Search Results (1,508)

This study presents a calibrated analytical micromechanical framework for predicting the linear elastic behavior of unidirectional glass fiber/epoxy and carbon fiber/epoxy composites over a wide range of fiber volume fractions. The approach combines the classical rule of mixtures for the longitudinal Young’s modulus with the semi empirical Halpin–Tsai equations to estimate the transverse Young’s modulus and the in-plane shear modulus. The framework is specifically formulated to support durability-oriented composite design through rapid and physically consistent estimation of elastic properties governing load transfer and stress distribution. Material parameters, including fiber and matrix Young’s moduli (Ef, Em), shear moduli (Gf, Gm), Poisson’s ratios (νf, νm), and fiber volume fraction (Vf up to 0.80), are taken from established material property databases and implemented within a literature-informed modeling scheme. To preserve physical realism at high fiber contents, a shear correction factor is introduced for Vf > 0.50 to account for microstructural interaction and fiber clustering effects. The predicted effective elastic constants (E₁, E₂, G₁₂, ν₁₂) exhibit consistent and physically meaningful trends across the full fiber volume fraction range. The model predictions were evaluated against trends widely reported in the composite micromechanics literature, and the results showed overall agreement in the nonlinear reduction in stiffness gains at elevated fiber volume fractions. Comparative results indicate that carbon fiber/epoxy composites achieve up to approximately 30% higher stiffness than glass fiber/epoxy systems at equivalent fiber contents, reflecting the influence of stiffness contrast on composite response. The analysis further indicates that stiffness saturation begins approximately in the Vf = 0.60–0.70 range, where the incremental gains in E2 and G12 become noticeably smaller for both composite systems. This behavior provides design-relevant guidance by showing that, beyond this range, further increases in fiber content may offer limited stiffness improvement relative to the associated manufacturing complexity. Overall, the calibrated Halpin–Tsai methodology offers a practical and computationally efficient tool for preliminary evaluation and design-stage optimization of the elastic performance of high-performance composite structures. Full article

This study investigates the shear performance of reinforced concrete (RC) beams strengthened with near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes under ambient and elevated temperature conditions. An experimental program comprising twelve RC beams was conducted, including both normal- and high-strength concrete specimens. The beams were strengthened using CFRP ropes installed at two orientations (45° and 90°) and two spacing configurations (150 mm and 200 mm). Ten specimens were exposed to a temperature of 600 °C prior to shear testing. The experimental results were evaluated against finite element (FE) simulations and shear strength predictions obtained from ACI 440.2R provisions. The FE models demonstrated close agreement with the observed experimental response, whereas ACI 440.2R consistently yielded conservative shear strength estimates, particularly for high-strength concrete beams. The results confirm that inclined CFRP configurations and reduced rope spacing significantly enhance shear capacity, even after severe thermal exposure, with measured strength gains reaching approximately 75% relative to unheated control beams and up to 135% compared to heated control specimen. The findings emphasize the sensitivity of NSM CFRP in terms of strengthening effectiveness to elevated temperature and highlight the limitations of existing design provisions when applied to fire-damaged RC members. Full article

With Aligned Formable Fibre Technology (AFFT^™), fibers are reformatted into highly oriented epoxy prepreg tapes, enabling the structural reuse of recycled composite waste. The present study investigates whether discontinuous fiber laminates produced with AFFT^™ can be characterized and optimized with the same finite-element workflows long established for continuous fiber composites and whether the resulting structures meet demanding stiffness targets. Initially, various manufacturing methods were adopted, including vacuum bagging, compression molding at 7 bar to simulate autoclave conditions, and compression molding at 90 bar, comprising the three most reasonable manufacturing processes for AFFT^™ laminates. Experimentally measured orthotropic properties were introduced into a finite-element model representing an idealized bicycle top tube, which was chosen as a case study. A genetic algorithm screened candidate stacking sequences, minimizing the combined bending-and-torsion deflection. The best lay-ups reduced deformation by more than 30% compared to a quasi-isotropic baseline, showing that well-oriented short fibers can significantly contribute to the stiffness of composites. Tubes produced with the optimized lay-up were tested in three-point bending tests, and the measured stiffness matched simulations within 5%. These results confirm a key point for sustainable engineering: despite the absence of continuous fibers, conventional simulation strategies accurately predict the performance of AFFT^™ laminates and can be used as the basis for effective genetic optimization. This validation is significant: it enables the design of stiff, high-performance structures from recycled materials using established, cost-effective methods. By proving that optimization strategies developed for traditional continuous fiber composites apply to AFFT^™, this study offers a trusted and accessible pathway to scale circular economy solutions in next-generation composite products. Full article

