In this study, 20 PVC-CFRP reinforced concrete beams are subjected to stress tests. The effects of specimen size, hoop reinforcement ratio, width and number of layers of CFRP strips, bonding method of CFRP strips, layers of CFRP sheets and shear span ratio on the damage mode and moment-curvature relationship curves of the specimens were analysed. The results indicate that, the failure of the specimen was governed by the yielding of the stirrups and bottom longitudinal reinforcement, and the CFRP strips were subsequently ruptured in tension. In the elastic stage, with the improvement of reinforcement ratio, CFRP strip width and number of layers, and longitudinal CFRP sheet layer, the slope of the ultimate bearing capacity and moment-curvature relationship curves of the specimens increased, and the curvature development of the specimens slowed down obviously. As the shear-to-span ratio increases, the ultimate bearing capacity of the specimens decreases and the change of the moment-curvature curve is not obvious. In addition, under the same fiber ratio condition, the effect of CFRP strip bonding method on the specimens' bearing capacity and bending moment-curvature curves is not significant. Furthermore, on the basis of the tests, considering the influence of various factors on the moment-curvature relationship of the specimens, the adjustment factor of the bending stiffness of the specimens is introduced, and the calculation model of the moment-curvature relationship of the specimens is established.

In order to explore new applications for the regeneration of waste clay bricks and to expand the use of bamboo plywood in structural engineering, this paper proposes a novel type of GFRP-plybamboo panel tube dual confined recycled brick aggregate concrete ecological laminated column (abbreviated as GPR laminated column). Compression failure tests were conducted on 18 GPR laminated column specimens to investigate the influence of brick aggregate replacement ratio in recycled brick aggregate concrete (RBAC), GFRP tube thickness, sectional bamboo content, spacing ratio of pull rods, load eccentricity, and slenderness ratio on the compressive bearing capacity and deformation of specimens. The test results indicate that the compressive failure mode of GPR laminated column specimens is mainly characterized by cracks and local fractures along the winding direction of GFRP tube fibers, as well as crushing of the outer RBAC. The location of GFRP fiber damage shifts upward with the increase of GFRP tube thickness. When subjected to eccentric loading, the failure mode of the GPR composite column involves tension-side GFRP fiber fracture, and slenderness ratio exceeding 32, compressive-side GFRP fiber fracture is observed. The compressive load-bearing capacity decreases with the increase of brick aggregate replacement rate, constrain tensile rod spacing ratio, load eccentricity, and slenderness ratio. Additionally, the load-bearing capacity decreases with an increase in GFRP tube thickness, while the section bamboo content has no significant effect on the ultimate load-bearing capacity of the specimens. Finally, a calculation model for the ultimate compression bearing capacity of GPR laminated columns was established based on experimental results, which is expected to provide reference for the engineering application of the GPR laminated columns.

To clarify the ultrasonic field characteristics of phased array ultrasonic testing (PAUT) in carbon fiber reinforced plastics (CFRP) cylindrical thick-walled shells, numerical simulation was carried out based on CIVA and COMSOL software. A comprehensive ultrasonic model was established, accounting for curved surfaces, layered structure, and elastic anisotropy. Subsequently, the influence of the array aperture, preset focal depth and inspection positions from inner or outer R side was studied. Results indicate that as the aperture increased from 3 to 12, the focal extent increased. Specifically, the width of focal range increased by 12.9 mm and the actual focal depth increased from 0.3 mm to 13.2 mm at the preset focal depth of 27.5 mm. The influence of the preset focal depth on the width of focal range remained relatively weak, while its impact on the actual focal depth depended on aperture, becoming pronounced only under substantial number of elements. Additionally, the adverse effect from inspection positions of inner or outer R could be mitigated with the primary axis of PAUT probe aligning with the axial direction of cylinder. Finally, three delaminations with different depths were prepared and PAUT experiments were conducted to validate the typical simulated condition, and a good consistency was observed. The results are anticipated to serve as a valuable reference and technical guidance for nondestructive testing of the CFRP cylindrical thick-walled shells.

