Search Results (642)

Eucommia ulmoides gum (EUG), a sustainable plant-derived natural polymer, was functionalized via three distinct routes, including vulcanization, epoxidation, and hydroxylation to yield vulcanized (VEUG), epoxidized (EEUG), and hydroxylated EUG (HEUG), respectively. We systematically characterized the effects of modification route and degree on the chemical structure, crystallization behavior, thermal stability, hydrophilicity, and mechanical properties of functionalized EUG and further evaluated the high/low-temperature performance, microstructure, and mechanical properties of the corresponding modified asphalt binders (VEMA, EEMA, HEMA) as a function of modifier type and loading. For VEUG, C-S cross-linking networks formed during vulcanization suppress EUG crystallization, enabling a rigid-plastic to elastic transition, while high-temperature cleavage of C-S bonds reduces its initial thermal stability. For EEUG, epoxidation breaks C=C double bonds and introduces epoxy groups to strengthen intermolecular interactions; subsequent ring-opening grafting of hydroxyl groups onto EEUG yields HEUG, which forms additional cross-links via dynamic hydrogen bonds. Increasing modification degree for both EEUG and HEUG reduces their number- and weight-average molecular weights with narrower distribution, diminishes crystallinity, enhances thermal stability and hydrophilicity, and drives a rigid-plastic to elastic transition, characterized by decreased strength (0.65 MPa < σ_HEUG < σ_EEUG < 10.18 MPa) and markedly improved ductility (143.6% < ε_EEUG < 262.0%, 679.9% < ε_HEUG < 1360.3%). In asphalt binders, VEUG’s cross-linked network endows VEMA with refined more abundant bee-like microstructures, drastically boosting high- and low-temperature performance: relative to pristine EUG-modified asphalt (EUGMA), VEMA’s DMT modulus decreases by 94%, and adhesion increases by 87%. EEMA forms covalent bonds with polar asphalt components via epoxy groups, while HEMA constructs a hydrogen-bonded cross-linked network; both effectively inhibit asphaltene aggregation. With increasing modifier loading, EEMA and HEMA exhibit increased modulus, reduced adhesion, and gradually improved high- and low-temperature performance, except for the non-significant high-temperature enhancement of HEMA at higher loadings. Full article

The limited availability of high-quality timber and the increasing demand for wood-based panels have encouraged the exploration of alternative and sustainable lignocellulosic resources. Rattan waste is abundant in Indonesia; however, its low mechanical strength and limited durability restrict its direct application in composite materials. This study investigated the effect of furfuryl alcohol (FA) modification and different adhesive systems on the performance of rattan-based particleboard. Rattan particles were immersed in FA for 24 h and used to produce particleboards (300 × 300 × 10 mm) bonded with phenol formaldehyde (PF), melamine formaldehyde (MF), and urea formaldehyde (UF) adhesives at a resin content of 12%. The boards were manufactured under controlled hot pressing conditions and conditioned for 14 days prior to testing. Furfurylation significantly improved dimensional stability by reducing moisture content, water absorption, thickness swelling, and leaching, with anti-swelling efficiency values ranging from 43.25% to 71.06%. Some selected mechanical properties, including internal bonding strength, hardness, and screw holding power, were also enhanced. However, the modification showed limited influence on the modulus of elasticity and, in some cases, reduced the modulus of rupture. Among the adhesive systems, MF-bonded boards exhibited the most balanced mechanical performance. Furfurylation also produced darker and more uniform board surfaces. These findings indicate that furfurylated rattan particleboards are suitable for non-structural and decorative applications. Full article

