Blister Test Research Articles

Adhesion energy of as-grown graphene on copper foil with a blister test

Interfacial adhesion energy between as-grown graphene and its growth substrate reveals the nature of bonding, as well as provides insights for large-scale roll-to roll graphene transfer. In this study, a novel sample preparation scheme was developed and a unique quasi-static blister test was performed to measure the adhesion energy between as-grown graphene and its copper foil substrate. The copper foil was treated with acetic acid for 4 h, 24 h and 48 h prior to graphene growth. The corresponding adhesion energy was determined to be 0.74 ± 0.13 J/m2, 1.10 ± 0.16 J/m2, and 1.53 ± 0.11 J/m2, respectively. Longer exposures to acetic acid led to rougher copper foil surfaces, and thus higher adhesion energy. This trend is in contrast to that for transferred graphene, which has been found to have weaker adhesion to rougher substrates. The experimental results from this study suggest that the interaction between as-grown graphene and its seed layer was mainly due to van der Waals, instead of covalent or ionic bonds and that surface roughness of the growth substrate could be a significant factor in determining the as-grown graphene adhesion energy.

Protocol to perform pressurized blister tests on thin elastic films.

This work aims to identify common challenges in the preparation of the blister test devices designed for the measurement of the energy release rate for brittle thin films and to propose easy-to-implement solutions accordingly. To this end, we provide a step-by-step guide for fabricating a blister test device comprised of thin polystyrene films adhered to glass substrates. Thin films are first transferred from donor substrates to an air-water interface, which is then used as a platform to locate them on a receiver substrate. We embed a microchannel at the back of the device to evacuate the air trapped in the opening, through which the pressure is applied. We quantify the height and the radius of the blister to estimate the adhesion energy using the available expressions correlating the normal force and the moment with the shape of the blister. The present blister test provided an adhesion energy per unit area of G = 18±2 mJ/m^2 for polystyrene on glass, which is in good agreement with the measurement of G = 14±2 mJ/m^2 found in our independent cleavage test.

Scanning Kelvin probe blister studies of the delamination of epoxy films on organosilane modified ZnMgAl alloy coated steel

The scanning Kelvin probe blister test (SKP‐BT) was applied to study the corrosive delamination of model epoxy films applied to ZnMgAl alloy coated steel substrates. This test allowed the superimposition of mechanical and corrosive load. Moreover, ultra‐thin 3‐aminoproptriethoxysilane (γ‐APS) films were studied as adhesion promoting and corrosion protecting films, which inhibit the delamination process. The surface of the ZnMgAl alloy coating with and without applied ultra‐thin organosilane thin films were analyzed by polarization modulation infrared reflection absorption spectroscopy (PM‐IRRAS) and X‐ray photoelectron spectroscopy (XPS). The spectroscopic results show films that are only few nanometer thick, and therefore cannot act as efficient barrier films. However, peel‐force studies and SKP‐BT results show an effective inhibition of the delamination process of the epoxy film for the interface which was chemically modified by γ‐APS. The effect of the interfacial layer is mainly assigned to the higher wet‐adhesion based on the interaction of silanol groups with thin surface oxides and carbonates of the alloy. Raman spectroscopic analysis showed that the delamination on samples without organosilane thin films is based on a preceding cathode and a subsequent mixed corrosion. Only a minor cathodic delamination was observed on γ‐APS modified samples.

Measured bond strength of asphaltic material using developed blister method

The blister test was aimed to develop and establish a simple, partial and reliable laboratory adhesion test method for direct measurement of the adhesive bond strength of bitumen and aggregate. Blister test was conducted by a device manufactured locally to measured bond strength of asphaltic material. Materials that used in this work were asphalt and aggregate. The local asphalt cement was obtained from Durah refinery, south–west of Baghdad .The aggregate used for comparison was limestone. This paper presents the development of pressure–loaded blister test and apparatus to measure the adhesion of asphaltic materials. The blister test provides the interfacial fracture energy, which is related to the adhesion strength. In this test air is injected at the interface between the substrate (aggregate disc) and adhesive layer (asphalt) to create blister. The air pressure and blister height were measured as function of time. By using two parameters, the interfacial fracture energy is calculated. In this paper was found that the energy required to displacement the asphalt binder increased with time until failure (adhesion failure) due to loss of adhesion between aggregate substrate and asphalt binder and also the required energy to failure decreased with increased binder thickness.