This study aims to reveal the fatigue life degradation mechanisms of carbon fiber reinforced polymer (CFRP) composites under pre-hygrothermal environments. The static tensile strength and fatigue life of composites were investigated under four moisture absorption conditions (0%, 40%, 70%, and 100% of saturated moisture content). The static tensile failure stress exhibited fluctuating characteristics, while the fatigue life showed a monotonic decreasing trend with increasing moisture absorption. The fatigue life distribution patterns of laminates under different stress levels were analyzed using log-normal distribution and two-parameter Weibull distribution theories, both demonstrating excellent fitting accuracy. Based on log-normal distribution analysis, the reliability life decreased with increasing reliability levels and increased with decreasing stress levels. The hygrothermal fatigue failure modes manifested as multiple damage mechanisms involving fiber bundle fracture spanning the entire working section and delamination damage. These findings provide theoretical support for the engineering application of composites in hygrothermal environments.

The composite-metal connection structure of aircraft will inevitably experience high or low temperature environment during service, and the stiffness and strength properties of composites will be degraded to different degrees under the action of high and low temperature loads, and the deformation mismatch caused by internal stresses arising from thermal expansion will have an negative impact on the bolt load distribution of the connection structure, which will endanger the safety and integrity of the structure. Therefore, this paper takes the composite-aluminium alloy double-bolt single-lap connection structure as the research object, and carries out a series of high-temperature (80 ℃) and low-temperature (-40 ℃) loading tests for different composite-aluminium alloy connection structures. The hole peripheral strain change law of the connection structure under the high and low temperature ambient loading is studied, and the influences of the composite material type, the adhesive layer and the bolt spacing on the hole peripheral strain of the connection structure are discussed. The results show that influence of temperature loading on the deformation non-coordination of carbon fiber composite-aluminium alloy connection joints is very significant, and the appropriate reduction of bolt spacing and the introduction of adhesive layer between the interfaces can effectively alleviate the impact of thermal stress caused by deformation mismatch. The research results of this paper can provide a certain reference for the design of connection structure of aircraft under temperature load.

In order to study the influence of bonding BFRP material at the bottom of beams on the mechanical properties of RC beams, tests were carried out on four reinforced beams and one control beam, and the influence laws of the reinforcement layers, reinforcement width, and anchoring mode of basalt fiber cloth on the mechanical properties of RC beams were analyzed. The applicability of the formulas for calculating the bearing capacity of reinforced beams proposed by GB 50367—2013 and ACI 440.2R-17 was verified by the test results. The results show that the use of basalt fiber cloth to strengthen RC beams can greatly increase the yield load and ultimate load of RC beams, and the maximum increase can reach 33.14% and 25.00% respectively. The more layers of basalt fiber cloth reinforcement, the greater the stiffness of the beam. Under the same reinforcement quantity condition, the smaller the reinforcement width, the greater the stiffness improvement. The reinforcement reduces the beam ductility, the maximum reduction is 34.96%. The average error of GB 50367—2013 and ACI 440.2R-17 ultimate bearing capacity calculation results is 4.00% and 6.00% respectively, which can give ideal calculation results and can be used for the calculation of ultimate bearing capacity of BFRP strengthened RC beams.

Fiber-reinforced resin matrix composites (FRP)are widely used in the nuclear industry, and investigating the factors influencing their gamma radiation resistance and performance evaluation methods can provide critical insights for the modification and development of radiation-resistant materials. In this study, four types of resins and three types of fibers were systematically evaluated. Initial screening via tensile strength tests before and after irradiation identified diglycidyl ether of bisphenol A (DGEBA) and unsaturated polyurethane resin (UPU) as the top-performing matrices. The underlying radiation resistance mechanisms were elucidated using Fourier transform infrared (FTIR) spectroscopy. These resins were then combined with glass fiber (GF), basalt fiber (BF), and carbon fiber (CF) to fabricate composites, which were subjected to tensile, flexural, compressive and short-beam shear strength tests before and after irradiation. The results revealed that DGEBA exhibited superior compatibility with BF and CF, while UPU showed optimal interfacial synergy with GF. Furthermore, the radiation resistance of composites required a comprehensive evaluation of multiple mechanical properties rather than relying on a single metric. This work establishes a foundational framework for designing gamma radiation-resistant FRP and offers practical guidance for simplified engineering assessments of radiation tolerance in structural materials.

