Showing papers in "Composite Interfaces in 2008"

Effect of chemical modifications of the pineapple leaf fiber surfaces on the interfacial and mechanical properties of laminated biocomposites

Abstract: Natural fiber reinforced renewable resource based laminated composites were prepared from biodegradable poly(lactic acid) (PLA) and untreated or surface-treated pineapple leaf fibers (PALF) by compression molding using the film stacking method. The objective of this study was to determine the effects of surface treatment of PALF on the performance of the fiber-reinforced composites. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to aid in the analysis. The mechanical properties of the PLA laminated composites were improved significantly after chemical treatment. It was found that both silane- and alkali-treated fiber reinforced composites offered superior mechanical properties compared to untreated fiber reinforced composites. The effects of temperature on the viscoelastic properties of composites were studied by dynamic mechanical analysis (DMA). From the DMA results, incorporation of the PALF fibers resulted in a considerable increase of the storage m...

Fibre matrix adhesion of natural fibres cotton, flax and hemp in polymeric matrices analyzed with the single fibre fragmentation test

Abstract: In this research the adhesion and the resulting interfacial shear strength (IFFS) between the natural fibres flax, hemp and cotton and the polymer matrices polypropylene with coupling agent (MAPP) and polylactide acid (PLA) was surveyed with the single fibre fragmentation test (SFFT). The adhesion between MAPP and the fibres was good enough to produce fragments, whereas the adhesion between PLA and flax was too weak to transmit enough tension for fibre cracks which is clearly visible on SEM-photographs. Comparing the IFFS values of the fibres in MAPP with an equal fibre diameter shows that the IFFS value of flax is highest with 7.09 N/mm2 followed by hemp 6.13 N/mm2. The IFFS of cotton is a lot smaller (0.664 N/mm2). The critical fragmentation or fragmentation length of the bast fibres flax (3.16 mm) and hemp (3.20 mm) in MAPP is smaller than the critical fragmentation length of cotton (5.03 mm). The adhesion between the lignocellulosic fibres and MAPP is much better than between the lignin and pectin fre...

Sorption characteristics of water, oil and diesel in cellulose nanofiber reinforced corn starch resin/ramie fabric composites

Abstract: Nowadays, utilisation of biodegradable materials has become necessary in order to maintain global environmental and ecological balance. Fully biodegradable nano 'Green' textile composites have been prepared from cellulose nanofibers reinforced corn starch resin and ramie fabric. Nanofibers having dimensions of approximately 1 μm long and 20–30 nm in diameter are used in the study. The nanofibers were incorporated in corn starch resin via ball mill mixing using ceramic balls. Textile composites were fabricated by pasting the reinforced resin onto the ramie fabric and by hot compression molding technique. Interactions at the fiber–matrix interface and the compatibility between cellulose and corn starch resin molecules will affect the properties of the system. The well dispersed cellulose nanofibers contribute higher interfacial area and good fiber networking within the matrix resin. This will lead to better barrier properties. Sorption characteristics of water, oil and diesel in the textile composites were ...

Microdeformation behaviour of Al–SiC metal matrix composites

Abstract: The satisfactory performance of metal matrix composites depends critically on their integrity, the heart of which is the quality of the matrix-reinforcement interface. The nature of the interface depends in turn on the processing of the MMC component. At the micro-level, the development of local concentration gradients around the reinforcement can be very different according to the nominal conditions. These concentration gradients are due to the metal matrix attempting to deform during processing. This plays a crucial role in the micro-structural events of segregation and precipitation at the matrix-reinforcement interface. Equilibrium segregation occurs as a result of impurity atoms relaxing in disordered sites found at interfaces, such as grain boundaries, whereas non-equilibrium segregation arises because of imbalances in point defect concentrations set up around interfaces during non-equilibrium heat treatment processing. The amount and width of segregation depend very much on (a) the heat treatment t...

Polypropylene-natural fibre composites. Analysis of fibre structure modification during compounding and its influence on the final properties

Abstract: The final properties of composite materials are highly dependent on the residual geometrical parameters (length, diameter, aspect ratio), orientation and distribution of the fibres in the matrix, which in turn are related to the processing conditions. This study analysed the fibre structure variation during the processing of a polypropylene matrix reinforced with cellulose flax pulp for different reinforcement concentrations. The fibre's geometrical parameters, length, diameter and aspect ratio have been measured and their statistical distributions have been assessed for each concentration. Furthermore, the effect of the microstructure variation on the final mechanical properties was analysed. In particular, changes in the interfacial area were evaluated based on the hypothesis that the fibres were cylindrical in shape and considering the average values of the diameters and the lengths calculated using a statistical distribution approach. The fibre interfacial area after the process decreases as the fibre...

