Search Results (1,826)

Evaluation of dentin-replacement materials (DRMs) is essential for optimizing material selection and restorative outcomes. Four restorative groups, each comprising a DRM (SDR^® Plus, group A; EverX Posterior^™, group B-control; Filtek^™ Z250, group C; Fuji II LC^®, group D) overlayed with a microhybrid composite (Filtek Z250) to replace enamel layer, were evaluated for mechanical, optical, and handling characteristics. Standardized specimens were prepared for color change (ΔEab/E00) and fracture toughness (K_IC) testing (n = 8/group/test), with application time and handling evaluated by two independent assessors. Data were collected and analyzed statistically. The greatest color difference was observed in group B, which was significantly higher than that in groups A and C (p < 0.05), while group D did not differ significantly from any other group. Groups A and B exhibited significantly higher (p < 0.001) fracture toughness than groups C and D with no significant differences within either pair of groups. Group A required the least application time (p < 0.001), followed sequentially by groups B, C, and D. Handling ratings varied by material, with moderate inter-rater reliability (κ = 0.53). Within the study’s limitations, restorations with SDR Plus composites offered clinical application efficiency with improved fracture toughness and favorable optical integration. Full article

The wood-based grid sandwich structure with a high load-to-mass ratio and specific strength was prepared with the core of KH-560-modified jute (Corchoruscapsularis) fabric-reinforced epoxy laminated composite (JFRELC). The compressing behavior and energy absorption characteristics of pure grid cores (GC50#, GC80#) and grid sandwich structures (GS50#, GS80#) were analyzed and compared. The failure mechanism of the fracture surfaces of jute fabrics of grid sandwich cores was clarified by SEM. The results showed that the core made of JFRELC-80# had a good performance for the grid sandwich structure by tenon-and-mortise linking. The load-bearing capacity and energy absorption performance of this wood-based grid sandwich structure can be comparable to that of some glass and carbon fiber reinforced composite sandwich structures, and even show certain advantages. The failure modes of the grid sandwich structure were panel cracking, core buckling and core collapse. The failure mechanisms of jute fabrics in epoxy resin were fiber pull-out and fiber splitting. Full article

End-of-life thermoset composite coatings removed from fuel storage infrastructure represent a difficult waste stream because they combine a cross-linked polymer matrix, glass fibre reinforcement, functional layers and possible contamination from long-term contact with petroleum products. This study presents a preliminary assessment of an epoxy-glass laminate removed from the internal surface of a large vertical diesel fuel storage tank. The work combined a simplified numerical analysis of the technical role of the coating with thermogravimetric analysis and microscopic examination of solid residues after thermal conversion. The numerical results confirmed that the coating had a real reinforcing function, reducing the maximum equivalent stress in the corroded steel shell from 228.80 MPa to 191.85 MPa. TG/DTG analysis showed that the main mass loss of the laminate occurred below 500–600 °C, while the residual mass depended strongly on the process atmosphere. The highest residue was obtained after pyrolysis (28.75%), followed by CO₂-assisted conversion (26.17%) and combustion (20.87%). Microscopic observations showed that pyrolysis favoured morphological preservation of the fibrous/mineral fraction, but the glass fibres remained partly associated with carbonised epoxy resin and graphite-containing particles. Combustion removed the organic fraction more completely, but the remaining fibres showed signs of degradation. The results indicate that pyrolysis should be treated as a promising preliminary pretreatment route when morphological preservation of the fibrous/mineral fraction is prioritised, although the retained mechanical performance and phase composition of the fibres were not assessed. The study should be regarded as a thermogravimetric and microscopic screening of a real post-service epoxy-glass coating, supporting preliminary selection of end-of-life management pathways rather than a complete recycling or environmental assessment. By linking the thermal behaviour of a real post-service composite coating with feasible end-of-life pathways, the study contributes to sustainable waste management by supporting more informed decisions on material preservation, energy recovery, industrial co-processing and avoidance of landfilling for difficult thermoset composite wastes. Full article