The surface of carbon fiber is smooth and it is inert, which results in poor compatibility with cement-based material. The surface properties of carbon fiber can be improved by electroless nickel plating. The surface elements and tensile strength of nickel-plated carbon fiber were characterized, and the nickel-plated carbon fiber modified cement-based material were prepared. Meanwhile, the mechanical properties, crack resistance, impermeability and frost resistance of nickel-plated carbon fiber modified cement-based materials were studied and compared with carbon fiber modified cement-based materials. The interfacial modification mechanism of nickel-plated carbon fiber/cement based material was analyzed by SEM. The results show that, compared with carbon fiber, nickel-plated carbon fiber exhibits higher surface oxygen content and greater tensile strength; it provides better improvement in the mechanical properties and durability of cement-based materials as well as superior dispersion in the matix, with an optimal content of 0.9%. With this fiber content, the flexural strength and compressive strength of the cement-based materials increase by 32.88% and 26.61%, respectively, while the total cracking weight, water seepage height, mass loss rate, flexural strength loss rate, and compressive strength loss rate decrease by 34.76%, 53.19%, 57.41%, 51.29%, and 45.42%, respectively. Numerous pores are observed at the interface of carbon fiber/cement-based material, but the interface of nickel-plated carbon fiber/cement-based material is well bonded. The oxygen element on the surface of nickel-plated carbon fiber improves its hydrophilicity, and the nickel coating enhances its mechanical interlocking force with cement-based material.

In this paper, numerical simulations combined with experimental investigations were carried out to study the strength and failure modes of the bonded-bolted double-lap sandwich composite-steel joints under tensile loads. The influences of the joint width, end distance and hole spacing on the strength of the joint were studied respectively, and single factor optimization design was conducted. The results show that the overall trend and failure modes of the numerical and experimental load-displacement curves are in good agreement. The initial failure occurs in the adhesive layer at the end of the bonding area. As the tensile displacement increases, the cracks of the adhesive layer propagate, and the bolt gradually bears the load together with the adhesive layer with compressive failure of the skin occurring at the screw hole. The final failure of the structure occurs when the adhesive layer completely fails and the sandwich panel and steel plate are completely detached. The single factor optimization design shows that the joint stiffness and ultimate load increase continuously with the increase of joint width, but the failure displacement and connection efficiency decrease. The results also show that the stiffness of the joint is not affected by the end distance and hole spacing, whereas the ultimate load and connection efficiency increase with the increase of end distance and hole spacing. The optimal combination of the design factors is as follows: the width-to-aperture ratio is 3.5, the end distance-to-aperture ratio is 3.0, and the hole spacing-to-aperture ratio is 3.5.

To explore the axial compressive behavior of reinforced concrete columns confined by fiber-wrapped glass fiber reinforced polymer (GFRP) tubes, axial compressive tests and finite element simulations were conducted on eight GFRP-confined reinforced concrete cylinders subjected to freeze-thaw cycles. The effects of concrete strength, number of freeze-thaw cycles, and slenderness ratio on the axial compression performance of the composite columns were studied. The results indicate that, under the same number of freeze-thaw cycles, the ultimate bearing capacity of the C60 columns is on average 9% higher than that of the C30 columns. The bearing capacity of the specimens decreases with the increase in freeze-thaw cycles, but the degradation rate is slower for the C60 columns than for the C30 columns. Additionally, the influence of slenderness ratio on the stiffness and bearing capacity of the specimens becomes more significant as the number of freeze-thaw cycles increases. A theoretical formula for calculating the axial compressive bearing capacity of GFRP-confined reinforced concrete columns was established, and the calculated results show a high degree of agreement with the experimental data. This study provides a valuable reference for related engineering designs.

