Search Results (566)

The embedded through-section (ETS) technique is a promising method for fiber-reinforced polymer (FRP)-strengthening reinforced concrete (RC) structures, offering higher bond resistance and reduced surface preparation compared to externally bonded or near-surface mounted FRP systems. A common failure in ETS applications is debonding at the FRP bar-to-concrete interface. However, current design standards often assume uniform bond stress and lack predictive models that account for debonding propagation and its effect on load capacity. Furthermore, a detailed analysis of interfacial stress development, including debonding initiation and progression along varying bond lengths, remains limited. To address these gaps, this study introduces an analytical model that describes the complete debonding process in ETS FRP bar-to-concrete joints, incorporating both long and short bond lengths and frictional effects. Based on a trilinear cohesive material law (CML), closed-form expressions are deduced for the load–slip response, maximum load, interfacial shear stress and strain distribution along the FRP bar. The proposed model is validated experimentally through pull-out tests on glass FRP (GFRP) bars adhesively bonded to concrete with different strength grades. The results show that the analytical predictions agree well with both the self-conducted experimental data for short joints and existing test results for long joints given in the literature. Therefore, the developed design-oriented solution enables accurate evaluation of the actual contribution of ETS FRP reinforcement to RC members by explicitly modeling debonding behavior. This provides a rigorous and mechanics-based tool for performance-based design of ETS FRP-to-concrete joints, addressing a critical gap in the future refinement of current design standards. Full article

This study explores the fabrication and characterization of Pickering high internal phase emulsions (P-HIPEs) stabilized by soy protein isolate (SPI) and coix polysaccharide (CP) complex. CP exhibited high purity (95.29%) with a molecular weight of 5.53 × 10⁵ Da and was predominantly composed of glucose, as confirmed by monosaccharide analysis and FT-IR spectroscopy. SPI/CP complexes formed well-dispersed nanoparticles with optimal stability at 2% CP concentration, demonstrated by minimal particle size and enhanced zeta potential. P-HIPEs stabilized by these complexes showed excellent physical stability without phase separation or oil leakage, with the creaming index decreasing as particle concentration increased, reaching optimal stability at 12% SPI/CP and pH 9. Particle size and zeta potential measurements indicated smaller, more uniform droplets and intensified electrostatic repulsion under these conditions, effectively preventing droplet coalescence. Confocal microscopy revealed a dense, multilayered interfacial network formed by SPI/CP complexes around oil droplets, enhancing emulsion stability. Rheological analyses confirmed that P-HIPEs exhibited elastic solid-like gel behavior with pronounced shear-thinning and superior thixotropic recovery at 12% SPI/CP and alkaline pH, highlighting improved gel strength and structural integrity. These findings demonstrate the critical influence of SPI/CP concentration and pH on the physicochemical, microstructural, and rheological properties of P-HIPEs, offering valuable insights for developing stable emulsions with enhanced performance and applicability in food systems. Notably, the results emphasize the critical role of SPI/CP concentration and pH in achieving optimal emulsion stability and rheological properties. Full article

Natural fiber-based composites are gaining attention as sustainable alternatives to synthetic fiber-reinforced materials. Herein, styrene-free unsaturated polyester (UPe) nanocomposites and flax-fabric laminates reinforced with vinyl-triethoxy-silane (VTES) functionalized zirconia nanoparticles (ZrO₂-VS) were studied. Nanoparticles were dispersed by high-shear mixing, and ZrO₂-VS was benchmarked against unmodified ZrO₂ and neat UPe. Fourier-transform infrared spectroscopy (FTIR) tracked cure conversion; scanning electron microscopy (SEM/EDS), tensile testing, and dynamic mechanical analysis (DMA) evaluated structure-property relationships. ZrO₂-VS improved dispersion and interfacial adhesion, yielding higher tensile strength and storage modulus compared with unmodified ZrO₂. In flax-fabric laminates, ZrO₂-VS/UPe achieved a tensile strength of 72.2 ± 3.6 MPa, exceeding both unmodified ZrO₂/UPe and neat UPe controls. DMA showed pronounced increases in storage modulus across temperature with small, non-significant changes in Tg. These results highlight a low-styrene-hazard UPe matrix and natural fiber reinforcement pathway to improved mechanical performance via silane-mediated nanoparticle-matrix-fiber bridging. Full article

