Surface Treatment Of Carbon Fibers Research Articles

Exceptional Damping of CFRPs: Unveiling the Impact of Carbon Fiber Surface Treatments

A significant body of research has concentrated on augmenting the interfacial slippage between carbon fiber (CF) fabrics and resin to improve the damping properties of CF reinforced plastics (CFRPs). However, a critical but commonly overlooked issue lies in the fact that a higher number of mutual slippage interfaces may lead to potential debonding at the interface. This, in turn, not only influences mechanical properties but also escalates the risk of structural damage. In this study, three distinct modification methods are proposed to alter the surface characteristics of CFs, achieving simultaneous enhancement of the damping and mechanical properties of CFRPs. Specifically, the polymerization of dopamine on the CF surface results in CFRPs with a loss factor of 0.227 at 1 Hz, which is 180% higher than the 0.081 of referenced CFRP. Additionally, using this modification method, the tensile modulus and strength of the CFRP are increased by about 11.3% and 6.7%, respectively. More importantly, the subtle relationships within the CFRPs interface are explored through the different surface modification methods. The interactions between surface wettability, specific surface area, roughness, and interfacial chemical bonding on the mechanical and damping properties are redefined and elucidated. This study demonstrates that surface modification can simultaneously enhance both the damping and mechanical properties of CFRPs, and a satisfactory balance of multiple enhancement effects can be achieved by adjusting the surface modification factors.

Interfacial adhesion of polycarbonate to graphene and silicon oxide: A comparative molecular dynamics analysis

In this study, molecular dynamics was used to evaluate the adsorption-free energy of polycarbonate on a solid wall surface that represented a fiber material. Three solid surfaces were used: clean graphene without functional groups to represent surface-treated carbon materials, graphene with OH groups without surface treatment, and SiO2 to represent glass fiber. The results showed that the adsorption free energy per unit area for clean graphene was greater than the adsorption free energy per unit area for the other two solid wall surfaces, which is different from the experimental results where the surface treated carbon fiber had a smaller adsorption free energy. The structure of benzene rings was analyzed, and it was found that benzene rings are deposited almost parallel to the solid wall on all solid walls and that the density of benzene rings with SiO2 and OH groups is the smallest on Graphene with the smallest angle and closest to the solid wall, resulting in smaller adsorption energy. This suggests that the π-π interaction between the benzene ring and the solid surface may account for a large proportion of the adsorption energy. It also suggests that chemical reactions between the solid surface and the polymer, which were not considered in this study, may have a significant effect on the adsorption energy.

The ablation threshold and incubation effect in picosecond laser surface treatment of CFRP

The ablation threshold of carbon fiber is a critical parameter to consider in the laser surface treatment of carbon fiber reinforced polymers (CFRP), as it is necessary to design process parameters based on the threshold fluence to ensure process quality and efficiency. The incubation effect is a key factor influencing the ablation threshold, and a more rational incubation model contributes to a more accurate prediction of the ablation threshold. The conventional incubation model describes the regular decrease of the ablation threshold with an increasing pulse number. However, experimental findings show that the time interval of pulses is also a significant factor affecting the ablation and incubation process. In this study, the conventional incubation model was improved by comprehensively considering the time interval and space interval of pulses, which shows better prediction ability of ablation threshold under different parameter sets. The temperature history of CFRP under picosecond laser irradiation was calculated to support the rationality of the optimized incubation model. In addition, the laser-induced periodic surface structures (LIPSS) and the ablation of carbon fibers and resin were investigated based on the ablation threshold.

Study on the picosecond laser surface treatment and tribological properties of 3D woven carbon fiber reinforced carbon matrix (Cf/C) composites

Carbon fiber reinforced carbon matrix (Cf/C) composites have demonstrated great significance in many fields, especially in aircraft and automobiles as brake materials. The surface physical/chemical states of Cf/C composites significantly affect their tribological properties. Although ultrafast laser machining technology has been proven to be an effective method for modifying material surfaces, there are some issues concerning the ultrafast laser surface treatment of Cf/C composites and the adjustment of their tribological properties by laser treatment. Here, the 3D woven Cf/C composites were treated with an infrared picosecond laser. The effects of machining parameters on the surface microscopic morphology, chemical compositions, and graphitization degree were investigated. The experiment results indicated that the ultrafast laser treatment could eliminate surface defects, improve surface quality, and reduce the porosity of the Cf/C composites due to photothermal-mechanical ablation. More importantly, the laser-induced photothermal effects led to a graphitization transformation of Cf/C composites from a disordered turbostratic structure into an ordered graphite structure with an increased graphitization degree. The abundant micro-nano structures and the graphitization transformation on the Cf/C composite surface contributed to forming a complete and dense friction film on the Cf/C composites. Therefore, the laser-treated Cf/C composites showed lower COF, higher wear rate, and more stable tribological properties. This study demonstrated a method to adjust the tribological properties of Cf/C composites by ultrafast laser surface treatment, which showed great significance for the surface treatment and tribological property enhancement of Cf/C composites.

