Blister Test Research Articles

Theoretical study of adhesion energy measurement for film/substrate interface using pressurized blister test: Energy release rate

In this paper, a new loading method able to subtly control the crack driving force for pressurized blister test was proposed. A theoretical study of the adhesion energy measurement for film/substrate interface using this loading method was presented. Problems considered include solving the exact volume under a circular blister and the elastic strain energy stored in a thin blistering film, determining the work done by the poured colored liquid as external force to the system and the elastic strain energy stored in the compressed air. A new formula of energy release rate was finally presented. A comparison between the work presented here and the existing work was made.

Characterization of thin film adhesion by MEMS shaft-loading blister testing

A new microelectromechanical system shaft-loaded blister test was developed and demonstrated to provide stability, repeatability, and simultaneous quantitative measurements of adhesion between thin films deposited on a silicon substrate. The authors assessed adhesion of sputtered platinum, copper, and chromium/copper (300 nm) to underlaying atomic layer deposited (ALD) aluminum oxide. The average adhesion energies for thin films on ALD aluminum oxide were found to be 1.15 ± 0.1 J/m2 for platinum thin films, 1.4 J/m2 for copper thin films, and 1.75 J/m2 for chromium/copper.

Selective molecular sieving through porous graphene

Membranes act as selective barriers and play an important role in processes such as cellular compartmentalization and industrial-scale chemical and gas purification. The ideal membrane should be as thin as possible to maximize flux, mechanically robust to prevent fracture, and have well-defined pore sizes to increase selectivity. Graphene is an excellent starting point for developing size-selective membranes because of its atomic thickness, high mechanical strength, relative inertness and impermeability to all standard gases. However, pores that can exclude larger molecules but allow smaller molecules to pass through would have to be introduced into the material. Here, we show that ultraviolet-induced oxidative etching can create pores in micrometre-sized graphene membranes, and the resulting membranes can be used as molecular sieves. A pressurized blister test and mechanical resonance are used to measure the transport of a range of gases (H(2), CO(2), Ar, N(2), CH(4) and SF(6)) through the pores. The experimentally measured leak rate, separation factors and Raman spectrum agree well with models based on effusion through a small number of ångstrom-sized pores.

Ultrathin Oxide Films by Atomic Layer Deposition on Graphene

In this paper, a method is presented to create and characterize mechanically robust, free-standing, ultrathin, oxide films with controlled, nanometer-scale thickness using atomic layer deposition (ALD) on graphene. Aluminum oxide films were deposited onto suspended graphene membranes using ALD. Subsequent etching of the graphene left pure aluminum oxide films only a few atoms in thickness. A pressurized blister test was used to determine that these ultrathin films have a Young's modulus of 154 ± 13 GPa. This Young's modulus is comparable to much thicker alumina ALD films. This behavior indicates that these ultrathin two-dimensional films have excellent mechanical integrity. The films are also impermeable to standard gases suggesting they are pinhole-free. These continuous ultrathin films are expected to enable new applications in fields such as thin film coatings, membranes, and flexible electronics.

Effect of Surface Topography, Cleaning, and Conversion Coatings in the Adhesion Strength of Organic Polymers to AA2024-T3 using the Blister Test

not Available.

Assessment of the Gas Permeation through Thin Coated Polymeric Membranes; Improvement of the Gas Barrier Ability for Hydrogen Storage

We investigate and simulate the permeation behavior of PET membranes on which thin coatings are deposited. Depending on the parameters of deposition and on the thin coating thickness, we assume this alteration could make it possible to decrease by one order of magnitude the permeation coefficient. Some specific developments have been necessary, all the more not only a decrease of permeation is expected but also the mechanical strength of the thin coating during severe mechanical loadings. We consequently design devices dedicated to the permeation test but also to the bulge and blister tests which permit to check the mechanical properties of the film and its adhesion on the PET surface. This paper focuses on the permeation test.