This study investigates hygrothermal durability of bio-epoxy composites reinforced with carbon, E-glass, basalt, and flax fibres. Fibre yarns and bio-composites were exposed for 3000 h at 60 °C and 98% relative humidity. The tensile strength reduction in the fibres and the interfacial shear strength (IFSS) reduction in the composites were assessed after ageing. Chemical deterioration was evaluated using energy-dispersive X-ray spectroscopy (EDS); morphological changes in fibres and composites fracture surfaces were examined using a scanning electron microscope (SEM). Results indicated that the durability was significantly influenced by fibre types. Tensile strength reduction was higher in carbon, glass and basalt compared to flax yarns because of chemical degradation of the sizing layer in synthetic fibres, while only physical damage was observed in flax. The IFSS reduction was highest in flax composites (10%), and lowest in carbon (4%). EDS indicated the hydrolysis and erosion of fibre sizing, with reduced silica content in glass and basalt fibres. SEM revealed matrix-dominated failure in carbon/bio-epoxy, interfacial debonding in glass and basalt composites, fibre slip and pull-out in flax/bio-epoxy. Overall, the results highlighted damage propagation pathways and demonstrated that bio-epoxy composites exhibited reasonable performance under hygrothermal ageing, supporting their potential as a sustainable alternative in durability-critical applications. Full article

Additive manufacturing via LCD vat photopolymerisation enables direct bonding of photopolymer to textile substrates, but optimal processing parameters remain unclear. A 3 × 3 factorial design investigated the effects of layer thickness (0.01, 0.025, 0.05 mm) and UV exposure time (40, 80, 120 s) on the single-lap shear strength of woven fabric-photopolymer joints (65% polyester/35% cotton) using a novel pause-and-bond methodology, following the EN ISO 4587:2003 standard. Five replicate specimens per condition yielded 45 samples for mechanical testing. All specimens (45/45) exhibited adherend-limited failure within the textile substrate rather than at the polymer-textile interface, yielding consistent shear strengths of 1.38 ± 0.04 MPa (range: 1.30–1.45 MPa). Two-way ANOVA revealed no significant parametric effects (p > 0.05), indicating that interfacial bond strength consistently exceeded textile cohesive strength across all parameter combinations. The minimum resource-efficient condition (0.01 mm/40 s) achieves equivalent performance to higher-parameter combinations, enabling substantial process optimisation for textile-integrated photopolymer sandwich structures while reducing material and processing time requirements. Full article

The roll bonding of 7075/1060 composite laminates offers a promising approach toward the increase in toughness of aluminum layered composites. In this paper, 7075 and 1060 aluminum alloy plates were hot roll bonded to fabricate multilayered composite laminates. Solid solution at 470 °C for different holding times and subsequent aging were carried out for all the laminates. This study investigated the effect of holding times on the interfacial microstructure and interfacial bonding strength of the laminates. The interfacial shear strength was found to increase with longer holding times, which was attributed to the solid solution strengthening of the 1060 layer resulting from element diffusion. The findings also reveal that both tensile strength and toughness are positively correlated with the holding time of the solid solution, and there is a simultaneous improvement of tensile strength and toughness as the holding time increases. Microstructural characterization of the crack path profile of the Charpy impact and bending test indicates that interfacial delamination and main crack deflection become pronounced with the increase in holding time, and these lead to an increase in the fracture resistance in the crack-arrester orientation. Full article

