Search Results (5,354)

A lightweight composite that simultaneously exhibits high strength and excellent thermal insulation is of great interest for thermal protection applications. In this study, dimensionally stable needled quartz fiber felt-reinforced phenolic aerogel composites were prepared using vacuum impregnation, sol–gel, and ambient pressure drying. The composites exhibit a multiscale porous structure formed by interconnected nanometer polymer skeletons and micronscale fibers. By regulating the thermoplastic phenolic resin concentration in the precursor solution, the pore structure of the material was refined; the average particle diameter reduced from 99.76 nm to 38.91 nm, and the average pore diameter decreased from 216.79 nm to 49.53 nm. At a phenolic resin concentration of 25%, the composite exhibits outstanding thermal insulation and mechanical properties: a low thermal conductivity of 0.0646 W·m⁻¹·K⁻¹ at room temperature, with a mere 19.5 °C temperature rise on the sample backside after 1800 s heating at 200 °C, and compressive strengths of 7.70 MPa in the XY-direction and 3.87 MPa in the Z-direction (at 10% strain). X-ray micro-CT characterized the internal structural evolution during loading, revealing a failure mechanism dominated by fiber buckling. Theoretical models and experimental data were used to analyze and quantify the contribution rates of gas and solid heat conduction in NQF/PR aerogel composites, with solid conduction accounting for over 80%. Combined with microstructural evolution, the mechanism for the high thermal insulation efficiency of NQF/PR aerogel composites was elucidated. This study prepared NQF/PR aerogel composites with promising application potential. By systematically evaluating their compressive behavior and quantifying the respective contributions of gas and solid conduction, this work provides a methodological framework to guide the rational design of similar aerogel composites. Full article

The widespread deployment of service robots in domestic and professional environments demands structural solutions that simultaneously achieve high stiffness, low mass, and intrinsic safety. Traditional metallic structural designs face a fundamental physical conflict: achieving high stiffness typically results in excessive mass, which compromises operational safety and battery life. To solve this, this paper presents a critical review of an integrated lightweighting strategy combining material selection, structural design, and additive manufacturing for Carbon-Fiber-Reinforced Polymer (CFRP) service robot structures. Three critical findings are presented. First, specific stiffness is established as the governing criterion for material selection, providing a unified basis to resolve the stiffness–mass conflict. Second, among current 3D printing techniques, Fused Deposition Modeling (FDM) with continuous-fiber reinforcement overcomes the geometric constraints of traditional molding, enabling the fabrication of complex, customized structures. Third, to realize the full potential of 3D-printed CFRP, we highlight the importance of integrating material properties (anisotropy), structural design (topology optimization), and manufacturing processes (path planning) into a concurrent framework. This integrated approach is validated through a collaborative robotic-arm case study, achieving a 30% reduction in structural mass. Full article

The growing interest in bio-based and biodegradable polymer composites reinforced with agricultural waste reflects global efforts to reduce dependence on fossil resources and improve the sustainability of materials. However, biocomposites are not necessarily more sustainable, and their environmental performance requires careful life cycle assessment (LCA). This review critically analyses recent LCA studies of biodegradable biocomposites reinforced with agricultural waste, focusing on methodological choices, data quality, results and limitations. A systematic literature review was conducted using the Scopus database, focusing on studies from the last five years. Selected studies were examined using a structure consistent with ISO 14040, with defined data extraction categories and key questions. The analysis shows that although biocomposites often demonstrate advantages in terms of climate change and fossil resource depletion compared to traditional materials, the results vary significantly depending on the definition of the functional unit, geographical context, processing pathways, and data assumptions. Limitations include reliance on laboratory data, uncertainties, incomplete system boundaries, inconsistent allocation methods, and limited end-of-life (EoL) modelling. Overall, the review highlights the need for improved data quality, performance-based functional units, geographically representative inventories, and more standardised LCA practices to ensure meaningful comparisons and support the sustainable development of biocomposites. 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

