Microbond Pull-out Test Research Articles

Influence of air plasma modification power on surface properties of basalt fibers and basalt/poly(butylene succinate) adhesion

In this study, basalt fibers were treated with air glow discharge plasma at the powers of 50, 100, 200, and 300 W to investigate the influence of plasma power on fiber surface treatment and basalt/poly(butylene succinate) (PBS) adhesion. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images showed rougher fiber surfaces when the plasma power was higher than 50 W. Water absorption measurement results demonstrated that the wettability of plasma-treated groups was significantly improved. X-ray photoelectron spectroscopy (XPS) showed that the atomic ratio of O/C increased to 0.91, 1.05, 1.86, and 1.86 for the 50 W, 100 W, 200 W, and 300 W groups, respectively. Tensile testing results of single fibers showed no strength reduction after modification. Microbond pull-out test revealed an increase in the interfacial adhesion of up to 39.2 % between basalt fiber and PBS for the 300 W group. This study demonstrates that our air plasma treatment technique was effective in the modification process for improving the basalt/PBS interfacial adhesion, where the selection of appropriate plasma treatment power was critical.

Microbond multiple fiber pull-out test to evaluate interface properties of UHMWPE/LDPE self-reinforced polymer composites

Interfacial properties of composite materials play an important role in overall efficiency and reliability of these materials in structural applications. The objective of this study is to develop a multiple fiber microbond pull-out test to determine the interfacial properties of self-reinforced polymer composites (SRPC) and compare it with single fiber multiple fiber pull-out tests. SRPC possess better interfacial adhesion due to their similarity in chemical structure. The system used in this study is LDPE sheet reinforced with plain weave ultra-high molecular weight polyethylene (LDPE/ UHMWPE). The optimal operating temperature was estimated with DSC and TGA analysis. The micromechanical and meso-mechanical approaches were compared to validate the results. A fractographic study was performed to correlate lamina and meso-mechanical properties found in this study. It was observed that the multiple fiber pullout test explained in this study is on par with or better than the other conventional methods to evaluate interface properties.

Study on Surface Properties of Aramid Fiber Modified in Supercritical Carbon Dioxide by Glycidyl-POSS.

The outstanding diffusivity and permeability of supercritical carbon dioxide (scCO2) are extremely beneficial for grafting reaction. In this work, aramid fibers (AF) are modified in scCO2 by glycidyl-polyhedral oliomeric silsesquioxane (POSS) with 2-ethyl-4-methylimidazole (2E4MZ) on the basis of cleaning with acetone. The surface morphology and chemical structure of the modified AF were measured and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Thermogravimetric (TG), and Atomic force microscope (AFM). The interfacial shear strength (IFSS) was measured by a micro-bond pull-out test, then the modified AF/EP composites were prepared and the interlaminar shear strength (ILSS) was characterized. Research has shown that some of the glycidyl-POSS molecular chains permeated into the surface of the fiber and grafted onto the surface of the AF after modification, and the other glycidyl-POSS self-assembled on the surface of the fiber. XPS indicated the introduction of C–O and –COO–, which confirmed the existence of chemical reactions between AF and glycidyl-POSS. AFM and SEM images revealed that 2E4MZ, not only promoted the grafting reaction of glycidyl-POSS, but also intensified the self-assembly of glycidyl-POSS, both of which increased the roughness of the fiber. A monofilament tensile test and micro-bond pull-out test showed that there was a negative effect on the tensile strength after scCO2 processing. The tensile strength of modified AF, with glycidyl-POSS, increased the highest strength of 25.7 cN dtex−1, which was 8% higher than that of pristine AF. The improvement of ILS roughness and the polar chemical groups produced in grafting reaction. These results indicated that AF, treated in scCO2, with glycidyl-POSS, which is a suitable way of fiber modification, can significantly improve the surface adhesion of AF reinforced composites.