Multi-scale analysis of the adhesive bonding behavior of laser surface-treated carbon fiber reinforced polymer composite structures

Laser surface treatment has considerable potential to provide high-quality adhesive-joining of carbon-fiber-reinforced polymer (CFRP) composites by removing contaminants and the top polymer layer and increasing the surface roughness without damaging the fibers. Yet, predicting the failure strength and mechanism of the laser surface-treated adhesively bonded joints under static and cyclic loads is important to designing reliable structures. In this study, a multi-scale Finite Element Analysis (FEA) of the adhesively bonded CFRP composite structures was developed to accurately predict the failure load and damage growth. Numerical simulations of the single lap joint (SLJ) specimen was executed, employing the cohesive zone modeling (CZM) technique between adjacent surfaces to simulate the bonding behavior of the secondary bonded CFRP parts. Using the homogenization procedure, the micro-scale simulation of the contact region of the laser-treated adherent surface and adhesive was performed to extract traction separation law (TSL) parameters. The mechanical interlocking contribution of the laser surface treatment was imported to the macro-scale FEA, analyzing the representative volume element (RVE) of the bonding interface region. We presented that the multi-scale analysis estimated the experimentally measured mechanical behaviour, strength values, and failure modes successfully with a negligible error (7 %).

The effects of carbon fiber surface treatment by oxidation process for enhanced mechanical properties of carbon fiber/epoxy composites for biomedical application

In this research, the production of carbon fiber composite (CFC) with epoxy resin was carried out for biomedical application. The surface of the carbon fibers was previously oxidized with concentrated nitric acid at a temperature of 100 °C for 30–120 min to create a rough surface impression on the carbon fibers to enhance interfacial bonding in the composite, increase surface area, and reduce surface tension. The carbon fiber/epoxy composite was fabricated using the vacuum assisted resin infusion method. Characterization of the oxidized carbon fibers and the composite products was performed using a digital microscope, scanning electron microscope, and Fourier Transform Infrared (FTIR) analysis. FTIR analysis results indicated that the carbon fiber oxidation process introduced new chemical functional groups, such as –CN and –CO groups. Mechanical characterizations included tensile testing of non-oxidized and oxidized carbon fiber and tensile testing of carbon fiber/epoxy composite. The results showed that the composite formed from oxidized carbon fibers/epoxy resin exhibited higher tensile strength compared to non-oxidized CFC. The longer the carbon fiber oxidation process, the higher the tensile strength values obtained.

Preparation of CNTs/SCF reinforcement using multiple continuous surface treatments to achieve synergistic improvement of epoxy resin-based composites interfacial properties: Towards industrial production of carbon fiber surface treatment

The silane/maleimide co-modified waterborne polyurethane (WPU-M-S) sizing agent and furan-functionalized carbon nanotubes (CNTs-FA) were prepared through chemical modification method. The continuous grafting of carbon nanotubes (CNTs) was realized on the carbon fiber surface by multiple continuous surface treatments, including electrochemical anodizing (EAO), sizing, and chemical grafting of CNTs. The stable physical and chemical connection between carbon fiber, sizing agent, and resin was constructed through the preparation of CNTs/SCF reinforcement. The results of different surface treatment processes such as ultrasound and CNTs grafting process were contrastively studied in terms of surface morphology, microstructure, and mechanical properties. It is reflected that carbon fiber grafted with CNTs-FA (CNTs/SCF) that were prepared by ultrasound assisted chemical grafting provide optimal wettability and interfacial performance. The interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CNTs/SCF reinforced epoxy resin composites are 115.37 % and 93.91 % higher than those of the untreated carbon fiber (UCF), respectively. The synergistic improvement mechanism of reinforcement on carbon fiber reinforced epoxy resin composites interfacial properties was proposed. This research provides a multiple continuous surface treatment technology that matches the industrial production of carbon fiber to prepare CNTs/SCF reinforcement.

