Interface Of Carbon Fiber Research Articles

Interfacial strength and its regulation in the carbon monofiber/epoxy binder system

The strength of polymer composite materials (CMs) is largely determined by the strength of interfacial interactions at a fiber/matrix interface. In this work the strength in a unit cell of CM carbon monofiber/cured epoxy matrix is investigated. The relevance of the work is due to direct measurements of strength at the monofiber/matrix interface, excluding defects of micro-droplet and technological errors associated with impregnation in a traditional assessment of polymer composite materials strength. Changes of surface morphology and energy characteristics of fibers in plasma chemical treatment process is shown. The study of fiber surface energy and formation of carbon monofiber/epoxy matrix interface of carbon fiber reinforced composite unit cell was carried out on the specially developed original device Drop-Sting test. Micro pull-out test was used to investigate the shear mechanical properties of interface and to determine the strength of carbon fiber reinforced composite unit cells before and after treatment in oxygen discharge plasma. It is shown that the increase in the strength of the monofiber/matrix interfacial interface after the treatment of carbon fiber in plasma occurs due to the increase in the surface energy and wettability of monofibers.

Energy induced carbon nanotube rapidly assemble variable interweaving networks at the carbon fiber interface

Regulating carbon fiber with carbon nanotubes (CNTs) is important to improve the interface mechanical properties of composite materials. Therefore, a “thermotropic flash assembly (TFA)” process for the synthesis of CNTs in liquid phase is proposed. This work achieves the continuous and controllable formation of a micro-nano interweaving network of CNTs, with predictions made from a thermal perspective through enhancements to the process. Firstly, 12 working conditions and a large number of sample data are established by microcontrolling carbon fiber energy, and the growth thickness of CNTs is predicted by self-learning algorithm. Secondly, the “liquid-solid-solid” thermotropic growth of CNTs is proposed for the first time, which is different from the existing “gas-liquid-solid” and “gas-solid-solid” growth mechanisms of CNTs. Theoretical deductions and calculations are made for the interfacial temperature, exothermic, and endothermic energies during the growth process, which leads to the determination of a thermal growth space radius of 2.4 μm at the interface. Finally, it is found that the shear strength is increased by at least 27.7 %, although some tensile strength is sacrificed. This work not only points out the direction for low-cost, large-scale and customized control of interface properties, but also lays a theoretical foundation for exploring the growth mechanism of CNTs in an open environment at low temperature.

Preparation, Microstructure and Thermal Properties of Aligned Mesophase Pitch-Based Carbon Fiber Interface Materials by an Electrostatic Flocking Method.

The mesophase pitch-based carbon fiber interface material (TIM) with a vertical array was prepared by using mesophase pitch-based short-cut fibers (MPCFs) and 3016 epoxy resin as raw materials and carbon nanotubes (CNTs) as additives through electrostatic flocking and resin pouring molding process. The microstructure and thermal properties of the interface were analyzed by using a scanning electron microscope (SEM), laser thermal conductivity and thermal infrared imaging methods. The results indicate that the plate spacing and fusing voltage have a significant impact on the orientation of the arrays formed by mesophase pitch-based carbon fibers. While the orientation of the carbon fiber array has a minimal impact on the shore hardness of TIM, it does have a direct influence on its thermal conductivity. At a flocking voltage of 20 kV and plate spacing of 12 cm, the interface material exhibited an optimal thermal conductivity of 24.47 W/(m·K), shore hardness of 42 A and carbon fiber filling rate of 6.30 wt%. By incorporating 2% carbon nanotubes (CNTs) into the epoxy matrix, the interface material achieves a thermal conductivity of 28.97 W/(m·K) at a flocking voltage of 30 kV and plate spacing of 10 cm. This represents a 52.1% increase in thermal conductivity compared to the material without TIM. The material achieves temperature uniformity within 10 s at the same heat source temperatures, which indicates a good application prospect in IC packaging and electronic heat dissipation.