Measurement of Adhesion Work of Electrospun Polymer Membrane by Shaft-Loaded Blister Test

The work of adhesion at the interface of electrospun membrane and rigid substrate is measured by a shaft-loaded blister test (SLBT). Poly(vinylidene fluoride) (PVDF) were electrospun with an average fiber diameter of 333 ± 59 nm. Commercial cardboard with inorganic coating was used to provide a model substrate for adhesion tests. In SLBT, the elastic response PVDF was analyzed and its adhesion energy measured. The average value of the adhesion work is 206 ± 26 mJ/m(2). Elastic modulus of electrospun membrane obtained by SLBT is found to be 23.42 ± 2.69 MPa, which is consistent with the value obtained from standard tensile tests. The results show SLBT presented a viable methodology for evaluating the adhesion energy of electrospun polymer fabrics.

Ultrastrong adhesion of graphene membranes

As mechanical structures enter the nanoscale regime, the influence of van der Waals forces increases. Graphene is attractive for nanomechanical systems because its Young's modulus and strength are both intrinsically high, but the mechanical behaviour of graphene is also strongly influenced by the van der Waals force. For example, this force clamps graphene samples to substrates, and also holds together the individual graphene sheets in multilayer samples. Here we use a pressurized blister test to directly measure the adhesion energy of graphene sheets with a silicon oxide substrate. We find an adhesion energy of 0.45±0.02 J m(-2) for monolayer graphene and 0.31±0.03 J m(-2) for samples containing two to five graphene sheets. These values are larger than the adhesion energies measured in typical micromechanical structures and are comparable to solid-liquid adhesion energies. We attribute this to the extreme flexibility of graphene, which allows it to conform to the topography of even the smoothest substrates, thus making its interaction with the substrate more liquid-like than solid-like.

Nonlinear elastic mechanics of the ball-loaded blister test

The nonlinear elastic mechanics of spherically capped shaft or ball-loaded blister tests is presented. In the test model, a thin film is attached to a substrate with a circular hole running through the thickness of the substrate. A central load is applied to the film through the hole by a spherically capped shaft or a ball with a finite radius. The deformed blister is divided into two parts: a circular region in contact with the sphere of the cap or ball and an outer noncontact annulus. The Reissner’s plate theory is employed to describe the deformation of the contact part and the von Kármán plate theory for the noncontact annulus. A constitutive equation of coupled linear springs is obtained to quantify the effect of the substrate deformation on the blister deflection. For small deflection, the analytical solution of load-deflection is derived. For large deflection, an iteration approach is adopted to predict numerically the load-deflection curve. Finite-element analysis is conducted to verify the analytical and numerical solutions. The influence of the substrate deformation, residual stress, radius of the spherical cap or ball and the friction between the film and ball on the load–deflection relation is investigated.

Measurements of Interface Fracture Strength between Fiber-Reinforced Composite Laminates and Thin Surface Films Using the Blister Test

The blister test is a promising test method to determine the interface fracture toughness of thin films adhering to rigid fibre reinforced plastics. In this paper nonlinear finite element analysis is used to determine a suitable layout for both the shaft loaded and the pressurised blister test. On the example of a PET film adhering to a quasi-isotropic fibre reinforced plastic, it is shown that energy release rates in a range of 0-1500N/m can be obtained for a 0.5mm thick film if test parameters are carefully selected. The two main causes for deviations of the analytic solution from the FEA results is attributed to infringement of the membrane limit condition and plastic deformation in the film.

Development of a Pressurized Blister Test for Interface Characterization of Aggregate Highly Polymerized Bituminous Materials

Bituminous crack sealants are commonly used for pavement maintenance. While cracks in pavement are inevitable, sealing the cracks helps maintain the integrity of the pavement by preventing water and debris from entering the structure. Sealing cracks increases pavement service life up to 5 years, and this can lead to significant cost savings for the U.S. highway system. Crack sealing is a cost-effective maintenance approach, provided that the right sealant is selected and properly installed. However, sealant selection is difficult because of the lack of a rheology-based standard test that correlates with field performance. To address this drawback, performance-based guidelines for the selection of hot-poured crack sealants have been developed by a research team, including the writers. To complement these guidelines, this paper describes a recently developed adhesion test procedure that predicts interface bonding based on a fundamental property of the interface, interfacial fracture energy (IFE). This recently developed pressurized blister test is a fracture test. The principle of the test is to break the interface bonding by pressurizing the interface between the adhesive and adherend. The amount of pressure and the deformation of the adhesive before and during the debonding period are used to calculate the IFE. The test variation is acceptable because its average coefficient of variation is 8.7%. This paper describes the test apparatus and procedure and discusses the adhesion of several hot-poured bituminous sealants to aluminum, limestone, quartzite, and granite.

