Search Results (131)

This study proposes a coupled constitutive model that captures the anisotropic failure characteristics and damage evolution of nickel-based single-crystal (SX) superalloys under various temperature conditions. The model accounts for both creep rate and material damage evolution, enabling accurate prediction of the typical three-stage creep curves, macroscopic fracture morphologies, and microstructural features under uniaxial tensile creep for specimens with different crystallographic orientations. Creep behavior of SX superalloys was simulated under multiple orientations and various temperature-stress conditions using the proposed model. The resulting creep curves aligned well with experimental observations, thereby validating the model’s feasibility and accuracy. Furthermore, a finite element model of cylindrical specimens was established, and simulations of the macroscopic fracture morphology were performed using a user-defined material subroutine. By integrating the rafting theory governed by interfacial energy density, the model successfully predicts the rafting morphology of the microstructure at the fracture surface for different crystallographic orientations. The proposed model maintains low programming complexity and computational cost while effectively predicting the creep life and deformation behavior of anisotropic materials. The model accurately captures the three-stage creep deformation behavior of SX specimens and provides reliable predictions of stress fields and microstructural changes at critical cross-sections. The model demonstrates high accuracy in life prediction, with all predicted results falling within a ±1.5× error band and an average error of 14.6%. Full article

This study evaluates the influence of fiber type, geometry, and interfacial behavior on the physical and mechanical performance of cementitious composites reinforced with recycled pulp from beverage cartons (RPBC), bamboo fiber (BF), and eucalyptus fiber (EF) as the sole reinforcing agents. The BF was rounded in shape and had the highest aspect ratio, while the ribbon-shaped EF exhibited the highest tensile strength index. The RPBC fibers were fibrillated and the shortest, with a ribbon shape. Flexural strength results showed that RPBCC achieved a maximum strength that was 47.6% higher than the control specimen (0% fiber), outperforming both BF- and EF-reinforced counterparts. This superior performance is attributed to the higher fibrillation level of the ribbon-shaped RPBC fibers, which promoted better fiber–matrix bonding. As the fiber content increased, the bulk density of EFC and BFC decreased linearly, while RPBC composites showed only a modest decrease in density. Porosity steadily increased in EFC and BFC, whereas a non-linear trend was observed in RPBCC, likely due to its unique morphology and fibrillation. Conversely, EFC exhibited significantly higher maximum fracture toughness (3600 J/m² at 10 wt.%) compared to PBFCC (1600 J/m² at 14 wt.%) and BFC (1400 J/m² at 14 wt.%). This enhancement is attributed to extensive fiber pullout mechanisms and increased energy absorption during crack propagation. Overall, all composite types demonstrated flexural strength values above 4 MPa, placing them in the Grade I category. Those reinforced with 10–14% RPBC exhibited strengths of 11–12 MPa, categorizing them as Grade II according to ASTM C1186-02. Full article

This study introduced basalt fibres as a reinforcing material and employed notched beam three-point bending tests combined with digital image correlation (DIC) technology to comprehensively evaluate key fracture parameters—namely, initial fracture toughness, unstable fracture toughness, fracture energy, and ductility index—of expanded polystyrene (EPS)-based geopolymer concrete with different mix proportions. The results demonstrate that the optimal fracture performance was achieved when the basalt fibre volume content was 0.4% and the EPS content was 20%, resulting in respective increases of 12.07%, 28.73%, 98.92%, and 111.27% in the above parameters. To investigate the toughening mechanisms, scanning electron microscopy was used to observe the fibre–matrix interfacial bonding and crack morphology, while X-ray micro-computed tomography enabled detailed three-dimensional visualisation of internal porosity and crack development, confirming the crack-bridging and energy-dissipating roles of basalt fibres. Furthermore, the crack propagation process was simulated using the extended finite element method, and the evolution of fracture-related parameters was quantitatively analysed using a linear superposition progressive assumption. A simplified predictive model was proposed to estimate fracture toughness and fracture energy based on the initial cracking load, peak load, and compressive strength. The findings provide theoretical support and practical guidance for the engineering application of basalt fibre-reinforced EPS-based geopolymer lightweight concrete. Full article