Effect of chemical treatment on dynamic mechanical properties of sisal fiber-reinforced polyester composites fabricated by resin transfer molding

Abstract: The dynamic mechanical properties of treated sisal fiber-reinforced polyester composites fabricated by resin transfer molding (RTM) have been studied with reference to fiber surface modifications, frequency and temperature. The sisal fibers have been subjected to various chemical and physical treatments like mercerization, heating at 100°C, permanganate, benzoylation and vinyl tris(2-ethoxymethoxy) silane to improve the interfacial bonding with isophthalic polyester resin. Results indicated that treatment changed the storage modulus (E′), loss modulus (E″) and damping factor (tan δ) drastically at a wide range of temperature. The E′ value increased for every treatment, and is maximum for the composites fabricated by benzoylated-treated fibers. The T g value obtained from the E″value showed an increase as compared to untreated fiber-reinforced composites. The alkali-treated fiber-reinforced composites showed lower tan δ value. Using Arrhenius' equation the activation energy was calculated and found maximum...

Discontinuous basalt and glass fiber reinforced PP composites from textile prefabricates: effects of interfacial modification on the mechanical performance

Abstract: Spun and blown basalt fibers and their PP matrix composites were investigated. The composites were manufactured by hot pressing technology from carded and needle punched prefabricate using PP fiber as matrix material. Glass and blown basalt fibers were treated with reaction product of maleic acid-anhydride and sunflower oil while spun basalt fibers had a surface coating of silane coupling agent. Fibers were investigated with tensile tests while composites were subjected to static and dynamic mechanical tests. The results show that blown basalt fibers have relatively poor mechanical properties, while spun basalt fibers are comparable with glass fibers regarding geometry and mechanical performance. The static and dynamic mechanical properties of glass and spun basalt fiber reinforced composites are similar and are higher than blown basalt fiber reinforced composites. Results were supported with SEM micrographs.

Preparation of PAN-based carbon nanofibers by hot-stretching

Abstract: Partially aligned and oriented polyacrylonitrile (PAN) nanofibers were electrospun from PAN solution in dimethylformamide (DMF) for the preparation of carbon nanofibers. The as-spun polyacrylonitrile nanofibers were hot-stretched by weighing metal in a temperature controlled oven to improve its crystallinity and molecular orientation. Then they were stabilized at 250°C under stress, and carbonized at 1000°C in N2 atmosphere by fixing the length of the stabilized nanofibers to convert them into carbon nanofibers. The result showed that the average diameter of the carbon nanofibers was 140 nm. The degree of crystallinity of the stretched fibers confirmed by X-ray diffraction analysis was enhanced 4-fold in comparison with that of as-spun fibers. The improved fiber alignment and crystallinity resulted in the increased modulus and tensile strength of the nanofibers as much as 5.7-fold and 4.7-fold, respectively. The modulus and tensile strength the of carbon nanofiber increased up to 2243 ± 120 MPa and 170 ± ...

Effect of MAPP and TMPTA as compatibilizer on the mechanical properties of cellulose and oil palm fiber empty fruit bunch-polypropylene biocomposites

Abstract: The effect of compatibilizers, namely, maleic anhydride grafted polypropylene (MAPP GR-205) and trimethylolpropane triacrylate (TMPTA), on the mechanical and morphological properties of the PP-cellulose (derived from oil palm empty fruit bunch fiber) and PP-oil palm empty fruit bunch fiber (EFBF) biocomposites has been studied. The ratio of PP : cellulose and PP : EFBF is fixed to 70 : 30 (wt/wt%) while the concentration of the compatibilizer is varied from 2.0 to 7.0 wt%. Results reveal that at 2.0 wt% of MAPP concentration, tensile strength of PP-EFBF biocomposite is significantly improved. This is due to the enhanced EFBF matrix adhesion resulting in an improvement in EFBF biocomposite performance. There are no significant changes observed in the PP-cellulose biocomposite properties upon the addition of MAPP. In contrast to the tensile strength, flexural modulus and impact strength are significantly improved with the addition of 2.0 wt% TMPTA to PP-cellulose biocomposite. The enhancement of mechanical ...

