Search Results (194)

Background and Clinical Significance: Traumatic dental injuries, particularly complicated crown fractures of permanent incisors, are common in adolescents, with maxillary central incisors most frequently affected due to their prominent position. These injuries, often resulting from sports or accidents, require prompt management to prevent complications such as pulp necrosis or infection, which can compromise long-term prognosis. Fragment reattachment offers a conservative, esthetically favorable approach when the fractured segment is intact, with outcomes comparable to composite restorations. This case report underscores the importance of timely intervention and advanced restorative techniques in pediatric dentistry. Case Presentation: A 16-year-old male presented with a complicated crown fracture of the upper left central incisor sustained during a soccer game. The fracture extended subgingivally with pulp exposure. The patient preserved the fragment in saline. Treatment involved fragment reattachment using a dentin bonding agent and flowable composite resin, followed by single-visit root canal therapy due to delayed presentation (48 h). A glass fiber post was placed to reinforce the restoration due to significant coronal loss. Three years of follow-up visits (1, 3, 6, 12, 24, and 36 months) revealed no clinical or radiographic complications, with the tooth remaining asymptomatic and functional. Conclusions: This case underscores the effectiveness of fragment reattachment when combined with meticulous technique and long-term monitoring. Full article

Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural longevity. Fiber-reinforced concrete (FRC) is widely used to improve durability; however, the effects of different fiber types on chloride resistance remain unclear. This study examines the influence of glass and polypropylene fibers on concrete’s microstructure and chloride penetration resistance. Cylindrical specimens were prepared, including a reference mix without fibers and mixes with 0.25% and 0.50% fiber content by volume. Both fiber types were tested for chloride resistance. The accelerated non-steady-state migration method was employed to determine the resistance coefficients to chloride ion penetration, while X-ray macrofluorescence (MacroXRF) mapped the chlorine infiltration depth in the samples. Compressive strength decreased in all fiber-reinforced samples, with 0.50% glass fiber leading to a 56% reduction in strength. Nevertheless, the XRF results showed that a 0.25% fiber content significantly reduced chloride penetration, with polypropylene fibers outperforming glass fibers. These findings highlight the critical role of fiber type and volume in improving concrete durability, offering insights for designing long-lasting FRC structures in chloride-rich environments. Full article

Fiber–aerogel composites have gained significant attention as high-performance thermal insulation materials due to their unique microstructure, which suppresses conductive, convective, and radiative heat transfer. At room temperature, silica aerogels in particular exhibit ultralow thermal conductivity (<0.02 W/m·K), which is two to three times lower than that of still air (0.026 W/m·K). Their brittle skeleton and high infrared transparency, however, restrict how well they insulate, particularly at high temperatures (>300 °C). Incorporating microscale fibers into the aerogel matrix enhances mechanical strength and reduces radiative heat transfer by increasing scattering and absorption. For instance, it has been demonstrated that adding glass fibers reduces radiative heat transmission by around 40% because of increased infrared scattering. This review explores the fundamental mechanisms governing radiative heat transfer in fiber–aerogel composites, emphasizing absorption, scattering, and extinction coefficients. We discuss recent advancements in fiber-reinforced aerogels, focusing on material selection, structural modifications, and predictive heat transfer models. Recent studies indicate that incorporating fiber volume fractions as low as 10% can reduce the thermal conductivity of composites by up to 30%, without compromising their mechanical integrity. Key analytical and experimental methods for determining radiative properties, including Fourier transform infrared (FTIR) spectroscopy and numerical modeling approaches, are examined. The emissivity and transmittance of fiber–aerogel composites have been successfully measured using FTIR spectroscopy; tests show that fiber reinforcement at high temperatures reduces emissivity by about 15%. We conclude by outlining the present issues and potential avenues for future research to optimize fiber–aerogel composites for high-temperature applications, including energy-efficient buildings (where long-term thermal stability is necessary), electronics thermal management systems, and aerospace (where temperatures may surpass 1000 °C), with a focus on improving the materials’ affordability and scalability for industrial applications. Full article

