Desized Carbon Fibers Research Articles

Study on mechanical performance of carbon fiber reinforced polyetherketoneketone prepreg and its composites prepared by slurry method

AbstractThe increasing demand for high‐performance materials in aerospace, automotive, and industrial applications has driven research into carbon fiber reinforced polyetherketoneketone (CF/PEKK) composites. This study introduces a novel slurry method for preparing CF/PEKK prepregs and investigates the impact of fiber surface treatments—desized and non‐desized carbon fibers—on the mechanical properties of the resulting composites. CF/PEKK prepregs were successfully prepared by dispersing PEKK powder in deionized water to create a slurry, which was used to impregnate carbon fibers. After hot‐pressing, mechanical testing revealed that composites with desized fibers outperformed those with non‐desized fibers in tensile strength (3.29%), flexural strength (22.12%), and interlaminar shear strength (18.29%). Furthermore, desized composites exhibited improved impact toughness (24.29%) and reduced fiber pull‐out during tensile testing. Scanning electron microscopy (SEM) analysis confirmed enhanced fiber‐matrix bonding in desized composites, with fewer voids and better fiber dispersion. These findings underscore the effectiveness of the slurry method and fiber desizing in improving the mechanical performance of CF/PEKK composites, offering potential for advanced applications in high‐performance sectors.Highlights Thermoplastic CF/PEKK prepregs successfully developed using slurry method. Novel slurry method enhances prepreg quality in CF/PEKK composites. Desized carbon fibers improve interfacial bonding and strength. Desized composites exhibit reduced fiber pull‐out during tensile testing.

Constructing Mechanochromic Fluorescent Interphase via Core-Shell Microcapsules: A Route for Interface Reinforcing and Damage Self-Reporting of CFRP Composites.

Perylenediimide-chitosan/γ-poly (glutamic acid) microcapsules sizing (PDI-CS/γ-PGA) core-shell microcapsule is designed and used to establish a novel interphase in carbon fiber/epoxy (CF/EP) composite, and the interfacial property, as well as the damage self-reporting of the composite, is compared with desized carbon fiber (CF-desized)/EP and commercial carbon fiber (CF-COM)/EP composite. The ruptured PDI-CS/γ-PGA microcapsule exhibits strong "turn-on" green fluorescence from the released PDI upon mechanical stimuli. The anchoring of PDI-CS/γ-PGA microcapsule on carbon fiber with PDI-CS/γ-PGA microcapsules sizing (CF@PDI-CS/γ-PGA) surface results in increased chemical activity and roughness, exhibiting a weak green fluorescence signal instead of non-fluorescence on CF-desized and CF-COM surface. The transverse fiber bundle tensile (TFBT) strength of CF@PDI-CS/γ-PGA composite is 80.97% and 31.09% higher than those of CF-desized/EP and CF-COM/EP composite, which is attributed to the mechanical interlocking and chemical bonding interaction between carbon fiber and epoxy matrix by introducing PDI-CS/γ-PGA microcapsule with spherular structure and active groups. After microdroplet testing, the strong "turn-on" green fluorescence signal of the released PDI from the microcapsules is detected in the interfacial debonding regions, realizing the microscopic damage self-reporting of CF@PDI-CS/γ-PGA composite.

Nanomechanical properties of sized and de-sized carbon fiber reinforced polypropylene composites

Most of the research to date has focused on tailoring the interphase adhesion by controlling the degree of chemical bonding between fiber and resin. However, recent studies suggest that apart from chemical bonding, mechanical interlocking plays a crucial role to enhance the interphase thickness and hence the interfacial shear strength. In this study, the effect of textured carbon fiber surface on the interphase thickness, and interfacial shear strength has been studied and analyzed. The hot water was used to remove the epoxy-based sizing agent from the carbon fiber (sized CF) surface and thereby to create a textured surface morphology in de-sized one (De-sized CF). To study the distinctions of the interphase between sized and de-sized CF/PP composites, the Derjaguin-Muller-Toporov (DMT) modulus by Peak Force Quantitative Nano-Mechanics (PF-QNM) was applied to determine the interphase thickness and its nanomechanical properties. It was found that no chemical changes occurred after hot water treatment albeit the surface morphology of de-sized carbon fiber became textured. The average interphase thickness in de-sized CF/PP composites was found to be 84.17% higher (212.9 ± 21 nm) as compared to 115.6 ± 21 nm in sized CF/PP composites. This study shows the potential for using mechanical interlocking effects without significantly affecting the chemical bonding, to improve the interphase thickness in fiber reinforced composites.