Creep behaviour of biopolymers and modified flax fibre composites

Abstract: Creep-recovery behaviour of natural fibre–biopolymer composite systems, poly(lactic acid)–flax and poly(hydroxybutyrate)–flax, with various additives, was quantitatively resolved into elastic deformation, viscoelastic deformation and viscous flow. Comparative interpretation of creep behaviour between composites with different additives was presented and the factors that influenced creep were identified. In comparison with unmodified composites, the additive that proved to be the most effective in reducing creep was thiodiphenol, which formed hydrogen bonds at the interface of polymer and fibre; while a decrease was observed with tributyl citrate, a plasticiser. The suppression of creep in the composites with thiodiphenol was due to reduction in the viscous flow contribution to total creep and a significant increase in both the elastic and viscoelastic deformation. The reduction in creep for the plasticised composites was mainly attributed to a reduction in the viscous flow contribution and an increase in ...

A study on sisal fiber-reinforced benzoxazine/epoxy copolymer based on diamine-based benzoxazine

Abstract: A diamine-based benzoxazine monomer has been synthesized via the Mannich condensation reaction of ethylenediamine, phenol and formaldehyde. The effect of solvent was investigated. The chemical structure and thermal properties of the diamine-based benzoxazine were characterized by FT-IR, NMR, DSC and TGA. Sisal fibers are incorporated in a mixture of benzoxazine and bisphenol-A type epoxy resins to form a unidirectionally reinforced composite. The effects of varying fiber contents and matrix composition on the mechanical properties of the composites are studied.

Thermal behavior of chemically treated and untreated sisal fiber reinforced composites fabricated by resin transfer molding

Abstract: Using thermogravimetric analysis (TGA), the thermal behavior of sisal fibers and sisal/polyester composites, fabricated by resin transfer molding (RTM), has been followed. Chemical treatments have been found to increase the thermal stability, which has been attributed to the resultant physical and chemical changes. Scanning electron microscopy (SEM) and infrared (FT-IR) studies were also performed to study the structural changes and morphology in the sisal fiber during the treatment. The kinetic studies of thermal degradation of untreated and treated sisal fibers have been performed using Broido method. In the composites, as the fiber content increases, the thermal stability of the matrix decreases. The treated fiber reinforced composites have been found to be thermally more stable than the untreated derivatives. The increased thermal stability and reduced moisture behavior of treated composites have been correlated with fiber/matrix adhesion.

Preparation of nanocomposite superabsorbents based on hydrotalcite and poly(acrylic-co-acrylamide) by inverse suspension polymerization

Abstract: Firstly, hydrotalcite (HT) was synthesized by the urea method. Then, sodium methyl allyl sulfonate (SMAS) was used as intercalation agent to prepare intercalated HT (SMAS–HT). Finally, a novel poly(acrylic-co-acrylamide)/HT nanocomposite superabsorbent was prepared by inverse suspension polymerization, using N,N′-methylenebisacrylamide (NMBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The morphology of the superabsorbents was characterized by FT-IR, XRD, SEM and TEM. The influences of the amount of SMAS–HT on the water (salt) absorbency were investigated. Results showed that the intercalation was successful and the intercalated SMAS–HT incorporated into the superabsorbent was completely exfoliated. The superabsorbent particles approach a spherical shape and the average size is 200–300 nm. The particle sizes of the superabsorbents decrease with increasing the content of SMAS–HT. In addition, the superabsorbent acquired its highest water (salt) absorbency when the content of SM...

Interfacial adhesion of cellulose fiber and natural fiber filled polypropylene compounds and their effects on rheological and mechanical properties

Abstract: Rayon fiber (RN) and pine wood fiber (PW) filled polypropylene (PP) compounds, PP/RN (90/05 and 75/25 wt%) and PP/PW (90/05, 75/25 and 50/50 wt%), are investigated for their interfacial adhesion, rheological properties, morphology, nucleation and mechanical properties. The interfacial adhesion of the RN-filled PP compounds is better than that of the PW ones. As the concentration of the RN and the PW particles is increased, the dynamic viscosity, the crystallization temperature, and the tensile modulus are increased; however, the tensile strain is decreased. The viscosity of the RN-filled compounds is higher than that of the PW ones at the same loadings. Significant differences are found in the elongation yield test. As the concentration of the particles is increased, the elongation yield stress of the RN compounds is increased. Elongation yield stress of the PW compounds is decreased and more spherulites are locally developed on the RN surface than the PW surface. The interfacial adhesion of the RN surfac...