The objective of this study is to review the literature on the natural resources needed for biodegradable materials underscoring the importance of natural fiber-based composites as a feasible alternative. The review focuses on the pivotal role of natural fiber-based composites in the formulation of industry benchmarks, the challenges associated with application of natural fibers, the application areas, and the mechanical properties as well as the determinants influencing the properties of the composites. The manufacturing methods were discussed and compared. In addition, the study highlights the successful instances where enset fiber-based composites have been adeptly implemented. The study also observed potential areas of future research to improve the performance of enset fiber-reinforced composites including the fabrication techniques and treatments. Hand lay-up and compression molding are the conventionally used composite fabrication methods, while the recent advances in 3D printing for composite fabrication bring new opportunities to solve many of the existing limitations. In addition, most research is currently limited to alkali treatment, whereas other fiber treatment techniques could further improve the mechanical performance by modifying the surface properties and removing the impurities. Moreover, hybridization, orientation of fiber, and addition of nano-particles are observed to have direct impact on the composite properties. The review scrutinizes comprehensive examination of the prevailing landscape and prospective courses for enset fiber applications within the realm of sustainable material science, utilizing diverse processing techniques and applications while pinpointing inherent challenges. Full article

Polyether Ether Ketone (PEEK) is a high-performance polymer increasingly utilized in additive manufacturing due to its exceptional thermal, chemical, and mechanical properties. Thus, they are used to produce aerospace brackets, fuel system parts, seals, compressor valve plates, etc. This study investigates the mechanical performance of both neat PEEK and glass fiber-reinforced PEEK (PEEK + GF) composites fabricated via fused deposition modeling (FDM). The effects of print speed, print orientation, and post-heat treatment were systematically evaluated. Among the tested orientations, the 0° print direction with post-heat treatment at 250 °C yielded highest tensile strength of ~80 MPa, outperforming the 45° and 90° orientations. Print speeds ranging from 5 to 20 mm/s and annealing temperatures between 250 °C and 300 °C significantly influenced material properties. For neat PEEK, both tensile strength and microhardness improved with increasing print speed and post-heat treatment, peaking at 20 mm/s and 250 °C. However, annealing at 300 °C led to performance degradation, attributing to gas-induced porosity within the material. The PEEK + GF composites achieved a maximum ultimate tensile strength (UTS) of approximately 83 MPa under the same optimal conditions (20 mm/s print speed and 250 °C post-treatment). This enhancement is attributed to improved fiber alignment along the print path, increased crystallinity, and superior interfacial bonding. Notably, the composites did not exhibit the microstructural damage observed in neat PEEK at the higher annealing temperature. Full article

Polymer nanocomposites offer significant potential for improving the strength-to-weight ratio and dynamic behavior of drone blades. This study examines the vibration characteristics of tapered aramid (Kevlar)/epoxy composite blades reinforced with nanocarbon fillers—graphene (2D), multi-walled carbon nanotubes (MWCNTs, 1D), and fullerene (0D)—to determine the most effective filler for enhancing stiffness and operational stability. The laminated blades (300 mm length, 200 mm width, root thickness 13 mm, tip thickness 8 mm) incorporate ply drop-offs and a central honeycomb core. Modeling was performed using classical laminate plate theory integrated with the finite element method (FEM) in MATLAB (R2016a). Under clamped–free–free–free boundary conditions, the study considered rotational speeds of 750–2250 rpm, setting angles of 30–60°, various fiber orientations, and nanofiller contents of 0–10 wt.%. The results indicate that while the setting angle minimally affects natural frequency, it significantly influences damping in modes (1,2) and (2,1). Increasing nanofiller content improves stiffness, with optimal performance observed near 5 wt.%. At 1500 rpm in mode (1,1), MWCNTs provided the greatest enhancement. Overall, MWCNTs exhibited superior stiffness improvement and rotational stability compared to other fillers. Full article