Physiochemical and thermodynamic mechanical behavior of injection molded sized and de-sized CF/PP composites

ABSTRACT In this paper, a cheaper and an environment friendly hot water treatment method is developed to de-size the carbon fiber surface without significantly affecting its chemical nature. The surface characterization of the sized (without hot water treatment) and de-sized (hot water treated) carbon fiber was evaluated from the scanning electron microscopic, atomic force microscopic, X-ray photoelectron spectroscopic, and Fourier Transform Infrared Spectroscopic test data. The effect of carbon fiber surface treatment on the physiochemical, static, and thermodynamic mechanical properties was studied. Also, the impact of carbon fiber surface treatment on the long-term durability and energy of activation of sized and de-sized CF/PP composites was evaluated by using the time-temperature-superposition principle. It was found that hot-water treatment changes the physical nature of CF by giving rise to a little surface roughness. However, its major functional groups (chemical composition) do not change significantly albeit their concentration changes to some extent. The de-sized CF/PP composites showed improved interfacial shear strength, Izod impact resistance, tensile and thermodynamic mechanical properties as compared to the sized CF/PP composites.

Effect of de-sizing on the structural and mechanical properties of carbon fiber reinforced polypropylene composites molded by the novel direct fiber feeding injection molding technology

Carbon fiber reinforced thermoplastic composites are rapidly emerging as alternative materials for auto parts due to recyclability, excellent stiffness, and strength to weight ratio. In the present study, the influence of carbon fiber de-sizing on the structural and mechanical properties of the sized and de-sized Carbon Fiber Reinforced Polypropylene (CFPP) composites molded by the recently developed novel Direct Fiber Feeding Injection Molding technology was studied. The effect of carbon fiber de-sizing on the structural properties was studied from the fiber dispersion status, fiber orientation factor, fiber volume fraction, and the fiber length. The surface morphology of the sized and de-sized carbon fibers was studied from the Scanning Electron Microscopy (SEM) and Atomic Force Microscope images. The static mechanical properties were studied based on the tensile tests at different loading rate and temperature. The Dynamic Mechanical Analysis tests were conducted to analyze the dynamic viscoelastic behavior of the sized and de-sized CFPP composites. The SEM images were used to observe the failure mechanism. The preliminary results indicated that de-sized composites had better fiber dispersion as compared to the sized CFPP composites. It was found that de-sizing the carbon fiber surface does not significantly affect the carbon fiber length, fiber volume fraction, and fiber orientation in the CFPP composites. Also, the de-sized composites showed better static and thermodynamic mechanical properties caused by the enhanced fiber matrix interaction in CFPP composites as compared to the sized CFPP composites. [Formula: see text]

Simulation of surface asperities on a carbon fiber using molecular dynamics and fourier series decomposition to predict interfacial shear strength in polymer matrix composites

ABSTRACT The objective of this paper is to predict the fiber/matrix interfacial debond strength in composites. Atomic force microscopy (AFM) images of the surface topography of a de-sized carbon fiber reveal that there are surface asperities present at various length scales ranging from a nanometer to several microns. These asperities are likely caused by shrinkage of the polyacrylonitrile (PAN) precursor during the graphitization process. In order to bridge the length scales, a Fourier series-decomposition covering a range of asperity wavelengths and amplitudes is necessary to effectively capture the roughness of the fiber surface at different length scales. Further, once a surface asperity profile has been resolved into individual subcomponents using Fourier-decomposition, MD simulations can then be employed to obtain the interfacial shear strength of the subcomponent asperity of a given amplitude and wavelength. Finally, by recombining the peak interfacial shear force obtained from each of these subcomponents into the overall shear force for the fiber surface profile, the length-scale-averaged shear strength can be obtained for any given asperity. The objective of this paper is to use this novel approach to determine the interfacial shear strength of de-sized carbon fiber embedded in an epoxy matrix and compare predicted results with experimental data.