The development of transparent multifunctional coatings capable of combining optical properties with mechanical durability remains a significant challenge in advanced materials engineering. In this study, novel hybrid coatings based on a poly(vinyl butyral)/epoxy resin (PVB/epoxy) matrix reinforced with tungsten disulfide (WS₂) nanostructures were developed and examined for potential application in camouflage protection of glass surfaces. Camouflage aims to reduce the detectability of an object by minimizing the optical contrast between the object and its surrounding environment. For transparent substrates such as glass, this objective is particularly demanding because the transparency must be preserved while reducing unwanted surface reflection and optical signatures over relevant spectral ranges. For this purpose, in this research two types of nanostructures were investigated: fullerene-like nanoparticles (IF-WS₂) and inorganic nanotubes (INT-WS₂). The coatings were fabricated via ultrasonically assisted solution dispersion followed by casting over the glass plates and Teflon molds, and solvent evaporation. Structural, thermal, optical, and mechanical properties were systematically evaluated using SEM, FTIR, DSC, UV-Vis-NIR spectroscopy, gloss measurements, hardness testing, and cavitation wear resistance analysis. The incorporation of WS₂ nanostructures led to improved mechanical performance, with increased hardness and enhanced resistance to cavitation-induced wear. Optical characterization showed moderate reductions in reflectance and controlled transmittance in the visible and near-infrared regions, while overall transparency was maintained. The results indicate that WS₂ nanostructures contribute to both light scattering and absorption, leading to reduced specular reflection and improved optical masking potential. The findings demonstrate that hybrid PVB/epoxy/WS₂ coatings offer a promising approach for designing transparent, mechanically resistant coatings with tunable optical properties, with potential applications in protective glass systems and advanced functional surfaces. Full article

The escalating environmental concerns associated with the non-renewable nature of petrochemical-based composite constituents have accelerated the development of sustainable and renewable alternatives. This study evaluates the potential of woven hemp-reinforced polyfurfuryl alcohol (PFA, furan) composites as fully bio-based composite materials. The use of PFA, a fully bio-based resin renowned for its high rigidity and fire-retardant properties, has been hindered by challenges associated with water vapour evolution, acid-catalysed fibre degradation, and porosity formation. Novel woven long hemp fibres were combined with a polyfurfuryl alcohol resin formulated with a mild acid catalyst, while an early-stage venting procedure during compression moulding was investigated to mitigate porosity and fibre degradation. Thermogravimetric analysis was used to determine the venting moments during the moulding cycle. Despite the limited improvement in porosity reduction achieved through the investigated venting strategy, the hemp balanced satin 6/6 fabric–furan composites exhibited commendable stiffness with a maximum modulus of 17.0 ± 0.4 GPa. However, the inherent brittleness of the resin and possibly the presence of fire-retardant fillers limited the tensile strength (a maximum of 71.8 ± 4.2 MPa) and failure strain (a maximum of 0.72 ± 0.07%). The bending properties of neat furan resin produced using an improved curing protocol were comparable to those of conventional thermoset resins, with a modulus of 3.2 ± 0.2 GPa, strength of 110.5 ± 17.3 MPa, and failure strain of 4.1 ± 0.8%. Although several challenges remain, this study demonstrates the potential of natural fibre–furan composites for high-performance natural fibre composite applications and provides guidance for their further development. Future research should focus on optimising venting strategies, avoiding fire retardants to minimise resin brittleness, incorporating matrix tougheners, and enhancing the inherent toughness of the matrix. Full article

