Study of the Diffusion Behavior of Seawater Absorption in Multi-Walled Carbon Nanotubes/Halloysite Nanotubes Hybrid Nanofillers Modified Epoxy-Based Glass/Carbon Fiber Composites

In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.

Experimental and simulation research on thermal stamping of carbon fiber composite sheet

To improve the manufacture efficiency and promote the application of composites in the automobile industry, a new composite forming method, thermal stamping, was discussed to form composite parts directly. Experiments on two typical stamping processes, thermal bending and thermal deep drawing, were conducted to investigate the forming behavior of composite sheets and analyze the influence of forming temperature on the formed composite part. Experimental results show that the locking angle for woven composite is about 30°. The bending load is smaller than 5 N in the stamping process and decreases with the increase of temperature. The optimal temperature to form the carbon fiber composite is 170 ℃. The die temperature distribution and the deformation of composite sheet were simulated by FEA software ABAQUS. To investigate the fiber movement of carbon woven fabric during stamping, the two-node three-dimension linear Truss unit T2D3 was chosen as the fiber element. The simulation results have a good agreement to the experimental results.

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.

EXPERIMENTAL STUDY ON PEK -C MODIFIED EPOXIES AND THE CARBON FIBER COMPOSITES FOR AEROSPACE APPLICATION

The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.

Surface Characteristics of Rare Earth Treated Carbon Fibers and Interfacial Properties of Composites

Effect of rare earth treatment on surface physicochemical properties of carbon fibers and interfacial properties of carbon fiber/epoxy composites was investigated, and the interfacial adhesion mechanism of treated carbon fiber/epoxy composite was analyzed. It was found that rare earth treatment led to an increase of fiber surface roughness, improvement of oxygeaa-containing groups, and introduction of rare earth element on the carbon fiber surface. As a result, coordination linkages between fibers and rare earth, and between rare earth and resin matrix were formed separately, thereby the interlaminar shear strength （ILSS） of composites increased, which indicated the improvement of the interfacial adhesion between fibers and matrix resin resulting from the increase of carboxyl and carbonyl.

Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites（CFGCC） with carbon fiber content（1% by the weight of cement）,graphite powder contents （0%-50% by the weight of cement） and CCCW（cementitious capillary crystalline waterproofing materials,4% by the weight of cement） were studied.The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena.The percolation threshold was about 20%.A clear piezoresistive effect was observed in CFGCC with 1wt% of carbon fibers,20wt% or 30wt% of graphite powders under uniaxial compressive tests,indicating that this type of smart composites was a promising candidate for strain sensing.The measured gage factor （defined as the fractional change in resistance per unit strain） of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22,respectively.With the addition of CCCW,the mechanical properties of CFGCC were improved,which benefited CFGCC piezoresistivity of stability.

Potential-aided recovery of iodide using 2-D nanosheet CuxO coating polymer/graphene/carbon fibers composite

2-D nanosheet Cu2O doped CuO coating poly m-phenylenediamine and melamine/graphene/carbon fibers composite(CuxO/MPM/GFs)was firstly fabricated by compound electrochemical method.CuxO/MPM/GFs was successfully used to the recovery of iodide(I-)from salt water by lower potential-aided sorption and desorption processes.The potential-aided recovery of I-at CuxO/MPM/GFs was characterized by FE-SEM,XRD,IR,Raman,XPS,UV-vis and electrochemical techniques in detail.The maximal adsorption capacity of 86.82 mg·g^-1 could be obtained with a pseudo-second-order model at 0.8 V for 210 min in pH 5.0,0.1 mol·L^-1 NaCl,and the process accompanied the generation of CuI,CuO and I5-.The I-could be quickly desorbed from the electrode with a transfer of CuI to Cu2O by cycle voltammetry from-1.0 to 0.5 V for 90 cycles in pH 9.0,0.1 mol·L^-1 KNO3.Thus,CuxO/MPM/GFs was renewable in the continuous electrochemical-adsorption-desorption processes.

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.

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.

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.