Hybridization of cellulose nanocrystals modified ZnO nanoparticles with bio-based hyperbranched waterborne polyurethane sizing agent for superior UV resistance and interfacial properties of CF/PA6 composites

The interface of carbon fiber (CF) reinforced composites has been a long challenging issue that restricts the full utilization of its excellent properties in industrial applications. In present work, a green solvent γ-valerolactone and biogenetic derived gallic acid and tartaric acid were used to prepare a hyperbranched waterborne polyurethane (HWPU) sizing agent. Meanwhile, cellulose nanocrystal modified zinc oxide (CNC–ZnO) nanohybrids were successfully synthesized using a facile one-pot method to improve the dispersibility and specific surface area of ZnO nanoparticles. The hybridization of CNC–ZnO substantially enhanced the thermostability and UV resistance of bio-based HWPU. The mechanical properties of the modified composites were thoroughly examined, revealing remarkable enhancements in flexural strength and interlaminar shear strength, with improvements of 46.5 % and 48.1 % compared to pristine CF. Additionally, the interfacial shear strength test demonstrated a significant increase of 63.6 %. Remarkably, the modified carbon fiber composites retained more than 97 % of their mechanical properties after being subjected to continuous xenon irradiation for a week, highlighting the exceptional ultroviolet resistance derived from the hybrid HWPU sizing agent.

Self-healing interface of carbon fiber reinforced composites based on reversible hydrogen-bonded interactions

The microscopic interfacial damages of carbon fiber reinforced composites (CFRCs) are difficult to repair and tend to initiate composites failure. Fortunately, the emergence of self-healing methods could effectively address this challenge. Herein, we report a self-healing interface based on the reversible hydrogen-bonded interactions in carbon fiber/polyvinyl alcohol (CF/PVA) composites system. By surface functionalization with dopamine (DA) containing active functional groups (e.g., –NH2 and –OH), the obtained polydopamine-functionalized CF (CF-PDA) possesses multiple reversible hydrogen bonds between PDA and PVA at the interface. The CF-PDA/PVA composites presented significantly higher interfacial bonding force (33%) than that of CF/PVA composites when hydrogen bonds were reconnected by thermal treatment. After five interfacial self-healing cycles, CF-PDA/PVA composites could recover a relatively high self-healing efficiency (∼73.6%). Moreover, the self-healing mechanism is further discussed by molecular dynamics simulation. The strategy of reversible hydrogen-bonded interactions is promising for developing high-performance self-healing carbon fiber reinforced composite materials.

Reinforcing interlaminar interface of carbon fiber reinforced metal laminates by graphene

Fiber metal laminas (FMLs) are disadvantaged by weak interlaminar strength limiting their application where dynamic loads are expected. In this study, graphene platelets (GnPs) were employed to strengthen the interlaminar interface in carbon fiber (CF) metal laminates. GnPs within range of 0–1 wt% were added into epoxy resin via ultrasonication. GnPs-based FML samples were prepared by wet lay-up method and tested under flexural loading, short beam shear and single lap shear. The reinforcing mechanism and failure modes were investigated. The results show that 0.5 wt% of GnPs increases the flexural strength and interlaminar shear strength by 39.7% and 53.2%, respectively. In addition, molecular dynamics (MD) simulations concluded that the addition of low content of GnPs increases the elastic modulus of the matrix and improves the resin adsorption on the surface of carbon fiber and Al sheets. The results from both the experimental and MD simulation indicate that adding GnPs can effectively improve the interlaminar mechanical properties of FMLs. In principle, the research method in this paper can be applied to the study of FMLs with other nanomaterials.

Interfacial behavior of graphene carboxyl‐grafted carbon fiber reinforced polymer composites at elevated temperatures: Emphasis on the effect of electrophoretic deposition time

AbstractElectrophoretic deposition (EPD) for decorating carbon fibers (CFs) was established to augment the interface of carbon fiber reinforced polymer (CFRP) composites and thereby their mechanical performance. In the current work, graphene carboxyl (G‐COOH) was grafted on to CF surface via EPD technique at three different deposition times, that is, 30, 45, and 60 min. The laminates obtained from these modified CFs were subjected to short beam shear (SBS) tests at room temperature (RT) and different elevated temperatures, that is, 70, 100, and 120°C. The effect of deposition time on mechanical behavior at various temperatures was evaluated. Modified composites showed a maximum improvement of ∼25%, ∼16%, and ∼13% in interlaminar shear stress (ILSS) values over neat composite at RT, 70, and 120°C, respectively. However, interestingly 100°C modified composites showed inferior shear behavior in comparison with neat composite. Scanning electron microscopy was used to observe the tested samples to find out the dominant mode of failure.

