Search Results (1,955)

This study investigates the combined effect of incorporating recycled concrete aggregates (RCAs) and glass fibers (GFs) on the properties of geopolymer concrete. The precursor binder consisted of a blend of ground granulated blast furnace slag and fly ash. Furthermore, two types of GFs (i.e., short and long) were incorporated, either individually or in hybrid combinations, to enhance the performance of the concrete. Experimental results revealed that replacing natural aggregates (NAs) with RCAs in geopolymer concrete production had no tangible impact on workability but resulted in a slight reduction in the density, ultrasonic pulse velocity, and bulk resistivity. Similarly, the compressive strength and modulus of elasticity decreased by up to 18 and 57%, respectively. Meanwhile, the addition of GFs, particularly in hybrid configurations, effectively mitigated these reductions. Among the hybrid mixtures, a short-to-long fiber ratio (A:B) of 1:3 yielded the most significant improvements of the physical, mechanical, and durability properties, with increases of up to 16%, 91%, and 61%, respectively. Several correlation equations were established to describe the relationships between the physical, mechanical, and durability properties of GF-reinforced geopolymer concrete and were compared with existing codified models. The outcomes provide critical insights into the synergistic roles of RCA and GFs in tailoring high-performance, eco-efficient concrete systems. This research supports the advancement of sustainable concrete production and promotes the broader structural adoption of geopolymer technologies. Full article

Solution electrospinning (SES) and melt electrowriting (MEW) are complementary fiber-based fabrication platforms extensively investigated in tissue engineering. SES generates fibers typically ranging from the nanometer to the low-micrometer scale, producing fibrous networks that mimic the native extracellular matrix (ECM) and support key cellular functions. MEW, by contrast, operates solvent-free and enables precise, layer-by-layer deposition of microfibers with well-controlled geometry, conferring the mechanical integrity and open-pore architecture that SES constructs inherently lack. Despite growing interest, the body of peer-reviewed literature reporting original hybrid SES–MEW fabrication and biological outcome data remains limited, with no comprehensive cross-tissue synthesis available to date. This narrative review examines the current state of SES–MEW hybrid strategies across five tissue engineering targets selected for their clinical relevance: skin, vascular grafts, bone, cartilage, cardiac valves, and skeletal muscle. For each application, the architectural rationale, the fabrication approach, and the in vitro and in vivo biological outcomes are discussed in an integrated manner, with attention to how the spatial organization of nano- and microfibers translates into tissue-specific functional responses. A comparative analysis across tissue types highlights both the versatility of hybrid constructs and their persistent limitations, including suture retention values that remain below clinically accepted thresholds in vascular applications, incomplete cellular infiltration through dense nanofibrous layers, and the absence of validated, reproducible scale-up protocols compatible with clinical-grade manufacturing. The review concludes by identifying the most critical open questions in the field, encompassing process standardization, regulatory classification, and the emerging role of machine learning in closed-loop MEW process optimization. This work aims to provide an evidence-based perspective on the current state of hybrid SES–MEW scaffold engineering and the key translational gaps limiting clinical application. Full article

The need to create lightweight materials with better mechanical properties has led to the use of Fiber Reinforced Composites (FRCs)s in the aerospace and automotive industries. The mechanical behavior of FRCs is heterogeneous, especially in conditions of low-velocity impact (LVI). The impact events cause structural damage, where most of the available literature deals with mono- or bi-composites in controlled situations. This work will present the results of studying the behavior of mono, bi- and tri-hybrids with carbon, glass and Kevlar fiber-reinforced epoxy. The sequences of the laminate stacks, number of plies and laminate thickness in the drop weight testing were across velocities of 1.91 to 3.91 m/s at drop heights of 19 to 79 cm. The dominant pillars of LVI, such as peak load, energy absorption and the modes of damage, were analyzed. The glass-dominated laminates peaked at 5.67 kN, while the Kevlar-dominated laminates reached peak flow in ductile collapse with greater quantities of absorbed energy. The leaders in strength and energy were the hybrids of Kevlar–glass (KG) cross-ply at 8.08 kN and 47.28 J and quasi-isotropic Kevlar–carbon–glass (KCG) at 9.12 kN and 47.25 J, showcasing a balance of strength and toughness. The rest, holding a greater quantity of Kevlar, ranging in thickness and cross-plies, were shaped with a load center. The experimental conclusion is that hybridization improved impact resistance and ductility, which is best supported by the glass/carbon rigidity-layered laminates. Such understanding directs the design work of future composite materials for better impact control. Full article

