Glass Fiber Surface Research Articles

Tunable negative permittivity behavior and excellent electromagnetic shielding performance of pyrolytic carbon‐glass fiber felt/epoxy resin metacomposites

AbstractEffective and accurate adjustment of negative permittivity behavior is worthy of further investigation. Herein, pyrolytic carbon‐glass fiber felt/epoxy resin (PyC‐GFF/ER) metacomposites with tunable negative permittivity were prepared using an impregnation‐calcination method. The permittivity, electrical conductivity, and electromagnetic shielding performance of the polymer metacomposites were investigated. Due to the inherent three‐dimensional structural network of GFF, the PyC adhering to the surface of glass fiber easily formed a conductive network in the composites. As the PyC content increased in the ER composites, the conductivity mechanism changed from hopping conduction to metal‐like conduction. The ER composites with high PyC contents showed negative permittivity behavior and the epsilon‐near‐zero response owing to the low frequency plasma state of free electrons in the PyC‐conduction network. By controlling the PyC content, the negative permittivity behavior of ER composites could be effectively tuned. With the increase in PyC content, the values of negative permittivity increased, and the epsilon‐near‐zero frequency shifted to a higher frequency. Moreover, the ER composites with high PyC contents showed excellent electromagnetic shielding properties (29.4 dB) at X‐band. This work not only provided a feasible method to realize the tunable negative permittivity of polymer metacomposites, but also promoted its application in the microwave field.Highlights The pyrolytic carbon‐glass fiber felt/epoxy resin composites were fabricated. The negative permittivity was first reported in the PyC‐GFF/ER composites. Tunable negative permittivity could be well explained by Drude model. The polymer composites had excellent electromagnetic shielding property.

Improved tribological properties of MXene nanosheet filler-modified PPO composites

MXenes, a class of two-dimensional (2D) nanomaterials, exhibit exceptional properties such as outstanding mechanical and thermal stability, along with diverse surface characteristics, making them highly promising in the tribology. However, their tendency to aggregate within the polymeric matrix adversely affects the tribological performance of the polymer. In this study, glass fiber (GF) surfaces were modified with polydopamine (PDA), allowing smaller MXene nanosheets to adhere to the GF surface, whereas the larger MXene nanosheets were dispersed throughout the matrix. This approach effectively enhanced the dispersion of MXene nanosheets in the polymeric matrix, facilitating the preparation of polyphenylene oxide (PPO)/MXene composite materials. Compared with the pure PPO sample, the results showed that the average friction coefficient and wear rate of the PPO/MXene composites were reduced by 46.25% and 98.34%, respectively, due to the distinct roles of different MXene nanosheet sizes in the polymeric matrix. Furthermore, a uniform lubricating film was formed during the friction of the polymer composite, enhancing its tribological performance. This study proposes a novel design strategy to enhance MXene nanosheet dispersion and optimize their lubricating properties.

Constructing ZSM-5 loaded with 2-mercaptobenzimidazole on glass fiber for enhancing the anti-corrosion and erosion resistance properties of epoxy coating

Glass fiber reinforced polymer coatings (GFRPC) are used to protect steel structures in harsh Marine environments due to high mechanical strength and chemical stability. The composite coating not only suffers from impact damage by seawater and sediment but also experiences corrosion damage in the splash zone. However, the GF has weak interfacial adhesion with polymer resins due to the chemical inertia and smooth surface, which limits the service lifespan of GFPRC. Hence, ZSM-5 zeolites were in situ prepared on the surface of glass fibers by hydrothermal synthesis, and 2-mercaptobenzimidazole (MBI) was further adsorbed to obtain difunctional hybrid glass fibers (ZGFM) to enhance the interfacial adhesion strength of glass fiber/resin and also the erosion resistance and anti-corrosion ability of composite coatings. Compared to GF/EP, the interfacial shear strength of ZGFM/EP was increased by 104.39 %. After immersion under an alternating hydrostatic pressure of 20 MPa for 12 days, the impedance value of the ZGFM/EP composite coating remained at 6.40 × 109 Ω•cm2, demonstrating outstanding deep-sea anti-corrosion performance. Following the erosion test, the ZGFM/EP exhibited a reduction in mass loss and volume loss by 10.65 % and 12.55 %, respectively, in comparison to the pure EP coating. The excellent interfacial strength between ZGFM and EP ensured effective stress transfer, which prevented crack propagation, thus enhancing the mechanical properties and erosion resistance of the composite coating. Meanwhile, electrochemical experiment proves glass fiber with MBI loaded obviously inhibited the corrosion reaction.

