This paper presents a novel approach combining numerical simulations and experiments to evaluate the mechanical behaviors of ring-shaped throat backups reinforced with needled C/C composites in solid rocket motors under room and high temperatures. First, the fracture pattern of the ring is examined experimentally. On this basis, a multiscale homogenization method is used to integrate microstructural features into a macroscale model by passing homogenized temperature-dependent material properties. The macroscale model is established according to the experimental condition, and combines the Tsai-Wu failure criterion for initiation and an instantaneous stiffness reduction method for evolution. Meanwhile, zero-thickness cohesive elements are employed to obtain fracture behaviors within the ring. Validation against experimental results demonstrates the predicted relative errors are both below 12.22 % for the critical load and displacement. Furthermore, investigations into the effects of the wall thickness and aspect ratio (beta) indicate that the peak load and compressive stiffness go up as the wall thickness or beta rises at 1200 degrees C. The results show that the ultimate load increases nearly 25-fold as the wall thickness grows from 1 mm to 5 mm, while it increases by 34.69 % as the beta rises from 0.86 to 1.2. Additionally, the ring length has little significant influence on the critical displacement. These findings provide theoretical guidance for the design and optimization of needled C/C composite ring-shaped parts.

Employing opening shielding gas in metal micro-droplet deposition enables lightweight, real-time, eco-friendly manufacturing. However, aluminum alloys, highly sought-after for manufacturing, face challenges in equipment development and experimental research due to their high oxidation reactivity and thermal sensitivity. This study presents a novel approach that combines piezoelectric actuation with dynamic coaxial gas shielding. The method enables stable aluminum droplet printing with micron-level precision in an open environment. Through combined experiments and theoretical models, the impact of oxidation on droplet deposition dynamics, surface morphology, and formation quality was investigated. Results show that even a slight change in the deposition distance would cause significant variations in deposition and oxidation behavior. Increasing the deposition distance not only exacerbates droplet oxidation and dampens droplet oscillation, but also forms oxidation wrinkles on the droplet surface. A higher substrate feed speed also reduces the shielding gas effectiveness. This effect is particularly significant in multi-layer droplet pileup, where heat accumulation delays solidification and exacerbates oxidation in the upper-layer droplets. To address these challenges, a variable-speed printing strategy based on thermal management was proposed. This method suppresses droplet surface oxidation, enabling metallurgical bonding and stable part formation in open environments. This work provides both practical strategies and theoretical insights for oxidation control in high-temperature metal droplet printing under open-environment conditions.

Wet friction materials are essential components in the transmission and braking systems of high-end equipment. However, their performance is often limited by weak interfacial adhesion between the carbon fibers and the resin matrix. In this study, zirconium-based metal-organic frameworks (MOFs), namely UiO66-NH2, are grown on the surface of carbon cloth via an in-situ solvothermal method. With the carbon fibers themselves acting as the support skeleton and core reinforcement of the entire structure, a unique organic-inorganic interwoven 3D porous network is constructed. By precisely controlling the concentration of acetic acid, we effectively tuned the morphology and distribution of the UiO66-NH2 crystals on the fiber surface. This interwoven structure creates abundant micromechanical interlocking sites and robust interfacial adhesion via combined physical and chemical interactions. By doing so, it facilitates efficient stress transfer, alleviates stress concentration, and effectively inhibits crack propagation. The results show that the modified sample, CFs/UiO66-NH2-6, had a 68.8 % increase in tensile strength to 513.61 MPa, a rise in the friction coefficient from 0.088 to 0.115, and a 71.8 % reduction in wear rate, all while maintaining highly stable friction performance. Our research offers an innovative and effective strategy for designing high-performance wet friction materials with superior mechanical and tribological properties.

Carbon fiber reinforced magnesium matrix (Cf/Mg) composites have emerged as attractive lightweight materials for aerospace, automotive, and consumer electronics applications. Significant progress has been made in developing Cf/Mg composites for load-bearing structures, wear-resistant components, and structural-functional integrated systems. To date, the translation of laboratory-scale advances into practical engineering applications remains limited. A growing body of evidence indicates that the spatial configuration of carbon fibers (fiber configuration) within the magnesium matrix is a key factor governing the mechanical and functional performance of Cf/Mg composites. However, unlike polymer matrix composites, where fiber configurations can be relatively easily tailored, the realization of tailored fiber configurations in metal matrix composites, particularly Cf/Mg composites, is intrinsically constrained by the high-temperature and high-pressure processing conditions required for fabrication. These constraints pose significant challenges to precise fiber arrangement and structural integrity, thereby restricting performance enhancement and large-scale manufacturing. In this review, recent advances in Cf/Mg composites are systematically summarized with a focus on configuration-property relationships, processing strategies for constructing diverse fiber configurations, and their engineering implementations for targeted performance. Critical challenges hindering industrial adoption are discussed, and potential strategies to bridge the gap between fundamental research and practical applications are proposed. This review aims to provide valuable insights into the design and development of high-performance Cf/Mg composites for both academic studies and engineering applications.

