm thickness was formed at the Cu/W phase interface, and there is no new phase generated at the CuW/CuCr interface. When CuCrCoFeNi 1.5 Ti interlayer was infiltrated into the CuW/CuCr interface, the electrical conductivity of CuCr side is 71.6%IACS, and the interfacial tensile strength reaches 484.5 MPa. Compared with the CuW/CuCr integral material without interlayer, the interfacial bonding strength is increased by 43.1%. And the SEM fracture morphology presents a larger amount of cleavage fractures of W particles. It indicates the appropriate solid solution layer on edge of W skeletons formed at the Cu/W phases interface. The Cu/W phase interface is strengthened, and it can effectively transfer and disperse the external load. Tungsten phase with higher elastic modulus endures a large amount of load, resulting in enhancing the CuW/CuCr interfacial bonding strength. When CuCrCoFeNi 2 Ti high entropy alloy interlayer was applied, the W skeleton near the CuW/CuCr interface was eroded, the imperfect W skeleton cannot withstand the tensile load effectively, resulting in decrease in the CuW/CuCr interfacial bonding strength. In the interfacial fracture, appears some fragmentations of W particles, and fewer W particles occur at the cleavage fracture.

The study aims to substitute river sand used in ultra-high performance concrete (UHPC) with pond ash (PA), a waste by-product from the Sikka thermal power station in Gujarat, India, at replacement levels ranging from 0 to 20%. Also, 20% of the cement was replaced with ground granulated blast-furnace slag, which is a sustainable, eco-friendly material. As a result, this concrete is both environmentally and economically feasible. Experimental analysis evaluated the workability, compressive strength, split tensile strength, flexural strength, and microstructure of the UHPC mixtures. Incorporating 10% PA as a sand replacement enhanced the compressive strength, reaching 117 MPa at 90 days, as well as the flexural strength of 23 MPa and the split tensile strength of 14 MPa. The strength is positively impacted when 10% of the river sand is replaced with PA, while the strength of UHPC appears to be diminished if PA content is increased beyond 10% replacement of sand. Petrographic microscopy and X-ray diffraction were used to study the microstructure of UHPC made with PA. When PA was used instead of sand, the mortar mass solidified and became denser, resulting in an improved microstructure of the UHPC with fewer surface cracks. With the inclusion of PA, the calcium silica hydrate gel content of the concrete increases, and enhanced performance of UHPC up to a certain amount of replacement has been observed.

In many infrastructural engineering techniques, a common challenge is how to control the continuous damage caused by the cracks of concrete slab/decks overlay under environmental impaction or vehicle load. It drives the development of a high-flowability hybrid polypropylene and steel fiber-reinforced concrete (HPSFC), which has peculiarities for the overlay construction. In this aspect, an experimental study of HPSFC was carried out considering the factors, the volume ratio of binder paste to aggregates (P/A ratio) varied from 0.48 to 0.60, and the polypropylene (PP) fiber content changed from 0.45 to 1.35 kg/m 3 with a hybrid steel fiber at 0.8% volume fraction. The workability of fresh mixes was evaluated by the indices of slump flowability and static segregation rate with an explanation of the rheological properties, and it was verified by a pumping test. The peculiarity of HPSFC applied for slab/decks overlay was determined using the tests including the early cracking resistance, the water penetration resistance, the bond strength to existing concrete, and the impact resistance. Meanwhile, the basic mechanical properties including cubic compression strength, flexural strength, and toughness were also measured. Results indicate that the fresh mixes met the requirement of high-flowing without segregation, although the indices varied with the influence of P/A ratio and PP fiber content. The resistances to early cracking and water penetration obviously improved by increasing the PP fiber content. The bond strength to existing concrete could be improved by increasing the PP-fiber content. The impact resistance enhanced with the increase of the P/A ratio and the PP-fiber content. The compressive strength and flexural strength presented an increased tendency with the P/A ratio, while the flexural toughness reached a peak at certain values of P/A ratio and PP fiber content. Comprehensively, for the high-flowability HPSFC designed with a water-to-binder ratio of 0.36, a fly-ash content of 30%, and a sand ratio of 52%, the optimal P/A ratio is 0.54 and the PP-fiber content is 0.90 kg/m 3 .