3D printing of high-stiffness and high-strength glass fiber reinforced PEEK composites by selective laser sintering

Glass fiber reinforced poly-ether-ether-ketone (PEEK) composites are emerging as structural materials of multifunctional devices in space applications, due to their outstanding mechanical properties, electrical insulating properties, and resistance to irradiation. Here, a new approach for preparing glass fiber/PEEK powders tailored for selective laser sintering (SLS) process is proposed. The surface of glass fiber is modified with the sulfonated PEEK following the designed procedure. The flowability of glass fiber/PEEK powders is also improved by adding the nano-scale SiO2 flow agent. The glass fiber reinforced PEEK composites are successfully 3D printed using the glass fiber/PEEK powders. Further, the enhancement of interfacial bonding between PEEK and glass fiber is analyzed through quasi-static tension tests and scanning electron microscopy (SEM) for the SLSed glass fiber reinforced PEEK composites. The average ultimate tensile strength reaches approximately 100 MPa using these optimal process parameters, while the average elastic modulus is around 7 GPa. Finally, the upper limit of fiber weight fraction is evaluated with the X-ray computed tomography (XCT) and the high-fidelity discrete element method (DEM) simulation.

Enhancing glass-ionomer cements with flake-shaped glass: A new frontier in dental restoration.

This study aims to investigate whether the combined use of thin sheet glass (FSG) and polyurethane acrylate (PUA) can enhance the mechanical properties and biocompatibility of glass ionomer cements (GICs) to improve the overall performance of commercial GICs. In this study, an innovative approach was employed by incorporating diluents and photoinitiators into PUA to develop a novel light-curable PUA material. The PUA was then used to modify the GIC to obtain PUA-modified GIC. Subsequently, physical and chemical methods were employed to corrode and chemically modify the glass fiber surface to acquire dried thin sheet glass (FSG). Different proportions of FSG (10%, 20%, and 30% by mass) were mixed with PUA-GIC to obtain FSG-PUA modified GIC. Mechanical and biocompatibility tests were conducted on regular GIC, PUA-GIC, resin-modified glass ionomer cement (RMGIC), and various proportions of FSG-PUA-GIC materials, including flexural strength, surface hardness, water absorption rate, solubility, shear strength, compressive strength (CS), in vitro cytotoxicity, as well as short-term oral toxicity and subcutaneous implantation trials. A novel FSG-PUA modified GIC was successfully prepared, which not only retained the excellent biocompatibility and fluoride ion release capacity of the original GIC but also significantly enhanced its mechanical strength and durability. The application of this innovative method provides a new direction for the development of dental restorative materials, particularly in addressing the shortcomings of GICs in terms of mechanical performance. The addition of FSG notably increased the flexural strength and surface hardness of GICs, especially at a 20% additive level, demonstrating superior performance compared with standard Fuji IX (F9) and slightly better than RMGIC. Water absorption rate and solubility initially decreased and then increased with an increase in FSG content, and significantly outperformed F9 and RMGIC at 10% and 20% additive levels. Shear strength and CS decreased with an increase in FSG content but remained superior to commercial groups. Material incubation with cells in vitro for 24-48 h showed no significant impact on cell viability, with cell viability exceeding 90%. Short-term oral toxicity tests demonstrated good biocompatibility of the material, and subcutaneous implant trials did not observe any significant inflammation or pathological changes within 12 weeks of observation. The use of FSG-PUA materials effectively enhances the mechanical properties of GIC materials, demonstrating excellent biocompatibility and significant potential as dental restorative materials. Among them, the 20% FSG-PUA modified GICs exhibited significantly superior flexural strength, surface hardness, shear strength, water absorption, and solubility compared with F9 and slightly surpassing RMGIC, showcasing the best mechanical performance.