Microstructural characterization of an irradiated RERTR-6 U-7Mo/AA4043 alloy dispersion fuel plate specimen blister-tested to a final temperature of 500 °C

The Material Management and Minimization (M3) Reactor Conversion Program, in the past called the Reduced Enrichment for Research and Test Reactor (RERTR) Program, is developing low-enriched uranium (LEU) fuels for application in research and test reactors. U–Mo alloy dispersion fuel is one type being developed. Blister testing has been performed on different fuel plate samples to determine the margin to failure for fuel plates irradiated to different fission densities. Microstructural characterization was performed using scanning electron microscopy and transmission electron microscopy on a sample taken from a U-7Mo/AA4043 matrix dispersion fuel plate irradiated in the RERTR-6 experiment that was blister-tested up to a final temperature of 500 °C. The results indicated that two types of grain/cell boundaries were observed in the U-7Mo fuel particles, one with a relatively low Mo content and fission gas bubbles and a second type enriched in Si, due to interdiffusion from the Si-containing matrix, with little evidence of fission gas bubbles. With respect to the behavior of the major fission gas Xe, a significant amount of the Xe was still observed within the U-7Mo fuel particle, along with microns into the AA4043 matrix. For the fuel/matrix interaction layers that form during fabrication and then grow during irradiation, they change from the as-irradiated amorphous structure to one that is crystalline after blister testing. In the AA4043 matrix, the original Si-rich precipitates, which are typically observed in as-irradiated U-Mo dispersion fuel, get consumed due to interdiffusion with the U-7Mo fuel particles during the blister test. Finally, the fission gas bubbles that were originally around 3 nm in diameter and resided on a fission gas superlattice (FGS) in the intragranular regions of as-irradiated U-7Mo fuel grew in size (up to ∼20 nm diameter) during blister testing and, in many areas, are no longer organized as a superlattice.

Adhesion Measurement of Coatings on Biodevices/Implants: A Critical Review

Thin films (e.g. diamond-like films) and coatings (e.g. polymeric coatings) are commonly applied on biomedical devices to achieve desired performance and functionality such as biocompatibility and durability. The adhesion of a film or coating to the substrate is a fundamental attribute for any intended application. Adhesion measurement of films and coatings thus is very crucial in biomedical applications. Mechanical test methods dominate adhesion measurement for biomedical applications, which include the peel test, the scratch test, the pull-off test, the blister test, the micro-indentation test, the small punch test, the edgedelamination test, and the four-point bend test. The correlation between the nominal adhesion parameter (practical adhesion) and the intrinsic or fundamental adhesion in most of these tests is explained. Although a plethora of techniques exists for practical adhesion measurement of films and coatings, in this review we have discussed only those techniques which have been already employed or offer potential for use in biomedical applications.

Scanning Kelvin Probe Blister test measurements of adhesive delamination – Bridging the gap between experiment and theory

The delamination of an epoxy-adhesive film from a zinc coated steel substrate was studied by means of the electrochemical Height Regulated Scanning Kelvin Probe Blister Test (HR-SKP-BT11HR-SKP-BT: Height Regulated Scanning Kelvin Probe Blister Test.) under controlled atmospheric conditions, applied pressure and interfacial electrode potential. The experimental studies focused on the analysis of the critical environmental water activity that leads to a corrosive delamination process under applied mechanical load and the analysis of the corrosion and delamination mechanisms at the front of delamination. The influence of applied pressure and relative humidity on the increase in the maximum blister height and the delamination rate was measured under constant polarization of the defect. 90° peel-tests were performed in order to correlate the water activity with the resulting peel force. The corrosion products that formed across the delamination front were analyzed by Raman microscopy. Through these HR-SKP-BT studies, a critical value was found for relative humidity for the delamination process. A transition zone was detected in which electrochemical degradation precedes mechanical delamination. In addition to the experimental studies, the critical energy release rates of the blister were calculated in finite element (FE22FE: Finite Element.) simulations so as to enable a better understanding of the delamination of adhesives on metal surfaces. The combined experimental and theoretical studies show that the delamination process is controlled by the interfacial electrochemical reactions at the delamination front and that a transition area of few hundred micrometers exists in which the adhesion strength is lowered by the cathodic oxygen reduction process to a value which can be overcome by the mechanical stress in this area.

Blister Testing for Adhesion Strength Measurement of Polymer Films Subjected to Environmental Conditions

A blister testing procedure combined with a numerical procedure can be used effectively for characterizing the adhesion strength. A challenge arises when it is implemented after subjecting samples to various environmental conditions. The concept of pseudoproperty is introduced to cope with the problem associated with property changes during environmental testing. The pseudoproperty set is determined directly from a deflection versus pressure curve obtained from a typical blister test. A classical energy balance approach is followed to evaluate the energy release rate from the critical pressure and pseudoproperty set. The proposed approach is carried out for an epoxy/copper interface after subjecting samples to full moisture saturation and a high temperature storage condition. In spite of significant change in property, the energy release rates are calculated accurately without extra tests for property measurements.