A novel microbond bundle pullout technique to evaluate the interfacial properties of fibre-reinforced plastic composites

The interfacial properties of the fibre composite systems decide the overall usability of a composite in simple and complex shapes, as they are the deciding factors in determination of the mechanical properties, structural properties and above all a complete understanding of the reliability of composite systems. In the present investigation, the interfacial properties of carbon fibre/epoxy composites viz., matrix shrinkage pressure, interfacial frictional stress, interfacial shear stress and coefficient of friction were evaluated through a novel microbond bundle pullout test. This test is different from the single fibre pull out, fibre fragmentation or the fibre push in test. Based on some of the physical principles involving the single fibre microbond pullout test, like the contact angle of the microbond matrix drop with the fibre surface, the surface tension/energy of the two surfaces before and after adhesion and the interfacial fibre/matrix chemistry, this is simple to perform and statistically averaged mesomechanical test is also easy to evaluate and is shown to be a test method that enables a conservative prediction of the laminate level or macromechanical shear properties of fibre composite systems. This test demonstrates the validity of the mesomechanical tests that are more relevant to the macromechanical tests than the micromechanical tests. Fractography carried out to corroborate the observed mechanical properties with the fracture features is also reported. The general advantages of the mesomechanical interfacial tests over those based on micromechanical assumptions is also discussed along with some common limitations.

Effect of atmospheric pressure plasma treatment condition on adhesion of ramie fibers to polypropylene for composite

In order to improve the interfacial adhesion between hydrophilic ramie fibers and hydrophobic polypropylene (PP) matrices, ramie fibers are modified by atmospheric pressure dielectric barrier discharge (DBD) plasma with our continuous ethanol flow technique in helium environment. A central composite design of experiments with different plasma processing parameter combinations (treatment current, treatment time and ethanol flow rate) is applied to find the most influential parameter and to obtain the best modification effect. Field emission scanning electron microscope (SEM) shows the roughened surfaces of ramie fibers from the treated groups due to plasma etching effect. Dynamic contact angle analysis (DCAA) demonstrates that the wettability of the treated fibers drastically decreases. Microbond pullout test shows that the interfacial shear strength (IFSS) between treated ramie fibers and PP matrices increases significantly. Residual gas analysis (RGA) confirms the creation of ethyl groups during plasma treatment. This study shows that our continuous ethanol flow technique is effective in the plasma modification process, during which the ethanol flow rate is the most influential parameter but all parameters have simultaneous influence on plasma modification effect of ramie fibers.

Surface grafting of flax fibres with hydrous zirconia nanoparticles and the effects on the tensile and bonding properties

In the present study, a flax fibre yarn was modified through grafting of hydrous zirconia nanoparticles by hydrolysis of zirconium oxychloride solution, and the effects on the fibre and fiber-bonding properties were investigated. The grafting of the nanoparticles was confirmed by microscopy and spectroscopy analysis. The tensile and bonding strength to an epoxy resin (diglycidyl ether of bisphenol – F) of the modified flax fibres were tested with a single fibre tensile test and microbond pull-out test, respectively. Grafting of the nanoparticles onto the flax fibres brings in an obvious increase in the tensile strength and the interfacial shear strength of the flax fibre to the epoxy resin. An unidirectional flax fibre reinforced epoxy model composite was prepared by hand and characterized in terms of the thermo-mechanical and antimicrobial properties. Surface grafting of the flax fibre leads to an increase in the glass transition temperature and storage modulus, which is attributed to the enhanced bonding strength between the grafted fibre and the epoxy resin. In addition, the treated flax fibre-based composites expressed an antimicrobial performance. The study demonstrates that the fibre surface treatment with grafting of hydrous zirconia nanoparticles is a potential method to enhance the tensile and bonding properties of flax fibres.

Helium plasma treatment voltage effect on adhesion of ramie fibers to polybutylene succinate

Plasma modification effect on fiber surfaces is closely related to the plasma treatment voltage. In this study, ramie fibers with ethanol pretreatment were treated by helium plasma under four different applied voltages of 1.5, 3, 6, and 9kV, respectively, to study the influence of plasma voltage on treatment effect. Scanning electron microscopy (SEM) showed rougher fiber surfaces with increasing plasma voltage. Dynamic contact angle analysis and X-ray photoelectron spectroscopy revealed that the fiber surface wettability decreased and more CC bonds were incorporated to ramie fiber surface by plasma treatment when the voltage was above 3kV. Microbond pullout test showed that interfacial adhesion between ramie and polybutylene succinate for 1.5, 3, 6, and 9kV group increased by 9.6, 29.6, 45.5, and 19.4%, respectively. Single fiber tensile strength test confirmed no significant strength loss for all groups after the plasma treatments. This study showed that proper selection of treatment voltage was critical for optimal improvement of bonding between cellulose fiber and thermoplastic resin using ethanol pretreatment followed by plasma treatment.