In the development of carbon nanotube (CNT)-reinforced cement-based matrices, one of the fundamental issues that investigators are confronting is CNT/cement-based matrix interfacial bonding, which determines the load transfer capability from the matrix to the CNT. In the present work, the stress transfer properties of multi-walled carbon nanotubes (MWCNTs) and ultralight foamed concrete matrices were studied using microscopic Raman spectrometry analysis. Two types of CNTs, such as MWCNT and MWCNT-COOH, were considered, wherein MWCNT-COOH was covered with fundamental COOH groups. The results show that the compressive and flexural strengths were 75 and 236% better for ultralight foamed concrete with a dry density of 200 kg/m 3 with 0.4 wt% MWCNT-COOH addition, respectively. This indicates that the fundamental COOH groups of the MWCNT play an important role in determining the interfacial bonding characteristics between the MWCNT and the ultralight foamed concrete matrix. Therefore, the attachment of COOH groups with a reasonable concentration to the MWCNT surface may be an effective way to significantly improve the load transfer between the MWCNT and the ultralight foamed concrete matrix, leading to increased compressive and flexural strength values of composites.

In order to determine the influence of the ondulations in fabrics on the damping properties of fiber-reinforced plastics, the structural dynamic properties of fabric- and unidirectionally reinforced plastics are investigated. The free decay behavior of flat beam-like specimens is investigated under fixed-free boundary conditions. As the material damping is consistently higher in fabric-reinforced specimens compared to unidirectionally reinforced ones, a contribution of an additionally acting mesomechanic kinematic in fabric weaves is implied. Based on a degree of ondulation, it is possible to classify the enhancement of the material damping and determine the corresponding energy dissipation. The study provides valuable quantitative relations of the additional damping effect due to the mesomechanic kinematic. Compared to the unidirectionally reinforced material, plain weave enhances the material damping by 37…52% at O ˜ PL = 0.0133 {\tilde{O}}_{{\rm{PL}}}=0.0133 , whereas twill weave 2/2 enhances it by 31…40% at O ˜ T2 = 0.0098 {\tilde{O}}_{{\rm{T2}}}=0.0098 . The consideration of the findings contributes to a deeper understanding of the visco-elastic dynamic behavior of fabric-reinforced plastics and allows further applications in research, development, and industry.

This study enhances the water resistance of mica paper/organic silicone resin composites through surface modification with 3-aminopropyltriethoxysilane (APTES). The Fourier-transform infrared spectroscopy and the X-ray photoelectron spectroscopy confirmed the formation of chemical bonds between APTES and mica. The results showed that at an optimal APTES concentration of 0.6%, the water diffusion coefficient decreased from 5.0 × 10 −3  mm²/min to 2.7 × 10 −3  mm²/min, and the permeability coefficient decreased from 5.71 × 10 −4  mm²/min to 1.94 × 10 −4  mm²/min, with a significant reduction in equilibrium water uptake. Additionally, the modified composites exhibited minimal mechanical strength loss after moisture aging, demonstrating excellent water resistance. The interface shear strength tests revealed a 28.6% increase in interfacial bonding strength after APTES modification. This study demonstrates the potential of silane coupling agents to enhance the performance of inorganic polymer composites, providing theoretical support for their industrial application.

In this work, the AA6063 Al alloy was processed by cooling at four different conditions. The impact of the type of cooling method on the corrosion behavior of the produced alloys after 1 and 24 h in 3.5% NaCl solutions was carried out. Various electrochemical measurements, such as cyclic potentiodynamic polarization (CPP), chronoamperometric, and electrochemical impedance spectroscopy (EIS) measurements, were employed. The CPP data revealed that the intensity of corrosion of the alloys is highly influenced by the cooling method. The change in the chronoamperometric current at −650 mV (Ag/AgCl) over time indicates the possibility of pitting corrosion, particularly after 24 h, where the recorded currents showed a continuous increase over time. The scanning electron microscopy images taken for the surfaces of the alloys after corrosion confirmed that the lowest deterioration occurring on the surface was for the AA6063 alloy that was quenched in water. The EIS plots also demonstrated that AA6063 alloy exhibits different corrosion resistances when different cooling methods are applied. All measurements indicated that the corrosion resistance increases in the following order: the quenched alloy in water > the air-cooled alloy > the furnace-cooled alloy > the as-received alloy. The exposure for 24 h decreases the corrosion damage of all alloys via the formation and thickening of a top layer of corrosion products on its surface over time.