The advancement of highly integrated and miniaturized electronic devices requires materials that combine excellent thermal conductivity with effective electromagnetic interference (EMI) shielding. However, the integration of those properties in pristine graphene (PG) reinforced magnesium matrix (PG/Mg) composites is hindered by their poor interfacial bonding and limited structural design. Herein, we creatively propose a multidimensional pyrocarbon-Cu nanoparticles (PyC-Cu NPs) co-modification strategy to construct a multi-scale 3D structured PG preform reinforced AZ91D matrix (PG/AZ91D) composite. The EMI shielding effectiveness of the PG@PyC-1.5@Cu/AZ91D composite is 91.53 dB, and the thermal conductivity of the PG@PyC-2@Cu/AZ91D composite can reach 73.83 W/(m & sdot; K), which exhibits 230.1% and 88.6% improvement compared with PG/ AZ91D composite, respectively. The electromagnetic wave attenuation of the PG@PyC@Cu/AZ91D composites originates from conductive loss and polarization loss. The multi-dimensional hetero-structure provides multiple electron and phonon transport channels for the composites. Our study offers a facile strategy for the preparation of functional electronic devices with superior EMI shielding and thermal conduction properties.

Aluminum (Al) alloys are pivotal structural materials, indispensable for advanced energy-saving solutions and lightweight technologies. However, the limited heat resistance and low critical strength of the present commercial Al alloys at elevated temperatures (300-400 °C) have constrained their broader applications. Here, we present a facile strategy to additively manufacture strong yet ductile heat-resistant Al alloys using laser powder bed fusion (PBF-LB). By embedding heat-resistant multicomponent intermetallic nanophases (HMINPs) at the solidified cell boundaries, the as-printed alloy forms thermally stable cellular structures containing a high-volume fraction (~14 vol%) of HMINPs. Without any additional post-treatment, our as-printed Al alloy exhibits an average room-temperature tensile strength of 582 MPa, combined with a tensile strength of 114 MPa and exceptional creep resistance at 400 °C. The partial solid-state amorphization of the HMINPs during tensile straining at 300-400 °C creates a nano-dual-phase glass-crystal structure, providing an additional toughening mechanism. This HMINP strategy and PBF-LB's freeform manufacturing capability enable large-scale industrial use of our high-performance Al alloy, holding great promise for advancing energy efficiency, carbon neutrality, and sustainable manufacturing.

In mechanical systems, friction and wear are ubiquitous phenomena that not only cause energy loss but also serve as key factors in mechanical failures. However, commonly used lubricant additives generally suffer from issues such as insufficient stability and susceptibility to oxidation. This study developed a co-precipitation method to grow zinc oxide nanoparticles on the surface of carbon spheres in situ, thereby preparing carbon sphere/zinc oxide (CS/ZnO) composite materials. The prepared CS/ZnO composite nanoparticles were used as a novel lubricant additive, significantly improving the anti-friction and anti-wear properties of the reference oil. When 0.5 wt% CS/ZnO was added, the lubricant demonstrated a significant reduction in the friction coefficient and wear rate by 38.4% and 45.5%, respectively, compared to the Ref-oil under a load of 100 N. The excellent friction performance is attributed to the friction film formed on the friction surface through mechanical deposition and friction chemical reactions during the friction process, as well as the filling, repair, rolling bearing, and polishing effects of CS/ZnO.

