Effect of carbon fiber surface functionality on the moisture absorption behavior of carbon fiber/epoxy resin composites

Polyacrylonitrile (PAN)‐based carbon fibers were electrochemically oxidized in aqueous ammonium bicarbonate with increasing current density. The electrochemical treatment led to significant changes of surface physical properties and chemical structures. The oxidized fibers showed much cleaner surfaces and increased levels of oxygen functionalities. However, it was found that there was no correlation between surface roughness and the fiber/resin bond strength, i.e. mechanical interlocking did not play a major role in fiber/resin adhesion. Increases in surface chemical functionality resulted in improved fiber/resin bonding and increased interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composites. The relationship between fiber surface functionality and the hydrothermal aging behavior of carbon fiber/epoxy composites was investigated. The existence of free volume resulted from poor wetting of carbon fibers by the epoxy matrix and the interfacial chemical structure were the governing factors in the moisture absorption process of carbon fiber/epoxy composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Interfacial studies on the ozone and air‐oxidation‐modified carbon fiber reinforced PEEK composites

In this work, ozone modification method and air‐oxidationwere used for the surface treatment of polyacrylonitrile(PAN)‐based carbon fiber. The surface characteristics of carbon fibers were characterized by XPS. The interfacial properties of carbon fiber‐reinforced (polyetheretherketone) PEEK (CF/PEEK) composites were investigated by means of the single fiber pull‐out tests. As a result, it was found that IFSS (interfacial shear strength) values of the composites with ozone‐treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PEEKcomposites was comparativelyinvestigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PEEK matrix. Thus the wear resistance was significantly improved. Copyright © 2009 John Wiley & Sons, Ltd.     

The effect of surface modification with nitric acid on the mechanical and tribological properties of carbon fiber‐reinforced thermoplastic polyimide composite

Polyacrylamideacrylate (PAN)‐based carbon fibers were submitted to nitric acid oxidation treatments to improve the interfacial adhesion of the carbon fiber (CF)‐reinforced polyimide (CF/PI) composite. The carbon fiber surfaces were characterized by X‐ray photoelectron spectroscopy (XPS). Nitric acid oxidation not only affects the oxygen concentration but also produces an appreciable change in the nature of the chemical functions, namely the conversion of hydroxy‐type oxygen into carboxyl functions. Nitric acid oxidation treatment modifies the element constituting the fiber, the nitrogen concentration being about 1.2 times higher at the fiber external surface compared to the untreated one. The mechanical and tribological properties of the polymide (PI) composites reinforced by the carbon fibers treated with nitric acid oxidation were investigated. Results showed that the tensile strength of the CF/PI composites improved remarkably due to nitric acid treatment along with enhancement in friction and wear performance. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel preparation of glass fiber reinforced polytetrafluoroethylene composites for application as structural materials

A novel method was developed to fabricate continuous glass fiber reinforced polytetrafluoroethylene (PTFE/GF) composites which includes the use of conventional sintering and vacuum assisted resin transfer molding (VARTM), successively. The RTM resin (coded as M4506‐1) “fills” the porosity and defects of original PTFE/GF composites prepared by traditional sintering processing, improves the overall interface bonding between the matrix and fibers, and thus significantly improves the mechanical properties such as the flexural and interlaminar shear strength of fiber reinforced PTFE composites. The present work suggests a new way to produce fiber (especially continuous fiber) reinforced PTFE composites with high mechanical properties, and thus make it potentially possible to use PTFE‐based composites as structural materials. Copyright © 2008 John Wiley & Sons, Ltd.     

New strategy to reinforce and toughen composites via introducing thorns-like micro/nanofibers

In this work, we report a new strategy of introducing thorns-like fiber into composites, so that the resultant composites substantially benefit from strong fiber–matrix interface adhesion. Specifically, the “thorns” could increase in interlocking molecules chains and entangle with the surrounding matrix resin, which could impede the mobility of polymer chains, as like the roots with uplift capacity. Strong interfacial adhesion between fibers and matrices is suggested by the SEM images and the DMA studies. After the thorns-like fibers are embedded into epoxy resin, the glass transition temperature (T_g) and the storage modulus (E′) are higher than these of neat epoxy and untreated fibers-reinforced epoxy, respectively, and the flexural properties of the composites reinforced with thorns-like fibers are significantly increased. Therefore these novel three dimensional thorns-like fibers will be applicable for composite materials based upon its unique architecture, making it an attractive alternative to increase the performance of any matrix resin.     

