Search Results (186)

The technology of 3D printing has become one of the most effective methods of creating various parts, such as those used for fast prototyping. The most important aspect of 3D printing is the selection and application of the appropriate material, also known as filament. The current review concerns mainly the description of the mechanical and physical properties of the different filaments and the possibilities of improving those properties. The review begins with a short description of the development of 3D printing technology. Next, the basic characteristics of thermoplastics used in the fused filament fabrication (FFF) are discussed, namely polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate glycol (PETG). According to modern con-cepts, the printed parts can be reinforced with the use of different kinds of fibers, namely synthetic fibers (carbon, glass, aramid) or natural fibers (wood, flax, hemp, jute). Thus, the impact of such a reinforcement on the performance of FFF composites is also presented. The current review, unlike other works, primarily addresses the problem of the aging of parts made from the thermoplastics above. Environmental conditions, including UV radiation, can drastically reduce the physical and mechanical properties of printed elements. Moreover, the current review contains a detailed discussion about the influence of the different fibers on the final mechanical properties of the printed elements. Generally, the synthetic fibers improve the mechanical performance, with documented increases in tensile modulus reaching, for instance, 700% for carbon-fiber-reinforced ABS or over 15-fold for continuous aramid composites, enabling their use in functional, load-bearing components. In contrast, the natural ones could even decrease the stiffness and strength (e.g., wood–plastic composites), or, as in the case of flax, significantly increase stiffness (by 88–121%) while offering a sustainable, lightweight alternative for non-structural applications. Full article

With the continuous increase in global energy consumption and the escalating severity of climate change, the development of high-performance thermal insulation materials is crucial for reducing energy waste and carbon emissions. In this work, a facile method was proposed to prepare thermal-insulating glass fiber wool/methyltrimethoxysilane aerogel (GFWA) composites through vacuum-assisted impregnation. The obtained results indicated that GFWA composites exhibited excellent thermal insulation and hydrophobic properties, with GFWA-30 containing 30 wt.% glass fiber wool having a thermal conductivity of 35.3 mW/m·K and a water contact angle of 125.8°. Additionally, the Young’s modulus of this composite was 21.2% higher than that of MTMS aerogel. In terms of thermal safety performance, compared to methyltrimethoxysilane aerogel, the GFWA-30 composite showed reductions of 21.6%, 18.8%, and 27.95% in peak heat release rate, total heat release, and gross calorific value, respectively. This study offers a simple and feasible approach to fabricating high-performance thermal insulation materials, which display huge potential for widespread application in the fields of building insulation and other fields with thermal insulation requirements. Full article

Dy³⁺:InF₃ fiber shows promise for 4.4 μm mid-infrared lasing, but the much shorter lifetime of its upper laser level compared to the lower level causes inevitable self-termination. While cascade 4.4 μm/3 μm lasing has been proposed as a potential solution, this method faces complex configuration and an extremely high pump threshold (>30 W under continuous-wave operation), rendering it impractical for high-power use, especially given InF₃’s soft-glass nature. To address the self-termination challenge and enable the low-threshold, high-efficiency lasing, this study proposes, for the first time to our knowledge, a dual-wavelength cascade-pumping scheme utilizing 2.8 μm and 2.4 μm pumps. Numerical simulations demonstrate that the dual-wavelength cascade-pumped Dy³⁺:InF₃ fiber laser exhibits an optical-to-optical efficiency of up to 18.4% and a maximum slope efficiency of 38.5%. The total pump threshold is as low as 5.4 W, remarkably lower than that required by the cascade lasing approach. This work provides a viable solution and design guidelines for the development of 4 μm-class mid-infrared fiber lasers. Full article

This study investigates seven advanced hybrid composite thermal protection system (TPS) prototypes, featuring an innovative internal air chamber design that reduces heat conduction and enhances overall thermal protection performance. Specimens were manufactured by fused deposition modeling (FDM), an additive manufacturing technique, using a fire-retardant thermoplastic. Selected configurations were reinforced with continuous carbon or glass fibers, coated with ceramic surface layer, or hybridized with carbon fiber reinforced polymer (CFRP) layers or a CFRP laminate disk. To validate performance, a harsh oxy-acetylene torch (OAT) protocol was implemented, deliberately designed to exceed the severity of most reported typical ablative assessments. The exposed surface of each specimen was subjected to direct flame at a 50 mm distance, recording peak temperatures of 1600 ± 50 °C. Two samples of each configuration were tested under 60 and 90 s exposures. Back-face thermal readings at potential payload sites consistently remained below 85 °C, well under the 200 °C maximum standard threshold for TPS applications. Several configurations preserved structural integrity despite the extreme environment. Prototypes 4.1 and 4.2 demonstrate the most favorable performance, maintaining structural integrity and low back-face temperatures despite substantial thickness loss. By contrast, specimen 6.2 exhibited rapid degradation following 60 s of exposure, which served as a rigorous and selective early-stage screening tool for evaluating polymer-based ablative TPS architectures. Full article