Prefabricated unidirectional carbon fiber reinforced polymer (CFRP) composite strips are extensively used as a means of infrastructure rehabilitation through adhesive bonding to the external surface of structural concrete elements. Most data to date are from laboratory tests ranging from a few months to 1–2 years providing an insufficient dataset for prediction of long-term durability. This investigation focuses on the assessment of the response of three different prefabricated CFRP systems exposed to water, seawater, and alkaline solutions for 5 years of immersion in deionized water conducted at three temperatures of 23, 37.8 and 60 °C, all well below the glass transition temperature levels. Overall response is characterized through tensile and short beam shear (SBS) testing at periodic intervals. It is noted that while the three systems are similar, with the dominant mechanisms of deterioration being related to matrix plasticization followed by fiber–matrix debonding with levels of matrix and interface deterioration being accelerated at elevated temperatures, their baseline characteristics and distributions are different emphasizing the need for greater standardization. While tensile modulus does not degrade appreciably over the 5-year period of exposure with final levels of deterioration being between 7.3 and 11.9%, both tensile strength and SBS strength degrade substantially with increasing levels based on temperature and time of immersion. Levels of tensile strength retention can be as low as 61.8–66.6% when immersed in deionized water at 60 °C, those for SBS strength can be 38.4–48.7% at the same immersion condition for the three FRP systems. Differences due to solution type are wider in the short-term and start approaching asymptotic levels within FRP systems at longer periods of exposure. The very high levels of deterioration in SBS strength indicate the breakdown of the materials at the fiber–matrix bond and interfacial levels. It is shown that the level of deterioration exceeds that presumed through design thresholds set by specific codes/standards and that new safety factors are warranted in addition to expanding the set of characteristics studied to include SBS or similar interface-level tests. Alkali solutions are also shown to have the highest deteriorative effects with deionized water having the least. Simple equations are developed to enable extrapolation of test data to predict long term durability and to develop design thresholds based on expectations of service life with an environmental factor of between 0.56 and 0.69 for a 50-year expected service life. Full article

Glass fiber reinforced polypropylene composite plates have gradually attracted more attention because of their repeated molding, higher toughness, higher durability, and fatigue resistance compared to glass fiber reinforced thermosetting composites. In practical engineering applications, composite plates have to undergo bending effect at different angles in corrosive environment of concrete, including bending bars from 0~90°, and stirrups of 90°, which may lead to long-term performance degradation. Therefore, it is important to evaluate the long-term performance of glass fiber reinforced polypropylene composite bending plates in an alkali environment. In the current paper, a new bending device is developed to prepare glass fiber reinforced polypropylene bending plates with the bending angles of 60° and 90°. It should be pointed out that the above two bending angles are simulated typical bending bars and stirrups, respectively. The plate is immersed in the alkali solution environment for up to 90 days for long-term exposure. Mechanical properties (tensile properties and shear properties), thermal properties (dynamic mechanical properties and thermogravimetric analysis) and micro-morphology analysis (surface morphology analysis) were systematically designed to evaluate the influence mechanism of bending angle and alkali solution immersion on the long-term mechanical properties. The results show the bending effect leads to the continuous failure of fibers, and the outer fibers break under tension, and the inner fibers buckle under compression, resulting in debonding of the fiber–matrix interface. Alkali solution (OH⁻ ions) corrode the surface of glass fiber to form soluble silicate, which is proved by the mass fraction of glass fiber decreased obviously from 79.9% to 73.65% from thermogravimetric analysis. This contributes to the highest degradation ratio of tensile strength was 71.6% (60° bending) and 65.6% (90° bending), respectively, compared to the plate with bending angles of 0°. A high curvature bending angle (such as 90°) leads to local buckling of fibers and plastic deformation of the matrix, forming microcracks and fiber–resin interface bonding at the bending area, which accelerates the chemical erosion and debonding process in the interface area, bringing about an additional maximum 10.56% degradation rate of the shear strength. In addition, the alkali immersion leads to the obvious degradation of storage modulus and thermal decomposition temperature of composite plate. Compared with the other works on the long-term mechanical properties of glass fiber reinforced polypropylene, it can be found that the long-term performance of glass fiber reinforced polypropylene composites is controlled by the corrosive media type, bending angle and immersion time. The research results will provide durability data for glass fiber reinforced polypropylene composites used in concrete as stirrups. Full article

