Search Results (6,310)

Corrosion of steel reinforcement is a major cause of deterioration in reinforced concrete (RC) structures exposed to aggressive environments. Although fiber-reinforced polymer (FRP) reinforcement provides excellent corrosion resistance, its confinement effectiveness in RC columns has not been fully understood. This study experimentally investigated the axial compressive behavior of rectangular RC short columns reinforced with steel, carbon fiber-reinforced polymer (CFRP), and glass fiber-reinforced polymer (GFRP) bars. Ten specimens with different reinforcement types and stirrup configurations were tested under monotonic axial compression to evaluate compressive strength, axial strain response, deformation behavior, failure mechanisms, and confinement performance. The results indicated that the contribution of FRP reinforcement depended on the reinforcement configuration and confinement mechanism. Specimens reinforced with CFRP longitudinal bars exhibited higher axial capacity than the steel-reinforced control specimen within the tested configurations; however, the influence of the longitudinal reinforcement ratio should also be considered. GFRP stirrups exhibited confinement behavior comparable to CFRP stirrups, whereas CFRP stirrups experienced premature fracture at bent corner regions, which reduced their confinement effectiveness and deformation capacity. Reducing stirrup spacing from 150 mm to 75 mm provided limited improvement in compressive strength because of premature stirrup failure and insufficient development of confinement effects. Existing confinement models tended to overestimate the post-peak response of FRP-reinforced columns. These preliminary findings provide experimental insights into the confinement behavior of FRP-reinforced concrete columns and contribute to the development of improved analytical models. Full article

The rapid expansion of fiber-reinforced polymers (FRPs) in wind energy, transportation, and aerospace is generating increasing amounts of accompanied waste, making effective valorization essential to a circular economy. This review compares FRP recovery technologies in terms of recovered-fiber quality, operating conditions, post-treatment, environmental impacts, and industrial applicability. Then, it also examines direct reuse, FRP remanufacturing, and reuse in cementitious composites. Quantitative synthesis indicates that high-quality recycled carbon fibers (rCFs) generally retain more than 90% of their original strength, whereas mechanically recovered glass fibers (rGFs) typically retain approximately 70–90%. The preferred pathway depends on the intrinsic value, damage state, morphology, and residual properties. Components with sufficient residual capacity should be directly reused; high-quality fibers are better suited to polymer remanufacturing; and heterogeneous or lower-grade glass-FRP (GFRP) fractions are more compatible with cementitious applications, where mechanically recycled GFRP can provide interfacial bond strengths comparable to conventional engineering macrofibers. Future research should establish quantitative links among recovered material quality, processing, interfacial behavior, and end-use performance, while adopting consistent environmental and economic assessment boundaries. A graded utilization framework is therefore required to support both large-scale and value-added reuse of FRP waste. Full article

Out-of-autoclave (OoA) manufacturing of Fiber Metal Laminates (FMLs) remains challenging because their mechanical performance and failure mechanisms are sensitive to processing-induced variations in phase distribution and interfacial bonding quality. Three FML-2/1 configurations (FML/Al-20, FML/Al-40, and FML/Al-60), where the numerical values indicate the exposure time (minutes) of 3003-H14 aluminum to NaOH alkaline etching, were physically characterized after bonding to a basalt fiber-reinforced polymer (BFRP) core to quantify constituent and void volumetric fractions. Based on previously reported differences in interlaminar strength, FML/Al-40 was selected to evaluate tensile behavior at room temperature and high temperature. The average density across all FML configurations was about 2.15 g/cm³, corresponding to a 21% reduction relative to aluminum. Compositional analysis revealed significant differences among configurations in both the complete FML and the renormalized matrix–fiber–void composition of the BFRP core, indicating that surface treatment is associated with changes in internal phase distribution beyond the metallic contribution. At room temperature, FML/Al-40 exhibited an ultimate tensile strength of 262.7 MPa. Relative to this value, tensile strength was retained at 83%, 54%, and 31% at 100, 150, and 200 °C, respectively, demonstrating a progressive reduction in strength with increasing temperature and a corresponding change in the thermomechanical response associated with evolving failure mechanisms. Full article