The anode assembly, as a key component in the electrolytic aluminum process, is composed of steel claws and aluminum guide rods. The connection quality between the steel claws and guide rods directly affects the current conduction efficiency, energy consumption, and operational stability of equipment. Achieving high-quality joining between the aluminum alloy and steel has become a key process in the preparation of the anode assembly. To join the guide rods and steel claws, this work uses Cold Metal Transfer (CMT) technology to clad aluminum on the steel surface and employs machine vision to detect surface forming defects in the cladding layer. The influence of different currents on the interfacial microstructure and mechanical properties of aluminum alloy cladding on the steel surface was investigated. The results show that increasing the cladding current leads to an increase in the width of the fusion line and grain size and the formation of layered Fe₂Al₅ intermetallic compounds (IMCs) at the interface. As the current increases from 90 A to 110 A, the thickness of the Al-Fe IMC layer increases from 1.46 μm to 2.06 μm. When the current reaches 110 A, the thickness of the interfacial brittle phase is the largest, at 2 ± 0.5 μm. The interfacial region where aluminum and steel are fused has the highest hardness, and the tensile strength first increases and then decreases with the current. The highest tensile strength is 120.45 MPa at 100 A. All the fracture surfaces exhibit a brittle fracture. Full article

To investigate the effects of heavy-metal-sludge sintered aggregates on the workability, mechanical properties, and fracture toughness of ultra-high-strength concrete (UHSC), this study systematically evaluated the influence of different aggregate replacement ratios and particle gradations on the fluidity, flexural strength, compressive strength, and fracture energy of UHSC. Microstructural characterization techniques including SEM, XRD, TG, and FTIR were employed to analyze the hydration mechanism and interfacial transition zone evolution. The results demonstrated the following: Fluidity continuously improved with the increase in the sintered aggregate replacement ratio, with coarse aggregates exhibiting the most significant enhancement due to the “ball-bearing effect” and paste enrichment. The mechanical properties followed a trend of an initial increase followed by a decrease, peaking at 15–20% replacement ratio, at which flexural strength, compressive strength, and fracture energy were optimally enhanced; excessive replacement led to strength reduction owing to skeletal structure weakening, with coarse aggregates providing superior improvement. Microstructural analysis revealed that the sintered aggregates accelerated hydration reactions, promoting the formation of C-S-H gel and Ca(OH)₂, thereby densifying the ITZ. This study identified 15–20% of coarse sintered aggregates as the optimal replacement ratio, which synergistically improved the workability, mechanical properties, and fracture toughness of UHSC. Full article

To elucidate the key material parameters governing the tribological performance of ceramic composites under dry sliding against steel, this study presents a comprehensive comparative assessment of the microstructural characteristics, mechanical performance, and tribological behavior of two alumina–zirconia (Al₂O₃–ZrO₂) ceramic composites, each reinforced with a 42 vol.% carbide phase: zirconium carbide (ZrC) and tungsten carbide (WC). Specifically, tungsten carbide (WC) was selected for its exceptional bulk mechanical properties, while zirconium carbide (ZrC) was chosen to contrast its potentially different interfacial reactivity against a steel counterface. ZrC and WC were selected as reinforcing phases due to their high hardness and distinct chemical and interfacial properties, which were expected to critically affect the wear and friction behavior of the composites under demanding conditions. Specimens were consolidated via spark plasma sintering (SPS). The investigation encompassed macro- and nanoscale hardness measurements (Vickers hardness HV₁, HV₁₀; nanoindentation hardness H), elastic modulus (E), fracture toughness (K_IC), coefficient of friction (COF), and specific wear rate (W_s) under unlubricated reciprocating sliding against 100Cr6 steel at normal loads of 10 N and 25 N. The Al₂O₃–ZrO₂–WC composite exhibited an ultrafine-grained microstructure and markedly enhanced mechanical properties (HV₁₀ ≈ 20.9 GPa; H ≈ 33.6 GPa; K_IC ≈ 4.7 MPa·m^½) relative to the coarse-grained Al₂O₃–ZrO₂–ZrC counterpart (HV₁₀ ≈ 16.6 GPa; H ≈ 27.0 GPa; K_IC ≈ 3.2 MPa·m^½). Paradoxically, the ZrC-reinforced composite demonstrated superior tribological performance, with a low and load-independent specific wear rate (W_s ≈ 1.2 × 10⁻⁹ mm³/Nm) and a stable steady-state COF of approximately 0.46. Conversely, the WC-reinforced system exhibited significantly elevated wear volumes—particularly under the 25 N regime—and a higher, more fluctuating COF. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) of the wear tracks revealed the formation of a continuous, iron-enriched tribofilm on the ZrC composite, derived from counterface material transfer, whereas the WC composite surface displayed only sparse tribofilm development. These findings underscore that, in steel-paired tribological applications of Al₂O₃–ZrO₂–based composites, the efficacy of interfacial tribolayer generation can supersede intrinsic bulk mechanical attributes as the dominant factor governing wear resistance. Full article