Elucidation of Surface Functional Groups Deposited by Electrochemical Surface Treatment of Discontinuous Carbon Fiber by NEXAFS and XPS.

Control of carbon fiber heteroatom (oxygen and nitrogen) functionalization using electrochemical oxidation is explored in a variety of electrolyte solutions. Results of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy indicate that most electrolytes in aqueous and anodic conditions are limited to heteroatom surface content of no more than 13 atomic percent (at %) with a majority C-O and/or C-N moieties; the remaining moieties include an oxidative sequence of carbon (alcohol to ketone to carboxylate) and more complex O- and N-containing groups. The pH of the electrolyte solution was found to be crucial in controlling the ratio of the amount of oxygen to nitrogen functionalities, with the increased basicity of solution resulting in higher nitrogen deposition. The oxidative (and/or thermal) decomposition of many electrolytes during electrochemical treatment can have a major impact on functionalization through changes to pH. Oxidation of carbon fiber in some electrolyte solutions showed higher surface concentrations of heteroatoms (25-30 at %) than most electrolytes (13 at %). Mechanisms were proposed to explain how some electrolytes can exceed 13 at % of heteroatom deposition. Specifically, we hypothesized that electrolytes that contain organic ions with chelation capabilities and moieties that produce additional sites of functionalization can overcome that threshold.

The effect of electrophoretic deposition of carbon nanotubes on carbon fiber on interfacial properties of the thermoplastic polyimide composite

In order to improve the interfacial properties of carbon fiber/polyimide (CF/PI) composite, silanization reaction carbon nanotubes (CNTs) were introduced to the surface of carbon fiber by electrophoretic deposition to prepare CF/CNT/PI composite. The effects of carbon fiber surface treatment on the mechanical properties of the composites were studied. The results showed that the interlaminar shear strength and bending strength of the composite materials were increased by 11% and 9%, respectively. The scanning electron microscope and Atomic Force Microscope (AFM) was used to analyze the fine structure of composite interface phase. The results show that the introduction of CNTs creates an interface transition layer of CNTs reinforced PI resin between the fiber and the matrix.

Effect of carbon fiber surface treatment with HNO3 and KOH on the interfacial bonding of PMMA resin composite

Abstract This work studied the surface, interface state and physicochemical properties of HNO3-treated and KOH-treated carbon fiber. Poly(methyl methacrylate) (PMMA) composites were prepared by the autoclave molding process using surface-treated carbon fiber as reinforcements. The physical and chemical states of the carbon fiber surfaces and the micro-interface properties and interlaminar shear properties of the composites were studied. The results show that the surface of the HNO3-treated carbon fiber has more groove structure and higher surface roughness and thus forms a better physical bond with the resin matrix. Although the oxygen-containing functional groups of the two carbon fibers are equivalent, the surface oxygen of the HNO3-treated carbon fiber is relatively high, which is beneficial to form a better chemical bond with the matrix resin, and the interfacial shear strength is about 14% higher than that of the KOH-treated carbon fiber composite.

Polyurethane with nano‐SiO2 based surface sizing method for 3D printed carbon fiber reinforced nylon 6 composites

AbstractContinuous carbon fiber reinforced polymer composite 3D printing has drawn more attention due to its ability to manufacture composite structures with complex shapes. The surface treatment of CF is necessary to improve the combination between carbon fiber (CF) and matrix. In this work, polyurethane with nano‐SiO2 (PU/SiO2) was used to size CF to enhance the compatibility of CF and nylon 6 (PA6). The chemistry and morphology of the CF were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The interface strength between CF and PA6 was tested by the fiber pull‐out test, and eventually obtained optimized concertation of PU/SiO2 sizing agents (with 25 wt% PU and 0.4 wt% nano‐SiO2). The results show that compared with untreated CF, the interfacial shear strength (IFSS) of CF and PA6 after sizing increased by 316.93%. In addition, several CF/PA6 composite specimens printed by a homemade composite 3D printer were used to do mechanical tests. The results show that the flexural strength increased by 33.87%, the tensile strength increased by 20.75%, and the interlaminar shear strength (ILSS) increased by 66.54%.

