Peel Test Results Research Articles

Bond strength and mechanical properties of three-layered St/AZ31/St composite fabricated by roll bonding

The aim of this research is bonding of three-layered St/AZ31/St composite by roll-bonding process. The roll-bonding process was performed at three preheating temperatures, 340, 400 and 450°C, with thickness reduction of 30 to 68% and different thicknesses of intermediate layer (AZ31). In order to improve the bonding strength, the as-rolled specimens were annealed at constant temperature of 375°C. For evaluation of bond strength and investigating the formation of a diffusion layer, the results of peel test and microscopic images were studied. Tensile specimens were prepared along the rolling direction to measure the mechanical properties of the composite. The results showed that by increasing deformation, using high preheating temperatures and decreasing the intermediate layer thickness will lead to a stronger bond. In addition, with annealing treatment, a diffusion layer is formed including intermetallic compounds (IMC) such as Al3Mg2 and AlFe3. If the thickness of diffusion layer is less than a critical value (~5μm), bonding strength will increase. Tensile strength was measured at two difference thickness reductions, 53 and 68%, and preheating temperature of 400°C. The tensile strength showed that coherent and well-bonded layers can support each other; this has a direct effect on tensile strength and elongation.

Adhesion, cohesion, and friction estimated from combining cutting and peeling test results for thin noodle sheets.

The aim of this study was to estimate the adhesive and cohesive fracture energies, and frictional characteristics of 7 types of cooked starch and flour sheets and combine these into a model framework for textural analysis. Cutting tests with wires of diameter 0.30 to 0.89 mm were performed with and without lubrication. Plots of the work done, normalized to the area cut by the wire, showed that this to be linearly related to wire diameter irrespective of lubrication. The oil had little impact on the intercept of these plots, giving cohesive fracture energy (Gc ) ranges for these foods between 6.8 and 32.5 J/m(2) . However, lubrication had a strong influence on the slope of the plots. From a comparison of the slopes for lubricated versus unlubricated tests, the kinetic coefficient of friction μkcould be calculated. Values for μk between 0.007 and 0.521 for different foods were obtained. Peeling tests were performed by lifting sheets vertically away from a fresh mica surface. The adhesive fracture energy Ga , varied from 2.5 to 4.8 J/m(2) . The results can be modeled by plotting the ratio of cohesive to adhesive fracture energy against the coefficient of friction. Thresholds in both axes suggest a physical basis for distinguishing textural perceptions. However, sensory testing with 12 subjects using the 7 food types could not establish whether this framework, however well-established physically, would apply to oral sensations. A much larger test would be required.

Estimating interface bonding strength in clad sheets based on tensile test results

The bond strengths of the three-layered aluminum/stainless steel/aluminum composite clad sheets produced by cold roll bonding were estimated by the tensile test results. The developed procedure was based on the drops in flow stress after the maximum point of the stress–strain curves, which are related to debonding of interfaces and signify the effect of bond strength on the tensile behavior. The shape of the stress–strain curve of a specimen heat treated at 600°C to form a brittle intermetallic layer at the roll bonding interface was found to be analogous to those obtained from the tensile test of conventional one-layer specimens, which was considered to be a good evidence of interface debonding during tensile test of roll bonded sheets that show sharp flow stress drops. An important contribution of this work is correlating the tension test to peel test results by simple calculations based on the principles of mechanics of materials.

Cladding of aluminum on AISI 304L stainless steel by cold roll bonding: Mechanism, microstructure, and mechanical properties

