Search Results (2,592)

A large number of wind turbine blades will be retired in the near future. Glass fiber-reinforced composites from retired blades, due to their extraordinary strength, toughness, and durability, are promising aggregate candidates in asphalt mixtures. This work studied the interfacial behavior between asphalt and glass fiber-reinforced composites through combined molecular modeling and experimental approaches. Predictions from molecular modeling were first verified through experimental findings using particle probe scanning force microscopy. Then, molecular simulations were conducted to examine the chemical adhesion between binders and aggregates made from minerals and wind turbine blades. The results showed that epoxy–binder adhesion was higher than calcite–binder and silica–binder adhesion but lower than alumina–binder adhesion, denoting that the glass fiber composite aggregates were comparable in chemical adhesion to mineral aggregates. The adhesion was primarily due to van der Waals forces (>80%). Furthermore, the dependence of epoxy–asphalt adhesion on loading rates was examined, during which the high-speed, transitions, and low-speed regions were identified. The impact of water on interfacial behavior was illustrated by examining how water molecules infiltrated interfaces between aggregates and binders at different speeds. The results showed that interfacial adhesion in a hydrated state at low speeds was 20–40% lower than that in a dry state, whereas at high speeds, interfacial adhesion in a hydrated state was 5–15% higher than that in dry conditions. These results could provide essential guidance for the application of retired wind turbine blades as asphalt aggregates. Full article

Warpage is among the most prevalent defects affecting injection molded parts. In this study, we aimed to develop methods to minimize warpage through mold design. Common strategies include matching the cavity geometry to the intended shape of the part, adjusting cavity dimensions to offset material shrinkage, and optimizing the cooling system and critical injection molding parameters. These optimization methods can offer significant improvements, but recently introduced methods that optimize the molded part and mold cavity shape result in higher levels of warpage reduction. In these methods, optimization of the shape of the molded part is achieved by shaping it in the opposite direction of warpage—a method known as inverse contouring. Inverse contouring of molded parts is a design technique in which mold cavities are intentionally modified to incorporate compensatory geometric deviations in regions anticipated to exhibit significant warpage. The final result after molded part ejection and warpage is a significant reduction in deviations between the warped and reference molded part geometries. In this study, a two-step approach for minimizing warpage was used: the first step was optimizing the most significant injection molding parameters, and the second was inverse contouring. In the first step, Response Surface Methodology (RSM) and Autodesk Moldflow Insight 2023 simulations were used to optimize molded part warpage based on three processing parameters: melt temperature, target mold temperature, and coolant temperature. For improved accuracy, a Computer-Aided Design (CAD) model of the warped molded part was exported into ZEISS Inspect 2023 software and aligned with the reference CAD geometry of the molded part. The maximal warpage value after the initial simulation was 1.85 mm based on Autodesk Moldflow Insight simulations and 1.67 mm based on ZEISS Inspect alignment. After RSM optimization, the maximal warpage was 0.73 mm. In the second step, inverse contouring was performed on the molded part, utilizing the initial injection molding simulation results to further reduce warpage. In this step, the CAD model of the redesigned, inverse-contoured molded part was imported into Moldflow Insight to conduct a second iteration of the injection molding simulation. The simulation results were exported into ZEISS Inspect software for a final analysis and comparison with the reference CAD model. The warpage values after inverse contouring were reduced within the range of ±0.30 mm, which represents a significant decrease in warpage of approximately 82%. Both steps are presented in a case study on an injection molded part made of polybutylene terephthalate (PBT) with 30% glass fiber (GF). Full article