Fabrication of solid-phase-sintered Si C-based composites with short carbon fibers

Solid-phase-sintered Si C-based composites with short carbon fibers（Csf/SSi C） in concentrations ranging from 0 to 10wt% were prepared by pressureless sintering at 2100°C. The phase composition, microstructure, density, and flexural strength of the composites with different Csf contents were investigated. SEM micrographs showed that the Csf distributed in the SSi C matrix homogeneously with some gaps at the fiber/matrix interfaces. The densities of the composites decreased with increasing Csf content. However, the bending strength first increased and then decreased with increasing Csf content, reaching a maximum value of 390 MPa at a Csf content of 5wt%, which was 60 MPa higher than that of SSi C because of the pull-out strengthening mechanism. Notably, Csf was graphitized and damaged during the sintering process because of the high temperature and reaction with boron derived from the sintering additive B4C; this graphitization degraded the fiber strengthening effect.

Effect of Water Absorption on the Impact Properties of Carbon Fiber/Epoxy Composites

In this paper, the effects of test temperatures and time on the impact damage behavior of unidirectional carbon fiber reinforced epoxy resin composites, immersed in pure water, on a pendulum impact tester, was studied. The results show that immersion in liquids has a significant effect on the impact resistance of the unidirectional composite material. It is obvious that after immersion, the mass of the material increases. The fracture initiation forces as well as the fracture initiation energy decrease as the immersion time lengthens. Moreover, the higher the temperature and the longer the time are, the more the crack propagation energy and the ductility index will be. Immersion makes the fracture mode change from the dominant fiber fracture into dominant delamination. All in all, immersion decreases the impact resistance of the composites and causes the fracture mode to change.

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.

Analysis on the Bonding Failure Mechanism of High Modulus Carbon Fiber Composites

In order to explore the bonding failure mechanism of high modulus carbon fiber composite materials,the tensile experiment and finite element numerical simulation for single-lap and bevel-lap joints of unidirectional laminates are carried out,and the stress distributions,the failure modes,and the damage contours are analyzed. The analysis shows that the main reason for the failure of the single-lap joint is that the stress concentration of the ply adjacent to the adhesive layer is serious owing to the modulus difference,and the stress cannot be effectively transmitted along the thickness direction of the laminate. When the tensile stress of the ply exceeds its ultimate strength in the loading process,the surface fiber will fail. Compared with the single-lap joint,the bevel-lap joint optimizes the stress transfer path along the thickness direction,allows each layer of the laminate to share the load,avoids the stress concentration of the surface layer,and improves the bearing capacity of the bevel-lap joint. The improved bearing capacity of the bevellap joint is twice as much as that of the single-lap joint. The research in this paper provides a new idea for the subsequent study of mechanical properties of adhesively bonded composite materials.

Pyrolytic Recycling of Carbon Fibers from Prepregs and Their Use in Polyamide Composites

Carbon fibers composites are well-known as high tech materials but are also recognized as a problem after use as they have to be deposited in landfills. Pyrolysis is an attractive process for recycling carbon fibers from used composites as well as offcuts from prepregs. Pyrolysis of carbon fiber composite prepregs is carried out in a pilot plant with a single screw reactor. The pyrolysis products, carbon fibers and pyrolysis vapor are fully characterized. Variation of pyrolysis temperature is carried out to obtain carbon fibers with the best possible surface properties. In order to compare the mechanical properties of the recycled carbon fibers with virgin material, composite materials with polyamide are produced and their properties compared.

Control of Fracture Behavior of Carbon Fiber/Pitch-based CarbonMatrix Composites with Microspace Modification Concept

Theoretical consideration was conducted on a relation between pore diameter and interfacialarea between pores and fibers when pores uniforinly distribute in C/C composites. It was shownthat bonding at the fiber/matrix interface apparently decreased with decreasing a pore diameter,and consequently a new idea of microspace modification concept was proposed for controllingfracture behavior of C/C composites. Four types of C/C composites with various pore structureswere fabricated by hot-pressing, and their fracture behavior was investigated by three pointbending tests. The fracture behavior of the C/C composites was changed from brittle one topseudo ductile one with decreasing the pore diameter. This result supported the validity of themicrospace modification concept proposed in this paper.