As one of the main problems in the processing of carbon fiber reinforced polymer (CFRP), tool wear affects the quality and efficiency of hole making. As a new CFRP hole making process, the suction-type internal chip removal method can effectively slow down the tool wear rate. In order to further clarify the reasons for this method to slow down the tool wear, this study investigates the wear mechanism of the internal chip removal tool. The main contents include: first, the experimental parameters such as drilling axial force, drilling temperature, and tool wear are obtained through the experimental method, and the drawing of the drilling temperature change curve of internal chip drilling is completed; second, the polar analysis method is used to study the influence of the drill parameters on the drilling axial force and the tool wear, and the basis for the selection of the structure of the internal chip drill is given; finally, the method of comparative experiments of the internal chip drilling process and the non-internal chip drilling process is used to conclude that the use of the internal chip drilling process can effectively slow down the tool wear rate. Finally, the method of comparing the internal chip removal and non-internal chip removal processes is used to conclude that the use of internal chip removal processing method can effectively reduce the axial force, drilling temperature, and slow down the tool wear.

The acoustic performance of metal hollow sphere (MHS) A356 aluminum matrix composites has a significant impact on their application, making it worthy of in-depth investigation. To investigate the acoustic performance and mechanism of MHS A356 aluminum matrix composites, in this study MHS A356 aluminum matrix composites with different structural parameters were fabricated using a casting method. The density of the MHS A356 aluminum matrix composites was measured using the direct measurement method, and the acoustic performance of the composites was measured using the impedance tube. The research results indicated that the average sound absorption coefficient of MHS A356 aluminum matrix composites increased with the decrease in sintering temperature and diameter of MHSs, and the increase in volume fraction of MHSs. When the sintering temperature of the MHS was at 1,100°C, with the volume fraction being 48.50% and the diameter being 1.88 mm, the average sound absorption coefficient of the MHS A356 aluminum matrix composites reached the optimal level, which was 0.23. Conversely, the sound transmission loss of MHS A356 aluminum matrix composites decreased with the increase in sintering temperature, volume fraction, and diameter of MHSs. When the sintering temperature of the MHS stood at 1,100°C, with the volume fraction being 40% and the diameter being 2.88 mm, the average sound transmission loss of the MHS A356 aluminum matrix composites attained the maximum value, which was 24.6 dB.

The aim of this study is to investigate the impact of various ambient temperatures on the mechanical properties of full aeolian sand concrete (ASC100). Using ordinary concrete (ASC0) as the control group, we analyzed the effects of different ambient temperatures (−20, −15, −10, −5, 0, and 20°C) on the mechanical properties of both ASC0 and ASC100 through cube compression, splitting tensile, and uniaxial compression tests. The results demonstrate that the compressive strength and splitting tensile strength of concrete cubes increased with decreasing temperature. At −20°C, the compressive strength of ASC100 increased by 30.1% and that of ASC0 increased by 27.31% compared to that at 20°C. Additionally, compared to normal temperatures, the elastic modulus of ASC0 and ASC100 at subzero temperatures increased by 28.2–61.4% and 6.8–65.7%, respectively, while the peak stress increased by 7–35% and 6.8–38%, respectively. The stress–strain curve of ASC100 showed three stages: elastic, elastic-plastic, and yield failure, serving as the reference group. Finally, based on the classical constitutive model, we modified the constitutive parameters by axial compressive strength and temperature, proposing a constitutive model of concrete suitable for different low-temperature environments, which is in good agreement with experimental data.

