Mechanical properties of plasma‐treated carbon fiber reinforced PTFE composites with CNT

This paper is concerned with the effects of the plasma surface treatment and the addition of CNT on the mechanical properties of carbon fiber/polytetrafluoroethylene (PTFE) composite. The tensile and flexural strength of composites containing CNT and plasma‐treated carbon fibers improved. The flexural strength first decreases with respect to the CF content. The flexural strength increases to 179 MPa for the plasma‐treated composite as compared with 167 MPa for the neat carbon fiber composites. The overall improvement is thus nearly 8%.     

The tensile properties of HNO3‐treated carbon fiber reinforced ABS/PA6 composites

In this study, acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with HNO₃‐treated short carbon fibers (SCFs) [(hollow carbon fibers (HCFs)]. The effects of HCF concentration on the tensile properties of the composites were examined. Increasing the HCF concentration in the ABS matrix from 10 to 30 wt% resulted in improved tensile strength and tensile modulus. To obtain a strong interaction at the interface, polyamide 6 (PA6) at varying concentrations was introduced into the ABS/10 wt% SCF composite. The incorporation and increasing amount of PA6 in the composites increased tensile properties of the ABS/PA6/HCF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/HCF composites, which exhibited an improved adhesion between the SCFs and the ABS/PA6 matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

The addition of clay on the mechanical properties of surface‐treated CF‐filled PA66 composites

Polyamide 66 (PA66) composites filled with clay and carbon fiber (CF) were prepared by twin‐screw extruder in order to study the influence of nanoparticle reinforcing effect on the mechanical behavior of the PA66 composites (CF/PA66). The mechanical property tests of the composites with and without clay were performed, and the fracture surface morphology was analyzed. The results show that the fracture surface area of the clay‐filled CF/PA66 composite was far smoother than that of the CF/PA66 composite, and there formed a tense interface on the CF surface after the addition of clay. The tensile and flexural strength of CF/PA66 composites with clay was improved. The impact strength decreased because of the high interfacial adhesion. In conclusion, the addition of clay favored the improvement of the higher interface strength and so had good effect on improving the tensile and flexural properties of the composites. Copyright © 2017 John Wiley & Sons, Ltd.     

The interlaminar shear strength and tribological properties of PA 6 composites filled with graphene oxide‐treated carbon fiber

The objective of this work is to improve the interlaminar shear strength and tribological properties of the PA 6 composites by graphene oxide‐treated carbon fiber (CF) and ultraviolet irradiation of PA 6. The morphologies of untreated and treated CFs were characterized by X‐ray photoelectron spectroscopy. Surface analysis showed that after treatment, the surface of CFs chemisorbed oxygen‐containing groups; active carbon atom, the surface roughness, and wetting ability were increased. The results show that the treated CF composites can possess excellent interfacial properties and tribological properties accordingly after treatment. Copyright © 2017 John Wiley & Sons, Ltd.     

The influence of polypyrrole coatings on the mechanical and friction and wear properties of bamboo fiber filled PA6 composites

The effects of polypyrrole coatings on the tensile and tribological properties of bamboo fiber reinforced polyamide 6 (PA6) composites were studied. Tribological tests were conducted using a block‐on‐ring arrangement. It was observed that the polypyrrole coatings played a main role in the tensile‐resistant and wear‐resistant properties of the PA6 composites. The tensile properties were ruled by the fiber‐matrix adhesion. And the excellent tribological performance of the fillers improved the tribological properties of PA6 composites. The optimum content of polypyrrole coating concentration is 7vol%.     

Effect of fiber length and composition on mechanical properties of carbon fiber‐reinforced polybenzoxazine