This paper presents an experimental and numerical study on the effect of steel fiber distribution on the flexural behavior of self-compacting mortars (FRSCMs). Six FRSCM mixtures were modeled in ABAQUS as prismatic specimens (40 × 40 × 160 mm³) subjected to static three-point bending. The methodology involved two steps: (i) preparation of six mortar variants composed of three layers with different hooked steel fiber dosages (20, 30, and 40 kg/m³ for M20, M30, and M40) assembled in various configurations to study fiber distribution effects; (ii) numerical modeling of prismatic specimens in ABAQUS, using structured meshing with C3D8R hexahedral elements. Each layer was meshed separately with aligned nodes to ensure proper assembly. Our results highlight the strong influence of fiber distribution: despite identical fiber content (90 kg/m³ of hooked steel fibers), flexural strength varied across beam configurations. Layered casting led to an increase in flexural strength of up to 71.83% compared to the reference. The numerical predictions closely matched the experimental results, with relative errors ranging from 1% to 8.13% for most variants, demonstrating the reliability of the model. The larger discrepancies observed for specimens M324 and M342 are attributed to the limitation of the study to the elastic domain, as damage and plasticity effects were not included in the simulations. The distribution and orientation of fibers (particularly steel fibers) in a cementitious matrix, namely concrete or cement mortar, has been the subject of several studies aimed at determining the best mechanical performance of fiber-reinforced concrete. The proposed modeling approach of bending mechanical behavior allows us to predict the effects of fiber distribution in fluid mortars and reinforced self-compacting mortars, thereby reducing the need for extensive experimental testing. It also represents a significant improvement over existing approaches reported in the literature. Full article

The development of durable road sealing materials capable of maintaining performance under combined mechanical and climatic loads remains a critical challenge for modern infrastructure. Conventional bitumen-based sealants exhibit limited resistance to high-temperature deformation, cracking, and adhesion degradation, leading to reduced service life. This study proposes a rheology-oriented approach to the design of polymer-reinforced bituminous sealants based on penetration-grade bitumen 50/70 and 70/100 modified with styrene–butadiene–styrene (SBS) copolymers up to 9 wt.% and reinforced with cellulose fibers. The rheological behavior of the developed composites was investigated using dynamic shear rheometry to determine the complex shear modulus (G*), phase angle (δ), and temperature–frequency dependencies in the range from −20 to +90 °C, while infrared spectroscopy was employed to assess intermolecular interactions. Adhesion performance was evaluated at different temperature. The modified systems demonstrated a 5–10-fold increase in G*/sinδ enhanced high-temperature stability, and improved adhesion and crack resistance compared to base bitumen. Based on the obtained rheological and performance indicators, the developed composition was approved for subsequent pilot-scale testing and field validation as a promising road sealing material. Full article

The increasing demand for sustainable materials has accelerated the development of environmentally friendly filaments for fused deposition modeling (FDM). In this study, the surface roughness and thermal degradation behavior of sustainable PLA-based filaments, including PLA, recycled PLA (Re–PLA), and wood-filled PLA (Wood–PLA), were systematically investigated under different FDM printing conditions. A full factorial experimental design was employed to identify the dominant processing parameters and optimize surface quality. Surface roughness was evaluated using values Ra, Rz, and Rq parameters measured on three different surface orientations (top surface at 0°, top surface at 45°, and side surface). Scanning electron microscopy (SEM) was used to examine the relationship between roughness measurements and surface morphology, while thermogravimetric analysis (TGA) was performed to evaluate the thermal degradation behavior of the filaments in relation to printing temperature. The results have shown that filament material is the most important parameter affecting surface roughness. While Wood–PLA exhibited the highest roughness due to fiber-induced surface heterogeneity, recycled Re–PLA showed moderate surface irregularities resulting from degradation compared to pure PLA. Despite a rougher filament surface prior to production, recycled PLA exhibited a surface morphology similar to that of pure PLA after printing, influenced by the processing parameters. Furthermore, SEM findings indicated that the Ra parameter predominantly reflects macro-scale surface topography, while local microstructural heterogeneity can be better characterized by complementary roughness parameters such as Rz. These findings support optimizing printing conditions to improve surface quality and more widespread use of sustainable FDM filaments in applications where surface roughness is critical. Full article

The research gap addressed in this study is the lack of a transparent and quantitative evaluation of the governing parameters influencing deflection behavior in reinforced concrete (RC) beams reinforced with glass fiber-reinforced polymer (GFRP) bars. The objective of this study is to identify and quantify the relative importance of the key parameters controlling deflection in GFRP-reinforced RC beams, which exhibit fundamentally different behavior compared to steel-reinforced beams due to the linear-elastic response of GFRP bars until rupture. To achieve this objective, the method integrates explainable artificial intelligence (XAI) techniques, including SHapley Additive exPlanations (SHAP), Pearson correlation heatmap, scatter plot analysis, and sensitivity analysis—with experimental structural data obtained from beams with three different concrete strength classes. The main contribution of this study is the quantitative ranking and interpretation of the governing parameters affecting deflection behavior through a transparent and data-driven framework. Key parameters—including elastic modulus (Ec), compressive strength (fck), creep coefficient (φ), failure moment (Mexp), effective moment of inertia (Ieff), and applied load (P)—were evaluated. The results consistently indicate that stiffness- and capacity-related parameters dominate the deflection response. Sensitivity analysis reveals that the failure moment (Mexp) is the most influential parameter, contributing approximately 23% of the total relative influence on deflection, followed by compressive strength (fck) and cracking-related parameters. Pearson correlation heatmap and scatter plot analyses further confirm strong relationships between deflection and Ec, fck, φ, and Ieff. The proposed framework improves the interpretability of deflection prediction in GFRP-reinforced RC beams and provides a transparent basis for serviceability-based structural design and performance-oriented assessment. Full article