Aggregate is the basic component of concrete, and its shape and surface properties largely determine the mechanical properties and durability of concrete. In order to further study the mesoscopic influence of aggregate shape on concrete interfacial phase, this study focuses on two aggregate shapes, circular and polygonal, and the elastic modulus and hardness of interfacial phase of specimens with different aggregate shapes were obtained by nano-indentation technology, and the mesoscopic component partition was quantified. Based on Gaussian statistical theory, the distribution model of nanomechanical properties of each phase was established, and the influence of aggregate shape on mechanical properties was studied by SEM test. The results show that (1) The width of the interfacial zone of natural rounded aggregate (∼50 μm) is slightly smaller than that of polygonal aggregate (∼60 μm), and the modulus of elasticity and hardness of the interfacial zone corresponding to the rounded aggregate ( e.g. , interfacial transition zone (E,H) ∼ (23.65 GPa, 0.9 GPa)) are larger than that of the interfacial zone of polygonal aggregate (interfacial transition zone (E,H) ∼ (21.66 GPa, 0.73 GPa)), indicating that the micromechanical properties of the interfacial zone of the circular aggregate are better than those of the polygonal aggregate; (2) The hydration products in the transition zone of the interface of different shapes of aggregates are almost the same, indicating that the influence of the shape of aggregates on the performance of concrete is mainly due to its own geometric characteristics. Based on the findings of the study, the direction of future research can focus on modeling with further refinement of the influence of aggregate shape parameters, such as shape factor and surface roughness, on the performance of concrete, so as to facilitate more accurate prediction and regulation of the performance of concrete. This study provides theoretical references for the design of aggregate proportioning and the simulation technology of fine data values in actual projects, and also provides theoretical basis and technical support for the standardization and performance evaluation of concrete materials.

Sport plays a crucial role in human society, fostering physical health, collaboration, and the spirit of rivalry. The importance of sports in promoting a sense of well-being, self-control, and cognitive sharpness should be considered. The efficacy of sports and athletic performance often relies on the caliber of clothing used. Traditional sportswear encounters many issues, including but not limited to restricted breathability, inefficient moisture management, and insufficient ultraviolet (UV) protection. To examine these concerns, the present study investigates the Intelligent Sportswear Design (ISWD), an innovative advancement rooted in conjugated nanomaterials. The field of ISWD covers the development of sports apparel and footwear specifically intended to boost performance and provide optimal comfort. Coatings of graphene, silver nanoparticles, and environmentally friendly green nanomaterials are employed in these multipurpose PES fabrics. This research looks at how we might better protect athletes from the sun by developing fabrics with UV-blocking qualities. Results show increased moisture-wicking efficiency, better UV-radiation protection, and enhanced electrical conductivity. The study found that fabric moisture management could be improved by 25%, UV-blocking performance could be increased by 30%, fabric conductivity could be increased by 15%, and heat retention could be decreased by 20%. The experimental results show that the proposed ISWD exhibits notable performance in several necessary measures, including moisture-wicking effectiveness (23.22%), UV-blocking performance (34.22%), fabric conductivity (20.88%), heat retention reduction (26.94%), and UV radiation shielding (35.68%).

In this article, the equivalent elastic modulus of the resin-impregnated Nomex honeycomb core is derived by considering the bending and stretching deformation of the honeycomb wall, based on the Euler beam theory. The elastic modulus obtained by the proposed theoretical method is proved to be in good accordance with both the experimental results and numerical results. Furthermore, the effect of the geometric parameters on the equivalent mechanical properties of the honeycomb core is discussed using a dimensionless method.

Vibration table is the key equipment to realize high efficiency and high quality forming and compacting of concrete in prefabricated component (PC) production line, and its performance directly affects the shape quality and compressive strength of PC components. However, the operating parameters of the vibration table are difficult to match the rheology of the concrete during the construction process, which directly leads to a low molding efficiency or unqualified shape quality in the case of slab-type components. Therefore, it is crucial to accurately describe the concrete flow behavior during vibration to improve the construction performance and compaction effect. In this work, the coupled theory of computational fluid dynamics and discrete element is used to study the concrete vibration and compacting characteristics, and the influence of process parameters on vibration performance is analyzed in order to realize the adjustment and optimization of key parameters. First, the concrete solid-liquid two-phase model parameters are calibrated by V-shaped funnel experiments and slump experiments. Then, based on the simulation results, the homogeneity and compactness of concrete are discussed using the segmented sieving method and the slicing method, and the indexes for evaluating the working performance of the vibration table are proposed. Finally, the relationship between vibration frequency (20–30 Hz), vibration amplitude (3–4 mm), and vibration time (15–35 s) and concrete vibration compaction characteristics is investigated to provide a theoretical basis for improving the molding efficiency and mold quality of PC components.