Background/Objectives: Chipping of the veneering part of the crown at the zirconia–porcelain interface remains a major complication of bilayered zirconia systems. This systematic review evaluated whether incorporating a lithium-disilicate (LD) liner or press-on or CAD-on interlayer between zirconia and veneer improves bond strength and fracture performance in vitro. Methods: Following PRISMA 2020, we searched PubMed, Scopus, and Web of Science up to 7 September 2025 for open-access English in vitro studies using LD-based interlayers at zirconia–veneer interfaces and reporting quantitative bond and/or fracture outcomes. Data included extracted materials, processing parameters, and mechanical results; due to heterogeneity, findings were synthesized descriptively and as the ratio-of-means (ROM). Results: Five in vitro studies from Korea, Thailand, and India met the criteria. LD interlayers increased microtensile bond strength from 18.83 to 44.20 MPa and from 19.6 to 47.7 MPa, and shear bond strength from 41.3 to 59.7 MPa, 11.40 ± 1.29 to 18.81 ± 1.76 MPa, and 21.5 to 60.2 MPa. Corresponding ROMs ranged from 1.46 to 2.80 (median 2.35), with thermocycled LD groups maintaining strengths >25 MPa. LD liners also raised crown fracture loads from ~2.18 to ~3.45 kN and characteristic strength from 3.42 to 5.64 kN, while chipping loads in implant crowns increased from ~0.34 to ~0.84 kN and global fracture from ~1.71 to ~1.93 kN. Conclusions: Across diverse zirconia–veneer configurations, LD interlayers consistently enhanced bond metrics and fracture/chipping resistance, supporting their use as a targeted interfacial strategy; however, clinical confirmation is still needed. Full article

An Ultrasonic Test (UT), a type of non-destructive test, is used to inspect the manufacturing integrity of carbon spar-caps of wind blades. When performing a UT, an intermediate medium is used to improve the signal detection ability between the inspection target and the probe. However, if the intermediate-medium residue is not removed, it acts as a contaminant in the interface between the spar-cap and the blade skin. This has a negative effect on the adhesion characteristics. A quantitative method is required for removing the intermediate medium and peel ply after the UT. After the UT, the interfacial characteristics of the spar-cap surface are examined according to the method of removing the intermediate medium in this study. The static contact angle and the work of adhesion (W_a) were measured according to various surface treatment conditions. In addition, shear strength of the Carbon Fiber-Reinforced Plastic (CFRP) spar-cap was evaluated by the lap shear test. An optimized method of peel-ply removal combined with an intermediate medium was found in this study. An optimal guideline for intermediate-medium treatment could be proposed when evaluating the manufacturing integrity of real wind blade spar-caps using UT. Full article

Fe–Al intermetallic compounds are promising candidates for hydrogen permeation barrier coatings owing to their excellent oxidation stability and inherent resistance to hydrogen embrittlement. However, the mechanical properties and interfacial behavior of different Fe–Al phases, particularly at Fe/Fe–Al interfaces, remain insufficiently understood, limiting their reliable application in hydrogen-containing environments. In this work, density functional theory (DFT) calculations were employed to systematically evaluate the bulk mechanical moduli, surface energetics, and interfacial adhesion of FeAl, Fe₃Al, and Fe₂Al₅. The results reveal that FeAl exhibits the highest elastic and shear moduli due to its B2-ordered structure and directional bonding, while Fe₂Al₅ shows pronounced anisotropy and the lowest strength as a consequence of its low-symmetry structure. Surface energy analysis indicates that Fe₂Al₅ possesses relatively stable facets, whereas interfacial adhesion calculations demonstrate that FeAl/Fe and Fe₃Al/Fe interfaces provide significantly stronger bonding compared to Fe₂Al₅/Fe. Charge density and electron localization function (ELF) analyses confirm that Fe–Fe bonds are dominated by metallic character with delocalized electrons, whereas Al-rich regions display enhanced localization, leading to weaker interfacial adhesion in Fe₂Al₅/Fe. These findings clarify the fundamental mechanisms governing Fe–Al mechanical and interfacial properties and provide theoretical guidance for the design of robust Fe–Al-based hydrogen barrier coatings. Full article

This study focuses on the synthesis of two new bisphenol-based polyimide (PI) sizing agents to improve the fiber–matrix interface of carbon fiber-reinforced poly (ether ether ketone) (CF/PEEK) composites. One of the synthesized polyimides contains bisphenol A (BPA) monomer, while the other has bisphenol S (BPS) monomer. The produced polyimide precursor resins were coated with carbon fibers by thermal imidization. The thermal, thermomechanical, and mechanical properties of the CF/PEEK composites produced by the autoclave process were investigated. According to the mechanical test results, there was a balanced performance between the BPS-containing polyimide-coated composites (CF-PEEK-PI-S) and the BPA-containing polyimide-coated composites (CF-PEEK-PI-A). While tensile strength is 291 MPa and interlaminar shear (ILSS) strength is 119 MPa, the CF-PEEK-PI-A sample showed superior mechanical properties in flexural (92.1 MPa) and compressive strength (54.9 MPa). As a result, it was concluded that bisphenol-based polyimide coatings significantly improve the interfacial interactions in CF/PEEK composites, which have great potential in aerospace, automotive and advanced engineering applications. Full article