Effect of alcohol pretreatment in conjunction with atmospheric pressure plasmas on hydrophobizing ramie fiber surfaces

To improve interfacial adhesion between hydrophilic cellulose fiber and hydrophobic polymer matrix, ramie fibers were pretreated with isopropanol and n-butanol and then plasma treated using an atmospheric pressure plasma apparatus. For the plasma-treated fibers, the scanning electron microscopy shows increased surface roughness and the X-ray photoelectron spectroscopy analysis shows a significant increase of C–C bond in isopropanol-pretreated group, whereas for n-butanol-pretreated group the raise of C=O bonds is most noticeable. For both alcohol-pretreated and plasma-treated groups, the water contact angles increase significantly. Microbond pull-out test shows interfacial shear strengths of fiber/polypropylene (PP) samples increase by 47 and 34%, respectively, for the two groups compared with the control. Therefore, it can be concluded that the reaction between both alcohols and cellulose induced by plasma can indeed create a fiber surface with increased roughness and decreased polarity, and thus is more compatible to PP.

Influence of atmospheric pressure plasma treatment on surface properties of PBO fiber

In order to improve the interfacial adhesion property between PBO fiber and epoxy, the surface modification effects of PBO fiber treated by atmospheric pressure plasma jet (APPJ) in different time, atmosphere and moisture regain (MR) were investigated. The fiber surface morphology, functional groups, surface wettability for control and plasma treated samples were analyzed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. Meanwhile, the fiber interfacial shear strength (IFSS), representing adhesion property in epoxy, was tested using micro-bond pull-out test, and single fiber tensile strength was also tested to evaluate the mechanical performance loss of fibers caused by plasma treatment. The results indicated that the fiber surface was etched during the plasma treatments, the fiber surface wettability and the IFSS between fiber and epoxy had much improvement due to the increasing of surface energy after plasma treatment, the contact angle decreased with the treatment time increasing, and the IFSS was improved by about 130%. The processing atmosphere could influence IFSS significantly, and moisture regains (MR) of fibers also played a positive role on improving IFSS but not so markedly. XPS analysis showed that the oxygen content on fiber surface increased after treatment, and CO, OCO groups were introduced on fiber surface. On the other hand, the observed loss of fiber tensile strength caused by plasma treatment was not so remarkable to affect the overall performance of composite materials.

Influence of absorbed moisture on surface hydrophobization of ethanol pretreated and plasma treated ramie fibers

The existence of moisture in the substrate material may influence the effect of atmospheric pressure plasma treatment. Our previous study has found that the employment of ethanol pretreatment and plasma treatment can effectively induce hydrophobic surface modification of cellulose fiber to enhance the compatibility to polypropylene (PP) matrix, and this study aims to investigate the influence of fiber moisture regain on the treatment effect of this technique. Ramie fibers with three different moisture regains (MR) (2.5, 6.1 and 23.5%) are pretreated with ethanol followed by atmospheric pressure plasma treatment. Scanning electron microscope (SEM) shows that the 2.5% MR group has the most significant plasma etching effect. X-ray photoelectron spectroscopy (XPS) analysis indicates an increase of CC and a decrease of CO bond in the plasma treated groups, and the largest raise of CC bond for the 2.5% MR group. The water contact angles of the 2.5 and 6.1% MR groups increase, whereas no significant change is showed in the 23.5% MR group. The interfacial shear strengths (IFSS) measured by microbond pull-out test are raised by 44 and 25% when moisture regains are 2.5 and 6.1%, while presented no apparent improvement at high moisture regain of 23.5%. Therefore, it can be concluded that moisture regain has negative influence on the surface hydrophobization of ramie fibers in the improvement of adhesion property to PP matrix.