Effect of different lateral dimension graphene oxide sheets on the interface of carbon fiber reinforced polymer composites

The interfacial performance is one of the most important factors that determine the mechanical properties of carbon fiber reinforced polymers (CFRPs). Recently, improving the interfacial properties of CFRPs using graphene oxide (GO) has received intensive attention from researchers. Using GO can effectively improve the interfacial properties of CFRPs, however, the effect of the size of GO on the properties of CFRPs remains unclear. In this study, GO sheets with different lateral dimensions are selected to elucidate the aforementioned issue. Results showed that GO sheets with smaller lateral dimensions are more advantageous to enhance the interfacial properties of CFRPs. The presence of a larger number of functional groups and higher roughness on the surface of CFs that modified by smaller GO sheets is believed to be contributing factor, as evidenced by XPS and AFM. Furthermore, higher surface energy is detected on the surface of smaller GO sheets modified CFs which is likely related to the size effect of nano-scale GO. The above suggests that nano-scale GO can significantly enhance the chemical bonding and mechanical interlocking of matrix-fiber interface. The proposed approach can be easily implemented which does not deteriorate the strength of CFs. This work provides an effective way to improve the interface properties of CFRPs using GO sheets with smaller lateral dimensions.

Self‐healing interface of carbon fiber reinforced composites using a thermally reversible sizing agent

AbstractA thermally reversible sizing agent was prepared by directly mixing the furfurylamine‐modified epoxy resin (FAE) and the maleimide‐functionalized Jeffamine T403 (MAT), and it was used to impart self‐healing ability at interface based on the reversible Diels–Alder reaction for potential application in carbon fiber composites. The surface characteristics of FAE/MAT‐modified carbon fibers were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and dynamic contact angle meter and tensiometer. The initial interfacial shear strength of modified carbon fiber composites and the multiple healings of the interface were investigated via a microbond test. The results demonstrated that the healing efficiency of the continuous and uniform FAE–MAT sizing layer functionalized carbon fiber composites was up to 93.8% for the first healing cycle. Furthermore, it is expected that the interface self‐healing of carbon fiber reinforced composites can be achieved from research laboratory to industrial applications by this strategy.

Interface properties of carbon fiber reinforced cyanate/epoxy resin composites at cryogenic temperature

Abstract This study focuses on the influence of cryogenic temperature on the interface of carbon fiber reinforced plastics (CFRPs). Results of interfacial shear strength (IFSS) and mode II interlaminar fracture toughness (G IIC ) at −196°C increased by 15.3% and 27.6% compared to the condition at room temperature (RT). By measuring the IFSS at −196°C, a new experimental method was designed based on microbond test. The layer shear fracture morphologies of CFRP were observed by atomic force microscopy and scanning electron microscopy, respectively. In order to study the interlaminar fracture mechanism, the interface and resin fracture hybrid model was built, and the shear-lag theory of interfacial toughness was adopted to analyze the energy release rate (G dc ) of microbond. The results showed that the G dc value was increased by 11.5% from RT to −196°C temperature. A higher G IIC of CFRP was dominated by the higher IFSS and resin energy absorption at −196°C.

Studies on electro-chemical corrosion of carbon fiber reinforced aluminium alloy AA7075

Carbon fiber reinforced AA7075 is known for good thermal properties and thus used as heat dissipating material. However, few such applications involve corrosive environments too, and hence there is a need to study the behavior of these composite materials under corrosive environment. In the present work, milled carbon fiber reinforced AA7075 composites were produced by vacuum hot pressing with varying amounts of milled carbon fibers. The relative densities of the composites were measured. SEM-EDS, TEM and XRD techniques were also employed for characterization. The composites were then characterized for electro-chemical behavior in 3.5 wt.% aqueous NaCl solution by electrochemical polarization technique. Results showed that the corrosion potentials Ecorr have shifted to more negative direction and thus showed increase in corrosion current density, leading to increase in corrosion rate with increasing vol.% of carbon fibers. These results were complemented by SEM micrographs of the composites after corrosion test, which revealed that corrosion occurred at the interface of carbon fiber and matrix due to formation of galvanic coupling between carbon fiber and matrix. Thus, reduced corrosion resistance in composites as amount of fibers increases, is attributed to increase in number of galvanic cells that form at the interface.

Synergistic effect of nano‐SiO2 and small‐sized graphene oxide on carbon fiber/epoxy composite

AbstractThe poor interface of carbon fiber (CF) reinforced composites has long been one that researchers want to facilitate. A hierarchical structure of nano‐SiO2 and small‐sized graphene oxide (sGO) on CF was constructed by a layer‐by‐layer method. The electrochemically treated CF was evenly coated with sGO sheets as a medium layer, which made nano‐SiO2 uniformly spread over CF by electrostatic adsorption. The hierarchical structure could provide the synergistic reinforcement on the mechanical properties of CF composite by improving interface adhesion, mechanical interlocking, and chemical bonding. The interlaminar shear strength value of SiO2‐sGO‐CF/epoxy composite reached 71.1 MPa, which was increased by 33.45% compared with the electrochemical etching CF/epoxy composite. The results show that the sizing of sGO and nano‐SiO2 plays a positive synergistic effect by hierarchical reinforcement.