This study evaluates the performance of foamed geopolymer concrete (FGC) incorporating rigid polyurethane (PU) waste as a partial sand replacement and aluminum powder (AP, 1%) as a foaming agent. The mixtures were based on metakaolin, fly ash, and silica fume. Fresh and hardened properties were assessed, including workability, setting time, density, compressive strength, flexural strength, splitting tensile strength, elastic modulus, water absorption, porosity, gas permeability, and chloride ion penetration. Microstructural characteristics were examined using scanning electron microscopy (SEM). The results show that moderate PU incorporation significantly enhances mechanical performance. The optimal mixture (PU30) achieved a compressive strength of 47.25 MPa at 180 days, representing a 15.6% increase compared to the control. Flexural and splitting tensile strengths improved by 19.9% and 16.7%, respectively, while the elastic modulus increased by 33.8% to 0.95 GPa. These improvements are attributed to enhanced particle packing and more efficient stress transfer within the matrix. In contrast, higher PU contents (>30%) reduced mechanical performance due to increased total porosity and weakened interfacial bonding. Durability-related properties indicated that mixtures PU20–PU30 exhibited reduced permeability and optimized pore structure, characterized by lower pore connectivity. SEM observations confirmed a denser matrix with uniformly distributed pores at optimal PU levels. Additionally, the integration of Random Forest regression with GLCM-based texture analysis demonstrated strong capability in predicting mechanical properties from SEM images. Overall, the combined use of PU waste and AP enables the production of lightweight, structurally efficient, and sustainable FGC with improved mechanical and durability performance. Full article

Fused deposition modeling (FDM)-based three-dimensional (3D) fabrication offers a viable approach to manufacturing highly customized carbon fiber-reinforced polyether ether ketone (CFR-PEEK) components with complex geometries. However, the mechanical properties and surface roughness of FDM-fabricated parts are strongly influenced by processing parameters, particularly layer thickness. This study investigates the influence of layer thickness (0.1 mm and 0.2 mm) on the surface roughness, crystallinity, mechanical properties, and morphological characteristics of FDM-printed 10% CFR-PEEK specimens. The specimens were characterized using mechanical testing, differential scanning calorimetry (DSC), confocal laser microscopy, X-ray micro-computed tomography (µCT), and scanning electron microscopy (SEM). The results show that specimens printed with a 0.2 mm layer thickness exhibit higher crystallinity and ball indentation hardness while also showing increased surface roughness and porosity, with µCT analysis revealing larger and more spatially clustered voids near the sub-perimeter regions. In contrast, specimens printed with a 0.1 mm layer thickness demonstrate higher tensile strength, elastic modulus, elongation at break, and compressive stress. SEM fractography further indicates improved interlayer bonding and a relatively cohesive fracture surface in specimens printed with a 0.1 mm layer thickness. These findings demonstrate clear layer-thickness-dependent processing–structure–property relationships in FDM-printed CFR-PEEK composites and provide guidance for optimizing printing parameters to achieve improved mechanical performance. Full article

To further improve the mechanical properties of shotcrete in coal mine roadways, end-hooked steel fibers and chopped basalt fibers were selected. Based on the optimal mix ratios identified in existing research, steel–basalt hybrid fiber shotcrete (SBFC) specimens were prepared. Dynamic impact tests under different impact loads and various hybrid fiber contents were conducted using an SHPB. The microstructure was characterized using SEM and XRD. The results show that the dynamic compressive stress–strain curve of steel–basalt hybrid fiber shotcrete can be classified as elastic deformation stage, plastic yield stage, and post-peak failure stage. The incorporation of hybrid fibers reduces the elastic deformation and plastic yield stage, and the post-peak failure stage under active confining pressure shows elastic aftereffect characteristics. The dynamic compressive strength, dynamic elastic modulus, and deformation modulus increase with the increase in impact pressure and fiber content. When there is no confining pressure, the maximum dynamic compressive strength, dynamic elastic modulus, and modulus of deformation of SBFC4 reached 53.1 ± 2.2 MPa, 4.51 ± 0.3 GPa, and 2.55 ± 0.1 GPa, respectively, representing increases of 37.20%, 264.01%, and 59.37% compared with the control group. The dynamic compressive strength increases with the average strain rate, demonstrating a favorable strain rate effect. The energy–time history curves can be roughly divided into initial, growth, and stable stages. Under the same impact load conditions, as the fiber content gradually increases, the incident energy, dissipated energy, and energy utilization rate of the specimens all show a gradual upward trend. SEM and XRD results show that steel fibers and basalt fibers maintain good bonding with the cement matrix, contribute to the formation of gel and crystalline products within the specimens, effectively delay the initiation and propagation of cracks, and thereby improve the mechanical properties of the concrete specimens. Full article