Balancing the Mechanical and Electrochemical Properties of Multifunctional Composite Electrolyte for Structural Batteries

The pursuit of energy-efficient for electric vehicles and aircraft has driven the exploration of structural batteries. In the material-level design of structural batteries, electrode and electrolyte materials act as both load-bearing structures and energy storage elements. During these developments, carbon fibers with excellent mechanical and electrical conductive properties were used as electroactive materials and current collectors. However, most of these systems are combined with electrolytes without mechanical integrity (such as liquid or gel-type electrolytes), thus limiting the load-carrying performance of the battery. Currently the development of electrolytes for structural batteries remains challenging because the parameters enhancing electrochemical properties are often in contradiction with that for mechanical properties. In response to this challenge, the present study proposes a multifunctional composite electrolyte with balanced mechanical and electrochemical properties, which uses polyvinylidene fluoride (PVDF) as the matrix and metal-organic frameworks (MOF) modified glass fabric (MOF@GF) as the reinforcement. This study systematically investigates the following factors on mechanical and electrochemical properties of the composite electrolytes. Firstly, MOF with high specific surface areas and metal open sites onto the surface of glass fibers establishes a robust ion transporting network. With 20% MOF modified glass fiber and resin content 89%, the electrolyte exhibits high ion conductivity (1.74 × 10-3 S cm−1). In addition, by carefully controlling the resin content, a key parameter for fiber-reinforced composites, a delicate balance between mechanical strength and ionic conductivity can be achieved. Furthermore, interfaces were investigated, including glass fiber-MOF and MOF-PVDF interfaces, revealing the importance of effectively transfers stress and maintains structural integrity. Finally, these findings were combined to create a structural lithium metal battery that utilizes carbon fiber (CF) as the positive electrode and lithium metal as the anode. The resulting battery exhibits ultra-high tensile strength while maintaining a moderate capacity, ensuring normal operation under high voltage stress. This breakthrough discovery not only enhances the understanding of multifunctional composite electrolytes, but is also expected to promote further research and applications in the field of structural batteries. The promise of enhanced system electrolytes opens new avenues for lightweight design, space efficiency and expanded energy storage capabilities in electric vehicles and aircraft. Figure 1 . SEM images of (a) bare glass fiber. (b) MOF grown in-situ on glass fiber. (c) Single fiberglass within polymer matrix. (d) Cross section of the composite polymer electrolyte membrane. Figure 1

High-performance hybrid glass fibre epoxy composites reinforced with amine functionalised graphene oxide for structural applications

Glass fibre-reinforced epoxy (GFRE) composites have had limited use as structural components in industrial applications (e.g., oil and gas, aerospace and civil infrastructure). The use of nanomaterials, such as graphene, has been explored recently to enhance the mechanical and long-term properties of GFRE to realise their full potential and increase their usage. This study evaluated the tensile, creep, and fatigue behaviour of amine-functionalised graphene oxide (fGO) modified glass fibre/epoxy laminate composites. A spray coating technique was used to coat the fGO particles onto the glass fibre surface, and epoxy composite laminates were manufactured using the vacuum resin infusion method. Creep and fatigue testing was performed under a load-controlled mode in tension. Adding fGO within the composites significantly improves the static, creep, and fatigue properties of the fGO-GFRE composites at both room and elevated temperatures. It is shown that fGO acts as a barrier to microcrack initiation and restrains the macrocrack propagation during cyclic loading under elevated temperatures in the GFRE composites. These factors, therefore, prevent the early delamination of the matrix and fibre interface during cyclic loading, which explains the fatigue life extension observed in the fGO-modified composites. With 0.05 wt% fGO, the fatigue life of the fGO-GFRE composites was extended by 8× and 30× at a maximum stress of 124 and 151 MPa respectively, in a 90 °C environment compared to the control GFRE composites. While the creep life compared to the control increased by 63×, 103× and 159× with 0.25 wt%, 0.5 wt% and 1 wt% fGO, respectively. These enhancements are attributed to the large surface area, high stiffness, and functional groups present, which provide a stronger bond between the composite phases. These features help restrict the mobility of the polymer chain during the creeping load and act as barriers to fatigue crack propagation, enhancing the composite’s durability. The nanocomposites produced display attractive properties for many possible industrial applications where improved performance is needed while maintaining a minimum cost.

Brake Fluid Condition Monitoring by a Fiber Optic Sensor Using Silica Nanomaterials as Sensing Components.