Laser micro-drilling was applied to Fe substrates to enhance the interfacial properties of carbon fiber-reinforced polymer/iron laminates. This architecture is referred to as a resin-interlocked Fe-CFRP hybrid composite. Inspired by human hair follicles’ exceptional adhesion and filling efficiency, novel biomimetic frustum-integrated cylindrical cavities were engineered for Fe surface modification. Experimental results demonstrate that laser-processed surfaces with varied hole geometries (conical, conical frustum, cylindrical, and frustum-integrated cylindrical cavities) exhibit significantly improved interfacial performance compared to untreated Fe controls. Specifically, RI-Fe/CFRP specimens containing frustum-integrated cylindrical cavities achieved the highest shear strength, with a 44.8% increase over non-drilled counterparts. Subsequent molecular dynamics simulations confirmed the critical role of the cavity geometry, demonstrating that the frustum-integrated cylindrical cavity elevates the Fe–Diglycidyl ether of bisphenol-A interfacial energy and van der Waals interactions by 45.44% and 50.66%, respectively, versus the flat surface. The interfacial energy enhancement mechanism via distinct hole configurations was systematically studied. Furthermore, comprehensive micro-hole topology analysis elucidated the reinforcement mechanism in resin-interlocked Fe-CFRP hybrid composites. Results demonstrate that frustum-integrated cylindrical cavities significantly enhance DGEBA-3,3′-diaminodiphenyl sulfone fluidity during interface simulation, promoting mechanical interlocking and optimized resin-filling efficiency. Laser micro-drilling effectively improves Fe-DGEBA interfacial performance. These findings provide critical insights for designing high-performance composites in aerospace and automotive applications. Full article

This study is motivated by the severe tribological regime of PA6 composites in VR platforms operating under dry or boundary lubrication, where alternating shear during foot rotation, localised contact pressures, and third-body abrasion concurrently challenge wear resistance and retention of strength. This paper presents the results of research into the properties of composites based on polyamide PA6 and molybdenum disulphide, obtained by combining the components through high-intensity mechanochemical activation in a planetary mill and classical mixing in a turbulence mixer. We demonstrate that varying the energy of the premixing stage (mechanochemical activation versus low-energy premixing) serves as an effective means of interfacial engineering in PA6/MoS₂ composites, enabling simultaneous enhancement of mechanical and tribological properties at low filler contents. Analysis of experimental composite samples using Fourier-transform infrared spectroscopy (FTIR) indicates the interaction between MoS₂ and oxygen-containing groups of polyamide while maintaining its overall chemical composition. According to the TG-DSC curves, modification of polyamide leads to an increase in the melting temperature by 2 °C, while mechanical activation ensures stronger interaction between the matrix and the filler. Compared to pure PA6, the tensile strength of composites increases by 10–20% for mechanoactivated materials and by 5–10% for materials obtained by conventional methods. The mechanical activation effect is observed even at minimal amounts (0.25 and 0.5%) of MoS₂ in composites. The toughness of all composites, regardless of the mixing method, increases by 5–7% compared to pure polyamide. All composites show a 10–20% reduction in the coefficient of friction on steel. Simultaneously, the water absorption of composites becomes 5–20% higher than that of the original material, which indicates a change in structure and an increase in porosity. The obtained composite materials are planned to be used for manufacturing platforms for the movement of virtual reality (VR) operators. Full article

