This paper presents double shear tests performed to investigate factors influencing the bond behavior between basalt fiber-reinforced polymer (BFRP), glass fiber-reinforced polymer (GFRP) laminate, ...and concrete blocks. In detail, thirty-six twin concrete blocks strengthened with the aforementioned FRP types were tested to evaluate the influence of FRP length, width, and thickness, and their bonding behavior. The 2D-DIC (digital image correlation) technique and several strain gauges bonded along the laminate were used to measure the strain distributions of the FRP-to-concrete interface. The failure mode, ultimate load, load–slip, strain distribution, and bond–slip relationships between the laminates and concrete were analyzed. Furthermore, bond–slip curves were compared with some other existing literature models. The results from the experiment showed that the ultimate load, peak bond stress, and slip increased with the increase in the BFRP and GFRP laminates length, width, and thickness. The values of peak shear stress and the corresponding maximum shear slip were significantly different because of the above-mentioned factors’ influence on them. The bond interface that contributes to the bearing of the shear load may grow to an extent and later shift from the loaded end when debonding progresses. Finally, the fractured surfaces of the failed FRP laminates were examined using scanning electron microscope (SEM), revealing that FRP rupture, debonding in concrete, and debonding in an adhesive–concrete interface were the main failure types.
This work aims to evaluate the failure mechanisms of plain glass and basalt fiber reinforced composites and a selected glass/basalt hybrid composite sequence subjected to artificial seawater ...conditions. Sets of plain and five hybrid composite configurations were fabricated by vacuum assisted resin injection technique (VARI), and subjected to seawater aged for 258 days at 30 °C and 70 °C followed by tensile, flexural and charpy impact testing, respectively. Failure analysis for dry and seawater-aged composites were undertaken using scanning electron microscopy (SEM). Results showed that some hybrid laminates with sandwich-like and alternating sequencing exhibited superior mechanical properties and ageing resistance than plain laminates. GB3 (B2G2S) type hybrid composite with basalt fiber outer plies retained 100% tensile strength and 86.6% flexural strength after ageing, which was the highest among all the laminates. However, GB4 (BGBGS) type specimen with alternating sequencing retained the highest residual impact strength after ageing. SEM analysis on the failed specimens showed fiber breaking, matrix cracking and debonding caused by fiber–matrix interface degradation due to seawater exposure. However different hybrid configurations to a considerable extent prevented crack propagation across specimens, hence altering the overall damage morphology among different specimens.
Glass and basalt fiber reinforced vinyl ester epoxy (GFRP and BFRP) composites offer considerable potential for underwater and deep sea applications. In spite of their increasing usage in various ...sectors, there are still questions concerning their long term reliability in marine environment. In this article, the response of GFRP and BFRP to seawater ageing and their subsequent mechanical properties were evaluated. The composites were fabricated by vacuum assisted resin injection technique and seawater aged at 30 0C for 18, 28, 38, 258 and 305 days. By using scanning electron microscope (SEM), the failure of dry and seawater aged specimen after mechanical testing showed fiber breaking, debonding and sporadic fracturing along the laminate. This was due to higher moisture concentration in these areas during ageing. The results also revealed an overall steady decrease in tensile, flexural and impact strengths of seawater aged laminates with increasing ageing duration. Overall, the seawater ageing property of BFRP composites is almost identical to that of GFRP. The use of different nano-materials could also be explored in future works to address some drawbacks in the fiber–matrix interface durability after seawater ageing.
The purpose of this study is to investigate the influence of adhesive types on the interfacial behavior of externally bonded basalt fiber reinforced polymer (BFRP) sheet-concrete substrate. Twelve ...manufactured double-lap shear samples were tested using four bonding adhesives. The strains on the surface of BFRP‐concrete joint were determined using electrical resistance strain gauge together with two‐dimensional digital image correlation technique (2D‐DIC). Experimental results show that properties of different bonding adhesives i.e., stiff (linear elastic, higher strength) and soft (nonlinear elastic, lower modulus, higher ultimate strain) has a significant impact on the failure mode, stiffness, ultimate load, strain and shear stress distribution nonetheless not so much on bond-slip relationship. The failure modes of specimens changed from interfacial debonding or cohesive failure in concrete substrate for stiff adhesive specimens to debonding in adhesive layer when soft adhesives are used. Stiff adhesive interfaces experienced higher ultimate loads from 1.1 to 1.3 times higher than soft adhesive interface. Meanwhile soft adhesives are shown to possess a lower maximum shear stress, higher interfacial fracture energy and longer stress transfer length.
Personal branding has attracted significant interest from researchers and practitioners in the last decade. There have been numerous scientific studies covering different facets of personal branding. ...However, studies covering the scope of the interest need to be more comprehensive. The paper analyzes various research papers on personal branding, encompassing theoretical underpinnings, the strategic nature of personal branding, and future research opportunities identified by the different articles. The review identified four major themes: personal branding skills and attributes, the strategic nature of personal branding, personal branding, and personal branding, politics, and social media. These findings give a broader view for further research and practical application.