This study extended a previously established intraoral scanning (IOS) and optical coherence tomography (OCT) dual-modality monitoring workflow for computer-aided design/computer-aided manufacturing (CAD/CAM) restorations to three additional crown material classes alongside a resin composite (RECO) reference. Four material classes were investigated ($n=8$ each): RECO, polymer-infiltrated ceramic network (PICN), lithium disilicate ceramic (LDSC), and zirconia-reinforced lithium silicate ceramic (ZLSC). Monolithic crowns were adhesively luted to standardized human molar abutment teeth and aged by cyclic loading (50500$\mathrm{N}$, 2$\mathrm{Hz}$, 37 2${}^{\circ }\mathrm{C}$, up to 1250000 cycles) in a mouth-motion simulator. IOS and handheld OCT were performed at baseline and after every 250000 cycles under phantom-head conditions; correspondence was assessed using Spearman’s rank correlation coefficient (exploratory, uncorrected for multiple comparisons). OCT consistently showed higher defect extents than IOS across all material classes and timepoints. While no significant IOS-OCT associations were found for RECO and the PICN, OCT detected full-thickness vertical subsurface damage propagation from the earliest timepoint in LDSC and ZLSC, with IOS-derived surface wear remaining markedly lower. Surface-based monitoring alone did not reliably reflect subsurface damage propagation, a dissociation most pronounced in the vertical dimension and silicate-based materials. Intraoral OCT may provide complementary, non-invasive subsurface information to support individualized recall scheduling and minimally invasive repair decisions. Full article

This study comprehensively investigates the thermal and mechanical degradation behavior of molded glass-fiber-reinforced plastic (GFRP) grating composites subjected to temperatures ranging from 80 °C to 320 °C. Three types of industrially produced GFRP gratings—open-type (OG), thin closed-skin (CG), and thick closed-skin (TCG)—were evaluated using mechanical, microstructural, chemical, and crystallographic analyses. Three-point bending tests revealed that TCG-type specimens exhibited superior thermal resistance, experiencing only a 43.9% loss in strength at 320 °C, whereas OG-type specimens showed significant resin degradation, fiber–matrix decomposition, and microcrack formation at temperatures above 200 °C. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed significant resin degradation, fiber–matrix decomposition, and microcrack formation. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) confirmed substantial mass loss and structural disintegration at temperatures above 200 °C. Dynamic Mechanical Analysis (DMA) results revealed that the glass transition temperature (Tg) occurred at approximately 115–120 °C. The second-order regression model developed to estimate flexural strength under increasing temperature provided high accuracy (R² > 0.99) for all grating types. It should be noted that this investigation focuses on the short-term thermo-mechanical response under fundamental flexural loading to provide an accurate baseline for preliminary engineering design. The findings emphasize that the effect of temperature should be considered a critical parameter in the structural design of GFRP systems, especially in industrial environments with temperatures above 120 °C. Accordingly, tables for material selection and load-carrying capacity should be recalibrated to account for short-term temperature effects. Full article

Multi-material structures such as carbon fiber reinforced polymer (CFRP) and epoxy resin are increasingly used in modern power equipment. However, significant differences in their thermophysical properties result in distinct defect thermal responses, which can reduce the reliability of infrared thermography inspections. To address this issue, this study investigates the thermal response mechanisms and quantitative analysis of defects in multi-material power equipment through finite element simulation and experimental validation. Three-dimensional transient heat transfer models containing air voids and heterogeneous insert defects were established using COMSOL Multiphysics for both carbon fiber reinforced polymer and epoxy resin matrices. Pulsed infrared thermography experiments were subsequently conducted to verify the simulation results. The effects of material properties, defect geometry, and cover-layer thickness on thermal response characteristics were systematically analyzed. The results show that thermal diffusivity is the key factor governing defect signal evolution. Carbon fiber reinforced polymer exhibits rapid thermal propagation and early transient responses, whereas epoxy resin produces delayed and slowly increasing thermal signals. Greater defect depth weakens thermal contrast and delays peak response time, while larger defect diameters enhance defect detectability. Increasing cover-layer thickness significantly attenuates defect signals and reduces imaging contrast. Experimental results are in good agreement with simulation predictions, confirming the validity of the proposed models. This work provides a quantitative analysis of defect thermal behavior in multi-material systems and offers a theoretical basis for adaptive infrared thermography inspection and condition assessment of power equipment. It should be noted that this study focuses on mechanistic understanding and parametric analysis rather than on proposing a dedicated quantitative defect-sizing or inversion method. Full article