Structural health monitoring (SHM) plays an increasingly important role in managing aging, safety-critical infrastructure under growing environmental and operational demands. In recent years, fiber-optic sensors (FOSs) have attracted significant attention for SHM applications due to their immunity to electromagnetic interference, durability in harsh environments, multiplexing capability, and suitability for both localized and fully distributed measurements. In parallel, advances in machine learning (ML) have enabled new approaches for extracting actionable insights from large, high-dimensional sensing datasets. This paper presents a systematic review of FOS-based SHM systems integrated with ML across civil, transportation, energy, marine, and aerospace infrastructures. Following PRISMA 2020 guidelines, peer-reviewed studies were identified and synthesized to examine sensing principles, deployment configurations, data characteristics, and learning-based analytical strategies. Fiber optic technologies are categorized into point-based, quasi-distributed, and fully distributed systems, and their capabilities for capturing strain, temperature, and spatiotemporal structural responses are critically evaluated. ML approaches are examined from a task-oriented perspective, including damage detection, localization, severity assessment, environmental compensation, and prognosis, with emphasis on the alignment between sensing configurations and appropriate learning paradigms. Key challenges remain, particularly regarding large data volumes, environmental variability, limited labeled damage datasets, model generalization, and system-level integration. Emerging directions such as physics-informed and hybrid learning, transfer learning, uncertainty-aware modeling, and integration with digital twins are discussed as pathways toward more robust and scalable SHM systems. By jointly addressing sensing physics and data-driven intelligence, this review provides a structured reference and practical roadmap for advancing intelligent FOS-based SHM in next-generation infrastructure. Full article

This study evaluated how the addition of 5 wt% bioactive glass and 15 wt% short glass fibers to EQUIA Forte HT affects the microhardness, micromorphology, and elemental composition of demineralized dentin. Class I cavities in 28 human third molars were demineralized with 37% phosphoric acid and restored with: (1) Filtek Universal composite, (2) EQUIA Forte HT, (3) EQUIA Forte HT + 5wt% BAG, or (4) EQUIA Forte HT + 15wt% short glass fibers. After 4 weeks of storage in phosphate-buffered saline at 37 °C, the teeth were cut in half, obtaining two samples from each tooth (n = 14). Vickers microhardness (HV0.1) was measured on demineralized dentin 50–100 μm apical to the restoration interface. Representative specimens (n = 2) were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Data were analyzed with one-way ANOVA (α = 0.05). Unmodified EQUIA Forte HT showed the highest mean dentin microhardness recovery (25.06 ± 1.42 HV0.1), followed by composite (17.31 ± 0.66 HV0.1), BAG-modified (23.74 ± 1.37 HV0.1) and fiber-reinforced (22.15 ± 1.06 HV0.1) groups (p < 0.001, all pairwise comparisons p ≤ 0.039). Glass hybrids showed prominent Ca/P peaks; modified groups had elevated Si (BAG) and Al (fibers). SEM revealed smoother surfaces with fewer cracks in modified materials. Unmodified EQUIA Forte HT produced the highest short-term microhardness recovery, while BAG and fiber additions altered surface morphology and elemental composition but slightly reduced early hardness. Full article

Mine rescue operations are frequently conducted in hazardous underground environments characterized by damaged infrastructure, unstable communications, heat stress, and hypoxia risk, all of which threaten the safety of rescue personnel. To address these challenges, this study proposes a prototype-oriented mine-rescue monitoring framework that combines a Wi-Fi/optical-fiber communication architecture with flexible wearable sensing modules for physiological monitoring. The communication design employs Wi-Fi for local wireless data aggregation and optical fiber for reliable long-distance backhaul to the surface command side. For wearable monitoring, two flexible sensing modules were developed: a temperature sensor based on a polyaniline/graphene–polyvinyl butyral composite film and a PPG-oriented flexible optoelectronic module based on an ITO/Ag/ITO multilayer transparent electrode structure. Experimental results show that the temperature sensor exhibits a clear temperature-dependent resistance response within the tested range, while the optoelectronic module demonstrates low sheet resistance and acceptable electrical continuity under repeated bending. These results provide preliminary support for combining hybrid underground communication architecture with flexible wearable sensing components in mine-rescue scenarios. However, the present work remains at the stage of architecture design and component-level validation, and full end-to-end system verification under simulated or field rescue conditions will be the focus of future studies. Full article