半晶聚合物复合材料中的横晶

半晶聚合物复合材料,尤其是纤维增强的半晶聚合物复合材料,在其界面区常有横晶结构生成。本文综述了横晶自发现至今的研究情况,对横晶的形成和生长机理进行了描述,对影响横晶生成和性质的因素进行了分析,着重介绍了几种典型半晶聚合物复合材料体系的横晶形态,并讨论了横晶对界面特性和复合材料性能的影响。     

Mechanical property evaluation of glass–jute fiber reinforced polymer composites

The natural fibers such as jute, coir, hemp, sisal etc. are randomly used as reinforcements for composite materials because of its various advantages such as low cost, low densities, low energy consumption over conventional fibers. In addition, they are renewable as well as biodegradable, and indeed wide varieties of fibers are locally available. In this study, glass–jute fiber reinforced polymer composite is fabricated, and the mechanical properties such as tensile, flexural and impact behavior are investigated. The materials selected for the studies were jute fiber and glass fiber as the reinforcement and epoxy resin as the matrix. The hand lay‐out technique was used to fabricate these composites. Fractured surface were comprehensively examined in scanning electron microscope (SEM) to determine the microscopic fracture mode. A numerical procedure based on the finite element method was then applied to evaluate the overall behavior of this composite using the experimentally applied load. Results showed that by incorporating the optimum amount of jute fibers, the overall strength of glass fiber reinforced composite can be increased and cost saving of more than 30% can be achieved. It can thus be inferred that jute fiber can be a very potential candidate in making of composites, especially for partial replacement of high‐cost glass fibers for low load bearing applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Short carbon fiber reinforced aromatic polydisulfide derived from cyclic (4,4′‐oxybis(benzene)disulfide) via ring‐opening polymerization

Morphology, mechanical and thermal properties of short carbon fiber reinforced poly(arylene disulfide) synthesized by ring‐opening reaction of cyclic(arylene disulfide) oligomers were studied. These macrocyclic oligomers were prepared from 4,4′‐oxybis(benzenethiol) by oxidation coupling cyclization. Ring‐opening polymerization (ROP) was carried out by in situ melt molding in air. Oxidation reaction during the ROP was detected using the Raman spectrum technique. Three‐point bending tests were performed to determine the flexural properties of neat polymers and the composites. The results showed that the flexural strength and modulus of poly(arylene disulfide)/carbon fiber composites were greatly enhanced with the carbon fiber addition. The maximum weight loss peak temperatures of the composites increased with increasing short carbon fiber content. Good adhesion between carbon fiber and the matrix was observed using scanning electron microscopy (SEM) technique. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Impact‐specific essential work of fracture of maleic anhydride‐compatibilized polypropylene/elastomer blends and their composites

Charpy drop‐weight‐impact and essential work of fracture (EWF) characteristics of maleic anhydride (MA)‐compatibilized styrene–ethylene butylene–styrene (SEBS)/polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS‐g‐MA) or PP (PP‐g‐MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP‐g‐MA. Drop‐weight‐impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS‐g‐MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass‐fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWF tests were carried out on single‐edge‐notched‐bending specimens at 3 m s^?1. The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high‐impact‐rate loading condition. The addition of SEBS or SEBS‐g‐MA elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1881–1892, 2002     

The oxidation‐treated interface on tribological properties of carbon fibers‐reinforced PTFE composite under oil‐lubricated condition

The effect of air oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil‐lubricated condition was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF–PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air‐oxidated composites. X‐ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen‐containing groups on CF surfaces was largely increased. The increase in the amount of oxygen‐containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with PTFE matrix and large scale rubbing‐off of PTFE was prevented, therefore, the tribological properties of the composite were improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Silane Coupling Agent and Compatibilizer on Properties of Short Rossells Fiber/Poly(propylene) Composites

Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix.     