This study investigates the degradation mechanisms of glass-fibre- and carbon-fibre-reinforced polymer (GFRP and CFRP, respectively) composites fabricated either with epoxy, vinyl-ester, or bio-epoxy resins under a hygrothermal environment. Composite laminates were manufactured using the vacuum-assisted resin infusion technique and exposed to high moisture and elevated in-service temperatures of 23 °C (room temperature), 40 °C and 60 °C for up to 125 days. Changes in the physical, microstructural, chemical and mechanical properties were then assessed. CFRP and GFRP composites showed distinct differences in their hygrothermal ageing depending on the resin system used in the manufacturing. CFRP composites consistently demonstrated higher stability than GFRP composites. Epoxy resin exhibited high resistance to water absorption and hydrolysis under hygrothermal exposure. After 125 days at 60 °C, glass/epoxy (GE) and carbon/epoxy (CE) composites retained 79.0% and 72.1% of their tensile strength and 46.9% and 72.6% of their interlaminar shear strength (ILSS), respectively. Vinyl-ester composites showed high mechanical retention, with glass/vinyl-ester (GV) and carbon/vinyl-ester (CV) retaining 70.8% and 83.1% of tensile strength and 67.5% and 80.3% of ILSS, respectively. Despite this mechanical stability, evidence of hydrolysis indicated ongoing chemical degradation of the vinyl-ester resin under prolonged hygrothermal exposure. In contrast, bio-epoxy composites exhibited relatively low overall durability. Glass/bio-epoxy (GB) retained 126.5% tensile strength and 68.8% ILSS, whereas carbon/bio-epoxy retained 61.0% tensile strength and 44.3% ILSS after 125 days at 60 °C. Overall, fibre and resin types were found to have a significant effect on the hygrothermal ageing of polymer composites. Full article

Carbon fiber-reinforced polymer (CFRP) has been widely used in various fields due to its significant advantages. However, research on their pyrolysis and combustion behavior under fire conditions, which directly affects structural integrity and safety, remains insufficient. To challenge this issue, thermogravimetric analysis was employed to investigate the pyrolysis characteristics of the CFRP in both air and nitrogen atmospheres at heating rates of 20–40 °C/min with relevant pyrolysis kinetic parameters calculated using the Kissinger method. Fourier-transform infrared (FTIR) spectrometer was utilized to analyze pyrolytic gas species and concentrations at 40 °C/min in nitrogen atmosphere. Cone calorimeter tests at 50 kW/m² were conducted to obtain combustion characteristic parameters. Based on atomic conservation and oxygen-consumption principles, the equivalent molecular formula (CH_5.787O_0.541) of the epoxy resin pyrolysis gas and its combustion reaction equation were derived through reverse deduction. The heating, pyrolysis, and combustion processes of the CFRP (cone calorimetry specimen) were numerically simulated using Fire Dynamics Simulator (FDS). The predicted heat release rate, mass loss rate, and gas production rate showed good agreement with experimental results. Full article

Carbon Fiber Reinforced Polymer (CFRP)-strengthened steel plate systems demonstrate remarkable advantages in civil engineering structural rehabilitation, with their overall performance critically reliant on the interfacial bond behavior between CFRP and steel plates. This paper systematically reviews the typical failure modes, key factors influencing interfacial bond performance, and corresponding testing methodologies. Research indicates that interfacial shear stress dominates the failure process. Enhanced strengthening efficacy can be achieved by employing CFRP plates with optimized adhesive layer thickness (recommended 0.5–1.5 mm) and double-sided bonding configurations. Concurrently, substrate surface treatment and environmental factors (temperature–humidity, corrosion, etc.) significantly affect interfacial bond performance. Current research primarily focuses on the single-factor and strength failure performance of standard specimens, lacking a systematic understanding of the long-term durability and failure mechanisms of complex structures under multi-field coupling effects. This review further summarizes the distinctive features and application scenarios of innovative strengthening systems—including prestressed, unbonded, and shape memory alloy composite systems—to provide guidance for engineering selection and standardized design. Full article

Background: Biomimetic principles have gained significant traction in contemporary dentistry. For this reason, biomimetic restorative materials have been designed with the goal of recreating the mechanical and optical behavior of natural dental tissues. However, the level to which these materials resemble the properties of enamel and dentin remains uncertain. Methods: A systematic review was carried out according to the PRISMA guidelines. Electronic searches were performed in PubMed and Scopus to identify in vitro studies examining restorative materials promoted as biomimetic. These included polymer-infiltrated ceramic network (PICN) materials, resin matrix systems (RMS), and short fiber-reinforced composites (SFRCs). Natural enamel and dentin served as reference comparators. Target outcomes included mechanical properties (flexural strength, fracture toughness, Vickers hardness, elastic modulus) and optical properties (translucency parameter and color matching). Results: PICN achieved hardness and translucency values closely resembling the natural enamel, while RMS approached the mechanical properties of natural dentin. SFRC showed high fracture resistance, comparative to dentin. Conclusions: Current biomimetic restorative materials exhibit promising mechanical and optical performance. Nevertheless, no single material fully reproduces the multifaceted behavior of natural dental tissues. Further studies with standardized testing protocols are needed to determine their clinical relevance. Full article