Hybrid composite laminates combining pseudo-woven meso-architectured composite (MAC) and unidirectional (UD) sub-laminates manufactured via automated fiber (AFP) placement are attractive as they combine the increased toughness of MAC and higher stiffness of UD while also reducing the manufacturing time. MACs are manufactured via a modified AFP process involving tow skips to create a woven-like architecture using unidirectional tows and introduce shallow crimp angles and complex fiber angle distributions in the architecture. Previous studies on hybrid MAC laminates have shown increased impact damage resistance/tolerance under high- and low-velocity impacts. This work presents an experimental study on the open-hole tension (OHT) and open-hole compression (OHC) response of T800-SC-24k carbon/epoxy laminates of nominal thickness 4.55 mm manufactured via AFP manufacturing. Two hybrid laminate configurations consisting of a UD core and pseudo-woven MAC sub-laminates on the outer surfaces are compared against a traditional UD quasi-isotropic control laminate. One of the hybrid laminate configurations has a plain-woven-like architecture while the other has a complex 3D woven type architecture. The hybrid laminates exhibited a marginal 7% increase in OHT strength and up to a 16% reduction in normal loading direction strains around the hole relative to the control. All three configurations showed comparable OHC strengths. Despite the complex meso-architecture of the MAC sub-laminates, failure in both OHT and OHC is found to be governed primarily by the UD core, which dominates load-carrying capability and failure mechanisms. The results demonstrate that the hybrid laminates maintained or improved in-plane OHT/OHC performance while previously demonstrating better damage resistance and tolerance under impact. Full article

Stability plays essential roles for Vertical Take-Off and Landing (VTOL) vehicles. This paper investigates the stability characteristics of a novel tail-sitter VTOL vehicle employing vector thrust control, specifically focusing on nonlinear modeling and parameter optimization. Firstly, the tail-sitter VTOL which employs vector thrust controlling principles, is designed, and manufactured using 3D printing and carbon-fiber reinforced techniques, with a customized flight controller implemented on the PX4 architecture. To address the nonlinear dynamic characteristics introduced by the vector thrust mechanism, a nonlinear dynamic model for cruise flight is established based on an offline database and validated against cruise flight test data. Flight tests show that the vector-thrust-based pitch control provides rapid response and accurate tracking during cruise flight. Furthermore, based on the validated model, a hybrid optimization strategy combining pattern search and sequential quadratic programming (SQP) is used to tune the cascaded control parameters. Simulation results demonstrate that the optimized controller reduces the rise time from 6.8 s to 0.2 s and the settling time from 10.1 s to 0.9 s under the tested cruise-condition step response, indicating a marked improvement in dynamic response performance. This study provides a practical framework for cruise-flight modeling, pitch-stability analysis, and control-parameter optimization of vector-thrust tail-sitter UAVs. Full article

To further improve the mechanical properties of shotcrete in coal mine roadways, end-hooked steel fibers and chopped basalt fibers were selected. Based on the optimal mix ratios identified in existing research, steel–basalt hybrid fiber shotcrete (SBFC) specimens were prepared. Dynamic impact tests under different impact loads and various hybrid fiber contents were conducted using an SHPB. The microstructure was characterized using SEM and XRD. The results show that the dynamic compressive stress–strain curve of steel–basalt hybrid fiber shotcrete can be classified as elastic deformation stage, plastic yield stage, and post-peak failure stage. The incorporation of hybrid fibers reduces the elastic deformation and plastic yield stage, and the post-peak failure stage under active confining pressure shows elastic aftereffect characteristics. The dynamic compressive strength, dynamic elastic modulus, and deformation modulus increase with the increase in impact pressure and fiber content. When there is no confining pressure, the maximum dynamic compressive strength, dynamic elastic modulus, and modulus of deformation of SBFC4 reached 53.1 ± 2.2 MPa, 4.51 ± 0.3 GPa, and 2.55 ± 0.1 GPa, respectively, representing increases of 37.20%, 264.01%, and 59.37% compared with the control group. The dynamic compressive strength increases with the average strain rate, demonstrating a favorable strain rate effect. The energy–time history curves can be roughly divided into initial, growth, and stable stages. Under the same impact load conditions, as the fiber content gradually increases, the incident energy, dissipated energy, and energy utilization rate of the specimens all show a gradual upward trend. SEM and XRD results show that steel fibers and basalt fibers maintain good bonding with the cement matrix, contribute to the formation of gel and crystalline products within the specimens, effectively delay the initiation and propagation of cracks, and thereby improve the mechanical properties of the concrete specimens. Full article