Surface modification of carbon fiber via electron‐beam irradiation grafting

In this paper, the surface properties of polyacrylonitrile‐based carbon fibers is improved by electron‐beam (EB) irradiation in maleic anhydride/acetone solution at 100, 150, 200 and 150 KGy. Experimental study of this paper is carried out to identify surface topography, surface chemical composition and functional groups, adsorption ability and interface properties of CF/epoxy composites. The results reveal that the roughness of carbon fiber surface is increased obviously after modification by EB irradiation grafting technology. The ratio value of O/C and the relative content of oxygen functional groups on fiber surface are improved effectively, comparing with the unmodified carbon fiber. Besides, adsorption of carbon fiber on epoxy and the mechanical performance of CF/epoxy composites are clearly enhanced after irradiation grafting modification. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface grafting of bamboo fibers with 1,2-epoxy-4-vinylcyclohexane for reinforcing unsaturated polyester

The present study focused on the surface treatment of bamboo fibers (BFs) with a bifunctional monomer, 1,2-epoxy-4-vinylcyclohexane (EVC), in the presence of N, N-dimethylbenzylamine as the catalyst, which results in the grafting of the fibers with C=C bonds on the surface. The modified BFs carrying C=C bonds were used to prepare bamboo fibers reinforced unsaturated polyester (UPE) composites by hand lay-up compression molding. Hence, chemical connections between the modified-fibers and UPE resins were formed via the free-radical polymerization of the C=C bonds during the preparation of the BFs–UPE composites. XPS analysis proved that the EVC was covalently bonded onto BFs. XRD analysis revealed that EVC-grafting did not alter the crystal structure of the fibers, but slightly decreased their crystallinity degrees. SEM images indicated an markedly improved interfacial adhesion between BFs and UPE matrices after fiber modification, which significantly increased the tensile strength, flexural strength, flexural modulus, storage modulus, glass transition temperature, and water resistance of the resulting BFs–UPE composites.     

Design and characterization of cellulose fibers with hierarchical structure for polymer reinforcement

This paper describes an approach to manufacture hierarchical composites from environmentally friendly materials by grafting cellulose whiskers onto regenerated cellulose fibers (Cordenka 700). Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy and X-ray diffraction analysis were performed to verify the degree of modification. The mechanical properties of the unmodified and modified fibers were analyzed using fiber bundle tensile static and loading–unloading tests. To show the effect of cellulose whiskers grafting on the Cordenka fibers, epoxy based composites were manufactured and tensile tests done on transverse uni-directional specimens. The mechanical properties were significantly increased by fiber modification and addition of the nano-phase into composite reinforced with micro-sized fibers.     

Short Twaron aramid fiber reinforced thermoplastic polyurethane

Mechanical, dynamic mechanical, and rheological behaviors of a short p‐aramid fiber reinforced thermoplastic polyurethane (TPU) have been studied in the range of 0–30 wt% of fibers. The tensile strength of the composite is improved slightly at higher fiber content with a minimum at around 10 wt% of fibers. The addition of fibers markedly reduces elongation at break and entails a steady increase in the elastic modulus, but decreases the wear resistance of the matrix. Storage modulus (E′) is increased and the shapes of loss tangent (tan δ) peaks point to a possible fiber–matrix interaction. Rheological studies show a power law behavior for all composites and increased viscosity with fiber loading. Study of the tensile and cryogenic fracture surfaces by scanning electron microscopy (SEM) indicates good correlation between the modes of failure and strength of the composites. The micrographs reveal good interfacial adhesion and extensive peeling and fibrillation of the fibers in the compounded and fractured composites. Theoretical models have been used to fit the experimental modulus data. Copyright © 2008 John Wiley & Sons, Ltd.     