In the automotive industry, there has been considerable focus on developing various sensors for engine oil monitoring. However, when it comes to monitoring the condition of brake fluid, which is crucial for ensuring safety, there has been a lack of a secure online method for this monitoring. This study addresses this gap by developing a hybrid silica nanofiber mat, or an aerogel integrated with an optical fiber sensor, to monitor brake fluid condition. The incorporation of silica nanofibers in this hybrid enhances the sensitivity of the optical fiber glass surface by at least 3.75 times. Furthermore, creating an air gap between the glass surface of the optical fiber and the nanofibers boosts sensitivity by at least 5 times, achieving a better correlation coefficient (R2 = 0.98). In the case of silica aerogel, the sensitivity is enhanced by 10 times, but this enhancement relies on the presence of the established air gap. The air gap was adjusted to range from 0.5 mm to 1 mm, without any significant change in the measurement within this range. The response time of the developed sensor is a minimum of 15 min. The sensing material is irreversible and has a diameter of 2.5 mm, making it easily replaceable. Overall, the sensor demonstrates strong repeatability, with approximately 90% consistency, and maintains uncertainty levels below 5% across specific ranges: from 3% to 6% for silica aerogel and from 5% to 6% for silica nanofibers in the presence of an air gap. These findings hold promise for integrating such an optical fiber sensor into a car's electronic system, enabling the direct online monitoring of brake fluid quality. Additionally, the study elucidates the effect of water absorption on the refractive index of brake fluid, as well as on the silica nanomaterials.

Surface Treatment Effect on the Mechanical and Thermal Behavior of the Glass Fabric Reinforced Polysulfone.

The chemical structure of the surface of glass fibers, including silanized fibers, was studied. Highly efficient heat-resistant composites were obtained by impregnating silanized glass fiber with a polysulfone solution, and the effect of modification of the surface of glass fibers on the physical, mechanical and thermophysical properties of the composite materials was studied. As a result of the study, it was found that the fiber-to-polymer ratio of 70/30 wt.% showed the best mechanical properties for composites reinforced with pre-heat-treated and silanized glass fibers. It has been established that the chemical treatment of the glass fibers with silanes makes it possible to increase the mechanical properties by 1.5 times compared to composites reinforced with initial fibers. It was found that the use of silane coupling agents made it possible to increase the thermal stability of the composites. Mechanisms that improve the interfacial interaction between the glass fibers and the polymer matrix have been identified. It has been shown that an increase in adhesion occurs both due to the uniform distribution of the polymer on the surface of the glass fibers and due to the improved wettability of the fibers by the polymer. An interpenetrating network was formed in the interfacial region, providing a chemical bond between the functional groups on the surface of the glass fiber and the polymer matrix, which was formed as a result of treating the glass fiber surface with silanes, It has been shown that when treated with aminopropyltriethoxysilane, significant functional unprotonated amino groups NH+/NH2+ are formed on the surface of the fibers; such free amino groups, oriented in the direction from the fiber surface, form strong bonds with the matrix polymer. Based on experimental data, the chemical structure of the polymer/glass fiber interface was identified.

Recycling of waste wind turbine blades for high‐performance polypropylene composites

AbstractGlass fiber‐reinforced epoxy resin composite materials are widely used in various fields because of their excellent properties, especially in the stringent performance requirements of wind turbine blades manufacture for wind power generation. However, the irreversible cross‐linking network of the epoxy resin makes it difficult to recycle. In recent years, the management of large amounts of decommissioned wind turbine blade waste has become spotlight. This study used self‐developed solid‐state shear milling technology to effectively remove the epoxy resin from the glass fiber surface while preserving its high aspect ratio, ensuring its mechanical reinforcement potential. Furthermore, this process also significantly reduced epoxy resin particle size. Subsequently, composites with filler contents up to 50 wt.% were formulated with polypropylene. In the optimized composition, the material exhibited a remarkable 37.1% increase in tensile strength, 147.3% increase in modulus, and 63.8% increase in flexural strength, 165.5% in modulus, respectively. In this research, we conducted a comprehensive exploration into the effects of modifier structure and powder content on different properties of composites, contributing to a deeper understanding of these key factors.

Constructing coral-like PDA layer on glass fiber to enhance the erosion resistance of epoxy coating