The application of precast assembled pier systems in high-seismicity regions is often constrained by their seismic performance limitations. To validate the optimization effect of GFRP confinement on the hysteretic performance of bridge piers, this study first conducted axial compression tests on 54 glass fiber-reinforced polymer (GFRP)-confined concrete cylindrical specimens. The investigation focused on the effects of fiber layers (6 and 10), orientation angles ($\pm 45°$, $\pm 60°$, $\pm 80°$), slenderness ratios (2 and 4), and compression section configurations (fully loaded vs. core concrete loading only) on confinement efficacy. The experimental results demonstrate that specimens with $\pm 60°$ fiber angles achieved an optimal balance between strength and ductility, exhibiting an average strength enhancement of 298.0% and a maximum axial strain of 2.7% compared to unconfined concrete. Subsequently, two GFRP tube-confined concrete bridge piers with varying fiber layers (PRCG1: 6 layers; PRCG2: 10 layers) and one unconfined reference pier (PRC) were designed and fabricated. All specimens employed grout-filled sleeves to connect caps and piers. Pseudo-static tests revealed that GFRP confinement effectively mitigated damage in plastic hinge zones and enhanced seismic performance. Compared to the PRC, PRCG1 and PRCG2 exhibited increases in ultimate displacement by 19.50% and 28.57%, in ductility coefficients by 18.56% and 27.84%, and in cumulative hysteretic energy dissipation by 13.90% and 26.43%, respectively. At the 5% drift ratio, their load capacities increased by 26.74% and 23.25%, stiffnesses improved by 28.91% and 25.51%, and residual displacements decreased by 20.89% and 11.17%. The accuracy and applicability of the GFRP tube-confined bridge pier model, developed based on the Lam–Teng model, were validated through numerical simulations using the OpenSees fiber element approach. Full article

The thermal, thermomechanical, and viscoelastic properties of continuous unidirectional (UD) glass fiber/high-density polyethylene (GF/HDPE) and ultra-high-molecular-weight polyethylene/high-density polyethylene (UHMWPE/HDPE) tapes are characterized in this paper in order to support their use in extreme environments. Unlike prior studies that focus on short-fiber composites or limited thermal conditions, this work examines continuous fiber architectures under five operational environments derived from Army Regulation 70-38, reflecting realistic defense-relevant extremes. Differential scanning calorimetry (DSC) was used to identify melting transitions for GF/HDPE and UHMWPE/HDPE, which guided the selection of test conditions for thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA). TMA revealed anisotropic thermal expansion consistent with fiber orientation, while DMA, via strain sweep, temperature ramp, frequency sweep, and stress relaxation, quantified their temperature- and time-dependent viscoelastic behavior. The frequency-dependent storage modulus highlighted multiple resonant modes, and stress relaxation data were fitted with high accuracy (R² > 0.99) to viscoelastic models, yielding model parameters that can be used for predictive simulations of time-dependent material behavior. A comparative analysis between the two material systems showed that UHMWPE/HDPE offers enhanced unidirectional stiffness and better low-temperature performance. At the same time, GF/HDPE exhibits lower thermal expansion, better transverse stiffness, and greater stability at elevated temperatures. These differences highlight the impact of fiber type on thermal and mechanical responses, informing material selection for applications that require directional load-bearing or dimensional control under thermal cycling. By integrating thermal and viscoelastic characterization across realistic operational profiles, this study provides a foundational dataset for the application of continuous fiber thermoplastic tapes in structural components exposed to harsh thermal and mechanical conditions. Full article

This study aimed to determine the practical efficacy of passive eDNA samplers (PEDS) for monitoring fish diversity in riverine ecosystems. It investigated the utility of environmental DNA (eDNA) in accurately depicting fish composition and diversity within the Lancang River. Environmental DNA technology, particularly PEDS, may be used as a substitute for traditional water filtration techniques. However, its effectiveness in natural water ecosystems remains to be proven. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). This study used four different types of filters, each with identical pore sizes and dimensions but constructed from various materials, to assess eDNA capture under laboratory and field conditions in the water samples. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). Environmental DNA macrobarcoding was used to analyze fish biodiversity and to understand the environmental effects on species distribution. Our study identified 50 fish species inhabiting the Lancang River, with equal representation of exotic and native species. A comparative analysis of four filter-based environmental DNA samplers and traditional environmental DNA sampling methods demonstrated comparable species richness. Redundancy analysis indicated that environmental variables, elevation, electrical conductivity, salinity, and chlorophyll-a significantly influenced the distribution patterns of both non-native and native fish species in the river. This study highlights the significance of eDNA technology in evaluating fish diversity across diverse habitats, thereby establishing a theoretical framework for the sustained monitoring and management of fish biodiversity in protected areas. Full article