This study signifies the development and characterization of a composite material with a metallic matrix of aluminum reinforced with a steel mesh, utilizing centrifugal casting technology. An evaluation was conducted to ascertain the influence of the formulation process and the presence of the insert on the mechanical behavior with regard to tensile strength. The aluminum matrix was obtained from commercial and scrap alloys, elaborated by advanced methods of degassing and chemical modification. Meanwhile, the steel mesh reinforcement was cleaned, copper plated, and preheated to optimize wetting and, consequently, adhesion. The structural characterization was performed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analyses (EDX), which highlighted a well-defined interface and uniform copper distribution. The composite was produced by means of horizontal-axis centrifugal casting in a fiberglass mold, followed by cold rolling to obtain flat specimens. A total of eight tensile specimens were examined, with measured ultimate tensile strengths ranging from 78.5 to 119.8 (MPa). A thorough examination of the fractured specimens revealed a brittle fracture mechanism, devoid of substantial plastic deformation. The onset of failures was frequently observed at the interface between the aluminum matrix and the steel mesh. The use of SEM and EDX investigations led to the confirmation of the uniformity of the copper coating and the absence of significant porosity or interfacial defects. A bimodal distribution of tensile strength values was observed, a phenomenon that is likely attributable to variations in mesh positioning and local differences in solidification. A correlation was established between the experimental results and an analytical polynomial model, thereby confirming a reasonable fit. In sum, the present study provides a substantial foundation for the development of metal matrix composites with enhanced performance, specifically designed for challenging structural applications. This method also demonstrates potential for recycling aluminum scrap into high-performance composites with controlled microstructure and mechanical integrity. Full article

In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash (PFA), which is a by-product of coal-fired electricity power stations. Steel fibres were used with different aspect ratios and hooked ends with single, double and triple bends corresponding to 3D, 4D and 5D types of DRAMIX steel fibres, respectively. Key parameters such as the concrete compressive strength f_lck, fibre volume fraction V_f, number of bends n_b, embedded length L_E and inclination angle ϴ_f were considered. The fibres were added at volume fractions V_f of 1% and 2% to cover the practical range, and a direct tensile test was carried out using a purpose-built pull-out test developed as part of the present study. Thus, the tensile mechanical properties were established, and a generic constitutive tensile stress–crack width σ-ω model for both plain and fibrous lightweight concrete was created and validated against experimental data from the present study and from previous research found in the literature (including RILEM uniaxial tests) involving different types of lightweight aggregates, concrete strengths and steel fibres. It was concluded that the higher the number of bends n_b and the higher the volume fraction V_f and concrete strength f_lck, the stronger the fibre–matrix interfacial bond and thus the more pronounced the enhancement provided by the fibres to the uniaxial tensile residual strength and ductility in the form of work and fracture energy. A fibre optimisation study was also carried out, and design recommendations are provided. Full article

Lightweight concrete (LWC) has emerged as a transformative material in sustainable and high-performance construction, driven by innovations in engineered lightweight aggregates, supplementary cementitious materials (SCMs), fiber reinforcements, and geopolymer binders. These advancements have enabled LWC to achieve compressive strengths surpassing 100 MPa while reducing density by up to 30% compared to conventional concrete. Fiber incorporation enhances flexural strength and fracture toughness by 20–40%, concurrently mitigating brittleness and improving ductility. The synergistic interaction between SCMs and lightweight aggregates optimizes matrix densification and interfacial transition zones, curtailing shrinkage and bolstering durability against chemical and environmental aggressors. Integration of recycled and bio-based aggregates substantially diminishes the embodied carbon footprint by approximately 40%—aligning LWC with circular economy principles. Nanomaterials such as nano-silica and carbon nanotubes augment early-age strength development by 25% and refine microstructural integrity. Thermal performance is markedly enhanced through advanced lightweight fillers, including expanded polystyrene and aerogels, achieving up to a 50% reduction in thermal conductivity, thereby facilitating energy-efficient building envelopes. Although challenges persist in cost and workability, the convergence of hybrid fiber systems, optimized mix designs, and sophisticated multi-scale modeling is expanding the applicability of LWC across demanding structural, marine, and prefabricated contexts. In essence, LWC’s holistic development embodies a paradigm shift toward resilient, low-carbon infrastructure, cementing its role as a pivotal material in the evolution of next-generation sustainable construction. Full article