Glass fiber (GF) reinforced epoxy resin composite materials are widely used in wind power, automobiles, and ships, etc. The failure of glass fiber reinforced epoxy resin composites (GF/EP) is mainly attributed to the smooth surface and chemical inertness of GF. Dopamine, extracted from the adhesive protein secreted by mussels, exhibits excellent adhesion performance especially in wet environments. Thence, we constructed a coral-like layer of dopamine nanoparticles on the surface of glass fiber (PDA@GF) by self-surface polymerization deposition, which could simultaneously improve the chemical activity and roughness of the fiber surface, and form mechanical meshing and chemical bonding with the epoxy resin, thereby enhancing the interfacial adhesion strength between GF and EP. PDA layer with different surface morphologies were constructed on the GF surface by finely adjusting the reaction parameters, and the influences of surface morphologies on the mechanical performance of GF/EP coatings were explored. Based on the results obtained from tensile test, friction test, and erosion test, it was evident that the PDA@GF/EP composite material exhibited superior mechanical properties when the PDA layer exhibited a coral-like morphology, in comparison to the other two kinds of surface morphologies. Meanwhile, the dispersion of the fiber within the epoxy resin was examined using X-ray computed tomography (X-ray CT). On this basis, we investigated the anti-wear performance and erosion resistance of composite coatings with different fiber contents, furthermore, we revealed the anti-wear and anti-erosion mechanism.

A functionalized glass fiber as the adsorbent for efficient analysis of endocrine disruptors in aqueous environments

Estrogens and bisphenols are typical endocrine disruptors (EDs) that pose a potential hazard to the human body due to their widespread presence in aqueous environments. In this study, a β-cyclodextrin porous crosslinked polymer (β-CD-PCP) was prepared in-situ on a glass fiber surface by a nucleophilic substitution reaction. An effective and sensitive solid phase microextraction method using functionalized glass fiber with β-CD-PCP coating as the adsorbent was established for the detection of 11 EDs in a water environment. The β-CD-PCP was in-situ prepared on a glass fiber surface by a nucleophilic substitution reaction. The β-CD-PCP successfully separated five estrogens (ESTs) and six bisphenols (BPs) through hydrophobic and π-π interactions. The conditions affecting extraction were optimized. Under the optimized conditions, the ESTs obtained a high enrichment effect (1795–2328), low limits of detection (0.047 µg L−1) and a good linearity range (0.2–15.0 µg L−1). Furthermore, the spiked recoveries of analyte ESTs in aqueous environments were between 82.9–115.7 %. The results indicated that the prepared functionalized glass fibers exhibited good adsorption properties, and the established analytical method was reliable for monitoring trace ESTs and BPs in aqueous environments.

The influence from PTFE on surface and sub-surface damages of glass fiber reinforced PPS

Polymer composites are common materials for tribological components, even at relatively high operating temperatures. One advantage is the possibility to add low friction additives, such as PTFE, to the base material. In this paper the influence of such additives was studied, with focus on surface and sub-surface damages. The polymer composites were PPS with glass fibers (PPS-F), PPS with glass fibers and PTFE (PPS-L) and PEEK with carbon fibers, graphite and PTFE (PEEK-L). A reciprocating ball-on-disc test set-up, with ball bearing steel balls as counter material, was used with 5 N and 15 N normal load. The tests were run for 2,000 and 10,000 cycles in room temperature, 80 °C and 120 °C. PPS-F showed high friction (µ ≈ 0.4–0.5) and severe surface damage of both the polymer and the counter surface. Sub-surface cracks, detachment of fibers from the polymer and a deformed surface layer was revealed, when studied in cross section. The load and temperature had negligible effect on the friction, however a higher temperature resulted in more surface damage of the PPS-F. PPS-L and PEEK-L showed relatively low friction (µ ≈ 0.1) and superficial surface damage. XPS analysis revealed a thin tribofilm of PTFE in the wear track for PPS-L.

Significant enhancement of mechanical properties for glass fiber fabric‐reinforced polyamide 6 composites by improving interfacial bonding

AbstractIn fiber‐reinforced composites, the interfacial bonding between fibers and the matrix is crucial for determining the material's performance. A vacuum‐assisted resin transfer molding (VARTM) process was utilized in this work to fabricate glass fiber fabric‐reinforced polyamide 6 (GFF/PA6) composites through in‐situ polymerization using caprolactam (CL) as the precursor. To enhance the fiber‐matrix interfacial bonding, polyethylene glycol (PEG) was incorporated into the polymerization system, improving the hydrogen bonding between the matrix and fibers. Morphological observations and interface layer analysis revealed that the introduction of PEG resulted in improved interfacial bonding and increased interface layer thickness. Molecular dynamics simulations indicated that the amino formate groups formed by the reaction with PEG exhibited more hydrogen bonds with the hydroxyl groups on the glass fiber surface, thereby promoting interfacial bonding between the matrix and fibers. When the PEG content was 10 wt%, the tensile strength and the elongation at break of the corresponding composite increased by 160% and 300% compared to GFF/PA6 composites without PEG. This study presents a promising strategy for enhancing the fiber‐matrix interfacial bonding by modifying the matrix, offering a prospective approach for developing high‐strength thermoplastic composites.Highlights GFF/PA6 composites were fabricated via the VARTM method. The addition of PEG for matrix modification improved the interfacial bonding. The modification enhances the hydrogen bonding between the matrix and fibers. Good interfacial bonding can greatly promote the crystallization of the matrix. The composites exhibited a significant increase in strength and toughness.