Tribological performance of B4C modified C/C-SiC brake materials under dry air and wet conditions

In this work, boron carbide (B4C) was selected as additive to improve the tribological performance of C/C-SiC brake materials. It contained four phases (C, B4C, Si and SiC) in B4C modified C/C-SiC (C/C-B4C-SiC) brake materials. Its wear rates were much less than that of C/C-SiC, especially at high braking speeds. The introduction of B4C particles could reduce the braking temperature. During the braking process, B4C in the material can be oxidized to B2O3. The flow of B2O3 could cover the interface of carbon fiber and PyC to prevent them from oxidation and thereby reduce the oxidative wear of the brake materials. Under wet conditions, the braking property of C/C-B4C-SiC brake materials did not degrade, whereas the braking process was found to be stable.

Variation of voids and inter-layer shear strength of advanced polymer-matrix composites at different pressures with high-pressure microwave

Due to its rapid and volumetric heating capabilities, microwave heating has been conceived as an alternative cost-effective route for curing advanced polymer-matrix composites. Different curing pressures were applied to the pre-impregnated laminates of advanced polymer-matrix composites in a given high-pressure microwave curing process. The variation of voids’ shapes in the advanced polymer-matrix composites was revealed, and the shear failure mechanism of advanced polymer-matrix composites with different porosity was analyzed. During the shear failure process of the advanced polymer-matrix composites, sounds ceaselessly occur. The experiment results of the optical digital microscopy, the scanning electron microscope, and the inter-laminar shear properties test showed that in high-pressure microwave curing process, pressure was not only the main factor that affects the porosity and the mechanical properties but also influences the bonding strength of the resin and the carbon fiber interface significantly. There is a threshold value for the effect of curing pressure on porosity and inter-laminar shear strength of advanced polymer-matrix composites. The internal relationship among porosity, inter-laminar shear strength, and curing pressure of advanced polymer-matrix composites could be summarized as a piecewise power function.

Influence mechanism of welding time and energy director to the thermoplastic composite joints by ultrasonic welding

CF/PEEK composites were welded assisted by ultrasonic. The influence of vibration time and using of energy director (ED) to the joints were investigated in details. The joints had defect of incomplete fusion at the interface under short welding time without ED, and defects of cracks and voids appeared at the interface of carbon fiber and PEEK resin, which attributed to too much heat accumulation at the heat affected zone (HAZ). By using flat ED, joint with sound bonding was realized under vibration time of 0.9 s. The lap shear strength of joint can reach 28 MPa, and the joint fractured at the HAZ. The real-time temperature at interfaces were monitored. It is found that the heating rate can be accelerated by using flat ED, and the peak temperature was lowered. At last, the influence mechanism of processing parameter to the joint were discussed in details.

Microstructure, properties and formation mechanism of SiO2/SiC nano-coating onto carbon fiber by non-electrode plasma electrolysis

Recently we have developed a novel non-electrode plasma electrolysis technique in order to rapidly prepare SiO2/SiC nano-coating onto carbon fiber. The surface and cross-sectional microstructures of the SiO2/SiC nano-coating were systematically investigated. The nano-coating was dense and roughly uniform, mainly composed of amorphous SiO2, where a small amount of SiC was distributed. A superior bonding was observed between the nano-coating and the fiber substrate. The cross-sectional TEM revealed ∼80 nm in the thickness for the coating. The SiO2/SiC nano-coating significantly reduced the oxidation rate with the burn-out temperature increasing from 880 °C to 1250 °C. It was proposed that the heat evolution, mechanical effect and plasma chemical reactions had a critical effect on the formation of the nano-coating. We believe that the novel non-electrode plasma electrolysis technique will find a wide range of applications in modifying the interface of carbon fiber reinforced composite materials.

Multifold interface and multilevel crack propagation mechanisms of graphene oxide/polyurethane/epoxy membranes interlaminar-toughened carbon fiber-reinforced polymer composites

Graphene oxide/polyurethane/epoxy (GO/PU/EP) membranes were directly fabricated by functionalization of graphene oxide with epoxy-grafted polyurethane (GO-UE), and the interface correlation and crack propagation mechanisms in GO/PU/EP membranes interlaminar-toughened carbon fiber-reinforced polymer composites were investigated. The functionalized GO-UE with corrugation and scrolling nature of graphene sheets was evenly dispersed in GO/PU/EP membranes below 0.50 wt% loading. Mode I fracture toughness, flexural properties and interlaminar shear strength of GO/PU/EP membranes-toughened composites were enhanced in comparison with untoughened composites and PU/EP membranes-toughened composites, which was ascribed to the multifold interface bonding between the GO-UE layers, epoxy matrix and carbon fiber. Schematic models of multilevel crack propagations were proposed based on different crack extension directions to GO-UE and the morphology evolutions of GO-UE in the interlaminar region and at the carbon fiber interface in toughened composites, which highlighted the toughening mechanisms of crack pinning, crack deflection and separation between GO-UE layers.