A novel alumina-filled ceramic-reinforced polymer (CRP) crown (Hassawat-01; HS) was developed. This study evaluated the effect of luting cement on the marginal and internal adaptation of HS and compared its performance with a commercial DLP-printed CRP (VarseoSmile Crown Plus^®; VS) and a milled resin nanoceramic (Cerasmart^® 270; CE). Ninety-nine crowns (n = 33/material) were fabricated with a 50 µm cement space and luted using Maxcem Elite^®, RelyX Unicem^®, or Ketac Cem^® (n = 11/subgroup). Adaptation was assessed without and with cementation using micro-computed tomography at 160 measurement points per crown. Without cementation, HS demonstrated the most favorable internal adaptation, whereas VS showed the best marginal adaptation. Following cementation, gap dimensions increased in all groups. Despite its superior non-cementation fit, HS exhibited the greatest increase in marginal and internal discrepancies, suggesting increased hydraulic resistance during seating. Among the evaluated cement–crown combinations, VS luted with RelyX Unicem^® showed the most favorable post-cementation adaptation. Post-cementation analysis was limited to HS and VS because the radiopacity of CE prevented reliable cement interface segmentation. These findings indicate that adaptation is influenced by both crown geometry and cement properties, and that highly adapted intaglio surfaces may require careful cement selection to optimize clinical fit. Full article

Vehicle crash boxes are elements that protect the integrity of vehicles and ensure the safety of occupants in potential vehicle accidents. These crash boxes are mounted on the chassis of vehicles. In this study, composite crash boxes fabricated from aluminum, which is known for its lightweight properties, as well as denim and ultra-high-molecular-weight polyethylene, both of which are widely available on the market, were investigated experimentally. Composite crash boxes composed of an epoxy resin matrix reinforced with denim fabric (DenimFRP) and ultra-high-molecular-weight polyethylene (UHMWPEFRP) fibers, as well as aluminum (Al), were produced. The crash boxes were manufactured using a vacuum infusion method. This combination was produced by wrapping these fibers around an aluminum core. The energy absorption values, peak force values, and specific energy absorption values of the manufactured crash boxes were obtained through quasi-static compression tests and then compared. The best energy absorption value was achieved with the Al+denimFRP composite crash box manufactured by wrapping denim around aluminum at a workload of 1645.22 J, and its specific energy absorption value was also calculated as 15.52 J/g. The difference between the highest and lowest energy absorption was determined to be 244.61%. The highest peak strength value was obtained with the Al+denim+UHMWPEFRP sample, which contained a combination of aluminum on the inside, denim fabric in the middle, and UHMWPE fabric on the outside. Among the individually produced samples, the Al+denimFRP composite crash box manufactured with denim fiber exhibited higher results compared with the UHMWPEFRP composite box manufactured with ultra-high-molecular-weight polyethylene. Full article

Carbon fiber-reinforced thermoplastic composites (CFRTPs) have attracted increasing attention in aerospace, transportation, marine engineering, and other advanced manufacturing fields owing to their high specific mechanical properties, impact resistance, weldability, reprocessibility, and potential recyclability. However, the high melt viscosity of thermoplastic matrices, the permeability limitations associated with different reinforcement architectures, and the chemical inertness of carbon fiber surfaces continue to restrict resin impregnation, interfacial bonding, defect control, and forming stability. This review systematically summarizes recent advances in CFRTP manufacturing from the perspective of material-derived processing challenges and interface engineering. First, representative thermoplastic matrix systems and reinforcement architectures are discussed, with emphasis on their effects on processability, crystallization behavior, resin flow, and load transfer. Subsequently, six major forming processes, including hot stamping, injection molding, pultrusion, filament winding, automated fiber placement, and additive manufacturing, are critically compared in terms of processing principles, typical defects, technical limitations, and application boundaries. Particular attention is given to process-induced quality issues such as voids, wrinkling, springback, fiber breakage, warpage, insufficient consolidation, and weak interlayer bonding. Finally, interface engineering strategies, including chemical surface modification, interfacial structural design, and functional interlayer design, are reviewed as practical routes to improve wetting, shorten impregnation pathways, and enhance fiber–matrix load transfer in high-viscosity thermoplastic systems. This review highlights that CFRTP manufacturing should be understood as a coupled materials–processing–interface problem rather than a single forming operation. Future development is discussed with emphasis on reproducible manufacturing, processability-oriented materials, scalable interface engineering, predictive modeling, and standardized structural validation. Full article