Bending Anchoring Reinforcement of Zinc Nanosheets for Carbon Fiber Composites

It has always been the goal of researchers to enhance the interfacial properties of carbon fiber composites on the basis of maintaining the mechanical strength of carbon fibers. Herein, the technology of zinc nanosheets (Zn NSs) electrophoresis on the surface of carbon fibers is studied, and a method of electrophoresis within 10 s is provided to realize the construction of Zn NSs on the surface of continuous carbon fibers. It is shown that the strength of carbon fibers can be improved by 13.0% due to the ability of Zn NSs to repair the surface defects of carbon fibers. Moreover, the Zn NS bends when the NSs are thermally treated during the curing process of CF/epoxy resin composite. Using the carbon fiber with thermally bent Zn NSs as the anchor, the interfacial interaction of carbon fiber/epoxy composites is improved from 33.5 MPa of desized carbon fiber to 63.3 MPa of Zn NSs‐modified carbon fibers, namely, improvement of 88.9%. The enhancement is ascribed to the special‐shaped anchorage structure on the surface of carbon fibers that are constructed by the bent Zn NSs.

Electrophoretic Deposition of Chitosan-modified Carbon Fiber to Enhance Hygrothermal and Mechanical Properties of Carbon Fiber/Polyamide 6 Composites

The surface of carbon fiber (CF) was modified by the electrophoretic deposition of cationic chitosan (CS), which is expected to enhance the hygrothermal and mechanical properties of carbon fiber/polyamide 6 (CF/PA 6) composites. Carbon fiber in various treatment stages was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The studies demonstrate that the chitosan-modified carbon fiber (CS-CF) increases the surface chemical activity and roughness of carbon fiber, which enhances the chemical bonding and mechanical interlocking of carbon fiber with PA 6. Compared with desized carbon fiber (D-CF), the O/C composition ratio of CS-CF increased from 20.34 % to 50.86 %, and the tensile strength and flexural strength of the CS-CF/PA 6 composites were enhanced by 50.31 % and 43.88 %, respectively. In addition, the hygrothermal properties of CS-CF/PA 6 were also improved. Fracture observation of the composite cross-sections further elucidates the mechanism of interfacial strengthening.

Continuous method for grafting CNTs on the surface of carbon fibers based on cobalt catalyst assisted by thiourea

This paper provides a continuous method for grafting carbon nanotubes (CNTs) on the surface of carbon fibers by chemical vapor deposition (CVD). The control of the morphology of CNTs/CFs can be achieved by adding thiourea to the cobalt nitrate precursor. The sulfur can increase the catalytic activity of the Co catalyst. Scanning electron microscopy reveals that a uniform layer of CNTs is grafted onto the surface of carbon fibers with the presence of thiourea. Through the single-filament tensile strength test, it can be found that the tensile strength of the fiber is increased by up to about 10% compared with the desized carbon fibers after the CVD process. And the reason for the enhancement is explored through X-ray diffraction. Raman spectroscopy reveals that the sample possesses the highest degree of graphitization at a thiourea concentration of 0.02 mol/L. It is found by high-resolution transmission electron microscopy that the growth mechanism of CNTs is tip growth mechanism, and the diameter of the CNTs is about 15 nm.

Preparation of carbon fibers coated with epoxy sizing agents containing degradable acetal linkages and synthesis of carbon fiber-reinforced plastics (CFRPs) for chemical recycling