This study addresses the urgent need for sustainable alternatives to single-use plastics by developing biodegradable composites from peach and apple processing waste employing hot compression molding. Utilizing a definitive screening design, the impact of the process variables, including recipe composition, grinding size, pressure, temperature, and holding time, on the physical (including water resistance) and mechanical properties of the composites was systematically evaluated. Physicochemical and thermal analyses of the dried by-products indicated that processing temperatures below 150 °C prevent the degradation of lignocellulosic constituents. The results demonstrated that increasing both the molding pressure and holding time decreased the composite thickness, while enhancing the stiffness and flexural strength, with modulus of elasticity values exceeding 1000 MPa under optimal conditions. Higher molding temperatures reduced water absorption and diffusivity, particularly in lignin-rich composites, by promoting lignin softening and particle consolidation, resulting in denser structures with limited moisture transport. Biodegradability was assessed through soil burial tests over 200 days, revealing a weight loss ranging from 54.2% to 90.7% among samples, with apple-based composites exhibiting greater degradation compared to peach-based ones. Overall, the study highlights the development of a “green composite” formulation inspired by biomimetic principles, exploiting the natural self-bonding capacity of lignocellulosic biomass, where two different-in-composition biowastes are combined to produce a plastic-free composite material with possible applications in the foodservice industry. Full article

Conventional adhesives for plywood are mostly derived from petroleum-based materials and commonly suffer from formaldehyde emission, posing threats to the environment and human health. In this study, a renewable resource, Xanthoceras sorbifolium Bunge oil, was used as the raw material. A high-performance bio-based adhesive was successfully prepared by synthesizing Xanthoceras sorbifolium Bunge oil dimethacrylate (MXOEA) as a reactive diluent, blending it with acrylated epoxy Xanthoceras sorbifolium Bunge oil (AEXO), and introducing 2-isocyanatoethyl methacrylate (IEM) to enhance crosslinking. The effects of the MXOEA/AEXO ratio and the IEM addition level on the properties of the adhesive and the resulting plywood were systematically investigated. The results showed that when the mass ratio of AEXO to MXOEA was 3:7, and the IEM content was 10%, the adhesive exhibited the best bonding performance: the resulting plywood achieved a modulus of rupture of 68.85 MPa, a modulus of elasticity of 8086 MPa, and dry and wet bonding strengths of 3.21 MPa and 2.32 MPa, respectively. Mechanistic analysis indicated that the introduction of IEM moderately reduced the viscosity of the adhesive system. Meanwhile, the isocyanate groups in IEM reacted with the hydroxyl groups on the wood surface, forming a chemical crosslinking structure at the adhesive-wood interface, which is considered one of the reasons for the improved mechanical properties of the plywood. This study provides a formaldehyde-free, high-performance bio-based adhesive derived from Xanthoceras sorbifolium Bunge oil for the field of wood-based composites. Full article