This study evaluates the effect of chemical treatments on the short-beam shear strength, vibrational, and acoustic performance of banana-fibre-reinforced carbon–Kevlar hybrid composites. Banana fibres were treated with 5% NaOH and 0.5% KMnO₄ to improve fibre surface characteristics and interfacial bonding within a sandwich laminate of carbon–Kevlar intraply skins and banana fibre core fabricated by hand lay-up and compression moulding. Short-beam shear strength (SBSS) increased from 14.27 MPa in untreated composites to 17.65 MPa and 19.52 MPa with KMnO₄ and NaOH treatments, respectively, due to enhanced fibrematrix adhesion and removal of surface impurities. Vibrational analysis showed untreated composites had low stiffness (7780.23 N/m) and damping ratio (0.00716), whereas NaOH treatment increased stiffness (9480.51 N/m) and natural frequency (28.68 Hz), improving rigidity and moderate damping. KMnO₄ treatment yielded the highest damping ratio (0.0557) with reduced stiffness, favouring vibration energy dissipation. Acoustic tests revealed KMnO₄-treated composites have superior sound transmission loss across low to middle frequencies, peaking at 15.6 dB at 63 Hz, indicating effective acoustic insulation linked to better mechanical damping. Scanning electron microscopy confirmed enhanced fibre impregnation and fewer defects after treatments. These findings highlight the significant role of chemical surface modification in optimising structural integrity, vibration control, and acoustic insulation in sustainable banana fibre/carbon–Kevlar hybrids. The improved multifunctional properties suggest promising applications in aerospace, automotive, and structural fields requiring lightweight, durable, and sound-mitigating materials. Full article

Tensile behavior governs the seismic safety of high concrete dams. This study integrates testing with mesoscale simulation to elucidate the tensile-failure mechanisms of dam fully graded concrete. Uniaxial tension, splitting tension, and flexural tests were performed on 450 mm-scale specimens using a 15 MN servo-hydraulic system. A two-dimensional random-aggregate model was then developed with globally inserted cohesive interfaces, and parameters were calibrated against the tests. Across ten random aggregate mesoscale models per loading case, simulations reproduced the measured responses. Predicted failure patterns matched observations, with cracks initiating along interfacial transition zones (ITZs), linking through mortar, and forming through-cracks. Quantified damage evolution revealed three stages—elastic response, ITZ crack initiation and extension, and mortar penetration—with >80% of cumulative damage localized in ITZs. One-at-a-time sensitivity analyses showed that (i) mortar tensile strength primarily controls peak strength but increases brittleness; (ii) ITZ tensile strength governs crack-initiation stress, ITZ shear strength shapes splitting-failure mode, and fracture energies mainly delay post-peak softening; and (iii) aggregate parameters exert comparatively weak influence on macroscopic behavior. The combined experimental–mesoscale framework provides mechanism-based guidance for selecting material parameters in seismic analyses, supporting performance-informed design and assessment of high dams. Full article

The rapid expansion of carbon-fiber-reinforced polymer (CFRP) applications in aerospace, automotive, and energy sectors has intensified concerns over end-of-life waste and the absence of efficient recycling solutions. Plasma-assisted solvolysis has emerged as a promising hybrid approach, combining oxidative chemical treatment with plasma activation to accelerate matrix degradation. In this study, CFRP cylinders (6.4 cm height, 5.5 cm internal, and 6.0 cm external diameter) were processed in a closed-loop plasma solvolysis system under varied operational parameters, including plasma power, plasma gas composition, and nitric acid concentration. The mechanical performance of the recovered carbon fibers was assessed through single-fiber tensile and microbond tests, evaluating both tensile and interfacial properties. In most cases, the recycled fibers retained—or even exceeded—the tensile strength of their virgin counterparts, reaching up to 1.49 times that of the virgin fibers. Young’s modulus, though more variable, ranged from 0.48 to 1.67 times the reference value depending on treatment conditions. Elongation at break generally increased, particularly in the 24K (24,000-filaments) fiber sets, suggesting improved surface ductility. Weibull statistical analysis indicated higher consistency in 3K (3000-filaments) fiber batches compared to 24K, whereas interfacial shear strength was moderately retained across conditions. Overall, balanced plasma and acid conditions enabled efficient fiber recovery with high strength and interfacial performance, validating plasma-assisted solvolysis as a viable route for recovering high-performance fibers suitable for structural reuse, in alignment with circular economy principles. Full article