Microplastic (MP) analysis in various environmental media currently faces significant challenges due to the complex and transportable nature of these materials. This study employed Fourier-transform infrared spectroscopy (FTIR) to investigate the presence of MPs in caddisfly larval cases, which incorporate vegetative fragments, sediment grains, and MP particles as building materials. The analysis of MPs in 2049 caddisfly larval cases revealed a total of 7553 items, resulting in an average of 3.7 items/case. The lowest recorded rate was 0.8 items/case, while the highest reached 18.2 items/case. Fiber MPs comprised 39.2% of the total, followed by fragment MPs at 30.8% and spherical MPs at 30%. Among the colors analyzed, blue MPs were the most prevalent, accounting for 36.6%, with white/transparent MPs at 22.1% and red MPs at 14.1%. MPs smaller than 100 µm were the most common, accounting for 37%, followed by MPs in the 100–250 µm range at 23.9%, larger than 500 µm at 22.3%, and those between 250 and 500 µm at 15.8%. Cellulose acetate was discovered to be the most abundant MP among different polymer types, followed by cellulose acetate butyrate, polyethylene terephthalate, poly(vinyl propionate), poly(ethylene glycol), poly(acrylonitrile-co-butadiene), cellulose propionate, hydroxyethyl cellulose, polyvinyl alcohol, glycerol triacetate, polystyrene, and poly(propylene glycol) methacrylate. These findings show the existence of MP in biotic components of these ecosystems, which has implications for aquatic biota health and freshwater quality, particularly in places influenced by human activity. Full article

This study investigates the compressive performance of fiber-reinforced polymer (FRP) rebar-reinforced Seawater and Sea Sand Concrete (SSC) columns through an integrated approach combining finite element analysis, theoretical derivation, and machine learning. Finite element models were developed to quantify the influence of key parameters on the ultimate bearing capacity and lateral deflection. The results indicate that the compressive capacity decreases significantly with increasing eccentricity and slenderness ratio. Columns reinforced with steel rebars demonstrated superior load-bearing and anti-lateral displacement capabilities compared to their FRP-reinforced counterparts. A theoretical formula for predicting the compressive capacity was derived; however, it systematically overpredicted the experimental measurements by approximately 36%. To develop data-driven predictive models for the ultimate load capacity of FRP–SSC columns, four machine learning models, backpropagation neural network (BPNN), bootstrap aggregating BPNN (Bagging-BP), genetic algorithm-optimized BPNN (GA-BP), and gradient boosting regression trees (GBRT), were employed. Using sectional dimension, concrete strength, reinforcement parameters, eccentricity, and slenderness ratio as inputs, the validation sets of the models achieved R-values of 0.942, 0.918, 0.933, and 0.990, respectively. Feature importance analysis based on SHAP identified eccentricity as the most influential parameter. Results from this work can help to understand the behavior of FRP–SSC columns under compression. Full article

In recent years, premature fatigue issues in heavy-duty steel crane girders have occurred frequently, underscoring an urgent need to establish targeted life extension methods. Compared with post-crack repair after macroscopic fatigue cracks have appeared, it is more practical to delay or even prevent the formation of such cracks in fatigue-sensitive zones of the crane girder. Extensive research has demonstrated that bonding Carbon Fiber-Reinforced Polymer (CFRP) plates can significantly enhance the fatigue life of defective components. However, most existing studies focus on thin plates with pre-existing macroscopic cracks, with limited attention given to scenarios involving thick plates or intervention before crack initiation. Therefore, this study focuses on the fatigue problem around bolt holes in the lower flange of heavy-duty steel crane girders. It investigates the life extension method of bonding CFRP plates prior to macroscopic crack formation. Through finite element analysis and comparative fatigue tests, the fatigue life enhancement mechanism was preliminarily interpreted. The effectiveness of this method is validated, and a practical CFRP bonding strategy is proposed to significantly improve the fatigue life of the lower flange in heavy-duty steel crane girders. Full article

