Effect Of Fiber Surface Treatment Research Articles

A study of the impact properties of composites consisting of surface-modified glass fibers in vinyl ester resin

In order to study the effect of fiber surface treatment on the impact properties of glass-fiber/vinyl ester composites, glass fiber was surface-treated with polybutadiene(PB), γ-methacryloxypropyltrimethoxysilane (γ-MPS), and γ-MPS-modified polybutadiene (PB/γ-MPS). The relationship between the interlaminar shear strength and impact properties of the composites was examined. In addition, scanning electron microscopy (SEM) was used to examine the fracture surfaces of impacted composites. PB-treated composites showed a higher impact-energy-absorption capability than untreated composites because of the interfacial strength and ductile failure of the composite. In contrast, γ-MPS-treated composites showed lower impact-energy-absorption capability as a consequence of brittle failure by fiber breakage. For PB/γ-MPS-treated composites, the highest impact-energy-absorption was exhibited by chain deformation and slippage of long and flexible entangled-PB/γ-MPS chains.

The effect of fiber surface treatment on its strength and adhesion to the matrix

A procedure is suggested of evaluating the efficiency of fiber treatments by the extent to which the fiber reinforcement strength is realized in the composite. For this purpose, the effects of surface treatments on the scale effect of carbon-fiber strength and adhesion to epoxy resin and polyamide matrices was investigated by the single-fiber composite test.The effect of electrochemical, ozone and cryogenic treatments on high-tenacity carbon fiber UKN-01 has been studied. All surface treatments result in a decrease of the scale dependence of fiber strength.It is shown that there are essential differences in the critical-length distributions for treated and untreated carbon fibers. This may be accounted for in terms of adhesion heterogeneity of the fiber surface. It is suggested that the average length of fragments formed at the beginning of adhesive failure should be used as the critical length for practical calculations because of the large scatter of fragment lengths at the end of a single-fiber composite test.The cryogenic treatment leads to the strengthening of carbon fibers by the removal of pyrolyzate deposits from the surface.The alternation of different kinds of carbon-fiber surface treatment (which change the structure of the surface layer to a certain depth) with cryogenic treatments (which remove these layers from the fiber) permits a study of the radial structure of the carbon fiber.

Effects of temperature and water content on impact properties of injection-molded glass nylon-6 composites

Instrumented drop-weight impact tests were conducted for injection-molded short glass fiber reinforced nylon-6 thermoplastic composites. The effects of fiber surface treatments, specimen temperatures and water contents on the impact fracture properties were studied. The first peak load P, or the corresponding absorbed energy E1 was found an appropriate parameter to evaluate the first cracking on specimen surfaces and also to compare the impact performance of thermoplastic composites. The effects of specimen temperatures and drying conditions were also found important in evaluating these materials. Microscopic observations revealed the microfracture mechanisms to explain the above macroscopic mechanical results. Static in-plane fracture toughness properties corresponded well with the impact properties.

Interphase Morphology of Liquid Crystalline Polymer/Glass Fiber Composites: Effect of Fiber Surface Treatment

The effect of surface treatment on the interphase morphology of liquid crystalline copolyester/glass fiber (LCP/GF) composites has been investigated by polarized light microscopy (PLM), SEM, DSC, and WAXD to identify the role of fiber in the formation of microstructure and morphology of the composites, particularly its influence on the anisotropic nature of LCP. Two coupling agents, γ-methacrylate propyltrimethoxysilane (γ-MPS) and phenyltriethoxysilane (PTS), were employed for the surface treatment of GF

The Effect of Fibre Surface Treatment on the Failure of Continuous Carbon Fibre/Epoxy Resin Composites

Abstract The failure mechanisms of a composite, consisting of continuous, aligned, high strength, polyacrylonitrile (PAN) based carbon fibre in an epoxy resin, under uniaxial tension, have been studied. In order to study the effect of the interphase/interface strength, six different levels of an electrochemical fibre surface treatment were used. Single tows containing approximately 12,000 treated carbon fibres were impregnated to produce composite rods with a fibre volume fraction of 0.55. Lengths of this impregnated tow were also set in the centre of glass-fibre/epoxy resin composite coupons which were used to study the mechanisms of failure of the embedded tows. Acoustic emission was used to monitor all samples and bundle failure was found to occur after a build-up of sub-critical damage events as previously modelled.1 Microdebond tests demonstrated an initial increase of interfacial strength which levelled out at the higher levels. In impregnated samples with high surface treatments, catastrophic failure occurred with the crack propagating approximately perpendicular to the fibre direction. However, in samples with lower fibre surface treatments, longitudinal splitting (not accounted for in current models), occurred, meaning that a greater length of composite was involved in the final failure process. Acoustic emission has been shown to have an approximately direct relation with the predicted number of single fibre breaks in composite test-pieces; however, there was no significant difference attributable to the different surface treatments. The hybrid test coupons allow a detailed assessment of the failure mechanisms within the impregnated carbon tow. The failure strains of the embedded tow is some 5% higher than that of unsupported tow. The Weibull modulus is of the same order.