Composites from Brazilian natural fibers with polypropylene: mechanical and thermal properties

Abstract: Brazil has a well established ethanol production program based on sugarcane. Sugarcane bagasse and straw are the main by-products that may be used as reinforcement in natural fiber composites. Current work evaluated the influence of fiber insertion within a polypropylene (PP) matrix by tensile, TGA and DSC measurements. Thus, the mechanical properties, weight loss, degradation, melting and crystallization temperatures, heat of melting and crystallization and percentage of crystallinity were attained. Fiber insertion in the matrix improved the tensile modulus and changed the thermal stability of composites (intermediary between neat fibers and PP). The incorporation of natural fibers in PP promoted also apparent T c and ΔH c increases. As a conclusion, the fibers added to polypropylene increased the nucleating ability, accelerating the crystallization process, improving the mechanical properties and consequently the fiber/matrix interaction.

Modified flax fibers reinforced soy-based composites: mechanical properties and water absorption behavior

Abstract: Flax fibers are often used in reinforced composites which have exhibited numerous advantages such as high mechanical properties, low density and biodegradablility. On the other hand, the hydrophilic nature of flax fiber is a major problem. In this study, we prepare the soybean oil based composites reinforced with protein coated and lipid acylated flax fibers and compare their water uptake properties. Results showed that water resistance properties of the composites are improved where treated flax fibers are used. The composite with lipid acylation of the flax fiber exhibited to enhance tensile strength and water resistance properties. Influences of fiber length, fiber loading and pressure on mechanical properties are also reported.

Processing and mechanical performance of SBS block copolymer/layered silicate nanocomposites

Abstract: Nanocomposites based on a SBS triblock copolymer and organomodified layered silicates were prepared by solution casting followed by melt shearing. The dispersion of the nanofiller in the polymer matrix and its influence on the mechanical behavior of the composites were determined by means of different microscopic techniques, tensile testing, dynamic mechanical analysis, and microindentation hardness measurements. It was found that the procedure used for the composite preparation was suitable to obtain optimum dispersion of the nanofiller. A significant improvement in the Young's modulus was observed at a filler content of 10 wt% while the other tensile properties remained unchanged. As demonstrated by microhardness measurements, the mechanical reinforcement was verified by a parallel increase in hardness with increasing filler content.

Preparation and properties of kenaf dust-filled chitosan biocomposites

Abstract: Kenaf dust filled chitosan biocomposites have been prepared using a solution blending method. Diluted acetic acid was used as medium to dissolve the chitosan powder. Kenaf dust particles were dispersed in the chitosan solution using a high speed homogenizer. Chitosan biocomposites with five different compositions of kenaf loading (w/w) were prepared. The biocomposites were evaluated in terms of mechanical, chemical and micro-structural properties. The maximum tensile strength, tensile strain and toughness values were obtained from biocomposites containing 28% of kenaf dust, while pure chitosan film exhibit the lowest value as expected. Morphological study on the tensile fracture surface of the biocomposites under FESEM showed the interconnected structure of chitosan matrix with fine distribution of kenaf dust. From the FT-IR spectrum, the finger print peak of chitosan was detected (3233 cm−1) as well as the increasing in intensity of typical functional groups (aldehyde, primary amine and ammonium ions), i...

A novel MD/FE coupled model for numerical investigation of interfacial thermal resistance in MEMS/NEMS packaging

Abstract: Thermal design of MEMS/NEMS packages is drawing more attention from both industrial and academic communities. When the system becomes extremely small, the atomistic effects have to be taken into account correctly. The finite element method is not capable of accurately capturing all the information, especially when it is applied to the small dimensions. In order to study failure behavior, precise modeling of interfacial thermal conductance is essential. In this paper, a multi-scale model is proposed to research interfacial thermal resistance in MEMS/NEMS packaging. The model combines a molecular dynamics simulation for the critical regions within the system with a FE method for a continuum description of the remainder of the system. For non-equilibrium simulations, the establishment of the proper boundary condition is very difficult. In this coupled model, the continuum subdomain serves primarily as a boundary model that provides the low frequency impedance and a sink for the energy associated with outgoin...