The AA1050 aluminum alloy and AISI 304L stainless steel sheets were stacked together to fabricate Al/304L/Al clad sheet composites by the cold roll bonding process, which was performed at temperatures of ~100 and 23°C to produce austenitic and austenitic–martensitic microstructures in the AISI 304L counterpart, respectively. The peel test results showed that the threshold reduction required to make a suitable bond at room temperature is below 10%, which is significantly lower than the required reduction for cold roll bonding of Al sheets. The tearing of the Al sheet during the peel test signified that the bond strength of the roll bonded sheets by only 38% reduction has reached the strength of Al, which is a key advantage of the developed sheets. The extrusion of Al through the surface cracks and settling inside the 304L surface valleys due to strong affinity between Al and Fe was found to be the bonding mechanism. Subsequently, the interface and tensile behaviors of three-layered clad sheets after soaking at 200–600°C for 1h were investigated to characterize the effect of annealing treatment on the formation and thickening of intermetallic compound layer and the resultant mechanical properties. Field emission scanning electron microscopy, X-ray diffraction, and optical microscopy techniques revealed that an intermediate layer composed mainly of Al13Fe4, FeC and Al8SiC7 forms during annealing at 500–600°C. A significant drop in tensile stress–strain curves after the maximum point (UTS) was correlated to the interface debonding. It was found that the formation of intermediate layer by post heat treatment deteriorates the bond quality and encourages the debonding process. Moreover, the existence of strain-induced martensite in clad sheets was found to play a key role in the enhancement of tensile strength.

Acidic pH resistance of grafted chitosan on dental implant.

Over the last decade, access to dental care has increasingly become a service requested by the population, especially in the case of dental implants. However, the major cause of implant failure is an inflammatory disease: peri-implantitis. Currently, the adhesion strength of antibacterial coatings at implant surfaces remains a problem to solve. In order to propose a functionalized implant with a resistant antibacterial coating, a novel method of chitosan immobilization at implant surface has been investigated. Functionalization of the pre-active titanium (Ti) surface was performed using triethoxysilylpropyl succinic anhydride (TESPSA) as a coupling agent which forms a stable double peptide bond with chitosan. The chitosan presence and the chemical resistibility of the coating under acid pH solutions (pH 5 and pH 3) were confirmed by FTIR-ATR and XPS analyses. Furthermore, peel test results showed high adhesive resistance of the TESPSA/chitosan coating at the substrate. Cytocompatibility was evaluated by cell morphology with confocal imaging. Images showed healthy morphology of human gingival fibroblasts (HGF-1). Finally, the reported method for chitosan immobilization on Ti surface via peptide bindings allows for the improvement of its adhesive capacities and resistibility while maintaining its cytocompatibility. Surface functionalization using the TESPSA/chitosan coupling method is noncytotoxic and stable even in drastic environments as found in oral cavity, thus making it a valuable candidate for clinical implantology applications.

Reliability analysis of an ACA attached flex-on-board assembly for industrial application

Purpose – The purpose of this paper is to examine the long-term reliability of an anisotropic conductive adhesive (ACA) attached polyethylene terephthalate (PET) flex-on-board (FOB) assembly for industrial application used in harsh environments. In addition, the possibility of reducing reliability testing time was studied. Design/methodology/approach – A−40/+125°C thermal cycling test with 5- and 14-minute soak times was used to study the reliability. To study the functionality of the FOB assembly during testing, a real-time resistance measurement was used together with a 90° peel strength test. Failure analysis was performed on samples using scanning electron microscopy and cross sectioning. Findings – No failures or noticeable increase in the measured resistance values were seen during testing. The peel strength, however, decreased significantly with both soak times used. The highest drop in the mechanical strength occurred at the start of the temperature cycling tests. The time spent at the high temperature extreme seemed to have a greater impact on the peel strength than the number of temperature cycles. The failure mode of peel tested samples changed due to temperature cycling from interfacial delamination to cohesive failure. The temperature cycling was also observed to induce voiding inside the adhesive. Originality/value – The paper illustrates the applicability of ACA attached PET flex in high reliability industrial applications. Additionally, testing methods for high reliability adhesive interconnections are discussed. Especially, the effect of temperature cycling soak time on peel test results and reliability testing time is studied.

Peel test of spinnable carbon nanotube webs

This paper presents results of peel tests with spinnable carbon nanotube webs. Peel tests were performed to study the effect of orientation angles on interface energies between nanotubes. In absence of any binding agent the interface energy represents the Van Der Waals energies between the interacting nanotubes. Therefore, the effect of the orientations on Van Der Waals energies between carbon nanotubes is obtained through the peel test. It is shown that the energy for crossed nanotubes at 90° angle is lower than the energy for parallel nanotubes at 0° angle. This experimental observation was validated by hypothetical theoretical calculations.