Two types of basalt fiber-reinforced polymer (BFRP) anchor cables—a Tension-concentrated anchor cable (TCAC) and a Pressure-dispersed anchor cable (PDAC)—were developed through structural modification of the rod body and implemented for reinforcing fractured rock masses on highway tunnel slopes in western Henan Province, China. The feasibility of replacing conventional steel rods with BFRP bars and the corresponding anchorage mechanisms were investigated. The experimental results indicate that the axial force distribution differs markedly between the two anchors. The TCAC exhibits a decreasing axial force with depth, forming a concave distribution under low load and a convex distribution under high load, with the force approaching zero beyond 100 cm. In contrast, the PDAC displays a relatively uniform axial force that sharply decreases near the bearing plate, and, under increasing load, the axial force at the anchorage end tends to rise; Both anchors demonstrate single-peak interfacial shear stress distributions. For the TCAC, the peak progressively shifts toward deeper regions with increasing load, whereas the peak of the PDAC consistently appears near the bearing plate, with only its magnitude increasing. Stability analysis using GEO5 software reveals that the slope safety factor increases from 1.32 (without anchors) to 1.36 (with anchors), thus satisfying the design requirements. The results reveal the different anchoring mechanisms of tension-concentrated anchor cables and pressure-dispersed anchor cables, providing practical guidance for their selection and application in slope stabilization engineering. Full article

Carbon fibre reinforced polymers (CFRPs) are increasingly used in biomedical and safety-critical applications, where embedded and real-time non-destructive testing (NDT) is essential to ensure structural integrity. This paper presents a cost-effective, AI-assisted thermographic inspection system designed from an embedded electronics and circuit-level perspective. The proposed platform integrates a long-wave infrared (LWIR) sensor, dedicated signal conditioning and power management circuits, and a Raspberry Pi-based processing unit within a unified hardware–software co-design approach. Infrared data acquired under surface heating conditions are processed on-board using a convolutional neural network based on a U-Net architecture, enabling automatic localisation and classification of subsurface defects in CFRP samples. Particular attention is devoted to embedded design constraints, including sensor interfacing, acquisition timing, end-to-end latency, and real-time processing scalability. Experimental results confirm the feasibility of real-time surface heat assessment and the robustness of the proposed architecture in detecting delaminations and voids. The presented system contributes to the development of intelligent embedded inspection electronics and provides a reference design for edge AI-enabled NDT systems in industrial and biomedical applications. Full article

The 4D printing of thermo-responsive shape-memory multicomponent polymer composites, which possess the ability to change shape by exposure to heat, has attracted much attention in recent years because of their scientific and technological significance. In the present study, we investigate shape memory performance of a polylactic acid-polycaprolactone-graphene nanocomposite activated directly by increasing the environmental temperature and indirectly, by Joule heating. The incorporation of graphene within the shape-memory biopolymer blend allowed formation of a programmable conduction path, whose electric properties are intimately coupled to thermo-mechanical processes. Advanced rheological, thermal, and thermo-mechanical properties were evaluated and related to the structure of nanocomposite. The electrically and thermally stimulated shape memory and self-healing behavior of the nanocomposite based on polycaprolactone/poly(lactic) acid blend reinforced with graphene nanoplatelets (PCL/PLA/GNP) were investigated. The shape memory tests revealed a good reversibility of 76% between the temporary and permanent states of the samples bent to 180 degrees and a high healing efficiency of 96% if stimulated by Joule heating. The highly electroactive nanocomposite demonstrated a great potential for 4D-printing of objects with complex structures, shapes, and electrically-stimulated shape-memory and self-healing functions. The nanocomposite is biodegradable, recyclable, and reusable, which may reduce the carbon footprint of the rapidly developing additive technology. Full article