The mechanical strength and modulus of chopped carbon fiber (CF)‐reinforced polybenzoxazine composites were investigated by changing the length of CFs. Tensile, compressive, and flexural properties were investigated. The void content was found to be higher for the short fiber composites. With increase in fiber length, tensile strength increased and optimized at around 17 mm fiber length whereas compressive strength exhibited a continuous diminution. The flexural strength too increased with fiber length and optimized at around 17 mm fiber length. The increase in strength of composites with fiber length is attributed to the enhancement in effective contact area of fibers with the matrix. The experimental results showed that there was about 350% increase in flexural strength and 470% increase in tensile strength of the composites with respect to the neat polybenzoxazine, while, compressive properties were adversely affected. The composites exhibited an optimum increase of about 800% in flexural modulus and 200% in tensile modulus. Enhancing the fiber length, leads to fiber entanglement in the composites, resulted in increased plastic deformation at higher strain. Multiple branch matrix shear, debonded fibers and voids were the failures visualized in the microscopic analyses. Defibrillation has been exhibited by all composites irrespective of fiber length. Fiber debonding and breaking were associated with short fibers whereas clustering and defibrillation were the major failure modes in long fiber composites. Increasing fiber loading improved the tensile and flexural properties until 50–60 wt% of fiber whereas the compressive property consistently decreased on fiber loading. Copyright © 2008 John Wiley & Sons, Ltd.     

Improved mechanical properties of epoxy composites reinforced with surface‐treated UHMWPE fibers

The surface treatment of ultra‐high molecular weight polyethylene fiber using potassium permanganate and the mechanical properties of its epoxy composites were studied. After treatment, many changes were happened in the fiber surface: more O‐containing groups (―OH, ―C═O, and ―C―O groups), drastically decreased contact angles with water and ethylene glycol, slightly increased melting point and crystallinity, and formed cracks. Different contents (0.1–0.5 wt%) ultra‐high molecular weight polyethylene fibers/epoxy composites were prepared. The results indicated that the surface treatment decreased the tensile strength of epoxy composites, but increased the bending strength. When the fiber content was 0.3 wt%, the above properties reached the maximum. At the same fiber content, the interlaminar shear strength of the composites was increased by 26.6% up to the as‐received fiber composites. Dynamic mechanical analysis of the composites suggested the storage modulus and tanδ were decreased due to the surface treatment. Fractured surface analysis confirmed that the potassium permanganate treatment was effective in improving the interface interaction.     

Effects of clay and surface plasma‐treated carbon fiber on wear behavior of thermoplastic POM composites

In engineering applications, experimental data and insight from scientific investigations on wear properties of polyoxymethylene (POM) composites are important for engineers to understand how to design and formulate POM materials with high resistance to wear. In this work, clay and carbon fiber were utilized and incorporated into POM and the mechanical and wear properties, in specific wear rate, were then assessed. The experimental results suggested that the addition of clay increased the tensile modulus and strength. The mechanical and wear properties of POM composites were found to improve with the addition of the carbon fiber. Carbon fiber/clay/POM composite exhibited the lowest specific wear rate and friction coefficient.     

The research on the mechanical properties improvement of HDPE/ABS blends reinforced with acid‐treated wood fiber

In this study, the effect of acid‐treated wood fiber modifications on the mechanical behaviors of HDPE/ABS blend is investigated. Wood fiber/HDPE/ABS composites were fabricated by incorporating acid‐treated wood fiber into HDPE/ABS blends. The results showed that both the tensile strength and flexural strength of wood fiber/HDPE/ABS composites were greater than those of HDPE/ABS blend, regardless of wood fiber modification. The results also showed that the impact strength of HDPE/ABS composites is improved by the addition of wood fiber. Scanning electron microscopic (SEM) examination of fractured surfaces showed that the improvement in the mechanical properties of the wood fiber/HDPE/ABS composites was attributed to the improved dispersion of wood fiber in the HDPE/ABS and the better interfacial characteristics caused by the acid treatment of the wood fiber.     

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.     

Improved mechanical properties of epoxy‐based composites with hyperbranched polymer grafting glass‐fiber

A glass‐fiber, grafted by hyperbranched polymer with hydroxyl group (GF‐HBPH), reinforced epoxy‐based composite was evaluated for mechanical properties and compared with the neat epoxy and silanized glass‐fiber, GF‐APS. The epoxy/GF‐HBPH composites were studied by attenuated total internal reflectance infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, mechanical properties analysis, and field emission‐scanning electron microscopy. The results showed that the incorporation of GF‐HBPH could simultaneously enhance the mechanical properties of the epoxy composites. Field emission‐scanning electron microscopy images of the fracture surfaces of the test specimens were used to support the results and conclusions. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of PPO‐g‐MA on structures and properties of PPO/PA6/short glass fiber composites