Interfacial effects in short sisal fiber/maleated castor oil foam composites

Abstract: In this study, bio-foam composites are produced using short sisal fiber as the reinforcement and modified castor oil as the matrix, respectively. The foam composites with an average cell size of 200 μm possess properties similar to those of commercial polyurethane foams. The effects of fiber loading, fiber length and foam density on the compressive properties of the foam composites are reported in relation to the interfacial interaction. It is found that the addition of chopped sisal alters cell structure of the foam. Surface pre-treatment of sisal by alkali or silane coupling agent helps to improve the mechanical properties and interfacial adhesion. The exposure of the fibers to the gas cells of the foam reduces the effectiveness of interfacial effect, which is different from the case of conventional bulk composites. As a result, the reinforcing ability of sisal fibers becomes a function of fiber length and so on.

Effect of mercerization of flax fibers on wheat flour/flax fiber biocomposite with respect to thermal and tensile properties

Abstract: New composites materials, 100% ecofriendly based on modified wheat flour as matrix and flax fiber as fillers have been obtained by means of an extrusion process. The wheat flour matrix contains non-toxic plasticizers and is mixed well with natural fibers. One sample series without specific fiber surface treatment and a second series with a mercerization surface treatment have been prepared. The content of fillers varies from 0% w/w to 20% w/w. In this work the performances of these new composites in term of thermal stability, mechanical behaviours are compared and discussed in regard to the fiber treatment efficiency and composition. We observe an interesting behaviour: the efficiency is found the best for a fiber composition close to 10% w/w.

Interfacial adhesion of pine wood filled PP compounds via effects of volatile extractives

Abstract: Effects of volatile extractives in pine wood (PW) particles are investigated upon interfacial adhesion, nucleation behavior and mechanical properties in polypropylene (PP) matrix. Various concentrations of the PW are filled in PP, i.e. PP/PW [90/10 (PP10), 75/25 (PP25) and 50/50 wt% (PP50)]. As the concentration of the PW particles is increased, the crystalline peak temperature is increased, the melting peak temperature is decreased, the elongation strain is decreased and the amount of volatile extractives in the PW is increased. Few spherulites are locally developed at the interface between the PW and the PP. The PW acts as a nucleating agent; however, it does not help reinforcing of the PP/PW compounds. The volatile extractives in the PW particles seems to evaporate- and migrate-out during the processing and then coats the pine wood surface, trapped in the compound, and migrats out to the wall surface. This results in a poor interfacial adhesion between the PW and the PP.

Effect of interfacial debonding and matrix cracking on mechanical properties of multidirectional composites

Abstract: In composites, debonding at the fiber–matrix interface and matrix cracking due to loading or residual stresses can effect the mechanical properties. Here three different architectures — 3-directional orthogonal, 3-directional 8-harness satin weave and 4-directional in-plane multidirectional composites — are investigated and their effective properties are determined for different volume fractions using unit cell modeling with appropriate periodic boundary conditions. A cohesive zone model (CZM) has been used to simulate the interfacial debonding, and an octahedral shear stress failure criterion is used for the matrix cracking. The debonding and matrix cracking have significant effect on the mechanical properties of the composite. As strain increases, debonding increases, which produces a significant reduction in all the moduli of the composite. In the presence of residual stresses, debonding and resulting deterioration in properties occurs at much lower strains. Debonding accompanied with matrix cracking l...

Actuator, sensor and MEMS devices based on regenerated cellulose

Abstract: In our early work, cellulose has been discovered as a smart material that can be used as sensors, actuators and smart devices. This newly discovered material is described as electro-active paper (EAPap) and has many advantageous properties: lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheapness and abundance. The actuation principle of cellulose EAPap is based on a combination of piezoelectric and ion-migration effect. This paper reports the fabrication of various micro-patterns and structures, such as rectifying antenna and inter-digital transducer on regenerated cellulose film by adopting a micro-transfer printing technique. Fabrication steps are briefly discussed herein and performance of the actuators was evaluated by means of a tip displacement test. Further, potential application of cellulose as humidity sensor was demonstrated by measuring the impedance change on the inter-digital transducer on cellulose film at different humidity levels.