Dielectric elastomer actuators (DEAs) are attracting much attention as candidates for next-generation flexible actuation. Among various DE matrices, polyacrylate rubber (AR) is especially promising owing to their intrinsically high dielectric constant (ε_r) and good mechanical performance. In particular, its mechanical behavior is close to that of porcine bladder tissue, making it a potentially good material for soft biomedical actuators for artificial bladder constructs. To achieve high actuated strain, which requires high ε_r, high breakdown strength, and low elastic modulus, an AR DE composite filled with silane-functionalized TiO₂ was fabricated, exhibiting good electromechanical performance enabled by strengthened interfacial polarization. To improve compatibility between TiO₂ and AR matrix, TiO₂ was preferentially modified with a silane coupling agent (CA) that features a double bond as its functional group, which can be introduced on TiO₂ surface and participate in vulcanization with AR, thereby forming co-crosslinking bridges that strengthen interfacial bonding, improve filler dispersion, and increase interfacial polarizability within the matrix. As a result, at relatively low filler loadings, the composite exhibits a significantly increased ε_r, while maintaining low modulus, low dielectric loss and high elasticity. The 10 CA@TiO₂/AR composite exhibits a maximal actuated strain of 7.9% at 31.9 kV/mm without pre-stretch, which is 1.48 times that of pure AR and 1.32 times that of the 10 TiO₂/AR composite. Full article

Resin and interlayer properties play significant roles in the resistance to impact of fibre-reinforced polymer composites (FRPCs). To investigate the contribution of each factor within the coupled variables to the impact resistance ability of FRPCs, in this work, waterborne polyurethane (WPU) with different tensile elastic modulus, tear strength and bonding strength was obtained. To systematically evaluate the impact resistance and failure mechanisms of the composite materials under varying external loads, impact resistance tests, numerical simulations, and relative weight analysis were conducted. The relative weight analysis results quantified the individual contributions of these three factors to the overall energy absorption capacity across diverse loading conditions. The results indicated that with the increasing rate of the external loading, the resin modulus consistently contributed more significantly to energy absorption than tear strength of resin and interlayer strength, reaching up to 44.3%. In ballistic penetration tests, with the increase in resin modulus, the ballistic performance of PE/WPU laminates demonstrated an S-shaped downward trend. Composites prepared with more rigid matrix could lead to unsatisfactory interlayer damage. A more robust structure could result in fibre pull-out and breakage to a greater extent at the point of forced impact while less in the secondary affected area, presenting comparatively lower impact resistant performance. Full article

To investigate the deterioration law of the mechanical properties of PVA-fiber-reinforced rubber concrete under the combined action of high-temperature and salt erosion, physical index tests, dynamic mechanical property experiments, and microstructural morphology observations were carried out on specimens subjected to different temperatures (ambient temperature, 100 °C, 300 °C) and various solution attacks (water, 5% NaCl, 5% Na₂SO₄, and 5% NaCl + 5% Na₂SO₄ mixture). The results show that, after exposure to 300 °C, the PVA fibers melt and the rubber pyrolyzes, since this temperature exceeds their melting points. A residual pore network is formed inside the matrix, and the damage degree of ultrasonic pulse velocity is about 2.3 times that of the 100 °C group. Although salt solution and its crystallization products can physically fill the pores and cause a partial recovery of pulse velocity, this change is mainly due to the alteration of the pore medium and does not represent a substantial restoration of the microstructure. The effects of different salt solutions on dynamic mechanical properties vary significantly: Sulfate erosion improves the dynamic performance significantly at ambient temperature by forming gypsum and ettringite to fill pores, but this strengthening effect disappears after 300 °C. Sodium chloride attack generates Friedel’s salt and consumes C₃A, leading to general strength deterioration. In composite salt erosion, the competitive and synergistic effects of Cl⁻ and SO₄²⁻ destabilize erosion products and weaken interfacial bonding, resulting in consistent decreases in dynamic compressive strength and elastic modulus under all temperatures and impact pressures. The strength reduction reaches 66.2% after 300 °C. Microscopic analysis confirms that composite salt erosion leads to the dissolution of ettringite and loose structure, which verifies the synergistic deterioration law of macroscopic properties. This study systematically reveals the damage evolution mechanism of PVA-fiber-reinforced rubber concrete under the coupled action of high-temperature and salt erosion, and provides a theoretical basis for the dynamic bearing capacity evaluation and durability design of concrete structures in such coupled environments. Full article