New epoxy resins containing degradable acetal linkages were synthesized by the addition reaction of bisphenol-A (BA) and epoxy-functionalized vinyl ethers containing hydrophilic oxyethylene chains, 2-(vinyloxy)ethyl glycidyl ether (VEGE) and 2-[2-(vinyloxy)ethoxy]ethyl glycidyl ether (VEEGE). Carbon fibers were applied with the obtained degradable epoxy resin-based sizing agents (designated as BA-VEGE and BA-VEEGE) in ordinary (1.4 ~ 2.2 wt%) or excess (6.4 ~ 13.4 wt%) amounts. Interfacial adhesion between the carbon fibers applied with the degradable epoxy resin-based sizing agents and matrix resins (bisphenol-A-type epoxy resin) was evaluated by the microdroplet method. Carbon fibers with both degradable epoxy resins as a sizing agent showed improved adhesive properties compared with the desized carbon fibers. Using the degradable sizing agent-applied carbon fibers, carbon fiber-reinforced plastics (CFRPs) were prepared by laminating prepreg sheets and heating them under pressure. The tensile properties of the CFRPs with [0]50 lay-up did not depend on the structure of the sizing agents, but the tensile strength decreased as the amount of sizing agent used increased. On the other hand, the tensile properties of the CFRPs with [0/90]12S lay-up were not dependent on the structure or volume of sizing agents used. The impact toughness of the CFRPs was evaluated by the charpy impact test. When an ordinary volume of sizing agent was applied, the CFRPs with degradable epoxy resin-based sizing agents exhibited higher levels of impact strength than the commercial sizing agent-based CFRPs. However, applying an excessive volume of sizing agent to carbon fibers led to a decline in impact strength. The degradation reaction was conducted under acidic conditions by the treatment of HCl at room temperature or 70 °C. CFRPs with degradable epoxy resins as sizing agents in ordinary volumes were barely decomposed due to insufficient degradable regions in the CFRP components. However, the CFRPs applied with excess degradable sizing agents decomposed and carbon fibers were recovered. The new epoxy resins containing degradable acetal linkages were synthesized and used as sizing agents for carbon fibers. Using the degradable sizing agent-applied carbon fibers, the carbon fiber-reinforced plastics (CFRPs) were prepared via laminating prepreg sheets and heating them under pressure. The mechanical properties of the obtained CFRPs were comparable with those of the conventional CFRPs. With the treatment of acidic conditions, the CFRPs with the degradable sizing agents on carbon fiber surface were decomposed and the carbon fibers could be recovered.

Incorporation of Carbon Nanotubes on Strategically De-Sized Carbon Fibers for Enhanced Interlaminar Shear Strength of Epoxy Matrix Composites

Carbon fiber reinforced polymeric matrix composites are enormously used in aerospace and automotive industries due to their enhanced specific properties. However, the area of interlaminar shear properties still needs investigation so as to produce composites with improved through-the-thickness properties. To improve interlaminar shear properties of these composites, acid-functionalized multiwalled carbon nanotubes were deposited on de-sized carbon fibers through electrophoretic deposition. De-sizing of carbon fabric was performed through three different methods: furnace heating, acidic treatment and chloroform usage. As the acid-treatment provided better results than other two techniques, the acid-de-sized carbon fibers were coated with nanotubes and subsequently incorporated in epoxy matrix to prepare a novel class of multiscale composites using vacuum assisted resin transfer molding technique. Nearly 30% rise in the interlaminar shear strength of the composites was obtained which was credited to the coating of nanotubes on the surface of carbon fibers. The increased adhesion between carbon fibers and epoxy matrix due to mechanical interlocking of nanotubes was found to be the possible reason of improved interlaminar shear properties.

Adhesion force measured by atomic force microscopy for direct carbon fiber-epoxy interfacial characterization

Adhesion force measurement by Atomic force microscopy (AFM) is used to investigate the interfacial interaction of the carbon fiber (CF)/epoxy composite for the first time. The epoxy functionalized AFM tip and three types of carbon fibers with different surface chemistry and morphologies were used in this study. Results show that the Bis (3-aminophenyl) phenyl phosphine oxide (BAPPO) modified CF possesses a much larger adhesion force (72.7 nN) than the as-received and de-sized CF (22.5 nN and 17.9 nN, respectively) due to formation of the chemical bonding between the BAPPO modified CF and the epoxy functionalized tip. Single fiber microbond test demonstrates that the interfacial shear strength (IFSS) of BAPPO modified CF/EP composite is 15% and 22% larger than that of as-received and de-sized CF/EP, respectively. This nanoscale manipulation by AFM provides a new avenue to measure the interfacial adhesion between the CF and epoxy at the molecular level.