The protective efficacy of hafnium carbide (HfC) coatings on Carbon/Carbon (C/C) composites is closely linked to the dynamic evolution of their oxide layer during ablation. While the dense hafnium oxycarbide (HfC1-xOx) acts as an effective barrier, its further oxidation into the loose HfO2 leads to the degradation of the protective performance of the coatings. This study extends a composition-evolution ablation model by explicitly resolving surface topography to investigate the spatiotemporal evolution of the heterogeneous oxide layer and the protective performance during ablation. The proposed ablation model is validated against experimental measurements of elemental (C, O, and Hf) distributions after ablation. The results reveal a two-stage ablation mechanism: an initial protective stage maintained by the growth of dense HfC1-xOx, followed by an accelerated degradation stage triggered by the accumulation of porous HfO2. This study also demonstrates that the geometric effect leads to a concentrated oxygen flux in the valley regions, resulting in a more rapid consumption of HfC compared to the peak regions. Furthermore, an elevated oxygen mole fraction (from 20% to 60%) accelerates the degradation of the oxygen barrier properties, causing an approximately 11% reduction in its optimal performance. These insights provide a basis for the reliability analysis and lifetime prediction of HfC-based ablation-resistant coatings.

Asymptotic expansion homogenization (AEH) offers a rigorous multiscale framework for predicting effective thermo-mechanical properties of periodic composites. In practical implementation, AEH requires solving a sequence of unit cell problems, yet existing finite-element (FE) implementations of AEH are often presented in disparate notations and constraint treatments, which hinders reproducibility and obscures their relationship with standard FE homogenization (FEH). This paper presents an implementation-oriented unification of coupled thermo-mechanical AEH. Four representative FE routes, i.e., UEL, Fish-type, Cheng-type, and Wang-type, are reformulated within a common notation and workflow. The assumptions, constraint treatments, and periodic boundary condition enforcement strategies are explicitly characterized, and the conditions under which these approaches yield consistent discrete responses are identified. Taking FEH as a reference, the formulations are compared in terms of weak forms, periodic boundary condition enforcement, and post-processing procedures for effective stiffness, coefficients of thermal expansion, and thermal conductivity. Benchmark studies on representative composite architectures show that, when implemented consistently, the different AEH-FE routes reproduce FEH results. Practical recommendations for robust and reproducible implementations are summarized, together with verification checks.

Hafnium carbide (HfC) coatings are critical for protecting C/C composites in high-temperature and oxygen-rich environments. During service, ablation-induced chemical reactions and the associated volumetric expansion generate complex internal stress fields. Ultimately, these stresses drive the cracking and spallation of the coating. This work proposes a coupled chemo-mechanical ablation model that incorporates the feedback loop between stress-dependent reaction kinetics and chemical expansion strain. The model is implemented via a user-defined element (UEL) subroutine. It is employed to investigate the critical role of surface roughness in the coevolution of composition and internal stress within HfC coatings. Its predictive accuracy is validated against experimental post-ablation residual stresses and oxygen distribution profiles. The results identify the peak-to-valley transition regions as critical failure sites, where prolonged ablation (up to 40 s) elevates shear stress to 375 MPa. Furthermore, increasing surface roughness (Ra) from 4 to 12 mu m accelerates the degradation of oxygen barrier properties and amplifies the maximum tensile and shear stresses by over 48%. These findings provide fundamental insights into the failure mechanisms of HfC-based thermal protection systems.

Carbon/carbon-silicon carbide composites (C/C-SiC) have gained widespread attention as a new type of braking materials, but the long preparation cycle and cost have limited the wide range of applications. In this work, a novel warm pressing-in-situ densification method was proposed to prepare TiN-Si2N2O modified C/C-SiC composites. This novel method reduced the preparation cycle time significantly. The results showed that CTNS-3 with 44.5 % TiN-Si2N2O content had the best flexural and compressive performance, with 145 % and 87 % improvement. CTNS-2 with 37.0 % TiN-Si2N2O content had the best tribology performance. Additionally, the wear rate of CTNS-2 achieved 0.433 mu m/cycle, representing an impressive decrease of 48 %. This work balance rapid preparation with excellent performance, providing a promising strategy for the development of C/C-SiC braking materials.

Hafnium carbide(HfC)serves as a critical ablation-resistant coating for C/C composites used on the wing leading edges of high-speed vehicles during atmospheric re-entry[1-3].Under the action of high-temperature,oxidizing gas flow,the HfC coating forms a high-melting-point heterogeneous oxide layer,significantly delaying oxidation of the underlying material and pre-serving the structural integrity of the C/C composites[4].

