Reliability analysis of carbon fiber rod-reinforced umbilical cable under tension using an improved sampling method

The umbilical cable is a vital component of subsea production systems that provide power,chemical agents,control signals et al.,and its requirement for reliability is exceedingly high.However,as the umbilical cable is a composite structure comprising multiple functional units,the reliability analysis of such cables involves numerous parameters that can impact calculation efficiency.In this paper,the reliability analysis of a new kind of umbilical cable with carbon fiber rod under tension is analyzed.The global dynamic analytical model is first established to determine the maximum tension load,then the local analytical model of umbilical cable including each unit are constructed by finite element method(FEM).Based on the mechanical analytical model,the reliability of umbilical cable under tension load is studied using response surface method(RSM)and Monte Carlo method.During the calculation process,a new tangent plane sampling method to calculate the response surface function(RSF)is proposed in this paper,which could make sampling points faster come close to the RSF curve,and it is proved that the calculation efficiency increases about 33%comparing with traditional method.

Microwave Absorption and Mechanical Properties of Short-cutted Carbon Fiber/glass Fiber Hybrid Veil Reinforced Epoxy Composites

This work aims at investigating the microwave absorption and mechanical properties of short-cutted carbon fiber/glass fiber hybrid veil reinforced epoxy composites.The short-cutted carbon fibers(CFs)/glass fibers(GFs)hybrid veil were prepared by papermaking technology,and composites liquid molding was employed to manufacture CFs/GFs hybrid epoxy composites.The microstructure,microwave absorbing properties and mechanical properties of the hybrid epoxy composites were studied by using SEM,vector network analyzer and universal material testing,respectively.The reflection coefficient of the composites were calculated by the measured complex permittivity and permeability in the X-band(8.2-12.4 GHz)range.The optimum microwave absorption properties can be obtained when the content of CFs in the hybrid veil is 6 wt%and the thickness of the composites is 2 mm,the minimum reflection coefficient of-31.8 dB and the effective absorption bandwidth is 2.1 GHz,which is ascribed to benefitting impedance matching characteristic and dielectric loss of the carbon fiber.Simultaneously the tensile strength and modulus can achieve 104.0 and 2.98GPa,demonstrating that the CFs/GFs hybrid epoxy composites can be a promising candidate of microwave absorbing materials with high mechanical properties.

High-sensitivity phase imaging eddy current magneto-optical system for carbon fiber reinforced polymers detection

This paper proposed a high-sensitivity phase imaging eddy current magneto-optical (PI-ECMO) system for carbon fiber reinforced polymer (CFRP) defect detection. In contrast to other eddy current-based detection systems, the proposed system employs a fixed position excitation coil while enabling the detection point to move within the detection region. This configuration effectively mitigates the interference caused by the lift-off effect, which is commonly observed in systems with moving excitation coils. Correspondingly, the relationship between the defect characteristics (orientation and position) and the surface vertical magnetic field distribution (amplitude and phase) is studied in detail by theoretical analysis and numerical simulations. Experiments conducted on woven CFRP plates demonstrate that the designed PI-ECMO system is capable of effectively detecting both surface and internal cracks, as well as impact defects. The excitation current is significantly reduced compared with traditional eddy current magneto-optical (ECMO) systems.

Impact Responses of the Carbon Fiber Fabric Reinforced Composites

To study the response characteristics of the carbon fiber fabric reinforced composites under impact loading, one dimensional strain impact test, multi gauge technique and Lagrange analysis method are used. The decaying rule of the stress σ , strain ε , strain rate ε · and density ρ with time and space is obtained. By the theory of dynamics, the impact response characteristics of the material is analyzed and discussed.

Shear strengthening of pre-damaged reinforced concrete beams with carbon fiber reinforced polymer sheet strips

This paper presents the results of an experimental investigation on the response of pre-damaged reinforced concrete （RC） beam strengthened in shear using applied-epoxy unidirectional carbon fiber reinforced polymer （CFRP） sheet. The reasearch included four test rectangular simply supported RC beams in shear capacity. One is the control beam, two RC beams are damaged to a predetermined degree from ultimate shear capacity of the control beam, and the last beam is left without pre-damaged and then strengthened with using externally bonded carbon fiber reinforced polymer to upgrade their shear capacity. We focused on the damage degree to beams during strengthening, therefore, only the beams with sidebonded CFRPs strips and horizontal anchored strips were used. The results show the feasibility of using CFRPs to restore or increase the load-carrying capacity in the shear of damaged RC beams. The failure mode of all the CFRP-strengthened beams is debonding of CFRP vertical strips. Two prediction available models in AC1-440 and fib European code were compared with the experimental results.