This study investigates the long-term mechanical performance of highly reinforced long glass fiber thermoplastic polypropylene composites, focusing on the effects of processing parameters, fiber length, and skin–core structures. Dynamic mechanical and creep analyses were conducted to evaluate the impact of injection molding on the final microstructure and long-term mechanical properties. The findings confirm that a significant microstructural change occurs at a fiber length of 1000 µm, which strongly influences the material’s mechanical behavior. Samples with fiber lengths above this threshold reveal greater creep resistance due to the reduced flowability that leads to more entangled, three-dimensional fiber networks in the core. This structure limits chain mobility and consequently improves the resistance to long-term deformation under load. Conversely, fiber lengths below 1000 µm promote a planar arrangement of fibers, which enhances chain relaxation, fiber orientation, and creep strain. Specifically, samples with fiber lengths exceeding 1000 µm exhibited up to a 15% lower creep strain compared to shorter fiber samples. Additionally, a direct relationship is observed between the findings in the viscoelastic response and quasi-static tensile properties from previous studies. Finally, the impact of the microstructure is more pronounced at low temperatures and becomes nearly negligible at high temperatures, indicating that beyond the glass transition temperature, the microstructural effect diminishes gradually until it becomes almost non-existent. Full article

The growing demand for sustainable materials has driven interest in natural fiber-reinforced composites as eco-friendly alternatives to synthetic materials. This research investigates the fabrication and mechanical performance of hemp and sisal fiber-reinforced composites, with a focus on improving fiber–matrix bonding through alkali and fungal treatments. Experimental results show that fungal treatment significantly improves tensile and flexural strength, while hardness slightly decreases. Water absorption tests revealed moderate reductions in hydrophilicity compared to untreated samples, although absolute water uptake remains higher than conventional glass/epoxy composites. Microscopy analysis further confirmed enhanced fiber adhesion and structural integrity in treated specimens. These findings suggest that hybrid composites reinforced with hemp and sisal, particularly with fungal treatment, hold promise for low-to-medium load sustainable applications in the automotive interiors, packaging, and construction industries, where moderate mechanical performance and partial biodegradability are acceptable. This research contributes to the advancement of bio-based composite materials while acknowledging current limitations in long-term durability and complete biodegradability. Full article

The work presented here describes an approach that separates the viscous stress from the quasi-static counterpart for polycarbonate (PC) and its short glass fiber composite (GF-PC), with the aim to characterize the influence of short glass fiber on the viscous behavior of PC as the matrix of GF-PC. A multi-relaxation (MR) test was used for the mechanical testing and a three-branch spring–dashpot model for the data analysis, using a genetic algorithm to establish 100 sets of fitting parameter values that enabled the three-branch model to regenerate the measured stress decay during relaxation. Using the spring modulus $\left(K_{v,s}\right)$ of the short-term branch in the three-branch model, two groups for these fitting parameter values were established as a function of specimen displacement (named stroke) of GF-PC, one of which shows a trend that is similar to the trend of the corresponding fitting parameters for the pure PC, and thus is believed to reflect the influence of glass fiber on the PC matrix of GF-PC. The study concludes that the short glass fiber increases the short-term viscous stress, but its role on the long-term viscous stress is marginal. Full article

Tissue conditioners are temporary lining materials applied to dentures to soothe and cushion inflamed or traumatized oral tissues, typically resulting from ill-fitting dentures. This laboratory study aimed to evaluate the physicomechanical properties of a clinical tissue conditioner with 0.5 and 1 wt.% of silanized, micron-sized, E-glass fibers. The experimental tissue conditioners were characterized based on their molecular structure, surface roughness, contact angle, tensile strength, dimensional stability, water sorption, and solubility. The results were analyzed by two-way ANOVA (factors: material composition and aging) and the post hoc Tukey’s test. FTIR analysis revealed characteristic peaks at 1710–1720 cm⁻¹, 2800–3000 cm⁻¹, and 1400 cm⁻¹, indicating a strong interaction between the tissue conditioner and the micron-sized glass fibers. Tensile strength was highest at baseline but declined in all groups after 14 days of aging, with the 0.5 wt.% glass fiber group showing the least reduction. Linear dimensional changes remained consistent across all groups. Surface roughness increased in all groups after 14 days, though the 0.5 wt.% glass fiber group exhibited the smallest increase. Water contact angles ranged from 71° to 92°, suggesting adequate surface wettability for clinical use. The experimental groups consistently demonstrated lower water sorption and solubility values. The 0.5 wt.% glass fiber formulation showed the potential to improve clinical performance by its reduced water sorption and solubility. However, long-term studies and clinical trials are necessary to validate the clinical effectiveness of this formulation. Full article