Analysis of vibration attenuation characteristics of large thickness carbon fiber composite laminates

The vibration attenuation and damping characteristics of carbon fiber reinforced composite laminates with different thicknesses were investigated by hammering experiments under free boundary constraints in different directions.The dynamic signal testing and analysis system is applied to collect and analyze the vibration signals of the composite specimens,and combine the self-spectrum analysis and logarithmic decay method to identify the fundamental frequencies of different specimens and calculate the damping ratios of different directions of the specimens.The results showed that the overall stiffness of the specimen increased with the increase of the specimen thickness,and when the thickness of the sample increases from 24mm to 32mm,the fundamental frequency increases by 35.1%,the vibration showed the same vibration attenuation and energy dissipation characteristics in the 0°and 90°directions of the specimen,compared with the specimen in the 45°direction,which was less likely to be excited and had poorer vibration attenuation ability,while the upper and lower surfaces of the same specimen showed slightly different attenuation characteristics to the vibration,the maximum difference of damping capacity between top and bottom surfaces of CFRP plates is about 70%.

High-Performance Recyclable Furan-based Epoxy Resin and Its Carbon Fiber Composites with Dense Hydrogen Bonding

The emerging biomass-based epoxy vitrimers hold great potential to fulfill the requirements for sustainable development of society.Since the existence of dynamic chemical bonds in vitrimers often reduces both the thermal and mechanical properties of epoxy resins, it is challenging to produce recyclable epoxy vitrimers with both excellent mechanical properties and good thermal stability. Herein, a monomer 4-(((5-(hydroxymethyl)furan-2-yl)methylene)amino)phenol(FCN) containing furan ring with potential to form high density of hydrogen bonding among repeating units is designed and copolymerized with glycerol triglycidyl ether to yield epoxy resin(FCN-GTE), which intrinsically has dual hydrogen bond networks, dynamic imine structure and resultant high performance. Importantly, as compared to the BPA-GTE, the FCN-GTE exhibits significantly improved mechanical properties owing to the increased density of hydrogen bond network and physical crosslinking interaction. Furthermore, density functional theory(DFT) calculation and in situ FTIR analysis is conducted to decipher the formation mechanism of hydrogen bond network. In addition, the FCN-GTE possesses superior UV shielding, chemical degradation, and recyclability because of the existence of abundant imine bonds. Notably, the FCN-GTE-based carbon fiber composites could be completely recycled in an amine solution.This study provides a facile strategy for synthesizing recyclable biomass-based high-performance epoxy vitrimers and carbon fiber composites.

Elevating mechanical and biotribological properties of carbon fiber composites by constructing graphene-silicon nitride nanowires interlocking interfacial enhancement

Carbon fiber reinforced dual-matrix composites(CHM)including carbon fiber reinforced hydroxyapatite-polymer matrix composites(CHMP)and carbon fiber reinforced hydroxyapatite-pyrolytic carbon matrix composites(CHMC)have great potential application in the field of artificial hip joints,where a combination of high mechanical strength and excellent biotribological property are required.In this work,the graphene-silicon nitride nanowires(Graphene-Si_(3)N_(4)nws)interlocking interfacial enhancement were designed and constructed into CHM for boosting the mechanical and biotribological properties.The graphene and Si_(3)N_(4)nws interact with each other and construct interlocking interfacial enhancement.Benefiting from the Graphene-Si_(3)N_(4)nws synergistic effect and interlocking enhancement mechanism,the mechanical and biotribological properties of CHM were promoted.Compared with CHMP,the shear and compressive strengths of Graphene-Si_(3)N_(4)nws reinforced CHMP were increased by 80.0% and 61.5%,respectively.The friction coefficient and wear rate were reduced by 52.8% and 52.9%,respectively.Compared with CHMC,the shear and compressive strengths of Graphene-Si_(3)N_(4)nws reinforced CHMC were increased by 145.4% and 64.2%.The friction coefficient and wear rate were decreased by 52.3% and 73.6%.Our work provides a promising methodology for preparing Graphene-Si_(3)N_(4)nws reinforced CHM with more reliable mechanical and biotribological properties for use in artificial hip joints.