Reinforcement effects of multiwall carbon nanotubes in elastomeric matrices: Comparison with other types of fillers

Abstract: Mechanical and electrical properties of composites based on butyl rubber and multiwall carbon nanotubes (MWNTs) are investigated. Gradual increases in elastic moduli are observed with the filler content. It was found that the degree of strain affects the electrical resistivity. Finally, the level of reinforcement imparted to a rubbery matrix by carbon nanotubes is compared with that provided by other types of fillers such as carbon black, clay fibers or layered silicates.

Interface tailoring of layered silicate/styrene butadiene rubber nanocomposites

Abstract: To improve the interfacial interaction in clay/SBR nanocomposites prepared by latex compounding method, a novel clay modification for the nanocomposites was introduced before latex compounding with SBR using three kinds of organic modifiers, namely, hexadecyl trimethyl ammonium bromide (C16), bis(hexadecyl) dimethyl ammonium bromide (DC16) and 3-aminopropyl triethoxy silane (KH550). On the other hand, bis(triethoxysilylpropyl)tetrasulfide (Si69) was added into the KH550 modified clay/SBR nanocomposite during later mechanical blending, and was designed to interact with both KH550 and rubber and thus improve the interface. Structure changes of the nanocomposites were followed by study of X-ray diffraction, transmission electron microscopy and rubber process analyzer. Dynamic mechanical analysis and tensile tests were carried out to obtain information about the mechanical properties of the nanocomposites. The results revealed that, with the organic modification, clay was dispersed finely in the rubber matrix...

Polyurethane nano-composite with functionalized silica particle

Abstract: Nano-size silica particles were functionalized with vinyl isocyanate and subsequently UV cured to synthesize polyurethane–silica nano-composites which were tested for mechanical, dynamic mechanical, cross-link density, contact angle and XPS. The modified silica provides composites with cross-links that are pinned at the surfaces and which effectively reinforce the materials mechanically as well as thermally.

Structural and transport properties of porous PVdF-HFP electrolyte membranes modified with an inorganic filler

Abstract: Novel porous poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) copolymer membranes were prepared with zinc chloride as an additive and silica as a ceramic filler. Porosity of the membranes was determined by Scanning Electron Microscopy (SEM). Inclusion of ceramic filler decreases the crystalline character of a polymer which facilitates the movement of ions leading to an increase in the conductivity. The infra-red spectroscopic and EDX measurements revealed the presence of acid moieties in the composite membranes. The thermal stability of these blend membranes lies above 400°C, which is sufficiently high for use in DMFC. The membranes prepared for this study exhibited the ionic conductivity in the range of 10−3 to 10−2 S/cm and the methanol permeabilities ranged between 10−9 and 10−7 cm2/s.

Processability of flax plant stalks into functional bast fibers

Abstract: Flax (Linum usitatissimum L.) is an agricultural crop that is being considered as cost effective alternative to glass in composites. Flax is nature's composite with strong bast fibers held together in bundles and located in the outer regions of the plant stem between the outermost cuticle-epidermis layer and the innermost, woody tissues. Agricultural production of this crop is environmentally beneficial because it is produced through photosynthesis and considered a naturally renewable and sustainable material. Its use in bio-based composites could help lessen our dependence on fossil fuels today and into the future. Despite the longevity of flax in world markets, particular problems exist to provide flax fiber economically for markets in the US and North America. Barriers to such provisions include consistent, high-quality retting methods, efficient processing of whole stems into cottonized fibers, and development of standards to judge fiber quality. Processability of plant stalks into usable fiber requir...

Influence of γ-ray radiation grafting on interfacial properties of aramid fibers and epoxy resin composites

Abstract: This research used Co60 γ-ray radiation to modify Armos fibers in 1,2-epoxy-3-chloropropane. After the treatment, the interlaminar shear strength (ILSS) values of aramid/epoxy composites were improved by about 20%. Surface elements of Armos fibers were determined by XPS analysis, which indicated that the oxygen/carbon ratio was increased. The surface of the fibers treated was rougher than that of the untreated fibers when examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Fourier transform infrared (FT-IR) spectra confirmed that the epoxy group was grafted onto the fibers. The wettability of the fibers' surface was also enhanced by the treatment. Nanoindentation technique analysis showed that the nanohardnesses of the various phases (the fiber, the interface and the matrix) in the composite, whose fibers were treated, were correspondingly higher than those in the composite, whose fibers were untreated. The results indicate that γ-ray irradiation grafting technique, which is ...