Introduction: High-performance fiber-reinforced technopolymers for computer-aided design/computer-aided manufacturing (CAD/CAM) of dental restorations offer superior durability and strength. However, exposure to acidic solutions may adversely affect these mechanical properties. Objective: This study aimed to evaluate the flexural properties of a high-strength commercially available CAD/CAM fiber-reinforced dental material in response to water, cola, and artificial gastric acid solutions. Method: Forty bar-shaped specimens (1 × 4 × 13 mm) were fabricated from a pre-polymerized glass fiber-reinforced composite (Trilor disks, Bioloren, Saronno, Italy). Ten specimens were randomly selected for baseline testing. The remaining specimens were subdivided into three groups based on the storage media (n = 10): artificial gastric acid solution, Coca-Cola, and deionized water (37 °C, 48 h). Mean flexural strengths and moduli were statistically compared at a significance level of p < 0.05. Results: No statistically significant change in flexural strength was observed after immersion in the different media. However, there was a statistically significant decrease in the flexural modulus after storage for 48 h, regardless of pH. Conclusion: Fiber-reinforced CAD/CAM technopolymers show promising strength stability in response to varying pH conditions. However, further studies are needed to investigate the material’s long-term strength stability. Full article

This study investigates the development of sustainable polymer composites for structural strengthening by incorporating waste glass fibers and natural fibers (flax and hemp) into an epoxy matrix, in response to the growing environmental concerns. Mechanical, thermal, and durability-related properties were evaluated through tensile testing, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), water absorption, and water immersion aging tests. Results showed that incorporating waste glass fibers enhanced the tensile strength and thermal decomposition temperature by 88% and 5.4%, respectively, compared to composites reinforced with solely natural fibers. Water absorption tests indicated that waste glass fiber-reinforced hybrid composites exhibited lower water uptake than flax and hemp fiber-reinforced composites. After water immersion, the tensile strength loss was recorded as 22, 25, and 8.5% for the composites reinforced with hemp, flax, and waste glass fiber, respectively. The findings confirm that incorporating waste glass fibers into natural fiber composites effectively mitigates moisture sensitivity and improves mechanical performance. Hybridizing flax and hemp fibers with waste glass fibers provides a practical and sustainable approach to enhancing composite performance, making them a viable alternative for strengthening reinforced concrete structures requiring long-term resistance. The recycled waste glass fibers employed in this study offered comparable mechanical performance while drastically lowering raw material consumption and environmental impact, in contrast to virgin glass fibers frequently used in earlier investigations. This demonstrates how recycling-oriented composite design can provide both sustainability and performance benefits. Full article

This study incorporated silane coupling agent KH550-modified nano-alumina (KH550-Al₂O₃) into vinyl ester resin (VER) for modification. The effect of KH550-Al₂O₃ on the flexural properties of VER and basalt fiber-reinforced vinyl ester resin (BF/VER) composites was investigated. In addition, dynamic mechanical analysis (DMA) and long-term elevated temperature aging of the composites were performed. The surface functionalization of KH550-Al₂O₃ was confirmed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS). It was revealed by scanning electron microscopy (SEM) that the aggregation of KH550-Al₂O₃ had been reduced within the VER matrix, the resin was effectively enhanced, and the fiber–matrix interfacial bonding was improved. Based on the experimental results, the optimal filler loading of KH550-Al₂O₃ was 1.5 wt%. Compared with the control group, the resin matrix exhibited 18.1% and 22.7% improvements in flexural strength and modulus, respectively, while the composite showed increases of 9.3% and 7.6% in these properties. At 30 °C, the storage modulus of the composites increased by 11.5%, with the glass transition temperature rising from 111.0 °C to 112.5 °C. After 60 days of thermal aging at 120 °C, the retained flexural strength and modulus were 64.3% and 87.4%, respectively. Full article