Influence of nonlinearities on the accuracy of the analytical solution for the shaft loaded blister test

Finite element analysis (FEA) is employed to study the effects of nonlinearities on the accuracy of the analytical solution for the shaft loaded blister test. The FEA model was validated using constrained blister test measurements showing a good correlation between the experimental and the FEA data. The analytical solution is then compared with the energy release rate obtained from J-integral evaluation in the FEA. For small and large shaft displacements deviations larger than 20% are encountered which is explained with the violation of the membrane limit condition and the onset of plasticity for larger displacements, respectively. Simplifications of the analytical solution are discussed using a random sampling method and it is shown that the thickness ratio between film and substrate can be neglected for thin films on rigid substrates. Further, values for the angular quantity, ω, which is required to calculate the mode mix phase angle are tabulated for the case of thin, elastic films on stiff substrates using a crack surface opening displacement extrapolation method.

Bonding Property of Bituminous Crack Sealants in the Presence of Water

Problem statement: Crack sealing and filling is the most widely used maintenance activity for in-service pavements. If an appropriate sealant material is selected and properly installed at the appropriate time of the pavement life, it retards pavement deterioration and increases its service life at a relatively low cost. However, in some cases it is reported that sealants failed prematurely, mainly due to environmental factors and water exposure. While there have been several studies on environmental factors, water related factors has not received appropriate attention. Nevertheless, various sealants have different water resistance property; hence, they perform differently when exposed to large amount of rain and humidity. Approach: Currently, there is no standard test method to evaluate sealant water resistance. Therefore, there is a need for a standard test method to precisely predict sealant performance when exposed to water. Such a test method can help examine various sealants in terms of their water resistance. This study introduces water conditioning procedure and a test method to measure bond strength of sealant under dry and wet condition. The effect of water on the Interfacial Fracture Energy (IFE) of bituminous sealants was measured by means of a blister test. This test allows the calculations of two fundamental parameters: tensile modulus and the Interfacial Fracture Energy (IFE). Results: Experimental results showed water exposure caused a significant drop in adhesion strength. However, no significant difference was observed between adhesion strength of specimens conditioned for 8 and 12 h of conditioning. Conclusion/Recommendations: The proposed approach and testing method can be used by the sealant manufacturers to improve their sealants’ adhesion properties at the presence of water. However, further research works are needed to examine how sealant adhesion strength varies with water exposure duration. Also, the effect of water pH on sealant adhesion strength can be studied.

A Theoretical Study of Thin Film Delamination Using Clamped Punch-Loaded Blister Test: Energy Release Rate and Closed-Form Solution

Using an exact analytical solution of axisymmetric deformation of a circular membrane centrally connected to a rigid plate under the action of concentrated load at its center, we present an exact formula for the energy release rate applicable to ultrathin film–substrate systems without residual stresses or with small residual stresses. Also, a closed-form solution of axisymmetric deformation of circular membrane under the action of concentrated load at its center is presented.

Specifications and qualification of uranium/aluminum alloy plate target for the production of fission molybdenum-99

In all probability, the same criteria applied to evaluate the safety of the reactor fuel shall be used to evaluate the safety of the targets used for the production of fission molybdenum-99. Thus, neutronic and thermal hydraulics considerations will dictate the maximum power of the targets, their uranium content, and the uniformity requirements for their loading. Radiography technique is capable of characterizing both meat location and density. Specifically, target plates that meet fuel density specifications can be irradiated with little risk of power peaking and hot spots. An adequate characterization and qualification of target plate cladding is also critical, because cladding breaches will contaminate the reactor coolant. Bend testing is a dependable way of testing bond strength while Ultrasonic Testing (UT) examinations qualify both bonding homogeneity and minimum thickness of that cladding. The bonding quality is inspected by means of a blister test. Lastly, optical microscopy is applied for clad thickness, which further supports the veracity of the UT characterization method. Natural U/Al alloy plate targets have been safely irradiated in the core of Pakistan Research Reactor-1.