In the development of spinal implants, the properties of materials play a very important role in the function of the implant. This study evaluates the mechanical properties and biocompatibility of Ti–31Nb–7.7Zr alloy compared to the widely used Ti–6Al–4V alloy for spinal implants. Mechanical properties and biocompatibility were tested by manufacturing commercially available screws and rods using Ti–31Nb–7.7Zr alloy. Static compression bending test, static torsion test, and static four-point bending test were performed using a mechanical testing machine in accordance with ASTM F1717-18 standard and ASTM F382-17 standard. Additionally, screw insertion torque analysis was measured through a cadaver experiment, and histologic analysis was performed through animal experiments using a rabbit. It demonstrates that Ti–31Nb–7.7Zr, with its high yield strength and low Young’s modulus, closely matches human bone’s elasticity, potentially reducing stress shielding effects. Mechanical testing shows Ti–31Nb–7.7Zr’s superior performance in static compression, torsion, and bending tests. Biocompatibility assessments in vivo reveal no significant difference between the two materials, suggesting Ti–31Nb–7.7Zr’s suitability for spinal surgery applications. This research supports Ti–31Nb–7.7Zr alloy as a promising candidate for spinal implants, offering improved mechanical compatibility with bone and excellent biocompatibility.

It has been proved by experiments that the soft layers can effectively adjust the load distribution ratio of composite pre-tightened tooth connection, but theoretical research on the composite pre-tightened tooth connection embedded with soft layers has not been carried out. Therefore, in this work, the load distribution theory of composite pre-tightened tooth connection embedded with soft layers is studied by spring stiffness method. First, based on deformation compatibility condition, the theoretical calculation formula of load distribution ratio of each tooth is derived by spring stiffness method. Then, load distribution ratio is obtained by experiments, and the theoretical calculation results are verified. Finally, through the derived formula, the load distribution ratio of the composite pre-tightened tooth connection embedded with soft layers is parameterized. Research shows that (1) The theoretical value is in good agreement with the experimental value, and the maximum error of calculation result of the load distribution of the joint is 8%; (2) Under the action of soft layers, each tooth of two-teeth and three-teeth joints are damaged at the same time, the ultimate bearing capacity is increased by 29.0 and 21.6%, respectively, compared with the traditional two-teeth and three-teeth joints; (3) The elastic modulus and thickness of soft layers have a significant impact on the load distribution ratio of each tooth.

Ceramic products is one of the important carriers of various civilizations, reflecting the lifestyle, aesthetic concepts, and technological level of society at that time. In order to study the surface treatment design features of ceramic craft products, this article analyzed the ceramic features through computer vision technology and used residual neural networks to detect the surface treatment features of ceramic craft products. The extracted texture features were classified to study and analyze the coupling features of different glazes, colors, and shapes on the formation of different textures. This study used ResNeXt50-SSD, which combined ResNeXt50 and SSD (Single Shot MultiBox Detector) algorithms, to compare feature detection with LeNet-5, VGG-16, and MobileNetV2 network models. From the experimental findings, it can be concluded that ResNeXt50-SSD was the most effective for feature recognition of ceramic craft products, with precision, recall, and mAP of 94.3, 92.1, and 89.5%, respectively. Therefore, the combination of ResNeXt50 and SSD algorithms is an effective method for detecting surface treatment features of ceramic craft products.

This study explores the effect of integrated superelastic shape-memory alloy fibers (SMAFs) on the mechanical performance of engineered cementitious composites (ECCs). Various SMAF configurations – linear-shaped SMAFs (LS-SMAFs), hook-shaped SMAFs (HS-SMAFs), and indented-shaped SMAFs (IS-SMAFs) – with diameters of 0.8 and 1.0 mm were incorporated into ECC matrices, and surface texturization was achieved through abrasive paper treatment. Their mechanical properties were assessed through single fiber pullout tests on ECC mixtures containing 1.5 and 2.0% polyvinyl alcohol (PVA), subjected to both monotonic and cyclic loading conditions. Qualitative analysis, employing scanning electron microscopy, demonstrated that the IS-SMAF configuration provided superior mechanical interlocking and fiber–matrix adhesion, with a distinct flag shape observed during tensile testing. Quantitative data indicated that IS-SMAFs significantly improved the tensile strength and pullout resistance, with slip distances of ≥5 mm and average pullout loads ranging from 263 to 403 N. LS-SMAFs demonstrated better performance compared to HS-SMAFs and LS-SMAFs in terms of tensile and pullout characteristics. Additionally, ECCs with increased PVA content exhibited enhanced withdrawal performance. Thermogravimetry analysis and X-ray diffraction provided insights into the high-temperature stability and crystalline structure of the composites. These results underscore the effectiveness of IS-SMAFs in enhancing ECC properties, offering significant implications for the development and optimization of high-performance composite materials in civil engineering applications. Graphical abstract