The surface wave suppression performance of electromagnetic functional composite materials applied to laminated structures was studied. The influence of electromagnetic parameters (complex permittivity, complex permeability) and layer thickness on surface wave attenuation was evaluated through simulations. By adopting the method of loading an impedance functional layer, the low-frequency surface travelling wave suppression ability of the electromagnetic functional composite was improved without increasing the weight and thickness of the composite materials. The results show that both the permittivity and the permeability have an impact on the travelling wave suppression effect, and the permeability has a relatively greater influence. With the increase of the permittivity, the surface travelling wave suppression ability of the high-frequency surface waves gradually increases. As the permeability increases, the attenuation intensity of both low- and high-frequency surface travelling waves increases. When the thickness of the material meets the condition of being an odd multiple of a quarter-wavelength, excellent travelling wave suppression performance can be achieved for the material. When the thickness of the material is 1 mm, through the composite design with impedance loading, the suppression coefficients of the travelling wave suppression effect of the material at the frequency points of 1.5 GHz, 3 GHz and 6 GHz can reach 4.41 dB/m, 13.98 dB/m and 27.31 dB/m respectively. Compared with that before the impedance loading, while maintaining the high-frequency surface travelling wave suppression ability, the travelling wave suppression effect of the material is improved by 1.86 dB/m and 4.90 dB/m at 1.5 GHz and 3 GHz respectively, achieving the improvement of the low-frequency surface travelling wave suppression ability, which can effectively guide the regulation of the travelling wave suppression performance of electromagnetic functional composites.

To address the issue of excessive weight in the mining wind measuring mechanical arm, which reduces transportation and installation efficiency, a lightweight design using carbon fiber reinforced polymer (CFRP) was implemented. Finite element simulation methods were employed for optimization and comparative analysis. The nested three-stage telescopic boom was selected as the optimization target, and structural optimization was carried out, followed by an analysis of the static mechanical properties of different materials after optimization. Through thickness optimization and ply angle optimization, the optimal design solution was determined. Finally, failure analysis and stability checks were conducted to ensure that the optimal solution meets safety requirements. Simulation results show that the total mass of the telescopic boom with CFRP optimization is reduced from 52.817 kg to 33.563 kg, achieving a weight reduction of 36.45%. Meanwhile, the total deformation decreases from 28.855 mm to 15.204 mm, with a 47.31% increase in stiffness.

The effective control of electromagnetic waves is crucial in cutting-edge fields such as modern wireless communication, intelligent sensing, and electronic counter measures. This paper proposes an optimization design method for coding metasurfaces based on a particle swarm optimization algorithm. The design utilizes carbon fiber composite surfaces coated with a graphene-copper mesh to suppress ultra-broadband backward scattering. The metasurface effectively reduces the radar cross-section by integrating scattering cancellation and vibration absorption mechanisms. Within the frequency range of 12 GHz to 40 GHz, two distinct unit cells of the metasurface exhibit a 180° reflection phase difference in both unit cells morphology and planar arrangement, accompanied by varying amplitude characteristics, achieving a broadband RCS reduction of 107.7% relative bandwidth. Furthermore, an unequal proportion design of the coding metasurface is employed to enhance the diffusion effect of backward-scattered waves at specific frequencies. The arbitrary coding sequences of unit cells are optimized using the PSO algorithm to achieve optimal unit cells arrangement. This novel coding metasurface enables high-frequency broadband microwave absorption, showcasing significant potential for applications in microwave absorption and electromagnetic shielding.

The resin filling process of carbon fiber/phenolic resin honeycomb composite material RTM molding is studied using simulation and experimental methods. Firstly, the parameters of carbon honeycomb preforms and phenolic resin materials were tested, and then PAM-RTM software was used to simulate the resin filling process under different channel designs and injection pressure conditions. Based on the simulation results, the resin flow behavior such as resin filling time, filling path, resin flow velocity distribution in the mold cavity, and pressure distribution was analyzed. The simulation results show that when the flow channel is designed with 4 injection ports, 1 or 4 overflow ports, and the injection pressure is in the range of 0.3 MPa to 0.5 MPa, it is an ideal method for setting process parameters. Finally, the simulation results were verified through experimental methods, proving that the simulation results provides valuable guidance for engineering applications.