The effect of electrophoretic deposition p‐aminobenzenesulfonamide grafted CNT on mechanical properties of carbon fiber filled polyamide 6 composite

The surface treatment of carbon fiber is carried out by electrophoretic deposition of p‐aminobenzenesulfonamide grafted carbon nanotube (CNT), and it is used as a reinforcement of polyamide 6. The monofilament tensile test and XPS were used to study the effect of p‐aminobenzenesulfonamide concentration on the tensile strength and surface functional groups of carbon fiber monofilaments. The results show that the higher the p‐aminobenzenesulfonamide concentration, the greater the decrease in the mechanical properties of carbon fibers, and the greater the content of oxygen‐containing functional groups on the surface. It is preferred that carbon fiber and thermoplastic polyamide 6 with higher retention rate of monofilament tensile strength and rich oxygen‐containing functional group content are made into composite materials, and the interlaminar shear strength (ILSS) is evaluated.

Comparison of the Influence of Two Types of Plasma Treatment of Short Carbon Fibers on Mechanical Properties of Epoxy Composites Filled with These Treated Fibers.

The interfacial interface between fibers and matrix plays a key role for epoxy matrix composites and short recycled randomly arranged fibers. This study used short recycled carbon fiber (RCF) as a filler. Plasma treatment was used for carbon fiber surface treatment. This treatment was performed using radio (RF) and microwave (MW) frequencies at the same pressure and atmosphere. Appropriate chemical modification of the fiber surfaces helps to improve the wettability of the carbon fibers and, at the same time, allows the necessary covalent bonds to form between fibers and the epoxy matrix. The effect of the plasma treatment was analyzed and confirmed by X-ray photoelectron spectroscopy, Raman microscopy, scanning electron microscopy, transmission electron microscopy and wettability measurements. Composite samples filled with recycled carbon fibers with low concentrations (1 wt%, 2.5 wt% and 5 wt%) and high concentrations (20 wt% and 30 wt%) were made from selected treated fibers. The mechanical properties (impact toughness, 3PB) were analyzed on these samples. It was found that the modulus of elasticity and bending stress increase with the increasing content of recycled carbon fibers. A more significant change in impact strength occurred in samples with low concentration.

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.

The mechanical properties of LDPE composite filled with CF coated by dimethylamine treated TiO2

In order to improve the surface wettability of carbon fiber and enhance its composite interface performance, dimethylamine treated TiO2 was coated on carbon fiber (CF). The surface morphology, surface chemical state, and surface wettability of CF were characterized by SEM, XPS, and TEM tests, and the interlaminar shear strength (ILSS) and cross‐sectional morphology tests were used to test the performance of CF/Low density polyethylene (LDPE) composites. The interface bonding status was analyzed and characterized. The results show that after the surface treatment of CF by dimethylamine treated TiO2, the O/C (atomic ratio) of the surface of CF is increased, and a certain amount of nano‐scale small convex micro‐mechanical structure is given, which improves the surface wetting of CF. The surface of the CF modified by the TiO2 is rough; the contact area between modified CF and LDPE increases.

Laser surface treatment of carbon fiber reinforced polymer using near-infrared laser wavelength with variated process parameters

In this study, the surface pretreatment of carbon fiber reinforced polymer with near-infrared laser radiation is investigated. Several primary and computable secondary laser parameters were varied to identify their influences and interactions. The generated surface structures were examined qualitatively and quantitatively using optical and electronic microscopes. To quantify the ablation behavior, depth measurements of the exposed and covered carbon fibers were performed on cross sections. A correlation analysis was applied to determine process parameters, which have an influence on the matrix and carbon fiber ablation. With regard to the detachment and removal of the matrix, it was shown that with a pulse overlap of 50% and a single pulse energy of 195–344 μJ or a laser energy density of 3–6 J/cm2, 70%–85% of the carbon fibers could be exposed with minimal damage or ablation of carbon fibers at the same time. With 90% pulse coverage, more matrix residues remain on the surface due to the melting of polyamide particles embedded in the matrix. These retain the detached matrix on the surface. To ablate these, more laser energy is necessary, which leads to a higher fiber damage and ablation. However, a completely damage-free processing could not be realized. It is also shown that the matrix layer thickness, the local carbon fiber density, and the resulting carbon fiber topography have an influence on the local matrix removal. Furthermore, the damage caused by processing, such as fiber breaks, cratering, and others, was recorded and described.