To investigate the effects of different needling parameters on the mechanical properties of quartz needled felts and their composites, this paper proposes a multi-scale modeling approach to simulate and calculate the mechanical properties of needled quartz fiber-reinforced composites. Firstly, based on the characteristics of needle-punching technology, the morphology of needle-punched composites was analyzed at a microscopic scale, and the quartz fiber structure was divided into three typical representative regions. Then, a periodic single-cell model of needled composites was established. Meanwhile, this article also analyzes the influence of parameters such as needling density, needle type, and needling depth on the mechanical properties of needled composites.

Needle-punched carbon/carbon (NP C/C) composites are widely used in thermal protection systems for aerospace engineering. Oxidation and ablation affect their mechanical properties at high temperatures of service environment. A thermo-mechanical coupling model is proposed to predict the residual strength of oxidized bundles. A multiscale oxidation behavior of an NP C/C composite is simulated to investigate the progressive damage and oxidation of structures with thermo-mechanical coupling effects. Uniaxial tension experiments on the NP C/C composite were carried out at room temperature and 750°C to verify the proposed model. It is shown that mechanical properties of the composite decreased significantly after oxidation at 750°C-up to 40%, while the ultimate strain reduced by 5%. The proposed thermo-mechanical coupling model could be used to predict the failure and residual mechanical properties caused by the oxidation process.

The composite material laying parameters are important factors affecting the carrying capacity and quality of the type Ⅳ hydrogen storage vessel. In this article, the composite laying scheme is designed and analyzed by the finite element method. Through 100 groups of laying schemes, the influence laws of circumferential winding layers, spiral winding layers, spiral winding angle, and laying sequence are summarized. The results show that, when the number of spiral winding layers and the number of circumferential winding layers exceed 35 and 25 respectively, the bearing capacity of the hydrogen storage vessel cannot be significantly improved with the increase of the layer number. With the increase in the spiral winding angles, the maximum S11 decreases first and then increases, while the maximum S22 stabilizes first and then increases. But, for different numbers of spiral layers, the turning point of stress rise is different, and the best winding angle is between 55° and 65°. It is found that performing circumferential winding first and then spiral winding is the best winding sequence.

Carbon nanotubes (CNTs) are renowned for their low density, high elastic modulus, and exceptional electrical and thermal properties. The continuously developing applications of CNTs provide higher specific stiffness and strength for composite materials. The unique characteristics of CNTs make them ideal reinforcing particles in aluminum matrix composites (AMMCs), which generally exhibit excellent mechanical properties. CNTs/AMMCs are usually prepared using methods such as powder metallurgy, casting, spray deposition, and reactive melting. The uniform diffusion of CNTs in composites is crucial for enhancing the properties of CNTs/AMMCs. The properties of CNTs/AMMCs largely depend on the content, morphology, and distribution of reinforcements in the matrix and the interaction between reinforcements and the matrix. By adding an appropriate volume fraction of CNTs, the hardness, tensile strength, compressive strength, and electrical properties of CNTs/AMMCs were significantly improved. The effects of CNT content on the mechanical properties of CNTs/AMMCs, including the tensile strength, yield strength, compressive strength, stress–strain curve behavior, elastic modulus, hardness, creep, and fatigue behavior, were revealed. The design of microstructure, optimization of the preparation process, and optimization of composition can further improve the mechanical properties of CNTs/AMMCs and expand their application in engineering. The design concept of integrating material homogenization and functional unit structure through biomimetic design of novel gradient structures, layered structures, and multi-level twin structures further optimizes the composition and microstructure of CNTs/AMMCs, which is the key to further obtaining high-performance CNTs/AMMCs. As a multifunctional composite material, CNTs/AMMCs have broad application prospects in fields such as air force, military, aerospace, automation, and electronics. Moreover, CNTs/AMMCs have potential applications in cell therapy, tissue engineering, and other areas. Graphical abstract The effects of CNT content on the mechanical properties of CNTs/AMMCs, including the tensile strength, yield strength, compressive strength, stress–strain curve behavior, elastic modulus, hardness, creep, and fatigue behavior, were revealed. CNTs/AMMCs have broad application prospects in cell therapy, tissue engineering, and other fields. Influence of the concentration of CNTs on mechanical characteristics of AMMCs.