Temperature Dependence of Morphology of Transcrystalline at the Interface of Carbon Fiber and Poly (L‐Lactic Acid) Composite Under a Temperature Gradient Stage

SummaryThin film of carbon fiber (CF) and poly (L‐lactic acid) (PLLA) composite was prepared by a solution casting technique. Influence of crystallization temperature (Tc) on morphology of transcrystalline (TC) on the interface between CF and PLLA was investigated under a temperature‐controlled gradient (T‐gradient) stage with temperature ranging from 90 °C to 140 °C. Morphology of TC was observed by polarized optical microscope (POM). Typical TC structure isothermally crystallized on the T‐gradient stage was obtained at the surface of CF when Tc = 111 ∼ 132 °C. As Tc decreased from 132 to 111 °C, nuclei density on the surface of single fiber increased while the thickness of TC layer decreased. Crystallization kinetics of TC was investigated through isothermal crystalization under POM equipped with a temperature‐controlled stage. As Tc decreased, the nucleation rate of TC increased and the growth rate of TC decreased. Furthermore, it revealed that the thickness of TC layer was conducted by the competition between heterogeneous nucleation on the surface of fiber and homogeneous nucleation in the bulk matrix around the fiber. The nucleation rate of TC structure was much higher than homogeneous nucleation rate of spherulites in the bulk matrix when Tc was above 118 °C. In this case, TC had enough space to develop perpendicular to fiber axis. Consequently, thickness of TC layer was larger at higher crystallization temperature. On the contrary, transcrystallization was suppressed by homogeneous crystallization when Tc was below 118 °C due to enhanced nucleation ability of spherulites.

Properties, mechanisms and their analysis of carbon fiber sandwich structures with short-aramid-fiber interfacial toughening

Carbon fiber sandwich structures are widely used as load-bearing structures in aerospace,automobile and other vehicles.Interfacial fracture,which frequently occurs in these structures,could lead to large-area debonding,face-sheet buckling and significantly affect the structural safety.Shortaramid-fibers were selected to toughen the interface of carbon fiber sandwich.Low density tissue of short-aramid-fibers were inserted at the interface during the manufacturing of sandwich structures,and the interfacial toughness was enhanced by bridging effect of short-aramid-fibers.The loaddisplacement curves and failure modes of toughened and plain sandwich specimens were firstly compared through bending tests and compressive tests.The experimental results indicate that various mechanical properties are all reinforced by short-aramid-fiber toughening.Then,the toughening effect and mechanism of interleaved aramid fibers were examined by asymmetric double cantilever beam test and scanning electron microscopy respectively.Finally,based on the singularity solution of uniform elastic material crack and displacement shock solution of crack tip of interface,an extended finite element model(XFEM),which considered the complex stress field at the crack tip of interface,was proposed for simulation of interfacial fracture of carbon fiber sandwich structures.This study will benefit the disclosing of fracture mechanism of short-aramid-fiber toughened interface,establishing the method of designing interfacial toughening parameters,increasing the mechanical properties of carbon fiber sandwich structures, and providing scientific basis for health monitoring and manufacturing of this kind of structure.

Characterization of the reaction products and precipitates at the interface of carbon fiber reinforced magnesium–gadolinium composite

In the present work, carbon fiber reinforced magnesium-gadolinium composite was fabricated by pressure infiltration method. The phase composition, micro-morphology, and crystal structure of reaction products and precipitates at the interface of the composite were investigated. Scanning electron microscopy and energy dispersive spectroscopy analysis revealed the segregation of gadolinium element at the interface between carbon fiber and matrix alloy. It was shown that block-shaped Gd4C5, GdC2 and nano-sized Gd2O3 were formed at the interface during the fabrication process due to the interfacial reaction. Furthermore, magnesium-gadolinium precipitates including needle-like Mg5Gd (or Mg24Gd5) and thin plate-shaped long period stacking-ordered phase, were also observed at the interface and in the matrix near the interface. The interfacial microstructure and bonding mode were influenced by these interfacial products, which were beneficial for the improvement of the interfacial bonding strength.