Many surfaces in nature possessing superhydrophobicity have hierarchical (nano- and micro- scale) structures. A three-dimensional (3-D) model of cylindrical hierarchical nanostructured is established ...to describe the superhydrophobicity of solid surface. Based on thermodynamic analysis, the expressions of free energy (FE) and free energy barrier (FEB) for four precisely different wetting states are established and theoretically discussed. This approach provides theoretical guidance for predicting the dynamic contact angle (CA), static CA and CA hysteresis (CAH). Additionally, the actual three-phase contact line with droplet motion has been simulated, and the process of droplet advancing and receding is closely linked with the movement of contact line. To a great extent, the transition between different wetting states go hand in hand with that of the cylinder height and base spacing of nanostructure. Under the existing geometric parameters, when the nano-cylinders height reaches 1.5 × 10−7 m, 2.36 × 10−7 m, 2.56 × 10−7 m, or when the nano-cylinders base spacing reaches 2.4 × 10−7 m, 2.65 × 10−7 m, 3.2 × 10−7 m, the system will have a transition between different wetting states. Combined with the existing literature data and our experimental results support the correctness of the theoretical research, which are helpful for designing dual-scale hierarchical structure surfaces for researching the wetting behavior of advanced superhydrophobic materials.
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•A three-dimensional micro/nano model of hierarchical cylindrical structure is proposed and analyzed for the first time.•The single and synergistic effects of the uniform geometric parameters of micron and nanometer on the wettability of the system are discussed.•The critical expressions (Nanometer cylinder height and base spacing) of transition between any two wetting states (existence) are given.•The final stable wetting state of the system can be accurately predicted.•By controlling the micro/nano parameters, the stable wetting state of the hierarchical structure system can be predicted.
A number of studies have identified interfacial debonding as a major challenge in externally bonded FRP strengthened systems. The addition of steel fiber into concrete enhances the debonding ...resistance, ductility and subsequently increase the strength of FRP laminate-concrete interface. The main purpose of this experiment is to explore the incorporation of different steel fiber contents in the interfacial bond between CFRP laminates and concrete substrate. Five groups of the double shear specimens were fabricated with hooked-end short steel fibers having five different volume contents namely; 0, 0.25%, 0.5%, 1.0%, and 1.5%. The impact of different fiber volume content on the maximum shear stress, slip at maximum shear stress and interfacial bond stress-slip relationship were analyzed. Results showed specimens with 0.25%–1.5% short steel fibers improved their maximum shear stress considerably over the control specimens. The failure modes of specimens were debonding in concrete substrate and concrete shear failure. Finally, an analytical interfacial bond-slip model considering the influence of volume fraction of short steel fibers is proposed.
The icephobic surface is of great importance for many industries and has been gaining much attention worldwide. The present work investigated the three-line (i.e., before icing, icing, and after ...icing) synergistic icephobicity based on CNTs/PDMS nanocomposites with different surface categories. Meanwhile, the mechanisms underlying the observed phenomenon were also elucidated within the framework of classical nucleation theory, thermodynamic analysis, and Joule heating. That is, before ice: the rebounding behavior for successive water droplets was investigated to verify the dynamic icephobicity on the as-prepared nanocomposite surfaces; Icing: the thermodynamic (temperature-time) curves were plotted to analyze the icing phase transition process for static water droplets on the nanocomposite surface according to classical nucleation theory, and the wetting state transition during the icing process was also claimed. After icing: the electro-thermal function of the nanocomposite surface provided a final line for active deicing, which served as an alternative strategy if the first two passive defensive lines lose efficacy.
The interlaminar bonding property between the facesheet and foam core plays an important role in enhancing the impact damage resistance ability of sandwich panels. In this paper, we filled short ...glass fiber (SGF) mat between the facesheet and foam core to enhance their bonding strength. The newly designed sandwich panels were manufactured by vacuum-assisted resin injection processing. A series of SGF mat filled sandwich panels with glass and/or carbon fiber facesheets were manufactured. The low-velocity impact as well as the compression-after-impact (CAI) performence were investigated. Failure modes of the sandwich panels were analyzed. Low-velocity impact results show that SGF mat filled sandwich panels with pure glass fiber facesheet displayed the maximum contact force. In the CAI test, wrinkling of the facesheet, buckling of the foam, and debonding between them are the major failure modes. Compared with contrast samples, SGF toughened sandwich panels show the highest strength increase rate.
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•We introduced SGF mat between foam core and face panel.•The SGF mat increased the energy absorb ability of the sandwich structure.•CAI increased by 6.37% of SGF mat filled sandwich with carbon fiber facesheet.•SGF mat changes the failure mode of the sandwich in CAI tests.
Composite materials are increasingly been used in a variety of fields such as transportation, civil engineering, etc. However, despite their unique characteristics, composite materials have been ...known to be highly susceptible to fire. To effectively access such risks, the current research studies the intumescent surface coating thickness effect on carbon, glass fiber reinforced epoxy and sandwich composites. These specimens were subjected to 30 kW/m2 flame for 150, and 300 s using butane burner as the fire source. The results showed that tensile, flexure, impact and compression properties decreased rapidly as the heat-exposure time increased. There was a significant improvement in the post-fire mechanical properties in thermally-protected carbon and glass/epoxy laminates and sandwich structures compared to specimens without intumescent protection. This result is due to the intumescent protection and ability of the charred layer to effectively reduce the transferring of heat to the substrate.
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