This study develops an integrated Analytic Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) multi-criteria decision-making (MCDM) framework to systematically evaluate and rank composite material combinations based on 24 fibers (16 natural and 8 synthetic), 15 matrices (thermosets, thermoplastics, and biopolymers), and 9 fiber volume fractions (30–70%) for UAV inlet applications. Ten evaluation criteria covering technical performance, environmental sustainability, and economic viability were weighted using AHP pairwise comparisons based on Saaty’s 1–9 scale, yielding a consistency ratio of CR = 0.009, which confirms the reliability of the judgments. The TOPSIS analysis identified Carbon (PAN-HM)/Epoxy as the optimal composite material, achieving the highest TOPSIS score of 0.8893. In contrast, Flax/Epoxy emerged as the best natural fiber composite, with a TOPSIS score of 0.2686, indicating a performance gap of approximately 231% in favor of the synthetic composite. Comprehensive sensitivity analysis across four weighting scenarios (Equal, Technical, Environmental, and Economic) confirmed the stability of the reinforcement rankings, with Carbon (PAN-HM) remaining the top synthetic fiber and flax the top natural fiber across all scenarios. The findings contribute to the growing body of knowledge on sustainable aerospace materials and provide practical guidance for UAV designers seeking to optimize material selection for micro-turbojet engine inlet components, supporting the development of more environmentally responsible UAV designs while maintaining the performance requirements for safe and reliable operation. Full article

Battery packs for new energy vehicles have evolved from simple load-bearing and protective assemblies into multifunctional safety structures integrating structural support, crash protection, thermal-runaway mitigation, flame retardancy, electrical insulation, electromagnetic interference shielding, waterproof sealing, and long-term reliability. Fiber-reinforced polymer composites are promising for upper covers, underbody shields, trays, cross beams, side frames, and local protective structures because of their low density, corrosion resistance, design flexibility, and functional-integration potential. However, composite-part performance is strongly governed by forming. Resin flow, impregnation, curing or cooling shrinkage, fiber orientation, filler dispersion, and interfacial bonding may induce voids, dry spots, resin-rich regions, delamination, warpage, and fiber waviness, thereby affecting load bearing, sealing, thermal protection, and durability. This review focuses on composite-forming technologies for new energy-vehicle battery packs. It summarizes component-level service requirements and material systems and compares representative forming routes, including sheet molding compound (SMC), prepreg compression molding/wet compression molding (PCM/WCM), resin transfer molding/high-pressure resin transfer molding (RTM/HP-RTM), vacuum-assisted resin transfer molding (VARTM), long-fiber thermoplastic direct processing (LFT-D), glass-mat thermoplastic (GMT), thermoplastic sheet forming, pultrusion, and multi-material joining. These routes are evaluated from six dimensions: material form, forming cycle, typical defects, representative mechanical performance, applicable components, and engineering maturity. The review further discusses defect mechanisms, performance effects, detection and control methods, and the roles of in-line monitoring, non-destructive testing, process simulation, machine learning, and digital twins in closed-loop quality manufacturing. Finally, engineering challenges are examined in multi-material joining, thermal-safety integration, low-carbon recycling, and standard certification. Composite-material battery-pack structures should therefore be developed as coordinated design and closed-loop manufacturing systems linking materials, processes, defects, performance, and validation. Full article

Polymer-fiber weft-knitted textiles are widely used in functional apparel and moisture-management materials, but their complex loop topology, yarn-level porosity, and interlayer hierarchy make simulation-oriented geometric modeling challenging. Conventional control-point and interpolated-curve methods often have limitations in representing knitting actions, maintaining yarn-path continuity, and generating meshable geometries. This study proposes a rule-driven geometric modeling method for polymer-fiber weft-knitted structures using the yarn centerline as the basic geometric carrier. Knitting actions, including knit, tuck, float, plating, and double-needle-bed assignment, are converted into reusable local path-generation rules and integrated through pattern-matrix input, action recognition, parametric centerline generation, continuous stitching, and standardized output. The method represents single-bed and double-bed structures within a unified framework, including plain, jacquard, plated, tuck, rib, interlock, half-cardigan, full-cardigan, and purl structures. Compared with an interpolated-curve method, the curvature-jump rate of four representative structures decreases from 40.78–69.23% to 0–0.31%, with markedly reduced maximum bending angles. Mesh-generation results show continuous meshes with improved element quality for complex double-bed structures. A moisture-transfer simulation of a fully plated plain-knitted structure gives one-way transport indices of −122.3187 and 122.2472 for face- and back-side liquid entry, with relative errors of 1.74% and 0.50% compared with experiments. These results indicate that the proposed method provides reproducible and meshable geometric input for structure–property modeling and moisture-transfer prediction of polymer-fiber knitted textiles. Full article