This review is focused on glass fibers and natural fibers, exploring their applications in vehicles and buildings and emphasizing their significance in promoting sustainability and enhancing performance across various industries. Glass fibers, or fiberglass, are lightweight, have high-strength (3000–4500 MPa) and a Young’s modulus range of 70–85 GPa, and are widely used in automotive, aerospace, construction, and marine applications due to their excellent mechanical properties, thermal conductivity of ~0.045 W/m·K, and resistance to fire and corrosion. On the other hand, natural fibers, derived from plants and animals, are increasingly recognized for their environmental benefits and potential in sustainable construction, offering advantages such as biodegradability, lower carbon footprints, and reduced energy consumption, with a sound absorption coefficient (SAC) range of 0.7–0.8 at frequencies above 2000 Hz and thermal conductivity range of 0.07–0.09 W/m·K. Notably, the integration of these materials in construction and automotive sectors reflects a growing trend towards sustainable practices, driven by the need to mitigate carbon emissions associated with traditional building materials and enhance fuel efficiency, as seen in hybrid composites achieving 44.9 dB acoustic insulation at 10,000 Hz and a thermal conductivity range of 0.05–0.06 W/m·K in applications such as the BMW i3 door panels. Natural fibers contribute to reducing reliance on fossil fuels, supporting a circular economy through the recycling of agricultural waste, while glass fibers are instrumental in creating lightweight composites for improved vehicle performance and structural integrity. However, both materials face distinct challenges. Glass fibers, while offering superior strength, are vulnerable to chemical degradation and can pose recycling difficulties due to the complex processes involved. On the other hand, natural fibers may experience moisture absorption, affecting their durability and mechanical properties, necessitating innovations to enhance their application in demanding environments. The ongoing research into optimizing the performance of both materials highlights their relevance in future sustainable engineering practices. In summary, this review underscores the growing importance of glass and natural fibers in addressing modern environmental challenges while also improving product performance. As industries increasingly prioritize sustainability, these materials are poised to play crucial roles in shaping the future of construction and transportation, driving innovations that align with ecological goals and consumer expectations. Full article

The variety of fiber types embedded in fiber-reinforced polymer (FRP) composites determines different tribology performance properties. In this work, the tribological properties under dry sliding conditions of glass fiber-reinforced polymer (GFRP) and basalt fiber-reinforced polymer (BFRP) were investigated and compared. Laminated composite specimens with different fiber content were manufactured by vacuum bagging and autoclave curing. Tensile and flexural mechanical properties, as well as pin-on-disk tribological properties of the composite specimens, were analyzed. A design of experiments was performed considering the influence of fiber weight fraction, fiber type, and sliding speed on the coefficient of friction (COF), specific wear rate (K), and contact temperature. A multifactorial ANOVA was performed to identify the significance and contribution percentage of each factor. Deep investigations to understand the wear mechanisms were performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results of the statistical analysis showed that the interaction between fiber type and sliding speed had the most significant influence on the COF (31.36%), while the fiber weight fraction had the predominant effect on the specific wear rate (22.04%), and the sliding speed was the most influential factor affecting temperature (82.88%). BFRP composites consistently performed better than GFRP in all tribological metrics, such as coefficient of friction, specific wear rate, and contact temperature. Full article