Microassembly of Heterogeneous Materials using Transfer Printing and Thermal Processing.

Enabling unique architectures and functionalities of microsystems for numerous applications in electronics, photonics and other areas often requires microassembly of separately prepared heterogeneous materials instead of monolithic microfabrication. However, microassembly of dissimilar materials while ensuring high structural integrity has been challenging in the context of deterministic transferring and joining of materials at the microscale where surface adhesion is far more dominant than body weight. Here we present an approach to assembling microsystems with microscale building blocks of four disparate classes of device-grade materials including semiconductors, metals, dielectrics, and polymers. This approach uniquely utilizes reversible adhesion-based transfer printing for material transferring and thermal processing for material joining at the microscale. The interfacial joining characteristics between materials assembled by this approach are systematically investigated upon different joining mechanisms using blister tests. The device level capabilities of this approach are further demonstrated through assembling and testing of a microtoroid resonator and a radio frequency (RF) microelectromechanical systems (MEMS) switch that involve optical and electrical functionalities with mechanical motion. This work opens up a unique route towards 3D heterogeneous material integration to fabricate microsystems.

Snap Transitions of Pressurized Graphene Blisters

Blister tests are commonly used to determine the mechanical and interfacial properties of thin film materials with recent applications for graphene. This paper presents a numerical study on snap transitions of pressurized graphene blisters. A continuum model is adopted combining a nonlinear plate theory for monolayer graphene with a nonlinear traction–separation relation for van der Waals interactions. Three types of blister configurations are considered. For graphene bubble blisters, snap-through and snap-back transitions between pancake-like and dome-like shapes are predicted under pressure-controlled conditions. For center-island graphene blisters, snap transitions between donut-like and dome-like shapes are predicted under both pressure and volume control. Finally, for the center-hole graphene blisters, growth is stable under volume or N-control but unstable under pressure control. With a finite hole depth, the growth may start with a snap transition under N-control if the hole is relatively deep. The numerical results provide a systematic understanding on the mechanics of graphene blisters, consistent with previously reported experiments. Of particular interest is the relationship between the van der Waals interactions and measurable quantities in corresponding blister tests, with which both the adhesion energy of graphene and the equilibrium separation for the van der Waals interactions may be determined. In comparison with approximate solutions based on membrane analyses, the numerical method offers more accurate solutions that may be used in conjunction with experiments for quantitative characterization of the interfacial properties of graphene and other two-dimensional (2D) membrane materials.

Assessment of Broiler Chicken Welfare in Southern Brazil

Scientific literature on broiler chicken welfare in Brazilian industrial systems is scarce. This study aimed at assessing broiler chicken welfare on industrial farms in the State of Rio Grande do Sul, Southern Brazil, using the Welfare Quality(r) assessment protocol for poultry, to provide directly applicable scientific information. Results are presented as criteria scores ranging from 0 to 100, with higher scores indicating better welfare; and percentages of prevalence. The scores classified as excellent (above 80) were absence of prolonged thirst, absence of prolonged hunger, litter quality, breast blister and touch test. Enhanced scores (between 55 and 80) were comfort around resting, plumage cleanliness and dust sheet test. Acceptable scores (between 20 and 55) were thermal comfort, stocking density, absence of injuries, footpad dermatitis and hock burn; and unacceptable scores (below 20) were lameness and qualitative behavioral assessment. The median percentage of mortality and culled birds were 5.2% and 0.6%, respectively. This study provides useful information to select priorities of action on assessed farms and may contribute for setting up legal standards and guiding decisions related to animal welfare issues in Brazil.

Solution-Blown Core-Shell Self-Healing Nano- and Microfibers.

Self-healing microfibers with core-shell geometry were studied. A commercial binary epoxy was encased in solution-blown polymer nano-/microfibers in the 0.2-2.6 μm diameter range. The core-shell microfibers were formed by coaxial nozzles, which encapsulated the epoxy resin and its hardener in separate cores. Solution blowing, the fiber-forming process used in this work, was at least 30 times faster than the electrospinning method used previously and has already been scaled up to the industrial level. These core-shell microfibers show self-healing capability, in which epoxy and hardener are released from the cores of damaged fibers, resulting in polymerization. The epoxy used had a higher strength and shorter solidification time than poly(dimethylsiloxane) (PDMS) used previously. Also, the larger fiber diameters in the present study facilitated faster release of the epoxy resin and its hardener from the fiber cores, shortening the solidification time in comparison to the previous studies. Blister tests were conducted, which measured the adhesion energy of microfiber mats to substrates and the cohesion energy between layers of microfiber mats before and after fatigue damage followed by self-healing.