An innovative bi-layered wound dressing made of silk and gelatin for accelerated wound healing

In this study, the novel silk fibroin-based bi-layered wound dressing was developed. Wax-coated silk fibroin woven fabric was introduced as a non-adhesive layer while the sponge made of sericin and glutaraldehyde-crosslinked silk fibroin/gelatin was fabricated as a bioactive layer. Wax-coated silk fibroin fabrics showed improved mechanical properties compared with the non-coated fabrics, but less adhesive than the commercial wound dressing mesh. This confirmed by results of peel test on both the partial- and full-thickness wounds. The sericin-silk fibroin/gelatin spongy bioactive layers showed homogeneous porous structure and controllable biodegradation depending on the degree of crosslinking. The bi-layered wound dressings supported the attachment and proliferation of L929 mouse fibroblasts, particularly for the silk fibroin/gelatin ratio of 20/80 and 0.02% GA crosslinked. Furthermore, we proved that the bi-layered wound dressings promoted wound healing in full-thickness wounds, comparing with the clinically used wound dressing. The wounds treated with the bi-layered wound dressings showed the greater extent of wound size reduction, epithelialization, and collagen formation. The superior properties of the silk fibroin-based bi-layered wound dressings compared with those of the clinically used wound dressings were less adhesive and had improved biological functions to promote cell activities and wound healing. This novel bi-layered wound dressing should be a good candidate for the healing of full-thickness wounds.

The Effect of Bonding Temperature and Curing Time on Peel Strength of Anisotropically Conductive Film Flex-On-Board Samples

Today, flex-on-board (FOB) attachments are commonly used in a variety of applications. By using anisotropically conductive adhesives (ACAs), low-cost flex materials that could not withstand typical soldering temperatures can be utilized. This paper examines the effect of manufacturing process parameters on the peel strength of a FOB assembly with an ACA attachment. The effects of bonding time and temperature on the curing properties of the ACA were also studied. The mechanical strength of the assembly was studied using a 90° peel strength test. The results showed that, by elevating curing temperature, better peel test results were obtained due to the higher degree of cure of the ACA. Additionally, longer curing time increased the peel strength. However, it also caused a considerably higher deviation in the results. Failure analysis using scanning electron microscopy showed that, with a higher degree of curing, the failure location in the peel strength test changed from the flex-adhesive interface toward the adhesive-substrate interface.

Investigation of the peel test for measuring self-cleanable characteristic of fluorine-modified coatings

The self-cleanable ability of coatings is important to prevent or remove polluting fingerprints, dust, water and oils for a number of applications. Fluorocarbon polymers have been used to provide self-cleanable ability due to their low surface energy. The efficiency of fluorine-modified coatings has been evaluated by measuring surface free energy using a contact angle measurement. However, this method is not sufficient to define the polluting-preventive ability or removability of fluorine-modified coatings due to the amount of fluorine content.A peel test can be used to determine the self-cleanable characteristics of fluorine-modified coatings by evaluating adhesion between the coating surface and pressure sensitive adhesives (PSAs). In addition, adhesion can be used to predict the amount of polluting-preventive ability or removability of coatings by comparing the peel strength of commercial PSAs. We designed fluorine-modified acrylic resins with different fluorine contents for a new testing method. Comparing the contact angle measurement with the peel test results, the peel test for the self-cleanable characteristic of coatings was more suitable than the contact angle measurement to predict the polluting-preventive ability and removability of coatings.

Interfacial Optimization of Acetate Taffeta Fabric/PLA Composites

For the interfacial optimization of Acetate Taffeta Fabric (ATF) with Poly Lactic Acid (PLA), steady-state uniform atmospheric glow discharge (AGD) and Silane treatments were studied, respectively. In AGD, the plasma polymerization time for ATF was varied up to 3 minutes. In silane treatments, three types of silane coupling agents, aminoethylaminopropyl-trimethoxysilane, 3-glycidoxypropyl-trimethoxysilane and 3-methacryloxypropyltrime-thoxysilane, were used respectively with concentrations ranging from 0 to 5%. Silane coupling agent was chosen since -OH in silane always reacts with -OH in PLA. Also, all three silanes have similar chemical structures with that of Lactic Acid. The sizing on the fabric was with a solution containing PVA, acryl and water at the ratio of 3:1:96. Peel tests were carried out for the surface modified fabrics before and after removing the sizing. Highest peel test results was obtained with 3% silane concentration. Tensile tests were carried out before analyzing the fracture surface of the composites by scanning electron microscope. Compared to raw fabric, plasma and silane treatments have improved the tensile strength at maximum of 30.4 and 27.4%, respectively.