The study investigated the addition of nanocellulose (NC) as a reinforcing agent in wood-phenol resorcinol formaldehyde (PRF) composites for thermoset extrusion-based manufacturing. Three types of NC (cellulose nanocrystals (CNC), bleached nanofibers (BNFs), and unbleached nanofibers (UBNFs)) at 1–3% loadings and new (NP) and 4-year old (OP) PRF resin were evaluated by a combination of thermal analysis, rheology and flexural testing. The NP was shown to gel at a lower temperature than OP. CNC addition advanced gelation and yield stress; whereas, UBNFs reduced viscosity and yield stress through plasticization but were suitable for extrusion. The NC-reinforced wood–PRF formulations were successfully extruded into continuous composite rods. A flexural modulus of 8.1 GPa and strength of 77 MPa was achieved. Moreover, NC was shown to reduce 24 h water absorption compared to controls. These findings show that NC reinforcement improves wood–PRF composites systems for potential sustainable additive manufacturing. Full article

The growing demand for implant-supported rehabilitative prosthetic treatments has reinforced the need to optimize biomechanical performance, particularly regarding force distribution. This study aimed to evaluate the stress distribution generated by different configurations of full-arch implant-supported prostheses using three-dimensional finite element analysis. Two mandibular models were created using SolidWorks 2010 (SolidWorks Corp., Waltham, MA, USA) and Rhinoceros^® 3D 4.0 (NURBS Modeling for Windows, USA). Each model represented a mandible restored with a full-arch fixed prosthesis supported by external hex implants (4.0 × 13.0 mm; Master, Conexão Sistemas de Prótese, São Paulo, Brazil) placed in the interforaminal region, differing only in implant angulation. Model 1 included four implants positioned perpendicular to the alveolar ridge, whereas Model 2 represented the All-on-Four configuration with distal implants tilted at 30°. The prosthesis was modeled in acrylic resin with a NiCr metal framework. The geometries were exported to FEMAP 11.0 for mesh generation. Axial loading of 300 N was applied bilaterally (75 N per tooth), and oblique loading of 150 N was applied unilaterally (75 N per tooth) on the first premolars and first molars. Obtained using NEiNastran^® 9.2 showed that the tilted-implant model exhibited higher stress concentrations under both loading conditions. The All-on-Four configuration generated the highest stress levels, particularly around the distal implants. The null hypothesis of this study was that there would be no difference in stress distribution among full-arch implant-supported prostheses supported by straight implants and those rehabilitated according to the All-on-Four concept with tilted distal implants. Full article

Although the use of three-dimensional-printed (3D-printed) denture base resins is becoming increasingly widespread in digital dentistry, information regarding the reinforcing effects of cellulose nanofibers and their most favorable concentration remains limited. We evaluated the effects of adding cellulose nanofibers (CNFs, 0–2.0 wt%) on the mechanical and physical properties of three-dimensional-printed denture base resins. The addition of cellulose nanofibers improved flexural strength (FS) and Vickers hardness (HV), with more balanced performance observed at low concentrations; no significant differences were observed in flexural modulus. Color stability did not show a linear concentration-dependent trend, and the 1.0 wt% group exhibited the most favorable overall performance. Water sorption slightly increased at higher CNF concentrations. SEM observations revealed relatively uniform CNF dispersion at lower concentrations, whereas agglomeration and void formation occurred at higher concentrations. Appropriate CNF incorporation may be a promising strategy for reinforcing 3D-printed denture base materials. Full article

Carbon fiber reinforced epoxy resin composites were manufactured using the vacuum infusion technique. Composite samples were subjected to impact and then exposed to various weathering conditions. Static and dynamic mechanical tests were performed to evaluate the effect of an additional process step, a plasma treatment of the carbon fiber fabric, before the composite is manufactured. Scanning electron microscopy and thermal analysis were used to get further information on the degree of damage after weathering. Treating the reinforcing carbon fibers with air plasma resulted in improved strength values and fatigue behavior of the epoxy resin composite. This performance enhancement persisted even after low-energy mechanical stress and subsequent weathering. Full article