Basalt fiber-reinforced cementitious composites (BF-RCC) have attracted considerable research interest in construction engineering owing to their excellent mechanical performance. However, some great challenges, such as limited ultimate tensile strain (typically less than 1%) and poor high-temperature resistance, have restricted its broader application. This study explores the influence of silane coupling agent (SCA) modification on the mechanical performance of the BF-RCC under high-temperature environments. The basalt fibers were treated with KH602 (SCA) to enhance interfacial bonding with the cement matrix under high-temperature environments. The mechanical performance of BF-RCC, including tensile strength, compressive strength, elastic modulus, crack propagation behavior and toughness index, was evaluated under different SCA concentrations (2.5% and 4.5%) and different temperatures (20 °C, 200 °C, 300 °C and 400 °C). The findings demonstrate that the tensile strength and compressive strength of the BF-RCC are elevated by 1.5 times and 1.7 times, respectively, while the toughness index and elastic modulus are enhanced by 1.6 times and 1.4 times, respectively. The incorporation of SCA significantly reduces the mass loss of the BF-RCC under high temperatures, with the 2.5% KH602 concentration exhibiting the optimal performance. However, when the temperature exceeds 300 °C, the mechanical properties of the BF-RCC deteriorate markedly. Digital image correlation (DIC) technology demonstrated that SCA-modified BF-RCC displays enhanced crack propagation resistance, with post-peak fracture energy showing a concentration-dependent increase, thereby reducing material brittleness. Full article

Laser powder bed fusion (LPBF) of SiCp/AlSi10Mg is promising in many industrial fields. In this paper, the characteristics of a 15 wt.% 1200 mesh SiCp/AlSi10Mg metal matrix composite fabricated by LPBF were investigated systematically, i.e., from a single track to a block. It was found that when the laser energy input was high enough, the single track was continuous and not distorted; when the laser energy input was low, the single track was unstable and wrinkled. The densification of the LPBFed composite sample was influenced significantly by the surface morphologies and geometric dimensions of the single tracks. As high as 98.9% relative density was achieved when the optimized processing parameters were used. Because of the good wettability and the interfacial reaction during the process, the interface of SiC and the matrix showed good bonding. Near the interface of SiC and the matrix, needle-shaped phase Al₄SiC₄ could be found both in the single track and block, and the faceted particle Si was formed in the block because of the interfacial reaction. The microhardness of the LPBFed SiCp/AlSi10Mg composites was much higher than that of the LPBFed unreinforced AlSi10Mg. A coefficient of friction of 0.178 and wear rate of 2.02 × 10⁻⁴ mm³/(N⋅m) were achieved for the LPBFed composites. The main wear mechanism was delamination wear, accompanied by abrasive wear. The maximum yield strength and ultimate compressive strength were 566.6 MPa and 764.1 MPa, respectively. The fracture mode of the LPBFed composites is mainly brittle fracture. This study provides a theoretical and technical basis for LPBFed SiCp/AlSi10Mg 3D parts. Full article

Poly(3,3-bis(azidomethyl)oxetane(BAMO)-tetrahydrofuran(THF)) copolymer (PBT) and ammonium perchlorate (AP) are critical components of solid rocket propellants, where their interfacial bonding mechanisms and temperature-dependent mechanical properties are pivotal to propellant reliability. In this study, density functional theory (DFT) calculations were employed to evaluate the adsorption energies between common AP crystal surfaces and PBT units, identifying the most energetically favorable adsorption configurations. The atomic configurations and charge transfer characteristics at the PBT-AP interface were systematically analyzed. Molecular dynamics (MD) simulations were further conducted to determine the thermally stable operating range of the PBT-AP system. The results reveal a strong temperature dependence of mechanical performance, with viscous failure mechanisms and damage thresholds during static tensile processes investigated across varying temperatures. Notably, mechanical properties remain stable below 60 °C but deteriorate significantly above this temperature. This study elucidates the influence of a PBT-AP interfacial microstructure and temperature on mechanical performance and tensile fracture damage boundaries, providing crucial insights for the design, formulation, and safe application of PBT-based solid rocket propellants. Full article