It is particularly important to ensure the safety of engineering structures, such as aerospace vehicles and wind turbines, most of which are made of composite materials. A sudden failure of the structure may happen following the accumulation of structural damage. Since they are sensitive to tiny damage and can propagate through engineering structures over a long distance, Lamb waves have been widely explored to develop highly efficient damage detection theories and methodologies. During propagation, affected by the mechanical properties of the structure, a large amount of information and features related to structural states can be reflected and transmitted by Lamb waves, including the occurrence and extent of structural damage. By analyzing the effect of damage acting on Lamb waves, a multi-scale wavelet transform analysis is adopted to extract multi-feature parameters in the time–frequency domain of the acquired signals. With the help of the nonlinear mapping ability of a neural network, a damage assessment model for composite structures is constructed to realize the evaluation of typical structural damage at different levels. The results of an experiment conducted on an epoxy–glass-fiber-reinforced plate show that the extracted multi-feature parameters of Lamb waves in the time–frequency domain are sensitive to the accumulated typical damage. The damage assessment model can properly evaluate the damage degree with satisfactory accuracy. Full article

Anti-resonant hollow-core fibers have exhibited excellent performance in applications such as high-power pulse transmission, network communication, space exploration, and precise sensing. Employing anti-resonant hollow-core fibers instead of light guiding arms for transmitting laser energy at the 2.79 μm band can significantly enhance the flexibility of medical laser handles, reduce system complexity, and increase laser transmission efficiency. Nevertheless, common anti-resonant hollow-core fibers do not have the ability to maintain the polarization state of light during laser transmission, which greatly affects their practical applications. In this paper, we propose a polarization-maintaining anti-resonant hollow-core fiber applicable for transmission at the mid-infrared 2.79 μm band. This fiber features a symmetrical geometric structure and an asymmetric refractive index cladding composed of quartz and a type of mid-infrared glass with a higher refractive index. Through optimizing the fiber structure at the wavelength scale, single-polarization transmission can be achieved at the 2.79 μm wavelength, with a polarization extinction ratio exceeding 1.01 × 10⁵, indicating its stable polarization-maintaining performance. Simultaneously, it possesses low-loss transmission characteristics, with the loss in the x-polarized fundamental mode being less than 9.8 × 10⁻³ dB/m at the 2.79 µm wavelength. This polarization-maintaining anti-resonant hollow-core fiber provides a more reliable option for the light guiding system of the 2.79 μm Er; Cr: YSGG laser therapy device. Full article

A spectral filter utilizing dispersive prisms and an optical fiber collimator is presented as an attractive alternative to diffraction grating-based spectral filters. A simplified analytical expression for this prism-based spectral filter is derived. A spectral filter constructed using SF11 flint glass prisms demonstrates Gaussian spectral filter profiles with bandwidths of 8 nm and 4 nm, closely matching with theoretical predictions. Using these filters, we demonstrate two types of mode-locking regimes: a dissipative soliton (DS) pulse and a self-similar (SS) pulse. The dissipative soliton pulses deliver 3.3 nJ with dechirped pulse durations of 206 fs, while the self-similar pulses deliver 2.1 nJ with durations of 120 fs. The results demonstrate that the prism-based filters are well-suited for ultrafast mode-locked fiber lasers. Full article

Icing represents a significant hazard to the flight safety of unmanned aerial vehicles (UAVs), particularly affecting critical aerodynamic surfaces such as air intakes, wings, and empennages. While conventional adhesive electrothermal de-icing systems are straightforward to operate, they present safety concerns, including a 15–25% increase in system weight, elevated anti-/de-icing power consumption, and the risk of interlayer interface delamination. To address the objectives of reducing weight and power consumption, this study introduces an innovative electrothermal–structural–durability co-design strategy. This approach successfully led to the development of a glass fiber-reinforced polymer (GFRP) component that integrates anti-icing functionality with structural load-bearing capacity, achieved through an embedded hot-pressing process. A stress-damage cohesive zone model was utilized to accurately quantify the threshold of mechanical performance degradation under electrothermal cycling conditions, elucidating the evolution of interfacial stress and the mechanism underlying interlayer failure. Experimental data indicate that this novel component significantly enhances heating performance compared to traditional designs. Specifically, the heating rate increased by approximately 202%, electrothermal efficiency improved by about 13.8% at −30 °C, and interlayer shear strength was enhanced by approximately 30.5%. This research offers essential technical support for the structural optimization, strength assessment, and service life prediction of UAV anti-icing and de-icing systems in the aerospace field. Full article