Effect of Glycerol Coating on the Atmospheric Pressure Plasma Treatment of UHMWPE Fibers

In order to investigate how coatings of glycerol affects atmospheric pressure plasma treatment, ultra high molecular weight polyethylene (UHMWPE) fibers were first pretreated with 0.2 and 0.6 mol/l glycerol solutions, respectively, and then were modified by an atmospheric pressure plasma jet (APPJ) using helium as the carrier gas with a flow rate of 20 l/min, discharge power of 30 W and a radio frequency of 13.56 MHz. After the plasma treatment, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis revealed that the glycerol coated-APPJ treated samples possessed smoother surface than the APPJ directly treated samples. The X-ray photoelectron spectroscopy (XPS) analysis indicated that the changed content of oxygen containing groups on the surface of the glycerol coated groups compared with the non-glycerol coated group was mainly due to the remaining glycerol on the fiber surfaces. The water contact angle test revealed that the wettability of the glycerol coated-APPJ treated fibers decreased slightly in comparison with the APPJ directly treated fibers. Furthermore, the microbond pull-out test indicated that the interfacial bonding of the fiber to epoxy resin decreased when the fiber was pretreated with glycerol before plasma treatment. Therefore, it was concluded that the presence of glycerol on fiber surface weakened the effectiveness of APPJ treatment of UHMWPE fibers in improving the interfacial bonding to epoxy. This was mainly attributed to the consumption of plasma energy in etching the glycerol layer on the fiber surface and a weak interfacial layer due to the presence of residual glycerol.

Influence of twist and filament location in a yarn on effectiveness of atmospheric pressure plasma jet treatment of filament yarns

A twist free polyethylene terephthalate (PET) filament tow and ultrahigh modulus polyethylene (UHMPE) filament tows with 0, 1, 2, and 3 twist/cm are used as model systems to investigate the penetration of atmospheric pressure plasma jet modification effects through a single yarn. The change in surface wettability is determined using static contact angle measurements. Morphological and chemical changes on the fiber surface are characterized by scanning electron microscopy and X-ray photoelectron microscopy. The adhesion improvement is analyzed by micro-bond pullout test. For the PET filament tow, the fibers from the middle layer tend to have poorer treatment effect than those from the top and the bottom layers in terms of surface roughness, wettability and surface chemical composition change. For the UHMPE yarns, as the twist level increases, the plasma treatment is less effective in improving the fiber surface chemical composition, wettability and interfacial shear strength to epoxy due to the tightened yarn structure.

P.261 Massive mandibular idiopathic osteolysis: A new syndrome?

In order to improve the interfacial adhesion property between PBO fiber and epoxy, the surface modification effects of PBO fiber treated by atmospheric pressure plasma jet (APPJ) in different time, atmosphere and moisture regain (MR) were investigated. The fiber surface morphology, functional groups, surface wettability for control and plasma treated samples were analyzed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements, respectively. Meanwhile, the fiber interfacial shear strength (IFSS), representing adhesion property in epoxy, was tested using micro-bond pull-out test, and single fiber tensile strength was also tested to evaluate the mechanical performance loss of fibers caused by plasma treatment. The results indicated that the fiber surface was etched during the plasma treatments, the fiber surface wettability and the IFSS between fiber and epoxy had much improvement due to the increasing of surface energy after plasma treatment, the contact angle decreased with the treatment time increasing, and the IFSS was improved by about 130%. The processing atmosphere could influence IFSS significantly, and moisture regains (MR) of fibers also played a positive role on improving IFSS but not so markedly. XPS analysis showed that the oxygen content on fiber surface increased after treatment, and CO, OCO groups were introduced on fiber surface. On the other hand, the observed loss of fiber tensile strength caused by plasma treatment was not so remarkable to affect the overall performance of composite materials.