Determination of Water Diffusion Coefficients and Dynamics in Adhesive/Carbon Fiber Reinforced Epoxy Resin Composite Joints

To determinate the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints, energy dispersive X-ray spectroscopy analysis（EDX） is used to establish the content change of oxy- gen in the adhesive in adhesive/carbon fther reinforced epoxy resin composite joints. As water is made up of oxygen and hydrogen, the water diffusion coefficients and dynamics in adhesive/carben fiber reinforced epoxy resin composite joints can be obtained from the change in the content of oxygen in the adhesive during humidity aging, via EDX analy-sis. The authors have calculated the water diffusion coefficients and dynamics in the adhesive/carbon fiber reinforced epoxy resin composite joints with the aid of beth energy dispersive X-ray spectroscopy and elemental analysis. The de- termined results with EDX analysis are almost the same as those determined with elemental analysis and the results al- so show that the durability of the adhesive/carbon fther reinforced epoxy resin composite joints subjected to silane cou- pling agent treatment is better than those subjected to sand paper burnishing treatment and chemical oxidation treat- ment.

Corrosion damage evolution and mechanical properties of carbon fiber reinforced aluminum laminate

Fiber metal laminates(FMLs),a kind of lightweight material with excellent comprehensive performance,have been successfully applied in aerospace.FMLs reinforced with carbon fiber have better mechanical properties than those with glass or aramid fiber.However,carbon fiber binding metal may lead to galvanic corrosion which limits its application.In this paper,electrochemical methods,optical microscope and scanning electron microscope were used to analyze the corrosion evolution of carbon fiber reinforced aluminum laminate(CARALL)in corrosive environment and explore anti-corrosion ways to protect CARALL.The results show that the connection between carbon fiber and aluminum alloy changes electric potential,causing galvanic corrosion.The galvanic corrosion will obviously accelerate CARALL corroded in solution,leading to a 72.1%decrease in interlaminar shear strength,and the crevice corrosion has a greater impact on CARALL resulting in delamination.The reduction of interlaminar shear strength has a similar linear relationship with the corrosion time.In addition,the adhesive layers between carbon fiber and aluminum alloy cannot protect CARALL,while side edge protection can effectively slow down corrosion rate.Therefore,the exposed edges should be coated with anti-corrosion painting.CARALL has the potential to be used for aerospace components.

Characterization of carbon fibers recovered through mechanochemical-enhanced recycling of waste carbon fiber reinforced plastics

In this study,we present the characterization of the carbon fibers recovered from the mechanochemical-enhanced recycling of carbon fiber reinforced fibers.The objectives of the study were to investigate the effect of our modified recycling method on the interfacial properties of recovered fibers.The reinforced plastics were recycled;the recycling efficiency was determined and the recovered fibers were sized using 1 wt%and 3 wt%concentration of(3-aminopropyl)triethoxysilane.We characterized the morphologies utilizing the electron spectroscopy for chemical analysis(ESCA),atomic force microscopy(AFM),FTIR-attenuated total reflection(ATR)spectroscopy and scanning electron microscopy(SEM).Although the surface of the fibers had no cracks,there was evidence of contaminations which affected the interfacial properties and the quality of the fibers.Results showed that the trends in the recovered and virgin fibers were similar with an increase in sizing concentration.The results highlighted the perspectives of increasing the quality of recovered fibers after the recycling process.

Entrance and Exit Defects During Coarse Pitch Orbital Drilling of Carbon Fiber Reinforced Plastic Plates

Formation of entrance and exit defects in coarse pitch orbital drilling(CPOD)of carbon fiber reinforced plastic(CFRP)plates was investigated.Deep observation on entrance and exit morphology shows tear and burr are typical defects.Meanwhile,tear is more obvious than burr,and more entrance tears emerge than exit tears.As one of the major causes of entrance and exit defects in CPOD,cutting forces were substaintially studied by contrast experiments.Then,the effect of cutting parameters on entrance and exit tear was qualitatively analyzed through a single factor test.Experiment results indicate that the variation of rotation speed has little influence on entrance and exit tear.Increasing tangential feed per tooth can enlarge entrance tear,but bring little effect on exit tear.By increasing axial feed pitch,the hole entrance and exit show severe tear.When revolution radius grows bigger and bigger,entrance and exit tear firstly decreases,and then increases.Finally,the models of tear and delamination during CPOD of CFRP were established,the formation mechanisms of entrance and exit defects were revealed,and the control strategies were accordingly put forward.

Effects of SiC interfacial coating on mechanical properties of carbon fiber needled felt reinforced sol-derived Al2O3 composites

3D carbon fiber needled felt and polycarbosilane-derived SiC coating were selected as reinforcement and interfacial coating,respectively,and the sol-impregnation-drying-heating(SIDH)route was used to fabricate C/Al2O3 composites.The effects of Si C interfacial coating on the mechanical properties,oxidation resistance and thermal shock resistance of C/Al2O3 composites were investigated.It is found that the fracture toughness of C/Al2O3 composites was remarkably superior to that of monolithic Al2O3 ceramics.The introduction of SiC interfacial coating obviously improved the strengths of C/Al2O3 composites although the fracture work diminished to some extent.Owing to the tight bonding between SiC coating and carbon fiber,the C/SiC/Al2O3 composites showed much better oxidation and thermal shock resistance over C/Al2O3 composites under static air.