Scalable manufacturing of carbon nanotubes on continuous carbon fibers surface from chemical vapor deposition

A novel process has been successfully developed to grow carbon nanotubes (CNTs) on continuously moving carbon fibers (CF) surface by a unique open-ended chemical vapor deposition (CVD) furnace. Systematic researches were carried out under various deposition temperatures, velocities of continuous carbon fibers and catalyst concentrations. The morphologies and structures of CNTs were investigated by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM), which indicated clearly that carbon fibers with uniformly distributed CNTs were achieved, with the optimum parameters of 650 °C deposition temperature and 6 cm min−1 velocity of continuous carbon fibers and 0.05 M catalyst concentration, respectively. By means of the single fiber push-out tests, the interfacial shear strength (IFSS) of carbon fibers growing CNTs was increased significantly by 84.4% compared to the desized carbon fibers. Furthermore, the results of single fiber tensile test verified that there is scarcely any degradation in the mechanical properties of carbon fibers after the growth of CNTs with the optimum parameters. This study provides a new and original vision for scalable manufacturing of CNTs on continuous moving substrate, when compared to the traditional batch process.

Preparation and Characterization of Carbon Nanotube Deposited Carbon Fiber Reinforced Epoxy Matrix Multiscale Composites

In this study, desized carbon fibers were coated with carbon nanotubes using two diverse coating techniques, i.e. dip coating and spray up process, while the factors affecting the coating techniques were investigated. The morphological study revealed better nanotube coating on carbon fibers from dip coating technique as compared to spray up process. Later, nanotube-coated fibers from dip coating were impregnated with epoxy to fabricate multiscale carbon fiber reinforced epoxy matrix composites. The nanotubes on fiber surface were expected to improve the interlaminar shear properties of the multiscale composites. According to short beam shear testing, 14% increase in interlaminar shear strength was observed in composite containing nanotubes as compared to reference composite. Microscopic observation under optical and electron microscopes confirmed the void-free impregnation of fibers with epoxy along with the presence of nanotubes on fibers and in matrix in the vicinity of fibers. Finally, the mechanisms involving the enhanced interlaminar properties were identified and discussed.

Improving Interfacial Adhesion of Sub-Micro PA6 Composites with De-Sized Carbon Fiber

In our previous study we showed the the potential of using of sub-micro Alumina/Titanium (ALTi) particles as a multifunctional reinforcement which can produce multifunctional polymer composites. This paper aims to investigate the interfacial shear properties for different contents of ALTi particles incorporated into PA6 with de-sized carbon fiber. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Sizing removal can reduce the acid parameter of carbon fibers surface promoting bonding strength at the fiber/matrix interface which is a desirable property for the carbon fiber composites. XPS also, showed that epoxide group still appeared with using acetone treatment while disappeared with conventional heating at the oven for 25min ate 450oC. SEM images did not show any damage for the carbon fiber after heat treatment. Interfacial shear strength (IFSS) showed an improvement in interfacial adhesion with de-sizing carbon fiber than neat PA6.

Effects of carbon fiber surface characteristics on interfacial bonding of epoxy resin composite subjected to hygrothermal treatments

The changes of interfacial bonding of three types of carbon fibers/epoxy resin composite as well as their corresponding desized carbon fiber composites subjecting to hygrothermal conditions were investigated by means of single fiber fragmentation test. The interfacial fracture energy was obtained to evaluate the interfacial bonding before and after boiling water aging. The surface characteristics of the studied carbon fiber were characterized using X-ray photoelectron spectroscopy. The effects of activated carbon atoms and silicon element at carbon fiber surface on the interfacial hygrothermal resistance were further discussed. The results show that the three carbon fiber composites with the same resin matrix possess different hygrothermal resistances of interface and the interfacial fracture energy after water aging can not recovery to the level of raw dry sample (irreversible changes) for the carbon fiber composites containing silicon. Furthermore, the activated carbon atoms have little impact on the interfacial hygrothermal resistance. The irreversible variations of interfacial bonding and the differences among different carbon fiber composites are attributed to the silicon element on the carbon fiber bodies, which might result in hydrolyzation in boiling water treatment and degrade interfacial hygrothermal resistance.