Mechanical Behavior of Unidirectional Curaua Fiber and Glass Fiber Composites

Summary: This work intends to promote the use of natural fibers by comparing the behavior of isophthalic polyester matrix composites reinforced with unidirectional curaua fibers with that of unidirectional glass fiber composites. The composites were produced varying the reinforcement angle (0°, 15°, 30°, 45°, 60°, 75° and 90°) with the aim of studying the fiber orientation effect on composite strength. Composites were also made varying the fiber volume fraction (10%, 20%, 30%, 40% and 50%). The efficiency of an alkaline (5% NaOH) surface treatment of the curaua fiber was also evaluated. The unidirectional composites were characterized using tensile, flexural and short beam tests as per ASTM standards. The properties of a lamina reinforced with either glass or curaua fibers were also studied using theoretical micromechanical approach available in commercial software. The curaua fiber alkaline treatment produced higher tensile strength results compared with untreated fibers. The increase in reinforcement angle significantly decreased strength and modulus of the composites, as expected, and the glass fiber composites showed a more pronounced dependence with fiber orientation. Although the glass fiber laminas showed the best mechanical performance, the results obtained with the curaua fibers were considered similar for angles greater than 45°.     

Environmental degradation of E‐glass/nanocomposite under the combined effect of UV radiation,moisture, and rain

This study seeks to investigate how the enhanced properties of the nanoclay E‐glass/epoxy composite can withstand the combined effects of ultraviolet radiation, moisture, and rain. The montmorillonite nanoclay's affinity to moisture compounded the moisture absorption ability of the nanoclay E‐glass/epoxy composites. The moisture in the polymer structure caused delamination, debonding of the fibers/matrix, microvoids, and fiber pullouts. The high clay content (2 wt %), therefore, recorded the highest rate of degradation of 15% in flexural stress for the first 20 days, compared to about 8 and 6% loss for the unmodified (0 wt %) and 1 wt % composites respectively. However, as the aging progressed beyond 20 days, the rate of degradation of the nanoclay E‐glass/epoxy composites laminates was steady at 10 and 18%, respectively, for the 1 and 2 wt %, while that of the unmodified polymer continued to degrade progressively. On the contrary, the viscoelastic properties of the nanoclay E‐glass/epoxy composites continued to deteriorate at a faster rate than the unmodified polymer composite. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1024–1029     

Recycled PP/EPDM/talc reinforced with bamboo fiber: Assessment of fiber and compatibilizer content on properties using factorial design

Thermoplastic composites reinforced with natural fibers have attracted the attention of many researchers, not only for environmental concerns, but also for economic reasons, recyclability, ease of processing, etc. One promising application is in the automotive industry due to their low cost and weight. This industry is increasingly pressured to produce vehicles that consume less fuel and are less polluting. Therefore, plastics reinforced with fibers are required to produce lighter parts to replace the much more abrasive glass fiber and mineral filled composites. One of the most widely used polymers in the automotive sector for manufacturing interior and exterior vehicle components is talc filled EPDM (ethylene-propylene-diene monomer) toughened polypropylene (PP). In this context, the aim of this study was to assess mechanical and thermal properties of bamboo fiber reinforced recycled talc filled PP/EPDM composites compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). Composites were prepared, according to a 2² factorial design with center point, in a Haake twin screw extruder with subsequent injection molding. Injected specimens were subjected to tensile, flexural, impact and fatigue testing. Morphological analyses were performed by scanning electron microscopy (SEM), and thermal analyses by thermogravimetry (TGA) and differential scanning calorimetry (DSC). Addition of bamboo fiber significantly increased tensile and bending strength, modulus and fatigue life, and decreased elongation at break and impact strength. On the other hand, addition of the compatibilizer had a positive effect only on tensile and flexural strength, and fatigue life whereas the effect was negative on elongation at break and impact strength. The addition of fiber and compatibilizer did not appreciably affect the matrix melting temperature, but slightly increased crystallization temperature and in some cases the degree of crystallinity.     

芳纶纤维/SMPU-SiO2复合材料的界面性能研究

选用形状记忆聚氨酯(SMPU)和正硅酸乙酯(TEOS)为前驱体,固体酸对甲基苯磺酸(PTSA)为催化剂,利用空气中的水分为水解水源,通过溶胶-凝胶法原位制备了形状记忆聚氨酯与二氧化硅( SMPU-SiO2)杂化材料,并将杂化材料应用于芳纶纤维增强的柔性复合材料中,以期改善芳纶纤维与基体的界面性能.同时,针对芳纶纤维表面...