Mixed-mode traction-separation relations between graphene and copper by blister tests

A blister test with associated analysis was developed to characterize the traction-separation relations associated with interactions between graphene and a copper substrate to which it had been transferred. Graphene grown by chemical vapor deposition was backed by a photoresist film and transferred to a highly polished copper substrate from its seed copper foil. The graphene/photoresist composite film was then pressurized with deionized water through a hole in the substrate. The blister profiles and normal crack opening displacements (NCOD) were measured by two microscopes with synchronized cameras. Different mixed-mode conditions were achieved by varying the thickness of the backing layers. The measured adhesion energy for the graphene/copper and photoresist/copper interfaces showed a strong dependence on the mode-mix. Cohesive zone models associated with traction-separation relations were then developed to study the damage initiation and crack propagation under various mixed-mode conditions. The numerical solutions for the resistance curves, pressure vs. deflection, and NCOD were in good agreement with measurements. The cohesive zone model was extended to a wider range of mode-mixes by making use of the asperity locking model which had provided a mechanism for the observed toughening effect. The interactions between graphene and copper were found to be stronger in all respects than those associated with photoresist and copper. Because the monolayer graphene was sandwiched between photoresist and copper, this result suggests that graphene was not transparent to interactions between photoresist and copper, but opaque. The use of pressure could provide another approach to transfer large-scale graphene.

Strain energy release rate in shaft-loaded blister tests for composite repairs on steel

The design of composite repairs of corroded oil and gas pipelines must take into account the strength of the interface adhesion between composite and metal. A shaft-loaded blister test is a common method to measure interface fracture toughness and energy release rate. The study aimed on evaluating shaft-loaded blister tests as replacements for more complex pressure blister tests. Specimens investigated were thick fibre-reinforced plates bonded on metal disks as substrates containing a circular through-hole defect. This paper presents the influence of different punch head geometries on the resulting energy release rates and compares the results with blister tests using fluid pressure. Test and simulation results are presented and analytical solutions were derived and evaluated to establish best fitting formulations. It was shown, that significant variations between the different means of loading exist.

Study on Chemical Interaction of U3Si2 Dispersoid and Aluminum Matrix in Plate Fuel Elements and Its Influence on the Mechanical Properties

Dispersion-type plate fuel elements are being fabricated with U3Si2 dispersoid (prepared by an innovative powder processing route) in aluminum matrix and clad in Al alloy for the modified core of the APSARA reactor by a standard picture frame technique followed by hot roll bonding operation at the Bhabha Atomic Research Centre Metallic Fuels Division. The fabrication regime allows the fuel elements to be exposed at 500°C for almost 5 h (total duration including hot roll bonding and blister test operation). Therefore, it is expected that during hot roll bonding and blister test operation, U3Si2 will chemically interact with aluminum and form an intermediate phase. Hence, the chemical interaction behavior of fuel dispersoid (U3Si2, prepared by powder metallurgy route) and matrix (aluminum) in plate fuel elements and its effect on mechanical properties is studied in the present paper.Therefore, a comparative study between an actual plate fuel element (i.e., U3Si2 dispersed in aluminum matrix and with Al alloy clad) and a sandwich plate with chemically inert material (i.e., Y2O3) as dispersed in aluminum matrix with Al alloy clad was carried out. The roll bonded samples were investigated through pull and peel tests, microhardness, tensile test, optical microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction for various metallurgical examinations. During the course of study, it was observed that U3Si2 dispersoids in actual plate fuel elements were enveloped by a different phase while the dispersoid of Y2O3 remained inert in the surrogate plate under a similar fabrication history. The study concludes that limited exposure of the actual fuel plate at 500°C for 5 h results in improvement of bond strength mainly due to chemical interaction between fuel dispersoid and aluminum. The study also concludes that the tensile strength and ductility of the fuel plates did not show any adverse effects during dispersoid-matrix chemical interaction; however, the modulus of elasticity was found lower than the theoretically estimated value calculated by composite theory. The observations derived in the study are critical from the viewpoint that a decrease in the elastic modulus of the plate would adversely affect its flow-induced vibration properties during reactor operation. It may also be concluded that exposing the plate fuel elements at 500°C for longer duration (i.e., 30 h) will result in excessive swelling because of the accelerated interaction between dispersoid and matrix, which will eventually deteriorate the desired properties.