Vol4 num4-8 FE Mechanical properties prediction of CFRP considering different carbon fiber surface treatments

Reinforcement/matrix interaction is recognized as a key issue in polymeric composite materials. From the mechanical point of view, being the link between the fibres and the polymer, a proper load transfer is ensured only if a good enough interphase exists. This is particularly critical in carbon fibre (CF) composites since, due to the non-polar characteristics and chemical inertness of carbon, sometimes they exhibit weak interfacial adhesion. In this sense, various surface treatments for CFs are currently being investigated, in order to improve their interaction with the polymeric matrices: wet chemical or electrochemical methods, chemically or physically activated oxidation procedures, application of thin coatings and plasma treatments. This is precisely one of the challenges addressed in the MODCOMP project. This paper describes part of the work carried out within the mentioned project in order to estimate the improvement of properties that can be achieved through enhancements of the CF/epoxy interphases. The study covers both elastic engineering constants and strengths predictions, and it has been performed using finite element models of RVEs of UD fibres and introducing cohesive elements to take into account the interfacial failure mode. The results obtained allow identifying which range of CF/epoxy interphase properties enhancement should be achieved in order to get significant effects in the composites mechanical response.

Mechanical Properties, Surface Assessment, and Structural Analysis of Functionalized CFRPs after Accelerated Weathering

The present study focuses on the effect of two novel carbon fibre surface treatments, electropolymerisation of methacrylic acid and air pressure plasma, on the mechanical properties and structural integrity of carbon-fibre-reinforced composites under operational conditions. Extensive mechanical testing was applied, both in nano- and macro-scale, to assess the performance of the composites and the interphase properties after ultraviolet/humidity weathering. The results of the mechanical assessment are supported by structure, surface, and chemistry examination in order to reveal the failure mechanism of the composites. Composites with the electropolymerisation treatment exhibited an increase of 11.8% in interlaminar shear strength, while APP treatment improved the property of 23.9%, rendering both surface treatments effective in increasing the fibre-matrix adhesion. Finally, it was proven that the developed composites can withstand operational conditions in the long term, rendering them suitable for a wide variety of structural and engineering applications.

Effect of the Segmental Structure of Thermoplastic Polyurethane (Hardness) on the Interfacial Adhesion of Textile-Grade Carbon Fiber Composites

In polymer composites, the fiber–matrix interface is primarily influenced by the surface treatment of the fibers and polymer morphology. Previous studies have investigated the effect of surface treatment of carbon fiber on the mechanical properties of the resulting composites. However, very few studies have explored the chemical structural modification of polymer effect on the fiber–matrix adhesion. In this work, the interfaces of soft thermoplastic polyurethane (S-TPU) and hard-segmented TPU (H-TPU) were investigated through surface, thermal, and mechanical characterization. A textile-grade carbon fiber (TCF) with 1% concentration of epoxy sizing (an emerging material for nonaerospace applications with 450 K filament tows) was used as a reinforcement to investigate the structure–property relationship at the interface. Atomic force microscopy results showed 39% higher surface roughness for S-TPU than for H-TPU. X-ray photoelectron spectroscopy results revealed a 550% increase in C═O content, which can provide multiple hydrogen bonding networks in H-TPU, and these C═O bonds can produce a strong chemical bond at the fiber–matrix interface. Dynamic mechanical analysis and differential scanning calorimetry results confirmed the presence of hydrogen bonding that enhances the cross-linked density by 232% in H-TPU compared to S-TPU. The improved mechanical properties of H-TPU composites, such as flexural, impact and tensile by 30, 50, and 130% compared to S-TPU composites, prove that the crystallinity and hydrogen bonding significantly increase the load bearing capacity due to the strong interface. The mechanical properties of TCF–TPU composites validate the formation of chemical bonds through a nucleophilic addition reaction at the interface and improve the bond strength of the composites. Thus, tailoring the polyurethane structure broadens the performance of segmented TPU in conjunction with TCF reinforcement, which has implications for cost-effective, high-strength composites.

A novel surface treatment of carbon fiber with Fenton reagent oxidization for improved cells immobilization and xylitol fermentation

A novel treatment of carbon fiber (CF) with Fenton reagent was used to improve its surface properties, immobilization efficiency (IE), and xylitol yield. The process realized the oxidized treatment and the introduction of iron ions on CF. The specific surface area, surface acidity and degree of moisture increased, while the contact angle and the pH of the point of zero charges decreased after the treatment by Fenton reagent. Notably, the high-affinity iron ions introduced by the modification that enhanced the intracellular coenzyme cycle for xylitol accumulation due to the higher NADPH/NADP+ ratio and NADPH content. In addition, introduced iron ion on the CF promoted the reduction of intracellular reactive oxygen species level and mitochondrial membrane polarization level. As a result, compared to the untreated-CF, the IE and xylitol yield were increased by 86.15 % and 43 % with the treated CF, respectively. Using Fenton reagent to treat CF provided an excellent method to prepare biocompatible immobilized carriers for industrial production of xylitol.