In the last few decades, tremendous effort is given to the production of various polymers and polymeric composites components through innovative polymer processing techniques. Fused deposition modeling (FDM) of polymers as a printing technique in additive manufacturing has been explored extensively due to its cost-effectiveness, manufacturing capabilities, flexibility in material selection, and dimensional accuracy. A few reviews of the literature have been done to investigate various applications for polymers, but none have focused on the research on commercial and in-house generated polymers and polymeric composites, particularly those made using the FDM printing technology. Consequently, the study data on the internal development of polymer and polymeric composite filament-based FDM printing is gathered and processed in this work. The work also highlights various types of polymeric composites and recycled polymeric composites with their detailed material characteristics. In addition, various applications of FDM printing of polymeric composites at the industrial scale and domestic level usage are highlighted as the potential to reduce carbon emission through the effective recycling process.

In cold areas, freeze–thaw damage seriously affects the long-term use and safe operation of concrete structures. The constitutive model is an important foundation for predicting deformation and strength characteristics of concrete materials and for the non-linear analysis of concrete structures. This study is based on the elaboration of methods for the constitutive model of damaged materials by using damage mechanics and others. This study focuses on the existing constitutive model results of concrete under the static axial compression load, dynamic load, and coupling environmental load, and analyzing the problems in existing studies. Research has shown that segmented models exhibit higher fitting accuracy of concrete freeze–thaw constitutive model under static axial compression loads. By defining coupled damage variables, it is possible to approach the actual freeze–thaw damage of concrete under environmental coupling, and attention should be paid to the differences or interactions between damage factors. In order to meet the actual engineering needs of high altitude and cold areas needs to expand the temperature range of freeze–thaw tests and consider the dynamic loads impact on concrete damage, the establishment of constitutive model of concrete under the actual freeze–thaw damage is the focus of frost-resistant durability research of hydraulic concrete in cold regions.

This study presents a novel integration of bibliometric and content analysis to comprehensively examine the research trends and scientific landscape of paver blocks. The investigation of 379 articles and reviews published across 174 journals reveals a steady growth in research output, with a notable surge in publications and citations from 2016 to 2024, underlining the increasing importance of this field. India, Malaysia, and the United States emerge as major contributors, with India leading in publication count (143) and the United States demonstrating high research impact through total citations (1,312) and citations per paper (48.59). Keyword examination highlights the prominence of sustainable materials, waste utilization, and innovative design strategies, while an in-depth review of highly cited papers unveils the potential for incorporating various waste streams to produce high-quality, eco-friendly paver blocks. Over the years, the research focus has expanded from conventional materials to recycled aggregates, permeable designs, and photocatalytic applications. This study identifies research gaps, such as the need for long-term performance assessment and life cycle analysis, and recommends future directions, including integrating paver blocks into urban planning and design strategies. The findings guide researchers and policymakers in the development of sustainable, resilient, and multifunctional paver block solutions.

Stone columns have garnered significant interest in geotechnical engineering as an effective ground improvement technique for enhancing the load-bearing capacity and mitigating settlement issues in soft soils. This study presents a comprehensive bibliometric analysis of scholarly literature on stone columns, utilizing data from the Web of Science database spanning from 1975 to 2023. The analysis aims to provide insights into publication trends, influential journals, key research institutions and authors, geographical distributions, and emerging themes in this domain. Through a systematic data curation process, 505 relevant publications were analyzed using Excel and VOSviewer software. The findings reveal a notable emphasis on geosynthetic encasements, load-settlement behavior, and soft soil reinforcement, with China being a major contributor. Over the past 48 years, the research has evolved from static loading to dynamic loading, sustainable structures, and artificial intelligence applications, as evidenced by the highly cited publications. This study maps the development, current state, and potential future directions of stone column research, serving as a valuable resource for researchers and practitioners in geotechnical engineering.