Carbon fabric (CF)-reinforced polymer composites show great potential in wet friction applications, but their performance is severely limited by poor interfacial adhesion and susceptibility to abrasive wear. Herein, we propose a “rigid-flexible” hierarchical interface strategy utilizing a conformal defect-filling carboxymethyl cellulose (CMC) layer and an in-situ grown rigid UiO66-NH2 octahedral array to enhance the mechanical and tribological properties of CF/phenolic composites. The CMC/UiO66-NH2 hierarchical modification reduced surface defects and increased the apparent single-fiber tensile strength by 89.3%. Meanwhile, the UiO66-NH2 array increased the surface roughness and promoted mechanical interlocking with the resin matrix. The combined CMC/UiO66-NH2 interface improved interfacial load transfer and reduced premature debonding, leading to a 75.1% increase in tensile strength. Furthermore, under alternating friction shear, the hierarchical interface promotes the formation of a protective tribofilm, promoting the in-situ formation of a continuous solid tribofilm. This transitions the wear mechanism from severe abrasive wear to mild sliding wear, resulting in an 81.1% reduction in the specific wear rate. This study provides an interfacial design strategy for designing high-load-bearing and highly durable fabric composites for demanding tribological applications.

Metal additive manufacturing (MAM) offers transformative potential for producing complex, high-performance components directly in space. However, a systematic understanding of which MAM processes are truly viable for in-space deployment, their current maturity levels, and the critical challenges that constrain further advancement remains limited. This review provides a comprehensive assessment of the adaptability of major MAM technologies, including Direct Energy Deposition (DED), Powder Bed Fusion (PBF), Material Extrusion (MEX), Material Jetting (MJT), and Vat Photopolymerization (VPP), to the unique conditions of microgravity and vacuum. By integrating dispersed findings into a unified framework that links process physics with environmental constraints, we offer a comparative analysis of terrestrial versus in-space operation, emphasizing how microgravity and vacuum reshape system architectures, melt-pool behavior, interlayer bonding, defect formation, and overall process capabilities. Key challenges related to equipment miniaturization and space adaptation, process monitoring and control, melt-solidification dynamics, and post-processing and quality assurance are critically examined, together with their implications for process-structure-property relationships under non-terrestrial conditions. Building on these insights, a technology-readiness roadmap is proposed to highlight priority research directions required to transition from isolated laboratory demonstrations toward robust, flight-ready MAM systems. This work establishes an integrated understanding of the state of the art and outlines future pathways for advancing metallic additive manufacturing in extreme space environments.

This study aims to investigate the infiltration behavior of molten Mg into low-strength, high-porosity graphene preforms and determine the minimum infiltration pressure required to achieve saturated infiltration, thereby providing theoretical guidance for the fabrication of graphene-reinforced magnesium matrix composites. By integrating the level-set method with the Navier-Stokes equations and extracting the pore network from the composite microstructure, a two-dimensional pore-scale infiltration model was established. The infiltration process under pressures of 30, 50, and 70 kPa was systematically simulated, revealing the evolution of pressure fields, velocity fields, and saturation levels. The results demonstrate that infiltration pressure significantly influences both the flow dynamics and final saturation: at 30 kPa, infiltration lasted approximately 0.8 ms with average flow velocities maintained within 0.5-1 m/s, resulting in a laminated structure with extensive un-infiltrated regions; at 50 kPa, the infiltration duration extended to 2 ms, with a maximum velocity exceeding 1 m/s and improved saturation level, though localized un-infiltrated zones persisted; at 70 kPa, near-complete saturation (>90 %) was achieved within about 2 ms, and experimentally fabricated composites exhibited uniform infiltration morphology. The established "image-based modeling - simulation - experimental validation" framework provides a reliable tool for optimizing liquid-metal infiltration in highly porous media and offers valuable guidance for the scalable production of high-performance metal-matrix composites.

Traditional advanced structural materials are strictly bounded by their intrinsic physical properties, creating persistent design trade-offs between load-bearing capacity, weight, and directional deformation control. Tension/compression-torsion mechanical metamaterial (T/C-T MMs) break through these classic limitations by utilizing artificially engineered micro-architectures to smoothly convert standard one-dimensional axial stress waves into continuous, programmatic in-plane torsional rotations. This critical review provides a comprehensive synthesis of the recent milestones driving the rapid advancement of T/C-T MMs. We systematically map the core framework of microstructural synthesis into three dominant methodologies: parametric optimization based on predefined inclined-strut or ligament typologies, continuous and discrete topology optimization, and advanced data-driven machine learning schemes for rapid inverse structural discovery. Beyond basic geometric design, we comprehensively evaluate the translation of this cross-axis coupling mechanism into exceptional engineering application frontiers, specifically analyzing its role in low-frequency vibration damping, high-efficiency mass-specific energy absorption, compliance-guided soft robotics, and reconfigurable mechanical logic concealment arrays. Finally, we critique the underlying bottlenecks regarding scale-dependent boundary constraints, structural fatigue, and fabrication sensitivity, outlining future development trajectories that integrate multi-field stimuli-responsive materials and advanced additive manufacturing to pioneer next-generation intelligent structures.