Development of a Mode III fatigue test method and a peel test method for tire specimens

Crack growth plays an important role in the durability of tires, and it is necessary to evaluate the characteristics of crack growth and tearing energy accurately. Since a crack around the belt edge is subjected mainly to interlaminar shear deformation, a Mode III fatigue test method was developed. In addition, a peel test method was developed to assess the tearing energy. Based on the fatigue and peel test results, the effects of heat aging, temperature and belt stiffness were analyzed.

Interfacial Optimization of Lyocell Fabric/PLA with Silane Treatments

In order to improve the interfacial bonding with polylactic acid, Lyocell fabric’s surfaces were treated with various silanes. The silanes applied were aminoethylaminopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane, respectively. Silane was chosen since hydroxyl group (-OH) in silane always reacts with -OH in Lyocell fabric. As received fabric’s sizing was with a solution containing polyvinyl alcohol (PVA), poly acrylic acid (PAA) and water at the ratio of 3 : 1 : 96. Highest peel test results was obtained with 3wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Highest tensile strength was obtained with 2wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Tensile tests were carried out before analyzing the fracture surface of the composites by scanning electron microscope. FT-IR run confirmed the silane on the surface of fabric.

Bondability Study of Chip-on-Film (COF) Inner Lead Bonding (ILB) Using Conventional Gang Bonder

Inner lead bonding (ILB) is used to thermomechanically join the Cu inner leads on a flexible film tape and Au bumps on a driver IC chip to form electrical paths. With the newly developed film carrier assembly technology, called chip on film (COF), the bumps are prepared separately on a film tape substrate and bonded on the finger lead ends beforehand; therefore, the assembly of IC chips can be made much simpler and cheaper. In this paper, three kinds of COF samples, namely forming, wrinkle, and flat samples, were prepared using conventional gang bonder. The peeling test was used to examine the bondability of ILB in terms of the adhesion strength between the inner leads and the bumps. According to the peeling test results, flat samples have competent strength, less variation, and better appearance than when using flip-chip bonder.

Longitudinal Ultrasonic Bonding of Electrodes between Rigid and Flexible Printed Circuit Boards

In this study, two electrodes between a flexible printed circuit board (FPCB) and a rigid PCB (RPCB) are bonded using longitudinal ultrasonic vibration. The surface finish of the electrode of the RPCB is fixed as an electroless Ni/immersion Au (ENIG), whereas two different surface finishes are employed for the FPCB: immersion Sn and ENIG. Electrodes of the RPCB and FPCB are successfully bonded using longitudinal ultrasonic vibration. While a continuous intermetallic compound (IMC) of (CuxAu1-x)6Sn5 is formed at the ENIG/Sn interface, a Au–Ni–P reaction layer is formed with an un-bonded region at the ENIG/ENIG interface. The peel strength of the ENIG/Sn joint is higher than that of the ENIG/ENIG joint. Results of peel tests show that the bonding conditions have a significant effect on joint integrity.

Numerical analysis of the energy contributions in peel tests: A steady-state multilevel finite element approach

The present work considers the numerical simulation of the steady-state fracture of adhesively bonded joints in various peel test configurations. The model is based on a multiscale approach involving the simulation of the continuum elastoplastic response of the adherends and the adhesive layer, as well as of the fracture process taking place inside the adhesive layer using a cohesive zone formulation. The model parameters are firstly identified by comparison with experimental results obtained with the wedge-peel test. Secondly, the ability of the model to predict peel test results obtained with different peel test configurations (e.g. wedge-peel or fixed-arm peel test geometries and various adhesive layer or arm thicknesses) is critically assessed by comparison with experimental data. Thirdly, the results of the steady-state simulations are post-processed in order to: (i) evaluate the adhesive fracture energy, (ii) quantify and discuss the different contributions to plastic dissipation within the adhesive layer, and (iii) explain how these mechanisms affect the adhesive fracture energy as a function of the peel test configuration. The values of adhesive fracture energy, G a, deduced from the numerical simulations proposed in the present paper, from all the various elastic–plastic peel test configurations, lie in the range of about 900±50 J/m 2; whilst the values from a previous analytical model and a node-release finite-element analysis model, for a cohesive fracture of the present adhesive, all lie in the range of about 1100±250 J/m 2. Thus, there is very good agreement between the different modelling methods. These values are clearly also in good agreement with the corresponding value from the well-established LEFM TDCB method of 1140±170 J/m 2.