Comparison of sizing effect of T700 grade carbon fiber on interfacial properties of fiber/BMI and fiber/epoxy

This paper aims to study impact of sizing agents on interfacial properties of two T700 grade high strength carbon fibers with bismaleimide (BMI) and epoxy (EP) resin matrix. The fiber surface roughness and chemical properties are analyzed for sized, desized, and partially desized carbon fibers, using atom force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. FTIR analysis indicates that the sizing agents are chemically reactive, and they can react with BMI and EP at high temperatures. The micro-droplet tests exhibit that the desized carbon fibers have lower interfacial strengths with EP than the sized fibers, however, for BMI matrix, opposite trend is revealed. This is consistent with the chemical reactions of the sizing agents with the EP and BMI resins, in which sufficient reactions are observed for the sizing/EP mixture, while only partial reactions are probed for the sizing/BMI mixture. Interestingly, un-extracted epoxy type sizing particles are observed on partially desized carbon fiber surface, which significantly improves the interfacial adhesion with EP matrix.

Preparation of Sizing Agents for Carbon Fiber Adapt to Various Polymer Matrix

Emulsion type sizing agent for carbon fiber was synthesized using epoxy resin (E-51) and epoxidized polybutadiene (EPB) by adding emulsifiers and other additives. Standing stabilization of sizing agents was analyzed. Meanwhile, abrasion resistance, fluffs and breakage, stiffness were used to analyze the processability of carbon fiber. The effect of sizing agents on interfacial adhesion of carbon fiber/resin composites was estimated by interlaminar shear strength (ILSS). The results showed that the sizing agent could significantly improve processability of carbon fiber due to the increase of abrasion resistance and reduce of fluffs and breakage. By adding EPB in sizing agent and adjusting the ratio to E-51, the flexibility of carbon fiber was ameliorated and the sizing agent could adapt to various resin matrices. Compared to the desized carbon fiber reinforced composite, ILSS of sized carbon fiber/epoxy resin composite was increased by 16.9%, and ILSS of sized carbon fiber/vinyl ester resin composite was enhanced by 19.1%.

Effect of sizing on carbon fiber surface properties and fibers/epoxy interfacial adhesion

This paper aims to study effect of sizing on surface properties of carbon fiber and the fiber/epoxy interfacial adhesion by comparing sized and desized T300B and T700SC carbon fibers. By means of X-ray photoelectron spectroscopy (XPS), activated carbon atoms can be detected, which are defined as the carbon atoms conjunction with oxygen and nitrogen. Surface chemistry analysis shows that the desized carbon fibers present less concentration of activated carbon, especially those connect with the hydroxyl and epoxy groups. Inverse gas chromatography (IGC) analysis reveals that the desized carbon fibers have larger dispersive surface energy γ S D and smaller polar component γ S S P than the commercial sized ones. Moreover, micro-droplet test shows that the interfacial shear strength (IFSS) of the desized carbon fiber/epoxy is higher than those of the T300B and T700SC. Variations of the IFSS for both the sized and desized carbon fibers correspond to γ S D / γ S tendency of the fiber surface, however the work of adhesion does not reveal close correlation with IFSS trend for different fiber/epoxy systems.

Mechanical property improvement of carbon fiber reinforced polybenzoxazine by rubber interlayer

AbstractThe rubber interlayer method was chosen in order to improve the properties of carbon fiber‐reinforced polybenzoxazine composites. The resin used is benzoxazine based on bisphenol‐A, formaldehyde and 3,5‐xylidine. The effect of rubber concentration on the flexural properties of the composites is investigated. Sized and desized carbon fiber woven fabrics are used to study the effect of the sizing materials on the mechanical properties. The delamination toughness of the composites is increased by the ATBN rubber interlayer with increasing ATBN concentration. The strength of the composite also increased, but an anomalous concentration effect has been observed.