The Adhesion of Carbon Fibers to Thermoset and Thermoplastic Polymers

The adhesion of three carbon fibers, AS1, AS4, and XAS to thermosetting and thermoplastic polymers has been investigated using the single, embedded filament test. All three fiber types exhibited strong adhesion to the thermosets (epoxies) whereas only the XAS bonded strongly to the thermoplastics. Common explanations for low adhesion, such as weak boundary layers and surface roughness, were investigated and shown not to be responsible for the differences in adhesion. Different levels of fiber surface treatment and various organic sizings also had no effect. Surface analysis of the fibers using XPS and retention time chromatography indicate a subtle difference in the surface chemical constitution of the three fibers but the exact nature of these differences was not determined.     

Some Physico-Chemical Aspects of the Fibre-Matrix Interphase in Composite Materials

This paper deals with the influence of interphase formation on the stress transfer capacity of the fibre-matrix interface in single fibre composites and constitutes a brief review of our recent work. This influence is studied through the deviation of the experimental results from a recent theoretical analysis relating the interfacial shear strength to the reversible work of adhesion established between the fibre and the matrix. Two examples of interphases are considered: a transcrystalline layer in carbon fibre-PEEK composites and a pseudo-glassy interphase in carbon fibre-elastomer systems. In the former case, the low transverse mechanical properties of the transcrystalline layer lead to a decrease of the interfacial shear strength, whereas, in the latter case, the glassy behaviour of the interphase explains the improved interfacial stress transfer capacity.     

On the Effects of Processing Conditions and Interphase of Modification on the Fiber/Matrix Load Transfer in Single Fiber Polypropylene Composites

The scope of this study was the investigation of the effects of both processing conditions (in terms of thermo-mechanical history) and interphase modification (fiber sizing and/or matrix coupling) on the interfacial shear strength (τ_i) of fiber reinforced isotactic polypropylene (iPP). Fiber/matrix load transfer efficiency was investigated by modified single fiber pullout and microdroplet pulloff test methods, respectively. It was established that τ_i of the neat microcomposite (unsized fiber/uncoupled matrix) is improved by quenching of the samples rather than by various spherulitic or transcrystalline supermolecular structures set under isothermal crystallization conditions. Enhanced interfacial shear strength for the quenched samples was attributed to a better wetting behaviour and a fine dispersion of the amorphous PP (aPP) fraction formed. An adhesion model was proposed based on which optimum τ_i is linked to both matrix strength and its wetting behaviour. It was demonstrated that the results from pullout and pulloff tests correlate very well with each other for the particular glass fiber/iPP model composite systems studied. It was shown further that matrix modification (coupling) or fiber sizing enhances τ_i practically to the same level, whereas a combination of matrix coupling and fiber sizing yields an even higher interfacial shear strength (synergistic effect).     

Adhesion of electrochemically formed polypyrrole coatings to low carbon steel

The lap shear strength of polypyrrole coatings formed on low carbon steel (～ 23 MPa) is shown to be significantly higher (by ～ 60%) than that obtained using uncoated steel as the adherend. The lap shear (adhesion) strength of polypyrrole‐coated steel varied with the pH of the monomer–electrolyte solution and the applied current. The low carbon steel‐containing polypyrrole coatings formed at low pH (pH ≤ 2.4) have higher adhesion strength than those coated with polypyrrole at higher pH (pH ≥ 6.0). However, poly(N‐methyl pyrrole)‐coated steel showed significantly lower adhesion strength. Increasing the applied current density decreased the adhesion strength. The surface free energies of polypyrrole coatings, ～ 49–53 mJ/m² are similar to that obtained for uncoated low carbon steel, ～ 53 mJ/m², indicating that polypyrrole will effectively wet low rbon steel. The extent of wetting of low carbon steel by the coatings was additionally confirmed by an interaction parameter, ?, of unity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2757–2763, 2002     

Effects of Microwave Processing on Fiber-matrix Adhesion in Composites

Experiments have been done using a single mode (TE₁₁₁, 2.45 GHz) cylindrial microwave cavity with single fiber composite specimens. After obtaining a cure cycle with microwaves to match that achieved with a conventional thermal cure cycle as measured by tensile tests, dynamic mechanical analysis and differential scanning calorimetry, quantitative measurements of interfacial shear strength and physical properties have been carried out and compared with the results from conventional thermally-cured systems. Under the conditions studied for single fiber specimens, the fiber-matrix interfacial shear strength decreases slightly in both glass-epoxy and aramid-epoxy cases as comapared with thermally-cured specimens. Graphite fiber-epoxy adhesion, on the other hand, increases significantly in these single fiber studies in microwave processed specimens as indicated by an increase in the interfacial shear strength. The failure mode changes from interfacial (thermal curing) to matrix failure.     