The Study of the Glass Fiber Surface Treatment Effect on the Base Strength Characteristics of the Composite Material

This article examines the impact of surface treatment of glass fibers on the strength of a composite material with an unsaturated polyester polymer matrix reinforced with glass fibers. The strength tests conducted include tensile, bending, and impact strength tests, as well as weight loss measurements. The research was conducted in two stages: in the first stage, the time was kept constant while the fibers were treated with varying concentrations of an alkaline NaOH solution; in the second stage, the concentration was fixed and the variable parameter was the treatment time. The results of the study indicate that surface treatment of glass fibers significantly improves their adhesion to the matrix materials, resulting in improved strength test results for the composite samples. The impact resistance, bending resistance, and tensile strength values all increased compared to the reference samples. However, certain changes in the individual parameters of fiber processing led to a slight decrease in tensile strength when it fell below the reference values. Additionally, it was observed that as the concentration of the solution and treatment time increased, the weight of the fibers decreased.

Accelerated naked-eye identification of cations using non-plasmonic amplification by functionalized GQDs: A novel photochemical microfluidic sensor for environmental/mineral analysis using Lab-on-paper technology

This study describes the synthesis of various types of thiolated-graphene quantum dots (GQDs) for the simultaneous multi-sensing of heavy metal ions using one-droplet microfluidic paper-based analytical devices (OD-µPADs). For the first time, functionalized GQDs were synthesized and stabilized on the surface of hydrophobic fiber-glass with simple manufacturing and assembly strategy towards colorimetric chemosensing of ions including iron, copper, cobalt, mercury, chrome, manganese, and nickel. For this purpose, GQDs are functionalized by various organic species including cysteamine, decanethiol, and mercaptopropionic acid (MPA) towards specific electrostatic interaction with metal ions of Fe (II), Cu (II), Co(II), Hg (II), Mn (II), and Ni (II). Therefore, an innovative GQDs-based miniaturized chemo-system was proposed for the environmental analysis. Additionally, the results were confirmed using fluorescence spectrometry as an optical detection method. Finally, this simple and efficient colorimetric platform was used for facile metal ions detection in human urine models, and environmental fluids, which can provide a commercial device for sensing contaminants by non-professional users in biomedical/environmental mixture. As an economical technique, this platform presents a “mix-and-sense” system without dye (as a side substance) or chemical treatments. The low instrumental requirements, the color uniformity, and the disposability of OD-μPADs approve the commercial application of the engineered ion-chemosensor.

The effect of plasma treatment on the mode II interlaminar fracture toughness of Glass/Epoxy laminates

Despite the key advantages of fiber-reinforced polymer composites, such as high specific strength and stiffness, these materials are characterized by low interlaminar fracture toughness. This study aims to investigate the effect of dielectric-barrier discharge (DBD) plasma treatment of glass fibers on the mode II interlaminar fracture toughness (GIIC) of glass/epoxy composite laminates. To this aim, first, end-notched bending (ENF) specimens were fabricated using the vacuum infusion process. During the laminating process of the specimens, the two adjacent glass layers at the top and bottom faces of the pre-delamination were exposed to an atmospheric DBD plasma for different exposure times (R: reference specimens without plasma treatment, PT2: specimens with two rounds of treatment, and PT5: specimens with five rounds of treatment). Afterward, the ENF specimens were subjected to three-point bending loading according to ASTM D7905 standard. The results showed an increase of ∼ 51% and ∼ 56% in GIIC for PT2 and PT5 specimens compared to the reference specimens (R), respectively. The Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the plasma treatment did not generate new functional groups at the surface of glass fibers; therefore, there was no increase in the chemical bonding strength of the fibers to the resin. However, scanning electron microscopy (SEM) revealed that the plasma treatment increased the adhesion of the glass fibers to epoxy by removing sizing of the glass fibers and increasing the surface roughness of the fibers. The results of the present study showed that the plasma treatment can be considered as a cheap, easy-to-use, cost effective and scalable method for toughening laminated composites instead of the costly and difficult methods such as electrospun nanofibers and z-pinning.