FRP bars are prone to alkali corrosion and performance degradation in high-alkalinity cement concrete. To address this issue, types of low-alkalinity cement(high-belite sulfoaluminate cement and slag sulfoaluminate cement) were proposed for the preparation of low-alkali cement concrete. The pH evolution of the pore solution in low-alkalinity concrete immersed in freshwater and seawater was measured. Experimental studies were conducted to examine the performance changes of FRP bars after immersion in simulated pore solutions, as well as the time-dependent evolution of the bond strength at the FRP bar-low-alkalinity cement concrete interface. The results indicate that the pore solution pH of the two low-alkalinity cement concretes is reduced by 0.7 to 2.0 compared to Portland cement concrete, with seawater exposure contributing to a further decrease in pH. The alkali corrosion rate of FRP bars is significantly lower in low-alkalinity simulated pore solutions. Based on experimental data and the Arrhenius degradation model, the estimated service life of FRP bars in low-alkalinity cement concrete simulated pore solutions increases by 10% to 30% compared to those in Portland cement concrete simulated pore solutions. Additionally, seawater exposure promotes strength development in low-alkalinity cement concrete while lowering the concrete pH. After 180 days of immersion in artificial seawater at 40 ℃, the bond strength at the FRP bar-low-alkalinity cement concrete interface increases by 10% to 30%, whereas that at the FRP bar-Portland cement concrete interface decreases by 10% to 15%. In conclusion, the adoption of novel low-alkalinity cement can significantly enhance the bond strength between FRP bars and concrete while improving the durability of structures in marine environments.

To address problems of tape edge deformation and gap control in the process of automatic winding forming of heat insulation, this paper proposes an optimization strategy of winding path of heat insulation based on particle swarm optimization algorithm. Firstly, the parametric model of variable curvature mandrel is established, and a calculation method of segmented geodesic winding path is proposed based on geodesic differential equations. Then, the multi-objective performance evaluation index is introduced to evaluate the performance of the winding path, so that the path planning problem is transformed into a multi-objective optimization problem. Finally, the optimization model of heat insulation winding is established, and the particle swarm optimization algorithm is used to solve the optimization problem. The simulation results show that compared with the ant colony optimization algorithm, the particle swarm optimization algorithm reduces the average number of iterations by 53.4%, shortens the average running time by 63.4%, and improves the quality of the winding path by 10.6%. It has higher solution efficiency and better path optimization ability, can meet the control requirements of tape edge deformation and gap, and ensure the winding quality of heat insulation winding forming.

This paper presents the design and fabrication of a pressure sensor based on reduced graphene oxide suspended film (rGO-SF). The rGO-SF was formed through in-situ growth on pre-etched SiO₂ cavities, where self-assembled graphene oxide (GO) films spontaneously separated from solution. Compared with conventional graphene-based pressure sensor fabrication processes, the rGO-SF sensor eliminates membrane transfer steps, significantly simplifying the manufacturing workflow and providing advantages for large-scale production. By introducing modified polymethyl methacrylate (M-PMMA) into the rGO interlayers, the oxygen transmission rate (OTR) of the M-PMMA/rGO composite film was reduced by 49.6% (at 20.0wt% M-PMMA loading), markedly enhancing the stability and reliability of the rGO-SF pressure sensor. Experimental results demonstrate that pressure differences between internal and external environments induce measurable resistance changes in rGO-SF. Leveraging this principle, precise pressure measurement can be achieved by monitoring resistance variations. Testing shows the sensor effectively detects pressure changes in the 0 kPa to 100 kPa range, with excellent linearity (S²=0.99) and sensitivity (1.298×10^-3 kPa^-1) particularly in the 30 kPa to 100 kPa differential pressure regime.

During the construction and maintenance period of road projects in flood detention areas, low roadbed and extremely shallow covering soil conditions often result in insufficient culvert burial depth. Traditional culvert structures, due to repeated exposure to heavy loads and prolonged submersion, have concerning durability. To assess the applicability of double-row glass fiber reinforced plastic (FRP) sand-filled pipe culverts under this special shallow burial condition, indoor fatigue tests and field vehicle load tests were conducted to study their mechanical response and fatigue performance under long-term vehicle loads. The results indicate that under low roadbed conditions, shallow burial environments are unfavorable for culverts to resist traffic loads. After 2 million cycles under a strain rate of 1%D to 3%D and low-frequency alternating loads, the maximum reduction in the ring stiffness of the FRP sand-filled pipe under extreme stress conditions was only about 20%, demonstrating excellent deformation resistance and fatigue performance. In double-row pipe culvert arrangements, the top of the loaded pipe and the inner sides between pipes are stress-concentrated weak areas. However, under shallow covering soil and heavy load conditions, the double-row pipe solution can meet structural requirements, and reducing the pipe diameter can resolve elevation conflicts between the low roadbed and drainage structures. Finally, the study evaluates the significant technical advantages of replacing large-diameter single-row pipe culverts with small-diameter double-row pipes in terms of drainage efficiency, stress and deformation characteristics, and construction convenience.