The precursor infiltration and pyrolysis (PIP) route is widely adopted to fabricate carbon fiber-reinforced silicon carbide (C_f/SiC) composites; however, the atomic-scale restructuring of the pyrolytic carbon/silicon carbide (PyC/SiC) interface during ceramization—and its impact on mechanical integrity—remains elusive. Here, reactive molecular dynamics (ReaxFF MD) simulations elucidate the coupled thermochemical–mechanical evolution of polycarbosilane (PCS) precursors on PyC substrates with orientation angles (OAs) of 0°, 25°, 55°, and 85°. Dynamic pyrolysis triggers a pivotal transition from sp² to sp³ hybridization at the interface. High-OA substrates (55° and 85°) present a dense population of reactive edge sites, fostering extensive cross-interfacial covalent bonding. Subsequent shear loading reveals that these pyrolysis-induced chemical bridges govern failure modes, shifting from interlayer sliding dominated by weak non-bonded interactions (0°) to ductile fracture featuring uniform plasticity and crack deflection. The OA = 55° interface attains a theoretical peak shear strength of 15 GPa and exhibits the most favorable combination of high strength and ductile failure under tensile loading, owing to an optimal balance between reactive site availability and interlayer steric openness. In contrast, the OA = 85° interface, despite comparable peak stress, fails via brittle crack penetration into the SiC matrix. By correlating atomistic structure with macroscopic performance, this study provides a bottom-up framework for engineering C_f/SiC composites via interfacial texturing and optimized pyrolysis protocols. Full article

This study discusses the thermal behavior of glass fiber-reinforced SiO₂-filled polymers in dry milling. Focus is put on the effects of the addition of SiO₂ particles on cutting-generated heat and the fresh-surface integrity of the composite. Cutting trials were developed using a Spinner U-620 5-axis CNC machine. Real-time temperature histories owing to the dry milling of both Glass/Epoxy and Glass/Polyester composites were recorded using thermocouples preinstalled within the composite specimen. SEM inspections were conducted to elucidate the prevailing failure mechanisms during the material removal process. The results showed that fiber orientation significantly dominated thermal responses. Cutting perpendicular to the fiber orientation results in a critical temperature, while the addition of SiO₂ particles effectively reduces the temperature overlaps and peak values, causing the temperature to drop. The addition of SiO₂ serves to keep the temperature sufficiently lower than the glass transition point of the matrix. However, increasing the feed rate from 50 mm/min to 150 mm/min reduced the overall temperature during cutting. Under similar cutting conditions, Glass/Polyester composites exhibited lower peak temperatures and heat quantities than Glass/Epoxy regardless of the feed rate and fiber orientation. Observations revealed that fiber orientation and matrix type strongly influence the intensity of the thermal and mechanical damages induced. These findings suggest that the addition of silicon dioxide can adjust the thermal balance in dry cutting and may improve the composite’s structural integrity significantly. Such a composite design promotes the heat control of sensitive parts in advanced engineering applications. Full article

Reinforcement congestion in reinforced concrete (RC) beam–column joints creates constructability difficulties and may compromise seismic performance due to inadequate consolidation and confinement. Although fiber-reinforced concrete (FRC) has been widely investigated as an alternative to dense transverse reinforcement, current seismic codes (e.g., ACI 318-19, TBEC-2018) do not provide explicit provisions to quantify the interaction between steel fiber dosage and joint shear demand. This study examines the feasibility of partial stirrup replacement through a hybrid confinement strategy that preserves minimum transverse reinforcement for bar stability while using steel fibers to compensate for joint shear demand. Two large-scale exterior beam–column assemblies were tested under quasi-static reversed cyclic loading: a code-compliant reference specimen and a hybrid specimen incorporating minimum stirrups with 0.5% hooked-end steel fibers. The hybrid specimen exhibited improved stiffness retention and energy dissipation without brittle joint shear failure. A validated nonlinear finite element model (VecTor2) was used to conduct a parametric investigation covering beam reinforcement ratios of 1.3–1.5% and fiber volume fractions of 0.5–1.2%. Results demonstrate a consistent non-linear interaction between beam-induced joint shear demand and fiber contribution. This interaction is formulated through a demand-based exponential relationship that links required steel fiber dosage to joint shear demand while preserving minimum transverse reinforcement for longitudinal bar stability. The proposed model provides a design-compatible framework for hybrid fiber-stirrup confinement in seismic design practice. Full article