Adhesion energy of Cu/polyimide interface in flexible printed circuits

The adhesion strength of interfaces was evaluated for two Cu/polyimide laminates, which had the same interface but different polyimide film thickness. A new technique was applied to evaluate the bond energy of the interface, where micro scale polyimide film blocks were scratched off from the interface-side surface of the copper film. Energy consumed during plastic deformation was successfully calculated with the help of a numerical simulation for crack extension. Contrary to the results of conventional peel tests which yielded 340 J/m 2 and 580 J/m 2, respectively for the two samples, the interfacial adhesion energy was obtained as 30 J/m 2 and 25 J/m 2 by the new technique.

Macro- and micro-surface engineering to improve hot roll bonding of aluminum plate and sheet

Hot roll bonding of aluminum plate and sheet currently is the primary manufacturing method of fuselage skin sheet for aircraft and brazing sheet for automotive applications. Tremendous challenges and opportunities exist to improve quality and productivity of these products. This work explored the effects of macro- and micro-surface engineering on hot roll bonding process. It was found that micro-surface engineering yielded better bonding quality than macro-surface engineering did. The critical surface roughness of the core was about 0.58 μm below which bonding quality in terms of area contact and bonding energy can be significantly improved. However, no marked improvement was observed when the surface roughness was reduced further to 0.03 μm. Also, the oxide layer on the surface of the core and local deformation on the surface of liner played a very important role. Ultrasonic test and roller peel test were employed to assess the bonding strength and quality. The quantitative ultrasonic test results are in good agreement with the roller peel test results.

Development and characterization of self‐reinforced poly(propylene) composites: carded mat reinforcement

AbstractSelf‐reinforced poly(propylene) (PP) composites were produced by film‐stacking using carded mats of α‐isotactic PP fibers and films of β‐isotactic PP. Composite sheets were produced at various consolidation temperatures (T = 150–170°C) and constant holding time (t = 2 min). In a test series the holding time was varied (t = 2–20 min) by keeping the consolidation temperature constant. The consolidation degree of the sheets was studied on polished sections by light microscopy and quantified by density and peel test results. Specimens cut of the sheets were subjected to in‐plane static tensile and out‐of‐plane dynamic impact (instrumented falling weight impact, IFWI) tests. It was established that the best indicators for the consolidation degree are the density, tensile strength and specific perforation impact energy and between them linear correlations exists. Increasing the density of the composites resulted in increased tensile strength (due to lower void content and better fiber/matrix adhesion) and reduced perforation impact energy (due to hindered delamination between the constituent layers). Copyright © 2006 John Wiley & Sons, Ltd.

Effect of poly(acrylic acid) on adhesion strength and electrochemical performance of natural graphite negative electrode for lithium-ion batteries

High-capacity natural graphite negative electrodes for use in prismatic lithium-ion batteries are fabricated from an aqueous suspension precursor. The effects of poly(acrylic acid) (PAA) on suspension stability and the resulting mechanical properties of the electrodes are investigated. Precursor suspensions consisting of graphite particles, sodium carboxymethyl cellulose (CMC), emulsified styrene-butadiene (SB) copolymer latex and PAA are prepared in an aqueous medium and tape-cast on to a copper foil. The addition of PAA enhances the stability of the suspension at low shear rates without compromising the solvent-thickening effect of CMC. Peel test results showed that the adhesion strength of the graphite electrode on the copper substrate is significantly improved by PAA. Graphite negative electrodes fabricated using PAA are characterized by gravimetric and volumetric energy densities of more than 340 mAh g −1 and 560 mAh cm −3, respectively. The PAA formulation also leads to improved cycle life, with a discharge capacity exceeding 90% of initial capacity after 500 cycles.