Fused filament fabrication (FFF) has become an important additive manufacturing technique for producing functional polymer-composite components. The tensile performance of carbon fiber-reinforced polyethylene terephthalate glycol (PETG/CF) fabricated by FFF depends on multiple printing parameters. This study presents an integrated experimental and predictive framework for investigating the effects of extrusion temperature, printing speed, layer height, infill pattern, and infill density on the tensile strength of PETG/CF containing 15 wt.% carbon fiber. A mixed-level Taguchi L36 orthogonal array was employed, comprising 36 experimental runs with three independently printed specimens per run, resulting in 108 ASTM D638 Type V specimens. Analysis of variance showed that the printing speed had the largest contribution to tensile strength (20.51%), followed by layer height (18.29%). The highest tensile strength of 33.225 MPa was obtained using grid infill, 60% infill density, 270 °C extrusion temperature with 40 mm/s printing speed, and 0.3 mm layer height. An artificial neural network (ANN) was developed for the tensile-strength prediction, achieving R = 0.9801, R² = 0.9569, and MAPE = 1.52% for the overall dataset. Scanning electron microscopy qualitatively revealed bead-interface defects, fiber pullout, and localized void-like features. The proposed framework provides a systematic approach for evaluating process-parameter effects and predicting tensile strength within the investigated PETG/CF parameter domain. Full article

Microplastics (MPs) have been reported in commercial beverages, but substantial differences in study design make direct comparisons difficult. This non-systematic, focused narrative review critically synthesizes a purposively selected core set of 17 particle-count studies published from 2020 to 2026 on soft drinks, beer, wine, tea, coffee, juices, energy drinks, and related beverages, while considering recent complementary thermal-analysis evidence. Data were compared for study location, beverage type, analytical method, abundance, particle size, morphology, color, polymer composition, and packaging. Fourier-transform infrared spectroscopy-based methods were most common; Raman spectroscopy, fluorescence microscopy, scanning electron microscopy, and laser direct infrared imaging were used in selected studies. Reported soft-drink concentrations ranged from approximately 0.30 particles/L to 166 ± 62 particles/100 mL (1660 ± 620 particles/L), but these values cannot support a geographic ranking because minimum particle-size thresholds, confirmation criteria, blank corrections, sample volumes, and reporting units differed. Fibers and fragments were the dominant morphologies, and polyethylene terephthalate, polyethylene, polypropylene, and polyamide were frequently identified. Findings from beverages packaged in glass and aluminum, as well as plastic, indicate that source water, ingredients, processing equipment, filtration, closures, ambient deposition, and packaging can all contribute. Current intake estimates describe potential particle ingestion rather than absorbed dose or toxicological impact. Because current data largely reflect analytical sensitivity rather than true contamination gradients, this review demonstrates that reliable cross-study exposure assessments currently remain associated with considerable uncertainty, and this uncertainty will be difficult to resolve until particle-count data are normalized to harmonized size thresholds and paired with mass-based thermal analyses. Full article

Replicating the nonlinear, pressure-dependent mechanical behavior of native arteries remains a central challenge in small-diameter vascular graft design, where compliance mismatch between synthetic grafts and host vessels is strongly linked to graft failure. Building on a silk fiber-reinforced alginate–polyacrylamide interpenetrating polymer network (IPN) hydrogel platform, we investigated whether biomimetic vascular structural motifs, specifically fiber reorientation and crimp, can be used as programmable design parameters to tune the tensile and pressure-dependent mechanical response of tubular constructs toward native coronary artery behavior. Three architectures were fabricated: a cross-plied (CP) baseline, a 25° reoriented configuration, and a crimped CP configuration. Under internal pressurization, fiber reorientation and crimp significantly increased compliance at low physiological pressures, with a consistent directional trend across the full pressure range, by extending the low-stiffness toe region preceding fiber recruitment while preserving tensile stiffness. Across the investigated pressure range, all architectures exhibited compliance within the reported range of native coronary arteries, with crimped constructs producing pressure–diameter behavior that most closely resembled young coronary arteries, whereas the CP baseline more closely resembled aged coronary arteries. These findings demonstrate that biomimetic structural motifs, without altering material composition, can serve as programmable design parameters for engineering vascular mechanics, enabling a single material platform to reproduce distinct physiological mechanical phenotypes through architecture alone. Full article