The Effect of chemical treatment on reinforcement/matrix interaction in Kevlar-fiber/bismaleimide composites

The thermal properties of all the bismaleimides have been examined by differential scanning calorimetry, thermogravimetry and thermomechanical analysis. Both 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (BMPP) and 2,2-bis[4-(4-maleimidophenoxy)phenyl]hexafluoropropane (BMIF) showed a large processing temperature range between their melting points and initial polymerization temperature, which decreased the cross-link density of the cured resins without significant reduction in their thermal resistance. The introduction of flexible groups to BMI structure improved the interfacial shear strength of the Kevlar/bismaleimide composites measured by means of the microbond pull-out test. The results of the pull-out tests show that both BMPP and BMIF have larger interfacial shear strength values than 4, 4′-bismaleimidodiphenylmethane (BMI-DMA). The surface modification with reactive functional groups can enhance both the interlaminar shear strength and T-peel strength of the Kevlar-fiber/BMPP resin system. The ILSS was markedly improved by chlorosulfonic-acid treatment. But higher concentrations of chlorosulfonic acid and longer reaction times caused a lower ILSS. From the ILSS and T-peel strength values, it can be concluded that treatment with 0.2% chlorosulfonic acid for 150 s is the optimum chlorosulfonation condition. In this study, the chlorosulfonation/allylamine treatment produced the best ILSS and T-peel strength. The fracture surfaces of the T-peel specimens were examined by SEM.

Improvement of the adhesion of Kevlar fiber to bismaleimide resin by surface chemical modification

Kevlar 49 fibers were surface-modified by chlorosulfonation and subsequent reaction of -SO2Cl with some reagents (allylamine, ethylenediamine, and deionized water) to improve the adhesion to 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (BMPP) resin. The change in fiber surface morphology and the surface functional groups introduced to the surface of the fiber were investigated by scanning electron microscopy (SEM) and electron spectroscopy for chemical analysis (ESCA), respectively. From the results of ESCA analysis, it was confirmed that the surface composition of the Kevlar fibers was significantly different from that of the bulk composition. After chlorosulfonation, the surface concentration of carbon was markedly decreased. The subsequent reaction with ethylenediamine, allylamine, and deionized water also changed the surface composition of the fiber; e.g. treatment with ethylenediamine and allylamine decreased the O/N ratio. On the other hand, the O/N ratio was increased by hydrolysis treatment. The synthesized 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (BMPP) resin was identified by FTIR, NMR, and differential scanning calorimetry (DSC). The microbond pull-out test was then used to measure the interfacial shear strength (IFSS) between Kevlar fibers and BMPP resin. The results showed that the IFSS increased by a factor of 1.07- 1.62 after chemical treatments. The fracture surfaces of fibers from microbond pull-out specimens were examined by SEM.

A comparison of micromechanical evaluation on interfacial shear strength using microbond pull-out and micro-indentation tests

Fibre-matrix interfacial adhesion in ®bre-reinforced composites plays an important role in controlling the mechanical properties and overall performance of composites. There are many different micromechanical tests that are used for characterizing the composite interface properties. Within these methods, the single-®bre pull-out test [1], microbond test [2], the single-®bre fragmentation test [3, 4], and the micro-indentation test [5, 6] are becoming more popular among these numerous test methods and are widely used for measuring the interfacial properties in composites. This paper describes the basics, concerns, and sensitivity of using the microbond pull-out test and micro-indentation test. Four types of Owens Corning glass ®bre with different surface treatments were investigated in this study. D.E.R. 331 epoxy resin from Dow Chemicals Company had Lindride 66 curing agent from Lindau Chemicals Inc., were selected as the matrix material which is commonly used in ®lament winding. The resin to curing agent mixing ratio was 100:85 by weight. Both microdroplet samples for microbond pull-out test and composite laminates for microindentation test, were prepared under the same curing cycles: 2 h at 120 8C and 2 h postcure at 180 8C. Table I summarizes a list of ®bre sample identi®cations used for composite laminates that were used in this study. The microbond pull-out test, considered as a modi®ed single-®bre pull-out test, consists of a single ®lament embedded in a polymer matrix. This experiment involves the deposition of a small amount of resin onto the ®bre surface in the form of a droplet which forms concentrically around the ®bre in the shape of an ellipsoid. A single microdroplet of the resin system with a dimension of 50±80 im embedded length was controlled to each ®bre specimen. In the test, a small aluminium microvise with two parallel shearing plates was attached to the base of a vertical Instron testing machine. Prior to the experiment, the shearing plates are positioned just above the sample microdroplet, and the two plates closed to slightly touch the ®bre surface. The plates then move downward and exert a shearing force to create a debonding between the matrix and the ®bre. Load-extension curves were recorded for each specimen, and a suf®cient number of tests were carried out to provide 40 interfacial shear strength values for each ®bre system, from which the mean and standard deviations were calculated. Upon debonding, the pull-out force is recorded, and the interfacial shear strength o is calculated using the equation