Nonlinear Large Deflection of Thin Film Overhung on Compliant Substrate Using Shaft-Loaded Blister Test

This paper presents the nonlinear large deflection of the thin film and the effect of substrate deformation on the thin film deflection through the shaft-loaded blister test. The blister of thin film can be divided into two parts, namely, the annular contact brim and the central noncontact bulge. A two-coupled line spring model is developed to describe the deformation of the contact part, and Föppl–Hencky equations are employed to study the constitutive relation between the applied load and the central deflection. The analytical and numerical solutions for the constitutive relation between the applied load and the deflection of thin film with considering the deformation of substrate are derived.

Self-healing Nanofiber-Reinforced Polymer Composites. 2. Delamination/Debonding and Adhesive and Cohesive Properties.

The capacity for core-shell nanofiber mats containing healing agents (resin monomer and cure) in their cores to adhere to a substrate was studied using blister testing. After extended periodic bending, the adhesion energy was measured, and the effect of self-healing on the composite's delamination from the substrate was considered. In addition, the cohesion of two layers of the self-healing nanofibers was examined using blister testing and compared to that of ordinary nanofiber mats. The damage inflicted by prolonged periodic bending to the interface of the two nanofiber mats was demonstrated to have self-healed, and the cohesion energy was measured.

Mixed-Mode Interactions Between Graphene and Substrates by Blister Tests

Many of the attractive properties of graphene will only be realized when it can be mass produced. One bottleneck is the efficient transfer of graphene between various substrates in nanomanufacturing processes such as roll-to-roll and transfer printing. In such processes, it is important to understand how the ratio of shear-to-tension at the interface between graphene and substrates affects the adhesion energy. With this in mind, this paper examines the mixed-mode adhesive interactions between chemical vapor deposition (CVD) grown graphene that had been transferred to copper or silicon substrates. The approach that was taken was to use blister tests with a range of graphene backing layer materials and thicknesses in order to provide a wide range of the shear-to-tension ratio or fracture mode-mix at the interface. Raman spectroscopy was used to ensure that graphene had indeed been delaminated from each substrate. Measurements of pressure, top surface deflection, and blister diameter were coupled with fracture mechanics analyses to obtain the delamination resistance curves and steady state adhesion energy of each interface. The results showed that the adhesive interactions between graphene and both substrates (Cu and Si) had a strong dependence on the fracture mode-mix. In the absence of plasticity effects, the most likely explanation of this effect is asperity locking from the inherent surface roughness of the substrates.

Effects of initial blister radius and shaft diameter on energy release rate of metal–polymer composite coating

Shaft loaded blister tests were performed to study the interfacial fracture behaviour of a polymer composite coating material adhesively bonded to a metal substrate. For this purpose, the energy release rate required to propagate the crack along the polymer composite coating–metal interface was measured. To do this, six different initial blister radii (a), three different loading rates and two different spherical ended shaft sizes were employed. Fresh water conditioning at 55°C for 1000h was also carried out on the blister specimens to study the environmental effect on the total energy release rate (GT) of initial blister debonding. For a 5mm diameter shaft, with the increase of loading rate, the GT values were found to increase for the controlled samples while the loading rate followed the similar trend with lower GT values for the conditioned samples. The GT values obtained using two different shaft sizes showed that the larger shaft diameter had higher GT values than the smaller shaft diameter. Conditioned specimens tested using both of the loading shafts were generally found to have lower GT values than the controlled specimens. A comparison with the linear and nonlinear finite element analyses reveals the application ranges of the solutions for determining the energy release rate based on the plate bending model or the nonlinear membrane model. It is shown that the plate based energy release rate solutions should be used for a small blister and the membrane based solution should be adopted for a large blister.

A clamped punch-loaded blister test for adhesion: a lumped parameter model and the bending-to-stretching behavior

This paper presents a clamped punch-loaded blister test and the corresponding lumped parameter model for the adhesion between thin film and rigid substrate. In the test, circular thin film is adhered to rigid substrate and an external load is applied with a clamped punch to cause the deflection of thin film. The relations among load, deflection, residual stress and strain energy release rate are thoroughly investigated. Analytical solutions in linear and nonlinear behaviors are obtained and the bending and stretching effects are associated through a lumped parameter model. The result of lumped-parameter model shows that the blister deflection is directly proportional to the applied load in the linear bending dominant region and the blister deflection is in direct proportion to the cubic root of the applied load in the nonlinear stretching dominant region. This has been proved by the result of nonlinear finite element analysis and the experimental result as well.