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6) blends were reactively compatibilized by maleic anhydride (MA) grafted PPO (PPO‐g‐MA) and reinforced by short glass fibers (SGF) via melt extrusion. An observation of the SGF‐polymer interface by scanning electronic microscope (SEM) together with etching techniques indicated that the PPO‐g‐MA played a decisive role in the adhesion of polymers to SGF. The rheological behavior was investigated by capillary rheometer, and the addition of PPO‐g‐MA, and SGF could increase the viscosity of the PPO/PA6 blends. The analysis of fiber orientation and distribution in the PPO/PA6/SGF composites showed PPO‐g‐MA favored to the random dispersion of SGF. The statistic analysis of SGF length showed that PPO‐g‐MA was helpful to maintain the fiber length during melt‐processing. For the composites at a given SGF content of 30 wt %, the addition of PPO‐g‐MA increased the tensile strength from 59.4 MPa to 97.1 MPa and increased SGF efficiency factor from 0.028 to 0.132. The experimental data were consistent with the theoretical predictions of the extension of Kelly‐Tyson model for tensile strength. The fracture toughness of the composites was investigated by single edge notch three‐point bending test. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2188–2197, 2009     

The research on the friction and wear properties of ionic liquid treated wood fiber filled PA6 composite

PA6 composites with various contents of wood fibers were prepared. The effects of fiber content and ionic liquid surface treatment on the tribological behavior of PA6 composite were studied under different nominal pressures ranging from 50 to 300 N. The tribological mechanisms were discussed based on scanning electron microscopy inspections of the worn surfaces. The surface treatment of wood fibers improves the tribological performance of the neat polymer matrix. The modification can improve O/C and N/C on the surface of wood fiber, while the increase of nitrogen and oxygen content on wood fiber surface can improve the surface polarity of wood fiber and improve the infiltration and bonding between wood fiber and PA6 resin.     

The investigation of the friction and wear properties of surface‐treated carbon fiber/SiO2 reinforced PMMA composites

The mechanical properties of SiO₂ filler particles on carbon fibers have been under discussion for several decades; the diverse models, and the properties of the components relevant to retention, are critically reviewed in the first part of this study. In addition, to gain an insight into some possible combined effect of the carbon fiber/poly(methyl methacrylate) (CF/PMMA), interfacial adhesion strength and the tensile properties and dielectric strength of the hybrid composites were studied. Simple modified rules of mixtures are used to estimate the fiber efficiency factors for the strength and modulus of the hybrid composites. Except, with the increasing fraction of CFs in PMMA, the weld line area's elongation percent is decreased. Whereas for case of SiO₂, the 10 wt% is the threshold for micro injection molded weld line tensile strength and dielectric strength turning from decrease trend to increase. Same as CF, elongation of micro weld line samples is in general lower than neat PMMA as well, due to the addition of SiO₂ particles.     

Acid and basic functionalities of nitrogen and carbon dioxide plasma‐treated polystyrene

The choice of plasma gas can determine the interaction between material and plasma and therefore the applications of the treated materials. Nitrogen plasma can integrate functional groups such as primary amines and carbon dioxide plasma can incorporate carboxylic groups on the surface of polymers. For specific adhesion such as bio‐adhesion, polar groups must be attached to the surface to enhance bio‐film formation but the acidic or basic character also controls the adhesion mechanism. Nitrogen and carbon dioxide plasmas are chosen to treat the surface of polystyrene and to show the effects of different functionalizations, i.e. attachment of acid or basic groups and degradation are compared in the present work. Nitrogen‐containing plasma induces mainly weak degradation at a rate of ～0.13 µg cm^?2s^?1. The roughness of the treated surface remains mostly unchanged. Functionalization leads to amino group attachment at a concentration of 1.2 sites nm^?2. We found that carbon dioxide plasma treatment shows more drastic degradation with a rate three times higher than that of nitrogen plasma and can create more functional groups (4.5 sites nm^?2) at mild plasma treatment. However, the roughness of the surface is altered. In both cases the aromatic groups are degraded through the plasma treatment (again this is more evident with the CO₂ plasma) and the induced functionalization was shown to be quick (the upper monolayer of polystyrene film can be functionalized rapidly). Copyright © 2005 John Wiley & Sons, Ltd.     