The rapid advancement of sustainable materials has driven the need for high-performance polymer nanocomposites with superior mechanical, thermal, and structural properties. In this study, a novel RPET/PA-11/Joncryl^® nanocomposite reinforced with halloysite nanotubes (HNTs) is developed for the first time, marking a significant breakthrough in polymer engineering. Six different proportions of HNT (0, 1, 2, 3, 4, and 5 phr) are introduced to the blend of rPET/PA-11/Joncryl^® through a twin-screw extruder and injection moulding machine. The incorporation of HNTs into the RPET/PA-11 matrix, coupled with Joncryl^® as a compatibilizer, results in a synergistic enhancement of material properties through improved interfacial adhesion, load transfer efficiency, and nanoscale reinforcement. Comprehensive characterization reveals that the optimal formulation with 2 phr HNT (NCS-H2) achieves remarkable improvements in tensile strength (56.14 MPa), flexural strength (68.34 MPa), and Young’s modulus (895 MPa), far exceeding conventional polymer blends. Impact resistance reaches 243.46 J/m, demonstrating exceptional energy absorption and fracture toughness. Thermal analysis confirms enhanced stability, with an onset degradation temperature of 370 °C, attributing the improvement to effective matrix–filler interactions and restricted chain mobility. Morphological analysis through FESEM validates uniform HNT dispersion at optimal loading, eliminating agglomeration-induced stress concentrators and reinforcing the polymer network. The pioneering integration of HNT into RPET/PA-11/Joncryl^® nanocomposites not only bridges a critical gap in sustainable polymers but also establishes a new benchmark for polymer nanocomposites. This work presents an eco-friendly solution for engineering applications, offering mechanical robustness, thermal stability, and recyclability. The results form the basis for next-generation high-performance materials for industrial use in automotive, aerospace, and high-strength structural applications. Full article

Nano-precipitates play a vital role in the development of ultra-high strength steels (UHSSs). In recent decades, the B2-NiAl phase, which forms highly coherent interfaces with the BCC-Fe matrix, has attracted significant attention for enhancing the strength of UHSSs. However, direct experimental investigation of alloying elements—specifically their atomic distribution and the resulting effects on the interfacial bonding strength of nano-precipitates—remains challenging. This study uses density functional theory (DFT)-based first-principles calculations to investigate the role of alloying elements in modifying interfacial characteristics. Six elements—Al, Ni, Co, Cr, Mo, and C—are introduced at various occupation sites within the coherent interface model to calculate the formation energy. The predicted preferential distribution of solid-solution atoms aligns well with experimental findings. Stable configurations of alloying segregation are selected for first-principles rigid tensile fracture tests along the <001> direction. Electronic structure analysis reveals that Co, Cr, and Mo segregation enhances interface strength due to solute-induced high charge density and the preservation of bonding characteristics of bulk phases at the interface. The results offer valuable insights and practical guidance for developing novel ultrahigh-strength structural steels strengthened by B2-NiAl. Full article

This research investigates the effects of steel (ST) and synthetic (SYN) fibers on the workability and mechanical properties of HPFRC. It also analyzes their influence on the material’s microstructural characteristics. ST fibers improve tensile strength, fracture toughness, and post-cracking performance owing to their rigidity, mechanical interlocking, and robust adhesion with the matrix. SYN fibers, conversely, mitigate shrinkage-induced micro-cracking, augment ductility, and enhance concrete performance under dynamic stress while exerting negative effects on workability. Hybrid fiber systems, which include ST and SYN fibers, offer synergistic advantages by enhancing fracture management at various scales and augmenting ductility and energy absorption capability. Scanning electron microscopy (SEM) has been crucial in investigating fiber–matrix interactions, elucidating the effects of ST and SYN fibers on hydration, crack-bridging mechanisms, and interfacial bonding. ST fibers establish thick interfacial zones that facilitate effective stress transfer, whereas SYN fibers reduce micro-crack formation and enhance long-term durability. Nonetheless, research deficiencies persist, encompassing optimal hybrid fiber configurations, the enduring performance of fiber-reinforced concrete (FRC), and sustainable fiber substitutes. Future investigations should examine multi-scale reinforcing techniques, intelligent fibers for structural health assessment, and sustainable fiber alternatives. The standardization of testing methodologies and cost–benefit analyses is essential to promote industrial deployment. This review offers a thorough synthesis of the existing knowledge, emphasizing advancements and potential to enhance HPFRC for high-performance and sustainable construction applications. The findings facilitate the development of new, durable, and resilient fiber-reinforced concrete systems by solving current difficulties. Full article