The combination of microplasma generation and optical multi-material fiber technologies enables real-time diagnostics. The stack-and-draw technique has emerged as a promising method for creating multimaterial fibers suitable for plasma-based diagnostics. The elaboration of such devices for the generation of long-lasting microplasma for real-time and remote analyses remains challenging due to the difficulties of reaching long lengths without defects and with continuous electrodes. Post-functionalization of the electrode surface is also required to increase the plasma emission duration. In this study, glass was preferred over polymers for producing rectangular fibers (ribbons) that are easy to stack without wasting space and are resistant to high operating temperatures. Conversely, an aluminum alloy was chosen for the electrodes to reduce discontinuity defects. With the chosen bi-electrode geometry, the cooling rate during drawing has to remain between 200 and 300 °C/s to limit defect formation and guarantee low electrical resistivity. During plasma generation, an in situ oxide layer forms on the tip of each electrode. This results in a significant increase in plasma emission duration without the need for an additional post-functionalization step after drawing. These ribbons were tested in combination with an optical emission spectrometer to create a miniature gas detector for hydrocarbons. Full article

A multimode magneto-optical fiber based on Tb³⁺-containing borogermanate glass was designed, fabricated, and characterized, aiming at potential sensing applications. There are continuing challenges in the development of single-mode (SMF) or multimode (MMF) optical fibers doped with rare-earth (RE) ions and exhibiting high Verdet constants, related to devitrification of the precursor glass. Most RE-doped glass compositions are not suitable as precursors for core-cladding fiber production due to devitrification processes and consequent poor optical quality. Application as Faraday rotators is limited by the intrinsically low Verdet constant of silica (~0.589 rad T⁻¹ m⁻¹ at 1550 nm and 0.876 rad T⁻¹ m⁻¹ at 1310 nm). Borogermanate glasses are good candidates for manufacturing optical fibers due to their excellent potential to solubilize high concentrations of Tb³⁺ ions as well as satisfactory thermal stability. In this work, a magneto-optical core-cladding borogermanate fiber with a 227 μm diameter was fabricated, with characterization using differential scanning calorimetry (DSC), thermomechanical analysis (TMA), viscosity measurements, M-lines spectroscopy, UV-Vis-NIR absorption spectroscopy, the cut-back technique, and magneto-optical measurements. The measured numerical aperture (NA) was 0.183, with minimum attenuation of 13 dB m⁻¹ at 1270 nm. The Verdet constant (V_B) reached −6.74 rad T⁻¹ m⁻¹ at 1330 nm. Full article

Alkali resistance is a critical factor for the long-term performance of glass fibers in cementitious composites. While zirconium oxide doping has proven effective in enhancing the durability of basalt fibers, its high cost and limited solubility motivate the search for viable alternatives. This study presents the first systematic investigation of titanium dioxide (TiO₂) doping in basalt-based glasses across a wide compositional range (0–8 mol%). X-ray fluorescence and diffraction analyses confirm complete dissolution of TiO₂ within the amorphous silicate network, with no phase segregation. At low concentrations (≤3 mol%), Ti⁴⁺ acts as a network modifier in octahedral coordination ([TiO₆]), reducing melt viscosity and lowering processing temperatures. As TiO₂ content increases, titanium in-corporates into tetrahedral sites ([TiO₄]), competing with Fe³⁺ for network-forming positions and displacing it into octahedral coordination, as revealed by Mössbauer spectroscopy. This structural redistribution promotes phase separation and triggers the crystallization of pseudobrukite (Fe₂TiO₅) at elevated temperatures. The formation of a protective Ti(OH)₄ surface layer upon alkali exposure enhances chemical resistance, with optimal performance observed at 4.6 mol% TiO₂—reducing mass loss in NaOH and seawater by 13.3% and 25%, respectively, and improving residual tensile strength. However, higher TiO₂ concentrations (≥5 mol%) lead to pseudobrukite crystallization and a narrowed fiber-forming temperature window, rendering continuous fiber drawing unfeasible. The results demonstrate that TiO₂ is a promising, cost-effective dopant for basalt fibers, but its benefits are constrained by a critical solubility threshold and structural trade-offs between durability and processability. Full article