The direct architecture of carbon fiber‐carbon nanofiber hierarchical reinforcements for superior interfacial properties of CF/epoxy composites

A simple and efficient chemical method was developed to graft directly carbon nanofibers (CNFs) onto carbon fiber (CF) surface to construct a CF‐CNF hierarchical reinforcing structure. The grafted CF reinforcements via covalent ester linkage at low temperature without any usage of dendrimer or catalyst was investigated by FTIR, X‐ray photoelectron spectroscopy, Raman, scanning electron microscopy, atomic force microscopy, dynamic contact angle analysis, and single fiber tensile testing. The results indicated that the CNFs with high density could effectively increase the polarity, wettability, and roughness of the CF surface. Simultaneous enhancements of the interfacial shear strength, flexural strength, and dynamic mechanical properties as well as the tensile strength of CFs were achieved, for an increase of 75.8%, 21.9%, 21.7%, and 0.5%, respectively. We believe the facile and effective method may provide a novel and promising interface design strategy for next‐generation advanced composite structures.     

Surface properties and corrosion resistance of SF6 plasma‐treated polyester‐based thermoplastic elastomer

Copolyester thermoplastic elastomers (COPE) have interesting mechanical properties but low chemical resistance in aggressive environments. Developing a treatment that would increase their chemical resistance while preserving their convenient bulk characteristics would be an advance. Radiofrequency plasma treatments in sulfur hexafluoride were undertaken. Surface properties and corrosion resistance of untreated and treated samples were investigated. Surface chemical composition was altered, resulting in a loss of organic elements and the incorporation of fluorine. Surface morphology and topography were changed by the removal of species during the treatment. Treatment tends to increase hydrophobicity; for the longer treatment times, hydrophobicity tends to be retained even after aging under atmospheric conditions. Resistance to chlorine attack was substantially increased upon fluorination, while resistance to oxygen attack was improved in some cases. The improvement in the corrosion resistance, which suggests an increase in lifetime under practical conditions, depends on fluorine incorporation and its effect on the physical stability of the structure.     

Additive manufacturing of continuous carbon fiber reinforced poly-ether-ether-ketone with ultrahigh mechanical properties

Continuous carbon fiber reinforced poly-ether-ether-ketone (CCF/PEEK) composites have attracted significant interests in mission-critical applications for their exceptional mechanical properties and high thermal resistance. In this study, we additively manufactured CCF/PEEK laminates by the Laser-assisted Laminated Object Manufacturing technique, which was recently reported by the authors. The effects of laser power and consolidation speed on the flexural strength of the CCF/PEEK composites were studied to obtain the optimal process parameters. Hot press postprocessing was performed to further improve the mechanical properties of the composites. Various fiber alignment laminates were prepared, and the flexural and tensile properties were characterized. The hot press postprocessing 3D printed unidirectional CCF/PEEK composites exhibited ultrahigh flexural modulus and strength of 125.7 GPa and 1901.1 MPa, respectively. In addition, the tensile modulus and strength of the composites reached 133.1 GPa and 1513.8 MPa. The results showed that the fabricated CCF/PEEK exhibited superior mechanical performance compare to fused filament fabrication (FFF) printed carbon fiber reinforced thermoplastics (CFRTP).     

Preparation and properties of natural rubber composites reinforced with pretreated carbon nanotubes

In order to achieve dramatic improvements in the performance of rubber materials, the development of carbon nanotube (CNT)‐reinforced rubber composites was attempted. The CNT/natural rubber (NR) nanocomposite was prepared through solvent mixing on the basis of pretreatment of CNTs. Thermal properties, vulcanization characteristics, and physical and mechanical properties of the CNT/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR composite. Through the addition of the CNTs treated using acid bath followed by ball milling with HRH (hydrated silica, resorcinol, and hexamethylene tetramine) bonding systems, the crystallization melting peak in differential scanning calorimetry (DSC) curves of NR weakened and the curing rate of NR slightly decreased. Meanwhile, the over‐curing reversion of CNT/NR nanocomposites was alleviated. The dispersion of the treated CNTs in the rubber matrix and interfacial bonding between them were rather good. The mechanical properties of the CNT‐reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR composite. At the same time, the CNT/NR nanocomposites exhibited better rebound resilience and dynamic compression properties. The storage modulus of the CNT/NR nanocomposites greatly exceeds that of neat NR and CB/NR composites under all temperature regions. The thermal stability of NR was also obviously improved with the addition of the treated CNTs. Copyright © 2008 John Wiley & Sons, Ltd.