Effects of Microwave Processing on Fiber-matrix Adhesion in Composites

Experiments have been done using a single mode (TE₁₁₁, 2.45 GHz) cylindrial microwave cavity with single fiber composite specimens. After obtaining a cure cycle with microwaves to match that achieved with a conventional thermal cure cycle as measured by tensile tests, dynamic mechanical analysis and differential scanning calorimetry, quantitative measurements of interfacial shear strength and physical properties have been carried out and compared with the results from conventional thermally-cured systems. Under the conditions studied for single fiber specimens, the fiber-matrix interfacial shear strength decreases slightly in both glass-epoxy and aramid-epoxy cases as comapared with thermally-cured specimens. Graphite fiber-epoxy adhesion, on the other hand, increases significantly in these single fiber studies in microwave processed specimens as indicated by an increase in the interfacial shear strength. The failure mode changes from interfacial (thermal curing) to matrix failure.     

聚酯线绳与橡胶粘合的研究

聚酯线绳通过由间苯二酚、甲醛及胶乳所组成的水乳液浸渍后．可使其与橡胶间具有优异的和稳定的粘合性能，若加人氯化酚醛树脂，则可使粘合强度得到提高。     

芳纶纤维与表面处理层界面粘合机理研究

用扫描电子显微镜（SEM）和电子能谱仪（XPS）研究芳纶纤维与表面处理层界面粘合机理。结果表明,采用封闭异氰酸酯以及RFL胶乳体系浸渍处理后的芳纶纤维表面增加了一种新的结合碳,而且其它碳的结合能向高能方向移动,纤维表面处理层的氮原子所占比例增大,提高了芳纶纤维的表面活性。     

A comparative investigation of interfacial adhesion behaviour of polyamide based self-reinforced polymer composites by single fibre and multiple fibre pull-out tests

Abstract

Interfacial adhesion of composite materials plays an important role in their mechanical properties and performance. In the present investigation, analysis of the interfacial properties of self-reinforced polyamide composites by using microbond multiple fibre pull-out test is emphasised. Microbond specimens prepared through thermal processing are tested for their interfacial properties by multiple fibre bundle pull-out tests and compared with that of traditional single fibre pull-out test specimens. Multiple fibre pull-out addresses the volume fraction as well as eliminates the possibility of fibre breakage before matrix shear. Higher scatter in the data in the samples is addressed in the present studies. FTIR and Fractographic studies are carried out for deep understanding of the post pull-out interfacial adhesion.     

藤壶剪切强度试验及探讨

简便有效的测试评价方法可以缩短防污漆的开发周期,为其实际应用提供可靠依据。评价低表面能防污漆的测试方法主要有动态模拟试验、藤壶剪切强度试验、涂层降阻试验等。本文以ASTM D5618—1994(2011)为参照进行低表面能防污漆和自抛光防污漆的浅海浸泡对比试验,测算藤壶剪切强度,通过对比试验探讨其防污性能等;通过推演的公式可用于估算剥离藤壶的水流剪切相对速率及航速,完善试验方法,使其更具实际应用意义和参考价值。     

Interface and Interphase in Carbon Fibre-Styrene Butadiene Rubber (SBR) Composites

The stress transfer capacity of carbon fibre-SBR interfaces is analysed in terms of interfacial shear strength and measured by means of a fragmentation test on single fibre composites. For all the cases studied, the experimental values of the interfacial shear strength are largely higher than theoretically expected. Such a result is explained by the existence near the fibre surface of an interfacial layer in which the polymer chain mobility is greatly reduced. Such an interfacial region of low mobility is pointed out by mechanical spectrometry on unidirectional composites at different fibre contents. This interphase could exhibit a pseudo-glassy behaviour and, in particular, an elastic modulus close to that of the elastomer in its glassy state whatever the temperature.     