Fracture Mechanisms and AE of Single-Fiber Composite. Effect of Fiber Surface Treatment and Roughness.

The fracture mechanisms and interfacial properties of single-fiber composites with different surface treatments of the fiber are examined by acoustic emission. The fracture surfaces are observed with a polarized microscope. As a result, it is confirmed that AE events are generated at every fiber breakage. It is found that the fracture mechanisms of SFC are different when the surface treatment of a fiber or a matrix resin is changed. A method to measure the mean fragment length and evaluate the interfacial shear strength of fiber/matrix is proposed using AE events which are almost equal to the number of fiber breakages. The difference in the interfacial shear strength due to the fiber surface treatment can also be identified by this method. From the observation of a fiber surface with SEM, it is also found that this difference in the interfacial shear strength depends upon the surface roughness of the fiber.

The effect of fiber surface treatment on the micro-fracture progress in glass fiber/Nylon 6 composites

The micro-mechanical behavior of fiber/matrix interfaces and macroscopic mechanical properties of glass fiber reinforced Nylon 6 composites have been characterized for four different fiber surface treatments using in situ microscopic observation techniques. A pull-out test under an optical microscope is conducted to determine the interfacial bond strength of single-fiber embedded composites. An elasto-plastic axisymmetric finite element analysis is then used to explain the experimentally-obtained different failure mechanisms and processes at a broken fiber end. In addition, micro-deformation and failure process in injection-molded composites are observed under tensile loading in a scanning electron microscope (SEM) for specimens reinforced with randomly-oriented short glass fibers with the same fiber surface treatments. It is revealed that micro-damage and fracture characteristics in injection-molded thermoplastic composites are well correlated with micro-mechanical properties of fiber/matrix interfaces o...

Interfacial micromechanics in model composites using laser Raman spectroscopy

The mechanisms of load transfer in single carbon-fibre/epoxy-resin model composites, are investigated. The composites are subjected to incremental tensile loading and the fibre fragmentation process is continuously monitored. The fibre strain distribution along the fibre fragments is derived through the Raman spectrum of the carbon fibre and its strain dependence. In turn, the interfacial shear stress distribution is evaluated by means of a balance of forces analysis. The effect of fibre surface treatment and fibre modulus upon the stress transfer profiles and the distribution of the interfacial shear stress along the fibre, are also examined. Finally, the importance of parameters, such as, fibre/matrix debonding and interphasial yielding at the vicinity of fibre breaks, is discussed.

Adhesion of polymers to reinforcing fibres

AbstractA single fibre pull out technique is presented which makes it possible to measure the strength in the interface between fibre and polymer with high precision even if the embedded length of the fibre is short. The method allows measurements for all kinds of fibres in thermoplastic or thermosetting polymers.The effect of fibre surface treatment can be investigated as well as the effect of morphology or internal stresses in the polymer. Examples are given.The shear strength results are compared with results of tensile shear tests performed on symmetrically notched unidirectional reinforced composite samples. The correlation is good and it is shown that the new single fibre pull out method is able to give a better discrimination between the composites than other methods.An analysis of mechanical stress induced during the pull out demonstrates the use and limitation of this method.

Anodic oxidation of pitch-precursor carbon fibres in ammonium sulphate solutions: the effect of fibre surface treatment on composite mechanical properties

Tonen HM pitch-based carbon fibres were electrochemically treated in solutions of ammonium sulphate using a pilot plant surface treatment apparatus. Embedded single fibre and short beam shear specimens prepared with these treated fibres exhibited strengths over 300% greater than those made with untreated fibres. The surface treatment did not, however, result in improvements in the longitudinal compressive strength. This suggests that the compressive strength is not limited by the shear strength of the fibre/matrix interface.

短繊維強化ポリエチレンテレフタレートの強化機構に対する繊維径の効果

Strengthening mechanisms of injection-molded, short-glass-fiber-reinforced polyethylene terephthalate) under uniaxial tension were studied with particular attention to the effect of fiber diameter (d=6, 10, 16, 23μm). Effects of fiber surface treatment were also investigated. Young's modulus was well described by the Cox model considering the fiber aspect ratio and the normalized center-to-center distance between fibers. Tensile strength was quantitatively analyzed on a presently modified version of Kelly's model. The version took into account the strength increase with increasing fiber lateral surface area as well as the strength decrease caused by failure occurrence. It was found that the version accounted for the obtained strength data rather well. Furthermore it was shown that failure strain and total strain energy were partly affected by the fiber lateral surface area. In conclusion, fiber aspect ratio, normalized center-to-center distance between fibers and fiber lateral surface area were significantly influenced by the change in fiber diameters and fiber surface treatment during injection molding. These values, rather than the fiber diameter itself, considerably affected strengthening mechanisms in short fiber reinforced thermoplastics.