This study investigates the shear-bending performance of GFRP (Glass Fiber Reinforced Polymer) connectors in sandwich insulation composite wall panels following tension–compression fatigue damage. A total of 24 specimens, divided into 11 groups, were prepared for experimental analysis. Three distinct load amplitudes (5.4 kN, 4.0 kN, 2.7 kN) and three fatigue loading cycles (30,000, 50,000, 80,000) were established as loading conditions. The experimental protocol included out-of-plane tension–compression fatigue tests followed by post-fatigue shear-bending tests. The influence of varying load amplitudes and fatigue loading cycles on failure modes, load–displacement relationships, and bearing capacity alterations was systematically examined. A two-factor analysis of variance (ANOVA) was utilized to evaluate the statistical significance of these factors. The findings reveal that the predominant shear-bending failure modes post-fatigue damage are connector fracture and concrete crushing in the anchorage zone. Specifically, under a load amplitude of 2.7 kN and 30,000 cycles, the shear-bending capacity of the specimens exhibited a minimal reduction of 1.82% compared to the ultimate capacity of undamaged specimens. Conversely, at a load amplitude of 5.4 kN and 80,000 cycles, the shear-bending capacity experienced a substantial decline of 37.11%. Both load amplitude and fatigue loading cycles were found to significantly impact the shear-bending capacity, with fatigue loading cycles demonstrating a more pronounced effect. This research provides critical insights for the design and assessment of sandwich insulation composite wall panels, particularly in the context of long-term fatigue damage and its implications on structural performance, thereby contributing valuable theoretical and practical knowledge to the field. Full article

This study evaluates the performance of lightweight aggregate deep beams strengthened with low-cost glass fiber-reinforced polymer composite (Lo-G) wraps as an alternative to expensive synthetic fiber-reinforced polymers (FRPs). The investigation includes side-bonded and fully wrapped configurations of Lo-G wraps, alongside carbon FRP (CFRP) strips for comparison. The experimental results show that epoxy-based anchors provided significantly better resistance against de-bonding than mechanical anchors, improving beam performance. Strengthening with Lo-G wraps resulted in a peak capacity increase of 17.0% to 46.9% for side-bonded beams in Group 2, 10.5% to 41.4% for fully wrapped beams in the strip configuration in Group 3, and 15.4% to 42.7% for CFRP strips in Group 4. The ultimate deflection and dissipated energy were also improved, with dissipated energy increases of up to 264.6%, 322.3%, and 222.7% for side-bonded and fully wrapped Lo-G wraps and CFRP strips, respectively. The side-bonded configuration with two or three Lo-G wraps, supplemented by epoxy wraps, outperformed fully wrapped 250 mm strips in peak capacity, with peak capacity improvements of up to 46.9%. However, beams with mechanical anchors showed poor performance due to premature debonding. They rely on friction and expansion within the concrete to resist pull-out forces. If the surrounding concrete is not strong enough or if the anchor is not properly installed, it can lead to failure. Additionally, reducing strip spacing negatively impacted performance. Lo-G wraps showed an 8.5% higher peak capacity and 32.8% greater dissipated energy compared to CFRP strips. Despite these improvements, while Lo-G wraps are a cost-effective alternative, their long-term performance remains to be investigated. None of the existing models accurately predicted the shear strength contribution of Lo-G wraps, as the lower elastic modulus and tensile strength led to high deviations in prediction-to-experimental ratios, underscoring the need for new models to assess shear strength. Full article

The substitution conventional steel reinforcement with glass fiber-reinforced polymer (GFRP) bars is a widely adopted strategy used to improve the durability of concrete structures in chloride environments, offering benefits such as enhanced corrosion resistance, reduced maintenance needs, and increased service life. This study investigates the bond behavior between glass fiber-reinforced polymer (GFRP) bars and concrete under long-term chloride dry–wet cycling exposure. Pull-out tests were conducted on various specimens subjected to exposure durations of 0, 3, 6, 9, and 12 months. The experimental results indicate that, after 12 months of chloride dry–wet cycling, the bond strength retention rates of threaded ribbed GFRP with a bond length of 5d, sand-coated GFRP with a bond length of 5d, and threaded ribbed GFRP with a bond length of 7d were 57.9%, 62.2%, and 63.8%, respectively. To predict the GFRP–concrete bond performance after chloride exposure, a novel bond strength model for GFRP bars embedded in concrete, considering the mechanical interlocking effect of ribs, was proposed and validated by the test results. The overall prediction errors for RG-5d, SG-5d, and RG-7d specimens were 0.98, 0.81, and 0.93, respectively. Additionally, a sensitivity analysis was conducted on the main parameters in the model. Finally, the long-term GFRP–concrete bond performance deterioration was estimated using the proposed model. These findings are expected to provide valuable insights into the long-term bond performance and service life prediction of GFRP–concrete members in chloride environments. Full article