Fracture Mechanics of aV-peel Adhesion Test - Transition from a Bending Plate to a Stretching Membrane

A linear elastic solution is proposed for a “V-peel” adhesion test for a thin film adhered to a rigid substrate. The mechanical responses of a stiff plate-like coating under pure bending, a semi-flexible film under mixed bending and stretching, and a flexible membrane-like film under pure stretching are discussed. For delamination to occur, the mechanical energy release rate is shown to be G = χ(Fw₀/2bl) with χ a numerical constant varying from 3/2 for a plate-like disc to 3/4 for a thin flexible membrane.     

A Direct Comparison of the Fragmentation Test and the Microbond Pull-out Test for Determining the Interfacial Shear Strength

Experiments were conducted to compare the fragmentation test with the microbond pull-out test for determining the interfacial shear strength between carbon AS4 fibers and a thermoset matrix consisting of a Di-Glycidyl Ether of Bisphenol A (DGEBA) resin cured with a diamine (meta-phenylenediamine, m-PDA) curing agent. The results indicate that, for the microbond test, diffusion of the rather volatile m-PDA curing agent at early stages of cure leads to low values of interfacial shear strengths when compared with results obtained for the same system with the fragmentation test.

With the microbond test, a distinct relationship between the glass transition temperature of the droplets and their size is noticed. Smaller (< 150 μm) droplets have very low Tg's and are incompletely cured. While changing to a modified curing cycle and/or using a m-PDA-rich curing environment alleviates the diffusion problem, the interfacial shear strength values are still not in good agreement with the fragmentation test results. Microbond data from another system consisting of DGEBA resin cured with a different, less volatile dimaine curing agent indicates that diffusion of the curing agent becomes less severe as the volatility of the curing agent decreases and the corresponding microbond interfacial shear strengths agree better with fragmentation test results.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (ς)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (?)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

A New Method to Evaluate Thin Film Adhesion

This paper discusses a new method of evaluating thin film adhesion both qualitatively and quantitatively via a combination of peeling and image processing techniques. The adhesion of thin film on the entire substrate can be quickly evaluated and quantified to a continuous response variable which is superior to a discrete response variable as described in the ASTM D3359-78 publication. Feasibility of this technique has been demonstrated through a gauge capability study which resulted in 2.7% P/T (precision to tolerance) ratio at six sigma standard deviation for a tolerance of 100. Experimental results using the proposed method to evaluate the process/property relationship of aluminum films as deposited onto various dielectric substrates such as polyimide, silicon dioxide, and silicon nitride have been obtained and have been shown to agree with conventional stud pull test results. The estimated cycle time to evaluate thin film adhesion is five minutes per 4-inch size wafer once the sample is prepared. This short process cycle time and proven reliability show that there is merit in implementing this technique both in the laboratory for process development and in the factory for statistical process control of products.     

Viscoelastic Analysis of Shear Adhesion Test for Pressure-Sensitive Adhesive Tape

A new shear adhesion tester of a pressure-sensitive adhesive tape is developed, by which the slippage of the tape under shearing force can be measured as accurately as 1 μm or 0.1 μm per digit by the aid of a linear variable differential transformer. When shearing force is exerted on a tape applied on an adherend, two kinds of slippages are expected, that is, the one between the surface of the adhesive and the adherend and the other of the shearing strain of the adhesive. In order to separate the two kinds of slippages, slippage under shearing force and the recovery displacement after removing the force are measured. Analysing the results of measurements it becomes clear that viscoelastic models of Voigt units connected in series are suitable for both of the slippages.     

Viscoelastic Analysis of Shear Adhesion Test for Pressure-Sensitive Adhesive Tape

A new shear adhesion tester of a pressure-sensitive adhesive tape is developed, by which the slippage of the tape under shearing force can be measured as accurately as 1 μm or 0.1 μm per digit by the aid of a linear variable differential transformer. When shearing force is exerted on a tape applied on an adherend, two kinds of slippages are expected, that is, the one between the surface of the adhesive and the adherend and the other of the shearing strain of the adhesive. In order to separate the two kinds of slippages, slippage under shearing force and the recovery displacement after removing the force are measured. Analysing the results of measurements it becomes clear that viscoelastic models of Voigt units connected in series are suitable for both of the slippages.