Paper electrophoretic enrichment-assisted ultrasensitive SERS detection

To achieve sensitive detection of trace substances in fluids by surface-enhanced Raman spectroscopy (SERS), effective enrichment of molecules at subwavelength regions (hot spots) with a large enhancement is adopted. In this work, a glass fibre paper with Ag nanoparticles (AgNPs) is employed for electrodynamic enrichment of analytes in fluids by paper electrophoresis integrated with field amplification sample stacking (FASS) and capillary effects to obtain both Raman and SERS convenient and sensitive detection. With the help of electrophoretic enrichment on the glass fibre paper and surface plasmon enhancement on the AgNPs, this paper electrophoretic enrichment could improve the detection limit of Raman and SERS detection by more than an order of magnitude, even achieving a SERS detection limit of 10−17 M for Nile Blue A. Furthermore, this flexible SERS detection method can also detect trace organic contaminants at the ppt level in aquaculture and food applications.

Reversible and irreversible effects on the epoxy GFRP fiber-matrix interphase due to hydrothermal aging

Epoxy R-Glass Fiber-Reinforced Polymer (GFRP) composite plates were hydrothermally aged at 60 °C for 23, 75, and 133 days. The water content reached 0.97 wt%, 1.45 wt% and 1.63 wt%, respectively. The studied GFRP matrix was inert to hydrolysis or chain scission, allowing for investigation of irreversible changes in the fiber-matrix interphase due to hydrothermal aging upon re-drying. During each period, a subset of the specimens was removed from the water bath and dried in a chamber. The weight loss upon drying was explained with epoxy leaching (impurities), sizing-rich interphase hydrolysis, glass fiber surface hydrolysis, accumulated degradation products escaping, and water changing state from bound to free. The influence of hydrothermal aging on the fiber-matrix interfacial properties was investigated. Lower interfacial strength of hydrothermally aged (wet) samples was attributed to plasticization of the epoxy, plasticization and degradation of the sizing-rich interphase (including formation of hydrolytic flaws), and hydrolytic degradation of the glass fiber surface. The kinetics of epoxy-compatible epoxysilane W2020 sizing-rich interphase hydrolysis provided an estimate of ca. 1.49%, 4.80%, and 8.49% of the total composite interphase degraded after 23, 75, and 133 days, respectively. At these conditions, the interface lost 39%, 48%, and 51% of its strength. Upon re-drying the specimens, a significant part of the interfacial strength was regained. Furthermore, an upward trend was observed, being 13%, 10% and 3% strength, respectively; thus, indicating a possibility of partial recovery of properties.

Enhancement of Alkali Resistance of Glass Fibers via In Situ Modification of Manganese-Based Nanomaterials.

Glass fibers are widely used in cement-based precast products, given the reinforcing requirements for toughness and strength. However, inferior alkali resistance hinders the effectiveness of glass fibers in reinforcing cement-based materials. In this paper, nanoparticle coatings were applied on the surface of alkali-resistant glass fiber (ARGF) as a protective layer via the in situ chemical reaction of oleic acid (OA) and potassium permanganate (PP). The morphology and constituents of the as-prepared ARGFs were examined using scanning electron microscopy (SEM) and obtaining X-ray photoelectron spectroscopy (XPS) measurements. Mass loss and strength retention were investigated to characterize alkali resistance of modified ARGFs. Results showed that ARGFs could be optimally coated by a layer of MnO2-based nanoparticles consisting of approximately 70% MnO2, 18% MnO, and 12% MnSiO3, when modified with an optimum OA to PP ratio of 10 for 24 h. The dissolution of ARGFs matrix in 4% and 10% NaOH solutions were distinctly delayed to 28 d, as a consequence of the introduction of the MnO2-based nanoparticle layer, compared with nontreated ARGF occurring at 3 d in 4% NaOH solution. For the optimally modified ARGFs, the mass loss was controlled to 1.76% and 2.91% after 90 d of corrosion in 4% and 10% NaOH solutions, and the retention of tensile strength was increased by approximately 25%. With respect to the increment in alkali-resistant performance, the modified ARGFs can be promising candidates for wide applications in alkaline cement-based products.