Effect of Organic Gas Plasmas on the Adhesion of Matrix Resins to Carbon Fibers

Abstract IM7 carbon fibers were surface treated in methane, ethylene, trifluoromethane and tetrafluoromethane plasmas. The surface chemical composition of the fibers was determined by X-ray photoelectron spectroscopy (XPS). The adhesion between as-received and plasma-treated carbon fibers and polyethersulfone (PES) and an epoxy resin was measured by the microbond pull-out test. XPS showed that the methane and ethylene plasmas deposited a thin layer of hydrocarbon on the fiber surface. The trifluoromethane plasma deposited a layer of fluorocarbon on the surface of the fibers. The tetrafluoromethane plasma etched the fibers and introduced a significant amount of fluorine on the surface. The microbond pull-out test results indicated that an etching plasma, such as the tetrafluoromethane plasma, improved the adhesion between carbon fibers and PES. These results are consistent with earlier work performed with ammonia plasma. The adhesion is believed to be due primarily to the differential thermal shrinkage between the fiber and the matrix. It was shown that in the case of a reactive matrix such as an epoxy resin, the fiber chemical composition plays a role in the fiber-matrix adhesion. However, this chemical effect is secondary to the cleaning effect of the surface treatment.

Surface modification of Kevlar 149 fibers by gas plasma treatment. Part II. Improved interfacial adhesion to epoxy resin

Kevlar 149 fibers were surface-modified by NH3, O2, and H2O plasmas to improve the adhesion to epoxy resin. Poly(p-phenylene terephthalamide) (PPTA) film prepared from Kevlar 149 fibers was also modified to estimate the changes in surface energy caused by the plasma treatments. The interfacial shear strength (IFSS) between the fiber and epoxy resin was measured by the microbond pull-out test. The fracture surfaces of microbond pull-out specimens were examined by scanning electron microscopy (SEM) to identify the failure mode of the microcomposites. The results showed that the IFSS of the Kevlar 149 fiber/epoxy resin system was remarkably improved (up to a factor of 2.42) by these plasma treatments and the treatment time was the governing factor in improving the IFSS. After the plasma treatments, the fracture mode of the microcomposites changed from failure at the interface to failure either in the fiber skin or in the epoxy resin. The surface free energy and the work of adhesion of water on the PPTA surfa...

The effect of microvise gap width on microbond pull-out test results

We have examined the effects of the location of load application in microbond pull-out experiments by varying the gap width between the microvise plates. Apparent IFSS values for Kevlar® 49/Epon 828 specimens increase as the gap widens, leveling off at higher gap widths. On analyzing the stress distribution and force balance, we conclude that this increase in IFSS represents an overestimation of the intrinsic value, which is best evaluated with the gap width as small as practicable.

Surface Characterization of Plasma Treated Carbon Fibers and Adhesion to a Thermoplastic Polymer

Abstract The surface chemistry of IM7 carbon fibers was characterized by x-ray photoelectron spectroscopy (XPS). The fiber surface energetics were determined from a two-liquid tensiometric method. The adhesion between as-received and plasma-treated carbon fibers and polyethersulfone (PES) was measured by the microbond pull-out test. The surface characterization techniques showed that the effect of any plasma treatment is attained within less than 15 seconds. It was found that both argon and air plasmas increased the oxidation state of the fiber surface and that they reduced the dispersive component (γs d) of the fiber surface free energy considerably. The ammonia plasma treatment resulted in a cleaning of the surface. This plasma treatment was also effective in improving the fiber/matrix adhesion of quenched samples. A similar adhesion enhancement between as-received fibers and PES is obtained by annealing the samples above the Tg of the polymer. The air plasma treatment did not have any significant effec...