The tribological performance of a novel nonmetallic composite casing coating is investigated under dry wear conditions and different side loads and rotational speeds. The coating is composed of a short-glass-fiber-reinforced epoxy matrix with silicon carbide, aluminum oxide, and calcium carbonate nanofillers to provide a protective barrier against contact with hardened drill pipe tool joints. The results revealed that the wear behavior was highly dependent on the applied side load and rotational speed. Under high-load conditions, the formation of a compacted tribofilm significantly reduced the coefficient of friction and specific wear factor by limiting direct surface contact. Lower rotational speeds and moderate side loads resulted in adhesive wear with formation of stable tribofilms that mitigated material loss. Full article

This work aimed to assess the influence of the iQ Weight Control System on the weight, dimensional stability, and mechanical properties of injection-molded samples. The properties of products made from glass fiber-reinforced polyamide and 50% regrind from post-production waste were evaluated. The mechanical properties, such as impact strength and tensile strength, were measured to determine the material’s performance. Additionally, a spiral flow test was conducted to verify the process robustness and repeatability when producing with either virgin material or a blend of virgin and regrind material. The spiral flow test, which involves injecting the polymer melt into a spiral mold, provides insights into the processability and flow characteristics of the polymer under high shear rates. This test is crucial for assessing the consistency of the injection molding process and ensuring that the material maintains its properties across different production batches. Results demonstrated that, despite the viscosity reduction associated with regrind, the system successfully maintained a consistent shot weight, thereby stabilizing the amount of material injected into the mold cavity. The iQ Weight Control System activation led to an increase in impact strength from 9.50 kJ/m² to 10.78 kJ/m² for virgin samples and from 9.26 kJ/m² to 9.73 kJ/m for a 50/50 virgin/regrind blend. Full article

The application of glass fiber reinforced polymer (GFRP) bars offers a promising solution for enhancing the durability of reinforced concrete structures, potentially reducing maintenance costs and associated socioeconomic impacts. However, concerns persist regarding the durability of GFRP bars in the highly alkaline environment of concrete, which can lead to physical, chemical, and mechanical degradation. This study evaluates the durability of GFRP bars composed of isophthalic polyester, vinyl ester, and epoxy matrices (6.0 mm diameter) under accelerated aging conditions. The bars were exposed to non-carbonated concrete (with and without silica fume) and carbonated concrete at temperatures of 23 °C, 40 °C, and 60 °C for durations of 500, 1000, and 3000 h. Interlaminar shear strength (ISS) was measured before and after aging. SEM and FTIR analyses confirmed degradation in the polymer matrix and fiber–matrix interface. Results indicated that silica fume significantly mitigated alkalinity effects, limiting ISS loss to 11.3%. Similarly, carbonation reduced the concrete’s pH, thereby decreasing ISS degradation to 10.7% after 3000 h. Among the tested materials, GFRP bars with vinyl ester matrix exhibited superior durability, followed by those with epoxy and polyester matrices. These findings emphasize the critical role of matrix selection and concrete mix design in improving GFRP durability. Full article

This study investigates the mechanical behavior of various plastic materials through tensile and scratch testing. Three polypropylene-based composites—PP-GB30GF10, PP-TD40, and PP-GF20—were subjected to uniaxial tensile tests in accordance with standard protocols to assess their strength, stiffness, and elongation characteristics. The results highlight notable differences in the tensile performance depending on the type and percentage of reinforcing fillers, such as glass fibers and talc. In parallel, the scratch resistance was evaluated for specimens produced via stereolithography (SLA) using Formlabs Black V4 resin, a common photopolymer used in prototyping applications. The scratch test aimed to characterize the surface durability under localized mechanical stress. The findings contribute to a better understanding of the mechanical performance of these materials and their potential applications in fields requiring both structural integrity and surface resilience, such as automotive components and functional prototyping. Full article