Mineral powder–based bone grafts exhibit excellent osteoconductivity; however, their clinical efficacy is often compromised by insufficient early-stage tissue ingrowth, leading to particle aggregation and pocket formation within the defect site during the initial healing phase. Here, we report a cotton-type nanofiber-guided mineral graft designed to overcome this early integration failure by creating fibrous pathways for tissue ingress. Cotton-type polycaprolactone (PCL) nanofibers were fabricated via electrospinning using a pin-based collector engineered to induce strong inter-fiber repulsion, resulting in a highly expanded, three-dimensional cottony architecture. Tetracalcium phosphate (TTCP) and α-tricalcium phosphate (α-TCP) mineral particles were subsequently deposited onto the surface of the cottony nanofibers, forming a fibrous–mineral hybrid graft (c-NF@T/α-TCP) in which the nanofibers act as a transient, functionally defined tissue-guiding framework during the early healing phase. The cottony nanofiber network effectively prevented mineral particle aggregation and generated continuous pathways within the graft, facilitating early tissue infiltration and vascular ingress during the first week after implantation. In vivo evaluation in a bone defect model demonstrated that c-NF@T/α-TCP significantly reduced tissue pocket formation at early time points and promoted subsequent bone regeneration compared to mineral powder-only grafts. This study highlights the critical importance of early-stage structural guidance in mineral-based bone grafts and introduces cotton-type nanofiber–guided pathway engineering as a simple yet effective strategy to unlock the regenerative potential of conventional inorganic bone substitutes. Full article

The transverse beam size is a key parameter for characterizing the performance of synchrotron radiation sources. Accurate measurement of the transverse beam size is crucial for assessing beam quality. In this study, a fiber array-photomultiplier tube (PMT) beam measurement system was developed to enable high-precision sampling of beam profile information for beam-size measurement. Furthermore, a hybrid method integrating nonlinear least squares (NLLS) fitting and Gaussian basis-function fitting was proposed to reconstruct the beam intensity profile from discrete sampling data. Before performing NLLS fitting, a median absolute deviation (MAD)-based threshold filter is employed to remove outliers and suppress random noise, thereby improving the stability and robustness of the parameter estimation. The filtered data are then fitted using NLLS to obtain the reconstructed distribution. To capture potential high-order modal features in the beam profile, a Gaussian basis-function fitting model was also introduced for comparison, and its performance was evaluated under complex intensity distributions. Additionally, the relationship between the full width at half maximum (FWHM) and beam intensity was experimentally verified while accounting for measurement effects in the system. The results demonstrate that the proposed hybrid algorithm improves reconstruction accuracy and robustness, enabling precise recovery of the beam-intensity profile in the fiber-array PMT system. Full article

The crack resistance of unidirectional fiberglass-reinforced plastics based on an epoxy matrix modified with polysulfone (PSU) and furfuryl glycidyl ether (FGE) was investigated. The combined addition of PSU/FGE modifiers to the epoxy matrix increases the crack resistance of glass-fiber-reinforced plastics (GFRPs). The effect of increasing the crack resistance of GFRPs varies depending on the modifier ratio. The greatest increase in crack resistance is achieved with a modifier ratio of 1/0.5. For this ratio, the value of $G_{IR}^{CM}$ is 1.18 kJ/m² (for unmodified GFRP, $G_{IR}^{CM}$ = 0.72 kJ/m²). With an increase in the FGE concentration in the polysulfone-modified epoxy matrix, the crack resistance of GFRP decreases to a level of ~0.8 kJ/m². The change in the crack resistance of GFRP is associated with the structure of the epoxy matrix containing different PSU/FGE ratios. A study of the fracture surfaces of GFRPs showed that the greatest increase in the crack resistance of composites is achieved with the formation of extended phases enriched with polysulfone in the epoxy matrix. The size of the dispersed phase is about 3 μm. A correlation has been established between the crack resistance of hybrid matrices and GFRPs. With an increase in the matrix crack resistance by 3.1 times (from 0.37 to 1.15 kJ/m²), the fracture toughness value of GFRP increased by 1.6 times (from 0.72 to 1.18 kJ/m²). Full article