The construction industry, as a major contributor to greenhouse gas emissions, urgently requires sustainable development solutions to achieve the Net Zero Emission Goal. Magnesium oxide (MgO)-based cementitious composites have emerged as promising alternatives due to their ability to reduce environmental impact and their potential to enhance structural integrity. Despite these advantages, limitations such as poor resistance to harsh environmental conditions and concerns over long-term durability continue to restrict their broader application. To better understand these strengths and limitations, this review investigates the influence of MgO; supplementary cementitious materials (SCMs) such as fly ash, silica fume, and rice husk ash. It also examines fibers, including polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), glass, sisal, and cellulose, and their effect on the mechanical and durability properties of MgO-based composites. Mechanical performance is assessed through compressive and tensile strength, while durability is evaluated in terms of porosity, permeability, water absorption, shrinkage (autogenous and drying), and carbonation resistance. Key challenges and future research directions to promote the use of MgO composites in sustainable construction are also identified. Full article

Compared with traditional continuous plant fiber-reinforced thermoplastic composites, their 3D-printed counterparts offer distinct advantages in the rapid fabrication of complex geometries with integrated forming capabilities. However, the impregnation process of continuous plant fiber yarn with thermoplastic resin presents greater technical challenges compared to conventional synthetic fibers (e.g., carbon or glass fibers) typically employed in continuous fiber composites, owing to the yarn’s unique twisted structure. In addition, low molding pressure during 3D printing makes resin impregnation more difficult. To address the impregnation difficulty within plant fiber yarn during 3D printing, we employed two low-viscosity resins, liquid thermoplastic resin (specifically, reactive methyl methacrylate) and thermosetting epoxy resin, to pre-impregnate flax yarns, respectively. A dual-resin prepreg filament is developed for 3D printing of flax fiber-reinforced composites, involving re-coating pre-impregnated flax yarns with polylactic acid. The experimental results indicate that liquid thermoplastic resin-impregnated composites exhibit enhanced mechanical properties, surpassing the epoxy system by 39% in tensile strength and 29% in modulus, attributed to improved impregnation and better interfacial compatibility. This preparation method demonstrates the feasibility of utilizing liquid thermoplastic resin in 3D-printed continuous plant fiber composites, offering a novel approach for producing highly impregnated continuous fiber filaments. Full article

The research investigated the potential of five novel additively manufactured (AM) fiber-reinforced thermoplastic composite (FRTPC) configurations as alternatives for ablative thermal protection system (TPS) applications. The thermal stability and ablative behavior of ten samples developed via fused deposition modeling (FDM) three-dimensional (3D) printing out of fire-retardant thermoplastics were investigated using an in-house oxyacetylene torch bench. All samples featured an innovative internal thermal management architecture with three air chambers. Furthermore, the enhancement of thermal benefits was achieved through several approaches: ceramic coating, mechanical hybridization, or continuous fiber reinforcement. For each configuration, two samples were exposed to flame at 1450 ± 50 °C for 30 s and 60 s, respectively, with the front surface subjected to direct exposure at a distance of 100 mm during the ablation tests. Internal temperatures recorded at two back-side contact points remained below 50 °C, well under the 180 °C maximum allowable back-face temperature for TPS during testing. Continuous reinforced configurations 4 and 5 displayed higher thermal stability the lowest values in terms of thickness, mass loss, and recession rates. Both configurations showed half of the weight losses measured for the other tested configurations, ranging from approximately 5% (30 s) to 10–12% (60 s), confirming the trend observed in the thickness loss measurements. However, continuous glass-reinforced configuration 5 exhibited the lowest weight loss values for both exposure durations, benefiting from its non-combustible nature, low thermal conductivity, and high abrasion resistance intrinsic characteristics. In particular, the Al₂O₃ surface coated configuration 1 showed a mass loss comparable to reinforced configurations, indicating that an enhanced surface coat adhesion could provide a potential benefit. A key outcome of the study was the synergistic effect of the novel air chamber architecture, which reduces thermal conductivity by forming small internal air pockets, combined with the continuous front-wall fiber reinforcement functioning as a thermal and abrasion barrier. This remains a central focus for future research and optimization. Full article