This study evaluated eleven resin cements used as core build-up materials by examining the following properties: (a) push-out force between root dentin and the fiber post; (b) pull-out force between the fiber post and the core build-up material; (c) shear bond strength of the resin cement to root dentin; (d) flexural strength of the resin cement; and (e) flexural modulus of elasticity of the resin cement. The purpose of this investigation was to clarify the relationships between recently available universal adhesives, core build-up materials, resin cements, and fiber posts. All experiments were performed at two evaluation periods: after 1 day of water storage (Base) and after 20,000 thermocycles (TC 20k). For the push-out test, simulated post spaces were prepared in single-rooted human premolars. The specimens were sectioned perpendicular to the long axis into 2 mm-thick slices and then subjected to push-out testing to assess the bond strength of the dentin–resin cement–fiber post complex. No significant differences in bonding performance were found between Base and TC 20k. These findings suggest that universal adhesives used for pretreatment of multiple substrates in fiber post cementation can provide not only strong but also durable adhesion over time. Full article

This study investigates the interplay between Portland cement strength class (32.5, 42.5, and 52.5) and fiber/cement ratio (ranging from 1/2 to 1/5 by weight) to optimize the physical-mechanical and thermal performance of cement-bonded fiberboards. The experimental data revealed a distinct trade-off: while reducing the fiber content towards a 1/5 ratio significantly improved flexural strength and dimensional stability through matrix densification, it inevitably compromised thermal insulation. Among the binders evaluated, the 42.5 strength class emerged as the most effective option, outperforming the 32.5 class and, notably, offering a more balanced profile than the 52.5 class. The highest stiffness was recorded with the 42.5 cement at a 1/5 ratio (modulus of elasticity (MOE): 5902 ± 532 N/mm²; modulus of rupture (MOR): 12.49 ± 0.6 N/mm²), yielding performance metrics comparable to the 1/4 ratio (MOR: 12.78 N/mm²). Furthermore, this formulation demonstrated superior moisture resistance, achieving water absorption (WA) values as low as 18.9%. Thermal conductivity (TC) measurements at 20 °C confirmed that while fiber-rich mixtures (1/2 ratio) favored insulation, the 42.5 cement at a 1/4 ratio maintained a competitive conductivity value (λ = 0.1625 W/mK), lower than that of the 52.5 grade, thereby striking a critical balance between structural integrity and thermal efficiency. Statistical analyses (Two-way ANOVA, p < 0.05) corroborated the significant influence of both cement type and mix ratio. Microstructural insights from Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) suggest that the superior performance of the 42.5 cement is associated with optimized hydration kinetics and a well-graded particle size distribution (D50 = 14.80 µm), which together facilitated effective fiber encapsulation. Full article

In this study, the flexural behavior of notched steel beams retrofitted with CFRP is investigated. Two series of tests, including W200 × 22 and W14” wide-flange notched beams rehabilitated with externally bonded (EB) CFRP are evaluated under static loading. The W200 × 22 beams were received directly from a factory, whereas the W14” wide-flange beams were extracted from the Original Champlain Bridge after roughly 60 years in service. The parameters considered include the CFRP elastic modulus, CFRP configuration, notch depth, anchorage system, and adhesive type. The effect of the CFRP elastic modulus on the rehabilitation technique is examined by using Normal Modulus (NM) and Ultra-High Modulus (UHM) CFRP with approximately the same tensile capacity. Failure modes, load–deflection behavior, strain distributions along the CFRPs, and Crack Mouth Opening Displacement (CMOD) are thoroughly discussed in this study. The results reveal that both UHM and NM CFRP significantly enhance the load-carrying capacity. However, specimens retrofitted with UHM CFRP exhibit a brittle behavior, whereas those strengthened with NM CFRP show a more ductile behavior. Full article