Spent coffee grounds (SCGs) and lignin-derived binders, such as ammonium lignosulfonate (ALS), are increasingly being explored as renewable resources to reduce reliance on conventional formaldehyde-based resins in wood-fiber biocomposites. Although prior work has shown that SCG–ALS adhesive systems can achieve promising mechanical performance, two practical aspects essential for industrial applications and circular design remain insufficiently explored: a predictable and reproducible visual appearance and credible end-of-life options. In this study, sustainable wood-fiber biocomposites bonded with SCG and ALS were assessed from an aesthetic performance and end-of-life perspective. Color was quantified in the CIE L*a*b* (CIELAB) space and expressed as total color difference (ΔE*) relative to a reference panel. Increasing total SCG + ALS content from 40 to 75 wt.% based on oven-dry fibers produced pronounced darkening, with lightness decreasing from L* = 47.1 to 34.3 and ΔE* increasing from 18.38 to 32.51. Short-term composting behavior was explored by embedding fragments from formulations with 40–60 wt.% total SCG + ALS (based on oven-dry fibers; equal SCG/ALS shares) into a mixed organic substrate adjusted to an initial C/N ≈ 30 and monitored for 30 days in pots and trays. The process remained predominantly mesophilic (≈14–22 °C); nevertheless, visible microbial colonization and progressive surface degradation were observed, indicating susceptibility to biological activity under moist, nutrient-rich conditions. Overall, the results show that SCG–ALS content strongly governs the visual identity of the biocomposites and suggest composting-oriented routes as a potential end-of-life direction at an exploratory level, while highlighting the need for standardized compostability assessment and longer-term monitoring to substantiate circularity claims. Full article

The increasing demand for sustainable and environmentally friendly construction materials has spurred interest in biopolymer composites reinforced with agricultural waste. Rice husk (RH), a byproduct of rice milling, is abundant and rich in lignocellulosic fibers and silica, making it excellent for use in fiber-reinforced biopolymers. The novelty of this study lies in its integrated and construction-oriented evaluation of rice husk (RH)-reinforced biopolymers, combining mechanical, thermal, environmental, and economic perspectives within a single framework. The study introduces a novel comparative approach by benchmarking multiple polymer matrices-including PP, recycled HDPE, epoxy, PLA, and bio-binders-under unified quantitative performance criteria. Another key novelty is the identification of the dual functional role of silica-rich RH in simultaneously enhancing structural strength and flame retardancy while contributing to carbon emission reduction. With a high silica content (15–20%) and lignocellulosic structure, RH serves as a natural filler that enhances the performance of polymer matrices such as polypropylene (PP), epoxy, polylactic acid (PLA), and recycled polyethylene. Mechanically, RH-reinforced composites demonstrate significant improvements in tensile, flexural, and impact strength. For example, PP composites with NaOH-treated RH and coffee husks achieved tensile strengths between 27.4 MPa and 37.4 MPa, with corresponding Young’s modulus values ranging from 1656 MPa to 2247.8 MPa. Recycled HDPE-RH blends reached tensile strengths up to 74 MPa and flexural values of 39 MPa, validating their structural applicability. Epoxy matrices embedded with 0.45 wt.% RH nanofibers showed degradation thresholds of 411 °C and 678 °C, reflecting substantial thermal resistance. Flame retardancy is further improved by the presence of RH biochar, which leads to reduced peak heat release rate (PHRR) and enhanced char formation. In building insulation applications, RH-based composites exhibit low thermal conductivity values between 0.08 and 0.14 W/m·K, contributing to energy efficiency. Economically, RH reduces material costs by 30–40%, while environmentally, its integration lowers carbon emissions in PP composites by up to 10%, and promotes biodegradability. Despite challenges such as moisture absorption and interfacial adhesion, these can be mitigated through alkali treatment, compatibilizers (e.g., MAPP), or hybrid reinforcement strategies. Full article