Carbon fiber reinforced AZ91D magnesium matrix composites (Cf/AZ91D) composites exhibit outstanding potential as lightweight, high-strength materials for aircraft and space vehicle applications. However, the thermal cycling environment encountered during aircraft (e.g., hypersonic vehicle) service can induce complex damage within these materials. This study systematically investigates the effects of thermal cycling (from room temperature to high temperatures) on the microstructure and thermomechanical properties of Cf/AZ91D composites fabricated by liquid-solid extrusion following vacuum-pressure infiltration (LSEVI), employing integrated fullfield digital image correlation (DIC) and infrared thermography (IRT) measurements to elucidate the underlying mechanisms governing their thermal cycling behavior through multiscale characterization and mechanical analysis. The findings reveal that thermal stress manifests as strain hysteresis during thermal cycling, with plastic deformation of the matrix resulting in residual plastic strain accumulation within the composite after each cycle. Thermal cycling of Cf/AZ91D composites induces interfacial damage and microcrack propagation proportional to cycle count, reducing tensile strength but enhancing ductility in early-stage cycling. Strength degradation originates from accumulated interfacial debonding and microcracks, while ductility improvement stems from thermal stress relief and weakened interfaces. Phase evolution reveals that Al8Mn5 precipitation at grain boundaries initially refines alpha-Mg grains yet dissolves after multiple cycles to coarsen the microstructure, while interfacial Al enrichment drives Al4C3 needle formation that acts as crack initiation sites accelerating performance deterioration.

Porous materials, prevalent in both natural and engineered systems, exhibit exceptional physical properties that make them indispensable for applications ranging from biomedical implants to aerospace structures. However, their mechanical performance is highly sensitive to microstructural characteristics, particularly pore morphology and distribution. This work develops a comprehensive set of mean-field homogenization (MFH) frameworks, to quickly and accurately predict the effective elastic properties of porous materials by treating them as solid-pore composites, including: (1) one-step models (Voigt, Reuss, Mori-Tanaka (M-T), and double inclusion (DI)) that establish property bounds; (2) two-step models incorporating pore orientation distributions; and (3) an improved hybrid model combining these approaches. The proposed methods demonstrate remarkable accuracy and efficiency, and the improved Voigt/Reuss-M-T/DI MFH schemes could narrow the relative error within 4% even for high-porosity porous materials. The results show that porosity dominates elastic property variation, causing over 70% reduction as porosity increases from 0% to 50%. Pore’s aspect ratio exhibits gentle influence, while pore aggregation significantly affects mechanical responses, as the concentration increase from 0 to 1, the elastic properties enhance by 10.8%. The models successfully capture the microstructure-property relationships, validated across diverse porous material systems. This work provides a powerful computational toolset for designing and optimizing porous materials in engineering applications.

This research was supported by the National Natural Science Foundation of China (52172102), the National Key Research and Development Program of China (2023YFE0200700), the Key Scientific and Technological Innovation Research Team of Shaanxi Province (2022TD-31), the Key Research and Development Program of Shaanxi Province

Carbon fiber reinforced friction materials are critical in aerospace and transportation braking systems, yet conventional organic matrix often fail under high temperatures. This study introduces a hybrid matrix combining alumina-based inorganic binder (AO) with phenol-formaldehyde resin (PF) and silicone rubber (SR), leveraging AO's high-temperature stability to compensate for organic limitations. Using an HMI-GA-BP artificial neural network, the matrix ratio was multi-objectively optimized and experimentally validated. The optimal formulation OPT-3M (AO:SR:PF= 22:12:66), compared to the PSA formulation, significantly improved compressive strength (192.0 MPa, +74 %) and shear strength (18.7 MPa, +34 %), while maintaining a volume wear rate below 0.45 x 10-7 cm3 /J and a stable friction coefficient above 0.4 across 100-350 degrees C without thermal fade. This work offers a new approach to designing heat-resistant, low-wear composites and advances the understanding of inorganic binders in friction materials.