Effect of fibre surface treatment on yielding and fracture behaviour of glass fibre-polypropylene composite

Two parallel studies of the mechanical properties of composites based on modified polypropylene is presented. The fillers used were either uncoated-glassy fibres or glassy fibres coated with aluminium. The tensile properties and fracture behaviour are investigated as a function of filler content over a range of temperatures and strain rates. The measured elastic modulus, tensile strength, and fracture parameters, Gc and Kc, showed dependencies on filler content. The observed enhancement is found to be remarkable in the case of composites containing uncoated surface treated glass fibres. The tensile yield stress of all the composites prepared showed strain rate and temperature dependence. Stress activation volume and activation energy of single-activated yielding processes are determined. The observed fracture morphology could explain the reinforcement behaviour of the measured mechanical properties.

The structure of the interface in carbon fibre composites by scanning Auger microscopy

Scanning Auger microscopy (SAM) has been used to study the fibre/matrix interface of composite materials. This novel application of Auger spectroscopy enables further understanding of the mechanism of failure in composites when applied to carbon fibre-reinforced epoxy material. Initial work was carried out on carbon fibres prior to their incorporation into the resin matrix. Auger spectroscopy can be used to detect the presence of thin polymeric layers on the carbon fibres if a suitable, matrix-specific element is chosen to form the scanning Auger image. Two composite materials have been investigated. They differ from each other by the fracture mechanisms. In the case of unidirectional continuous fibre composites, a high volume fraction of conducting carbon fibres makes Auger analysis possible although the failure surface is predominantly polymer residues. For short-fibre composites the technique is more difficult considering the low volume fraction of fibres, but Auger spectroscopy enables the identification of microfailure mechanism and of the effect of fibre surface treatment on the failure mode.

The Effects of Fiber Surface Treatments by a Cold Plasma in Carbon Fiber/Bismaleinide Composites

AbstractThe effects of plasma treatments on the physical and chemical characteristics of carbon fiber surface and on the mechanical properties of carbon fiber/bismaleimide (BMI) resin composites were investigated. Scanning tunneling microscopy (STM), scanning electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and wettability measurements were applied for fiber surface characterization. Oxygen plasmas were found to be effective in enhancing the interfacial adhesion between carbon fiber and BMI matrix. Possible mechanisms of interfacial adhesion promotion were suggested and discussed.

Filament Fragmentation Phenomena

AbstractThe effect of fiber surface treatments on the relationship between the tensile strength of a filament and the shear strength of its interphase is one of the central issues facing composite materials technologists today. We demonstrate here that analysis of fragmentation phenomena in monofilament composites can simultaneously yield information about these two parameters. Characterization of shear stress transfer zones in non-critical fragments has led us to the determination of interphase strength.A phenomenological treatment that highlights the role of the matrix in the fragmentation process is presented here. This analysis considers issues such as the strain energy exchange between a failing fiber and the matrix, as well as interphase relaxation due to the viscoelastic nature of the matrix. Our observations of the fragmentation phenomena in AU4/polycarbonate monofilament composites indicate that the fiber/matrix interaction in this system is governed by micromechanical locking.

Effect of Fiber Surface Treatment on the Properties of Carbon Fiber Reinforced Nylon Composites

The mechanical properties of injection-molded, carbon fiber reinforced nylon 6,6 com posites were characterized for four different fiber surface treatments. It is demonstrated that, for similar fiber length distributions, improvements in both ultimate and impact strengths can be effected by increasing the degree of fiber-to-resin bonding through modification of the surface treatment. Micrographs of composite fracture surfaces are shown for selected treatments. Composite electrical properties are also presented.

Moisture Absorption Characteristics of Aramid-Epoxy Composites

Tests were conducted measuring the changes in weight of aramid fiber reinforced epoxy matrix composites during exposure to humid air. Composites containing surface treated fibers and composites containing fibers without surface treatment were tested. In addition, for the purpose of comparison, the weight changes of glass fiber reinforced epoxy com posites and pure epoxy were measured. From the weight change data the values of the maximum moisture contents and diffusivities were determined. The effects of fiber surface treatment on the moisture absorption characteristics of the aramid fiber reinforced com posite were assessed. An expression was developed for estimating the transverse diffu sivities of composites from the known resin and fiber properties when fibers absorb a sig nificant amount of moisture.

The effect of fibre surface treatment, resin type and fabrication process on the interlaminar shear strength of carbon fibre composites

AbstractSome data related to the preparation of carbon fibre composites is summarised.A limited investigation concerned with presenting markedly different fibre surfaces to the resin by coating with metals and stearic acid is also described.There are carbon fibre surface treatments which lead to improved shear strength, but it is not clear how they are affecting the fibre surface. It also seems likely that some facets of the processing technique can have a large effect on composite quality as indicated by shear strength measurements.The difficulties in interpreting results and identifying sources of variability points to the advisability of statistically planned experiments to assess the significance of changes when investigating possible materials and processing improvements.