Mechanical joint performances of friction self-piercing riveted carbon fiber reinforced polymer and AZ31B Mg alloy

Carbon fiber reinforced polymer(CFRP) and AZ31B Mg alloy were joined by the friction self-piercing riveting(F-SPR) with different steel rivet shank sizes. With the increase of rivet shank size, lap shear fracture load and mechanical interlock distance increased. Ultrafine grains were formed at the joint in AZ31B as a result of dynamic recrystallization, which contributed to the higher hardness. Fatigue life of the CFRP-AZ31B joint was studied at various peak loads of 0.5, 1, 2, and 3 kN and compared with the resistance spot welded AZ31B-AZ31B from the open literature. The fatigue performance was better at higher peak load(>2 kN) and comparable to that of resistance spot welding of AZ31B to AZ31B at lower peak loads(<1 kN). From fractography, the crack initiation for lower peak load(<1 kN) case was observed at the fretting positions on the top and bottom surfaces of AZ31B sheet. When peak load was increased, fretting between the rivet and the top of AZ31B became more dominant to initiate a crack during fatigue testing.

Feasibility study of wave-motion milling of carbon fiber reinforced plastic holes

Carbon fiber reinforced plastic(CFRP)has been applied in aeronautics,aerospace,automotive and medical industries due to its superior mechanical properties.However,due to its difficult-to-cut characteristic,various damages in twist drilling and chip removal clog in core drilling could happen,inevitably reducing hole quality and hole-manufacturing efficiency.This paper proposes the wave-motion milling(WMM)method for CFRP hole-manufacturing to improve hole quality.This paper presents a motion path model based on the kinematics of the WMM method.The wave-motion cutting mode in WMM was analyzed first.Then,comparison experiments on WMM and conventional helical milling(CHM)of CFRP were carried out under dry conditions.The results showed that the hole surface quality of the CFRP significantly improved with a decrease of 18.1%–36%of Ra value in WMM compared to CHM.WMM exerted a significantly weaker thrust force than that of CHM with a reduction of 12.0%–24.9%and 3%–7.7%for different axial feed per tooth and tangential feed per tooth,respectively.Meanwhile,the hole exit damages significantly decreased in WMM.The average tear length at the hole exit in WMM was reduced by 3.5%–29.5%and 35.5%–44.7%at different axial feed per tooth and tangential feed per tooth,respectively.Moreover,WMM significantly alleviated tool wear.The experimental results suggest that WMM is an effective and promising strategy for CFRP hole-manufacturing.

Electrical resistance stability of high content carbon fiber reinforced cement composite

The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50 °C, increases relatively by 4% when ambient temperature decreases from 15 °C to ?20 °C, and decreases relatively by 13% with temperature increasing by 88 °C. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

Preparation of three-dimensional braided carbon fiber reinforced mullite composites from a sol with high solid content

To prepare the three-dimensional braided carbon fiber reinforced mullite （3D C/mullite） composites, an Al2O3-SiO2 solwith a solid content of 20% （mass fraction） and an Al2O3/SiO2 mass ratio of 2：1 was selected as the raw material. Characteristics andmullitization of the sol were analyzed throughly. It is found that the formation of mullite is basically completed at 1300℃ and thegel powders exhibit favorable sintering shrinkage. The 3D C/mullite composites without interfacial coating were fabricated throughthe route of vacuum impregnation-drying-heat treatment. Satisfied mechanical properties with a flexural strength of 241.2 MPa anda fracture toughness of 10.9 MPa·m1/2are obtained although the total porosity reaches 26.0%. Oxidation resistances of the compositesat 1200, 1400 and 1600 ℃ were investigated. Due to the further densification of matrix, the 3D C/mullite composites show tiny massloss and their mechanical properties are well retained after oxidation at 1600 ℃ for 30 min.

Square concrete columns strengthened with carbon fiber reinforced plastics sheets at low temperatures

Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.

Toughness and Fracture Mechanism of Carbon Fiber Reinforced Epoxy Composites

The fracture toughness of carbon fiber reinforced epoxy composite(CFRP)was investigated through mode I and mode II shaped fracture system in this paper.A novel polyimide with trifluoromethyl groups and grafted nanosilica were used to modify epoxy resin.Effect of modified resin and unmodified resin on fracture toughness of CFRP was compared and discussed.Lay-up angles and thicknesses effects on fracture toughness of composites were also investigated.The fracture toughness of CFRP was obtained through double cantilever beam(DCB)and end notched flexure(ENF)tests.The results showed that the composites prepared by modified resin exhibited high fracture toughness compared with unmodified composites.The fracture toughness value of mode I increased from 1.83 kJ/m2 to 4.55 kJ/m2.The fracture toughness value of mode II increased from 2.30 kJ/m2 to 6.47 kJ/m2.