The hyperloop transportation system is a promising ultra-high-speed mobility solution operating in a reduced-pressure environment, where pod performance is governed by the coupled behaviour of structural integrity, aerodynamics, and electromagnetic propulsion. This paper presents the design, numerical analysis, and performance evaluation of a lightweight hyperloop pod equipped with a linear induction motor (LIM)-based propulsion and electromagnetic stabilisation system. The pod chassis was fabricated using Carbon Fibre-Reinforced Polymer (CFRP) and Aluminium 6061-T6, achieving a significant weight reduction while maintaining structural safety. Finite Element Analysis reveals a maximum von Mises stress of 82 MPa, which is well below the material yield strength, and a maximum deformation of 0.64 mm under worst-case loading conditions. Modal analysis indicates the first natural frequency at 47.6 Hz, ensuring sufficient separation from operational excitation frequencies. Computational Fluid Dynamics analysis conducted inside a rectangular tube shows a drag coefficient reduction of approximately 18% compared to a baseline blunt design, with stable velocity distribution and no flow choking at operating speeds. The optimised nose geometry enables rapid acceleration, achieving 25 km/h within 1.1 s in prototype testing. The LIM analysis demonstrates a peak thrust of 1.85 kN at an optimal slip range of 6–8%, with operating currents between 35 and 55A and power consumption of 18–25 kW. Thermal analysis confirms a maximum stator temperature of 78 °C, remaining within safe operating limits. The integrated numerical and experimental results confirm the feasibility, efficiency, and stability of the proposed hyperloop pod design. Full article

Composites based on rPE and OPEFB waste are considered sustainable materials. However, their performance is limited by hydrophobic–hydrophilic incompatibility, which weakens interfacial adhesion. This study investigated the atmospheric-pressure air plasma treatment of rPE to enhance its compatibility with OPEFB fibers and evaluated its role as a compatibilizer. Atmospheric plasma treatment for 120 s introduced oxygen-containing groups onto the rPE surface, as evidenced by C-O and OH peaks in the FTIR spectra and the higher O/C ratio in the XPS analysis. Consequently, the water contact angle decreased, reducing the difference in surface tension between rPE and OPEFB from 45.61% to 7.80%. Composites containing 20 wt.% OPEFB were fabricated by varying the proportion of untreated rPE with p-rPE. All p-rPE-based composites exhibited fewer interfacial voids than untreated rPE composites, indicating improved fiber–matrix adhesion. The tensile strength and elastic modulus increased with the p-rPE content, whereas the elongation at break remained higher than that of the untreated composite. Therefore, p-rPE shows potential as a compatibilizer, enabling agricultural and plastic waste value enhancement. Full article

This study explores the use of banana pseudostem fibers from Córdoba, Colombia, as reinforcement in polymer composites manufactured through vacuum-assisted resin transfer molding (VARTM). The fibers were decorticated, oven-dried at 40 °C, and subjected to mercerization and epoxy coating treatments. Plain-weave fabrics were produced using continuous yarns composed of 10 and 15 fibers, both treated and untreated. Experimental analyses included pull-out tests, thermogravimetric analysis, fourier-transform infrared spectroscopy, winding speed, surface twist angle, and tensile strength tests for yarns, as well as tensile load, adhesion, and permeability tests for fabrics and tensile and flexural strength tests for composites. Treated yarns exhibited a slight increase in diameter and a lower extraction (25%) compared to untreated yarns (33%). Although treated fabrics showed enhanced permeability and improved resin infiltration, untreated fabrics demonstrated superior mechanical performance, with a tensile load of 2.33 kN in comparison to 1.37 kN for treated yarns. The highest tensile strength of 76.56 MPa was achieved in composites reinforced with three layers of untreated fabric, while the best flexural strength of 86.93 MPa was observed in single-layer composites with the same configuration. These results emphasize the potential of untreated banana fiber fabrics as promising reinforcement in structural composite applications. Full article

Silica aerogel microspheres demonstrate tremendous potential as fillers for diverse materials across various fields. Enhancing the strength of silica aerogel microspheres is therefore crucial for their practical applications. This study aims to develop novel hydrophobic polymer-reinforced silica aerogel microspheres using water glass as the precursor, hexamethyldisilazane (HMDS) as the modifier, and styrene as the crosslinking agent, with further strength enhancement achieved through short-term thermal post-treatment. The effects of varying polystyrene coating levels, crosslinker dosage, and short-term heat treatment on the structure and properties of silica aerogel were investigated. The optimized silica aerogel microspheres (Sample A-6) exhibited a specific surface area of 604.8 m²/g and a thermal conductivity of 0.030 W·m⁻¹·K⁻¹ and demonstrated excellent hydrophobicity and mechanical stability. Full article