The effects of ultrasonic amplitude (A; 50–80%), sonication time (T; 5–10 min), and pumpkin seed oil (PSO) concentration (C; 10–30%) on the physicochemical and rheological properties of gelatin–acetic acid polymer solutions and their corresponding PSO emulsions prior to electrospinning as well as on properties including morphology, thermal properties (DSC and TGA), FTIR spectra, fiber diameter (FD), and the encapsulation efficiency (EE%) of fatty acids (FAs) and carotenoids (TC) of the resulting electrospun fibers were evaluated. Stirred agitation (24 h) was used as a control. The viscosity of the polymeric solutions was significantly reduced by A for short time periods (p < 0.05). The addition of PSO increased the emulsion viscosity, affecting morphology, FD, and the EE%. The EE% of TC, oleic (OA), palmitic (PA), and stearic (SA) acids showed no significant difference compared to the control. However, for linoleic acid (LA), the EE% was lower with ultrasound treatment. Treatments with A = 50% for 10 min with 10% PSO resulted in homogeneous fibers (0.29 µm) without agglomerates with thermal stability and an EE% of 42% and 26–34% for TC and FAs, respectively. These results show that ultrasound is an effective alternative for homogenization that promotes the formation of nanofibers with PSO via electrospinning. Full article

Given that large-scale storage and transportation of liquid hydrogen are key to realizing the hydrogen economy, tank containers have attracted much attention for their flexibility. To minimize evaporation losses, efficient support structures are essential for these liquid hydrogen tank containers. Herein, a carbon fiber-reinforced polymer (CFRP) suspension ring is developed to support the inner vessel of liquid hydrogen tank containers. By using a special resin matrix and optimizing its curing process, the suspension ring capitalizes on a small cross-sectional area and low thermal conductivity, thereby significantly mitigating the cold-bridge heat transferred from the outer vessel to the inner vessel. Experimental results demonstrate that the tensile strength, outgassing rate, and fatigue performance of the suspension ring at both 77 K (liquid nitrogen temperature) and 4 K (liquid helium temperature) can meet the design targets. Notably, its equivalent thermal conductivity was approximately 88% lower than that of a stainless steel structure of the same size. With the integration of this suspension ring into a 40 ft liquid hydrogen tank container, the daily liquid nitrogen evaporation rate was recorded below 0.082%/d. Furthermore, the holding time before the pressure reached 0.14 MPa exceeded 192 h with a 90% liquid hydrogen filling ratio. This work provides key technical support for high thermal insulation, long-endurance liquid hydrogen storage and transportation equipment. Full article

Carbon nanotubes (CNTs) are widely used as nanoscale reinforcements in polymer composites because of their high stiffness, high aspect ratio, and ability to enhance interfacial stress transfer. In woven Kevlar/epoxy composites, however, the mechanical benefit of CNT addition depends not only on nanotube presence, but also on whether the fabric Fiber orientation enables the CNT-modified interface to participate effectively in the dominant load path. In this study, woven Kevlar/epoxy composites with and without 4 wt.% multi-walled carbon nanotube (MWCNT) treatment were investigated under three displacement rates, namely 1, 10, and 100 mm/s, for two specimen orientations relative to the woven yarn directions: 0°/90° and ±45°. The 0°/90° Fiber orientation represents a tension-dominant load path, whereas the ±45° Fiber orientation promotes yarn rotation and matrix-shear-dominant deformation. The experimental results show that CNT treatment produces a clear increase in elastic modulus in the 0°/90° composites, with an improvement of approximately 40–50% at the lowest loading rate and continued enhancement at higher rates. In contrast, only limited gains are observed in the ±45° composites. The calculated CNT engagement index reached 0.8667 in the 0°/90° Fiber orientation but remained low or negative in some ±45° loading conditions, indicating that the effectiveness of CNT reinforcement depends strongly on Fiber orientation relative to the woven yarn directions. To interpret this behavior in a design-oriented manner, three Fiber orientation-sensitive comparison parameters are introduced: the CNT engagement index, the Fiber orientation sensitivity factor, and the rate amplification factor. These descriptors distinguish absolute stiffness from actual reinforcement utilization and indicate that modulus improvements depend on specimen orientation relative to the woven yarn directions. This study indicates that fabric Fiber orientation governs whether the CNT-modified interface is effectively mobilized or largely bypassed. This provides a useful framework for selectively deploying CNT reinforcement in woven protective composite systems and for rethinking nanotube reinforcement as a load-path-dependent design feature rather than a universally effective additive. Full article