Experimental Study on Electric Properties of Carbon Fiber Reinforced Concrete

According to the phenomenon that the physical properties have,a great effect on the electric capability of carbon fiber reinforced concrete, the author researched the relationship between DC resistance of carbon fiber reinforced concrete and curing age using the two-probe method. Then the effect of insulative area, location and quantity on DC resistance of carbon fiber reinforced concrete was investigated at different curing age with analysis of hydration. The results suggest that DC resistance increases greatly with its curing age, which illustrates the relationship like Gaussian curve. In every curing ages the electric capability of carbon fiber reinforced concrete weakenes with the increase of insulative area. In same curing ages, section and insulative area, the more the quantity of insulation, the stronger the conductibility. The insulative location in optimal position can only result in optimal conductibility.

Experimental Study on the Influence Mechanism of Carbon Fiber/Epoxy Composite Reinforcement and Matrix on Its Fire Performance

The effects of the number of layers,the arrangement of carbon fiber(CF)tow and the epoxy resin(ER)matrix on the fire performance of carbon fiber/epoxy composites(CFEC)were studied by a variety of experimental methods.The results show that the number of layers of CF tow has influence on the combustion characteristics and fire propagation of the composites.The arrangement of CF tow has influence on flame propagation rate and high temperature mechanicalproperties.The mechanism of the influence of the number of layers of CF tow on the composite is mainly due to the different thermal capacity of ER matrix.The effect of the arrangement of CF tow on the fire performance of the composite is mainly due to the inhibition and obstruction of the tow on the combustion of ER matrix.The influence on the high temperature mechanicalproperties is mainly due to the different arrangement direction of CF tow.The fitting equation of the mechanicalproperties of the samples was obtained.This equation could be used to predict the samples’tensile strength from 25°C to 150℃by comparing with the experimental results.Taking the carbon fiber woven cloth(C)applied in the fuselage material as an example,combining the influencing factors of various parameters in the fire field,some suggestions are put forward combined with the research conclusion.

Flexural rigidity evolvement laws of reinforced concrete beams strengthened with carbon fiber laminates

Extensive research has shown that externally bonded carbon fiber reinforced polymer （CFRP） laminates are particularly suitable for improving the fatigue behavior of reinforced concrete （RC） beams. This paper presents the research on flexural ngidity evolvement laws by testing 14 simple-supported RC beams strengthened with carbon fiber laminates （CFL） under cyclic load, and 2 under monotone load as a reference. The cyclic load tests revealed the peak load applied onto the surface of a supported RC beam strengthened with CFL is linear to the logarithm of its fatigue life, and the flexural rigidity evolvement undergoes three distinct phases： a rapid decrease from the start to about 5% of the fatigue life; an even development from .5% to about 99% of the fatigue life; and a succedent rapid decrease to failure. When the ratio of fatigue ＂cycles to the fatigue life is within 0.0.5 to 0.99, the flexural rigidity varies linearly with the ratio. The peak load does not affect the flexural rigidity evolvement if it is not high enough to make the main reinforcements yield. The dependences of the flexural rigidity of specimens formed in the same group upon their fatigue cycles normalized by fatigue life are almost coincident. This implies the flexural rigidity may be a material parameter independent of the stress level. These relationships of flexural rigidity to fatigue cycles, and fatigue life may be able to provide some hints for fatigue design and fatigue life evaluation of RC member strengthened with CFL; nevertheless the findings still need verifying by more experiments.

Orthogonal design of experiment and analysis of abrasive water jet cutting on carbon fiber reinforced composites

The carbon fiber reinforced composite is a new type of composite material with an excellent property in strength and elastic modulus,and has found extensive applications in aerospace,energy,automotive industry and so on.However,this composite has a strict requirement on processing techniques,for example,brittle damage or delamination often exists in conventional processing techniques.Abrasive water jet machining technology is a new type of green machining technique with distinct advantages such as high-energy and thermal distortion free.The use of abrasive water jet technique to process carbon fiber composite materials has become a popular trend since it can significantly improve the processing accuracy and surface quality of carbon fiber composite materials.However,there are too many parameters that affect the quality of an abrasive water jet machining.At present,few studies are carried out on the parameter optimization of such a machining process,which leads to the unstable quality of surface processing.In this paper,orthogonal design of experiment and regression analysis were employed to establish the empirical model between cutting surface roughness and machining process parameters.Then a verified model was used to optimize the machining process parameters for abrasive water jet cutting carbon fiber reinforced composites.