Fiber-reinforced composites (FRCs) have emerged as transformative alternatives to traditional marine construction materials, owing to their superior corrosion resistance, design flexibility, and strength-to-weight ratio. This review comprehensively examines the current state of FRC technologies in marine deck and underwater applications, with a focus on manufacturing methods, durability challenges, and future innovations. Thermoset polymer composites, particularly those with epoxy and vinyl ester matrices, continue to dominate marine applications due to their mechanical robustness and processing maturity. In contrast, thermoplastic composites such as Polyether Ether Ketone (PEEK) and Polyether Ketone Ketone (PEKK) offer advantages in recyclability and hydrothermal performance but are hindered by higher processing costs. The review evaluates the performance of various fiber types, including glass, carbon, basalt, and aramid, highlighting the trade-offs between cost, mechanical properties, and environmental resistance. Manufacturing processes such as vacuum-assisted resin transfer molding (VARTM) and automated fiber placement (AFP) enable efficient production but face limitations in scalability and in-field repair. Key durability concerns include seawater-induced degradation, moisture absorption, interfacial debonding, galvanic corrosion in FRP–metal hybrids, and biofouling. The paper also explores emerging strategies such as self-healing polymers, nano-enhanced coatings, and hybrid fiber architectures that aim to improve long-term reliability. Finally, it outlines future research directions, including the development of smart composites with embedded structural health monitoring (SHM), bio-based resin systems, and standardized certification protocols to support broader industry adoption. This review aims to guide ongoing research and development efforts toward more sustainable, high-performance marine composite systems. 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 investigates the production and characterization of basalt continuous fibers (BCFs) with varying oxide contents (including Na₂O, SiO₂, CaO, TiO₂, and Al₂O₃), derived from modified basalt bulk glasses. The fibers were created through a two-stage process that included the preparation of basalt glasses followed by fiber drawing. A key focus of the research was on evaluating the mechanical properties of BCF after low-temperature treatments. Tensile testing revealed that the maximum tensile strength of the fibers was 1915 MPa at room temperature, which decreased to 1714 MPa at −196 °C, representing a shift of −10.5%. The addition of sodium oxide not only broadened the fiber-forming temperature range but also increased the strength to 2351 MPa. However, significant reductions in strength were observed at cryogenic temperatures, particularly for the Na-rich sample, which experienced a decrease of 32.8%. These findings highlight the importance of optimizing oxide content and minimizing hydroxyl (OH) groups to enhance the performance of basalt fibers in low-temperature applications, positioning them as viable materials for use in extreme environments. Full article

Flying wing Unmanned Aerial Vehicles (UAVs) are an interesting flight configuration, considering its benefits over aerodynamic, structural and added stealth aspects. The existing configurations are thoroughly studied from the literature survey and useful observations with respect to design and analysis are obtained. The proposed design method includes distinct calculations of the UAV and modelling using 3D experience. The created innovative models are simulated with the help of computational fluid dynamics techniques in ANSYS Fluent to obtain the aerodynamic parameters such as forces, pressure and velocity. The optimization process continues to add more desired modifications to the model, to finalize the best design of flying wing frame for the chosen application and mission profile. In total, nine models are developed starting with the base model, then leading to the conventional, advanced and nature inspired configurations such as the falcon and dragonfly models, as it has an added advantage of producing high maneuverability and lift. Following this, fluid structure interaction analysis has been performed for the best performing configurations, resulting in the determination of variations in the structural behavior with the imposition of advanced composite materials, namely, boron, Kevlar, glass and carbon fiber-reinforced polymers. In addition to this, a hybrid material is designed by combining two composites that resulted in superior material performance when imposed. Control dynamic study is performed for the maneuvers planned as per mission profile, to ensure stability during flight. All the resulting parameters obtained are compared with one another to choose the best frame of the flying wing body, along with the optimum material to be utilized for future analysis and development. Full article

With the growing need for lightweight, durable, and high-performance structures, additively manufactured (AM) polymer composite structures have captured significant attention in the engineering community. These structures offer considerable advantages in various dynamic engineering sectors including automotive, aviation, and military. Thus, this investigation emphasizes the numerical analysis of the dynamic properties and vibration control of AM polylactic acid (PLA) composite structures reinforced with continuous glass fibers (CGFR-PLA) and carbon fibers (CCFR-PLA), with 0°–0° and 0°–90° layer orientations. The findings of this numerical study are compared and validated against earlier published experimental results. Initially, the numerical models were created using the Abaqus CAE 2024, replicating the actual experimental models. The numerical bending modal frequency of each numerical model is determined, and the 0°–0° oriented models exhibited considerably higher values compared to the corresponding 0°–90° models. Significant differences were noted between the numerical and experimental values in the higher modes, mainly due to existence of voids and misalignment in the actual models that were not considered in numerical models. Following this, a numerical amplitude frequency response (AFR) analysis was conducted to observe vibration amplitude variations as a function of frequency. The AFR numerical results demonstrated consistent trends with the experimental results despite differences between the absolute values of both scenarios. Afterwards, vibration amplitude control analysis was performed under the influence of a macro fiber composite (MFC) actuator. The findings from both numerical and experimental cases revealed that vibration control was noticeably higher in 0°–0° oriented structures compared to 0°–90° structures. Experimental models demonstrated higher vibration control effectiveness than the corresponding numerical models. Although significant differences between the numerical and experimental vibration response values were observed in each composite structure, the numerical results exhibited consistent trends with the experiments. This discrepancy is attributed to the challenge of capturing all boundary conditions of the experimental scenario and incorporating them into the numerical simulation. Full article