Background/Objective: Resin-based composite (RBC) gained wide popularity in dentistry due to its excellent biocompatibility, superior aesthetics, and good bonding to enamel and dentine. However, they have several shortcomings, including mechanical insufficiency and shrinkage tendency. Many researchers have utilized nanoparticles (NPs) as a reinforcing filler for RBCs. This article focused on assessing the impact of three different nanoparticles, ZrO₂, TiO_2, and SiO_2, with concentrations of 3 wt% and 7 wt%, on the elastic modulus (E) and fracture toughness (K_IC) of one commercial light-activated dental resin composite. Methods: 140 rectangular specimens were constructed according to ISO 4049 with dimensions (25 × 2 × 5 ± 0.03 mm) and (25 × 2 × 2 ± 0.03 mm) for fracture toughness and elastic modulus, respectively. Specimens were categorized into four main groups based on nanofiller types. Control: plain without filler (CC) and three modified ones with ZrO₂ (ZC), TiO₂ (TC), and SiO₂ (SC). Furthermore, modified groups were divided into two subgroups according to nanofiller concentration, 3 and 7 wt% (ZC3, ZC7, TC3, TC7, SC3, and SC7), n = 10. Mechanical testing for fracture toughness was completed using a single-edge notched beam, while a three-point bending test was used for elastic modulus. Analysis of data was based on two-way ANOVA and Bonferroni post hoc (α = 0.05). Results: ZrO₂ provided the most substantial improvement in both E and K_IC, with the optimal performance observed at 3 wt% for stiffness and 7 wt% for toughness. TiO₂ groups also enhanced these properties at both concentrations; however, the gains were less pronounced compared to ZrO₂. SiO₂ improved mechanical performance at 3 wt%, but a higher loading of 7 wt% resulted in reduced values. Conclusions: Resin-based composite modified with 3 wt% of NPs tends to possess higher fracture toughness and modulus of elasticity. Fracture toughness enhancement was concentration-dependent with ZrO₂ NPs, where the best result was obtained with 7 wt%. Nanoparticle-reinforced composite, particularly ZrO₂, may be suitable for prosthodontic applications. Full article

This research developed an active food packaging system featuring a tailored controlled-release mechanism. The system was fabricated using temperature-responsive poly(N-vinylcaprolactam) (PNVCL) nanofibers with a core-shell architecture. The resulting film incorporated cinnamon essential oil (CEO) as a natural preservative within a composite structure consisting of PNVCL, polyvinyl alcohol (PVA), polylactic acid (PLA) and CEO. The nanofiber film obtained via coaxial electrospinning exhibited a sandwich-like structure; the obtained fiber membrane is abbreviated as PP/PC, and the number represents the essential oil content. The PP/PC-4 composite demonstrated exceptional physical barrier properties and mechanical strength, with a WVP as high as 5.74 ± 0.37 (g·mm)/(m²·h·kPa). It also achieved the highest maximum force, elastic modulus, and tensile strength, recorded at 3.08 ± 0.31 N, 228.86 ± 15.46 MPa, and 5.26 ± 0.72 MPa, respectively, along with superior thermal stability. FTIR spectroscopy confirmed molecular interactions, specifically through C–H bonding, between the PLA/CEO core and the PNVCL shell layers. After 5 d of storage at 40 °C, the PP/PC-4 film retained substantial antibacterial efficacy. The antifungal efficacy demonstrated the highest performance, exceeding the control group by 32%. The weight loss rate on day four was 28%, significantly lower than other groups, while the hardness retention rate was 73% higher than the control group and 44% higher than PLA/CEO (4%). Application of this material prolonged the shelf life of Chinese bayberry (Myrica rubra) by 4 d while enhancing key preservation metrics. Owing to its advanced barrier properties, mechanical performance and temperature-modulated release characteristics, this PNVCL-based nanofiber film demonstrated strong potential as an intelligent packaging material for prolonging the freshness of perishable food products. Full article