Desertsand concrete (DSC) is a sustainable alternative to natural river sand; however, its application in cold regions is restricted by inadequate crack resistance and freeze–thaw durability. This study investigates the freeze–thaw performance of steel–polypropylene hybrid fiber-reinforced desert sand concrete (SPHF-DSC), with emphasis on durability enhancement and service life prediction. A three-factor, three-level orthogonal experimental design was employed to evaluate the effects of desert sand replacement ratio (DSR), steel fiber (SF) content, and polypropylene fiber (PPF) content on mass loss, relative dynamic elastic modulus, and compressive strength under 25–100 freeze–thaw cycles. The results demonstrate that hybrid fiber reinforcement significantly improves freeze–thaw resistance due to the synergistic interaction between SF and PPF. After 100 cycles, the mass loss of all specimens remained within a narrow range of 0.65% to 0.73%, and the relative dynamic elastic modulus retention stayed above 90%. The optimal mixture (DSR = 30%, SF = 2%, PPF = 0.05%) exhibited superior frost resistance with the lowest deterioration indices among all groups. A freeze–thaw damage model based on damage mechanics was established and validated ($R^2$ > 0.96), enabling prediction of a service life exceeding 38 years under typical cold-region climatic conditions. These findings provide a durability-oriented design reference for the engineering application of DSC in cold-region infrastructure. Furthermore, the utilization of local desert sand reduces transportation energy consumption and promotes the sustainable development of energy infrastructure. Full article

The growing need for lightweight, multifunctional, and high-performance structures in the automotive, aerospace, electronics, and medical industries has driven the development of advanced joining technologies for polymers and metal-polymer combinations. Among these, ultrasonic welding (USW) and friction stir spot welding (FSSW) have emerged as promising solid-state techniques capable of producing reliable joints with minimal thermal degradation and enhanced interfacial bonding. This review focuses on recent developments in USW and FSSW of thermoplastics, fiber-reinforced composites, and hybrid metal–polymer systems, with a particular emphasis on process mechanics, microstructural evolution, and joint performance. The mechanisms of heat generation, material flow behavior, and consolidation are discussed in relation to key process parameters, including applied pressure, rotational speed, vibration amplitude, plunge depth, and dwell time. Microstructural transformations such as polymer chain orientation, recrystallization, interfacial diffusion, and defect formation are analyzed to establish process–structure–property relationships. Mechanical performance metrics, including lap shear strength, fatigue resistance, impact behavior, and environmental durability, are critically compared across different materials and welding methods. Furthermore, recent advances in numerical and thermo-mechanical modeling, in situ process monitoring, and data-driven optimization are discussed to highlight pathways toward predictive and scalable manufacturing. Current industrial applications and existing limitations such as challenges in automation, thickness constraints, and hybrid material compatibility are also evaluated. Finally, key research gaps and future directions are identified to improve joint reliability, sustainability, and broader industrial adoption of advanced solid-state welding technologies. Full article

The Fiber-Reinforced Composites (FRCs) are instrumental in contemporary engineering as they offer a high weight-to-strength ratio as well as durability. They are, however, anisotropic and heterogeneous; as a result it is a major challenge to predict their mechanical properties when subjected to tensile and flexural loading. Conventional techniques such as experimental testing and finite element analysis are usually resource intensive, time consuming or simplistically constrained. In this review, we explored in detail how the data-driven machine learning (ML) models could overcome these constraints and thus constitute the paradigm shift. It is a synthesis of studies in the use of a broad range of ML techniques such as regression models, Artificial Neural Networks (ANNs), Convolutional Neural Networks (CNNs) and ensemble models for predicting the tensile and flexural properties of FRCs. The analysis shows that although models such as Gaussian Process Regression (GPR), Random Forest (RF) and state-of-the-art neural networks (NNs) have a very high predictive accuracy (often R² > 0.90), there are issues related to model generalization, data quality and modeling of physical principles. The paper ends with critical research gaps which include over-reliance on single-fiber systems and simulated data, while future directions include hybrid ML–physics models, multiscale modeling and exploration of a wider range of material and environmental variables to facilitate the development of safer and more efficient next-generation composites. Full article