The constitutive relation of an axisymmetric detached coating on a rigid substrate

In this work, the constitutive relation between the external force ( P) and central deflection ( w 0) of the coating in a blister test is studied by elasticity theory. The studied cases are that the coating in the presence of the residual tensile stress is deflected by a concentrated force on the central area of the coating surface. Closed-form solutions for force and deflection are obtained, and used to analyze the feature of the constitutive relations without and with delamination. The results show that the constitutive relation expresses as P ∝ w 0 n with n=1–3 for the case without delamination, while it expresses in a non-monotonic fashion for the case with delamination. The details of the constitutive relation are influenced by the radius of detached coating, residual tensile stress and interfacial toughness.

Characterization of the interface adhesion of elastic–plastic thin film/rigid substrate systems using a pressurized blister test numerical model

The quality of interface adhesion of an elastic–plastic thin film/rigid substrate system can be characterized by its interface adhesion energy. To estimate the interface adhesion energy, a numerical model for the pressurized blister test has been proposed, which includes three steps: dimensional, forward and reverse analyses. The dimensional analysis is applied to derive a preliminary nondimensional relationship of the interface adhesion energy, and then the forward and reverse analyses are carried out to establish its explicit form and to extract the interface adhesion energy, respectively. The results are in good agreement with experimental measurements, which confirms the effectiveness of the model.

Microvalves for Natural-Gas Analysis With Poly Ether Ether Ketone Membranes

We present the use of poly ether ether ketone (PEEK) as a membrane material for a new type of gas microvalve, which is suitable for the harsh environments of natural gas. The design, fabrication, and experimental characterization of the PEEK-based microvalves are presented first, revealing leakage levels of less than 230 nL·min-1 under nitrogen and helium. Then, the main mechanical properties of the PEEK membranes are derived from both static and dynamic measurements, leading to a Young's modulus of 3.1 GPa and an inplane anisotropic stress field, with both tensile and compressive components in two perpendicular directions and whose magnitudes are + 33.9 MPa and -6.8 MPa, respectively. A blister test gave an adhesion energy estimated between 61 and 158 J·m-2. Finally, temperature cycles have been conducted on the microvalve, showing a resistance of up to 300°C, together with an improved closing of the membrane.

Adhesion and adhesion degradation of a pressure sensitive tape on carbon steel

Corrosion protection of carbon steels by organic coatings is dependent on a good adhesion between coating and substrate. In this work the blister test method was used to study the adhesion of a pressure sensitive tape applied on carbon steel. Deionized water was used to pressurize a blister formed by the tape covering a through-hole in the steel substrate. Values of adhesion strength as measured by the strain energy release rate were determined for two different blister pressurization rates or water injection rates. The adhesion strength was higher for the larger injection rate, which is expected for pressure sensitive tape. These values were probably overestimates of the true adhesion strength owing to plastic yielding of the membrane. Resistance to adhesion degradation near coating defects or macroscopic scribes was characterized using a height regulating scanning Kelvin probe on samples exposed to sodium chloride solution or a salt spray environment. Although the tape exhibited good barrier properties to water and ions, cathodic delamination was observed near the scribe after salt spray exposure. Wet/dry cycles were more aggressive than continuous salt spray exposure, since during continuous exposure corrosion products are washed away. It was observed that the oxide layer grows to a larger extent during wet/dry cycles; therefore, acceleration of the delamination process is probably associated with a “wedge effect” of the oxide on the interface.

Mechanics of shaft-loaded blister test for thin film suspended on compliant substrate

Based on the von Kármán plate theory, the mechanics of a shaft-loaded blister test for thin film/substrate systems is studied by considering elastic substrate deformations and residual stresses in these films. In testing, films are attached to a substrate provided with a circular hole, through which loading is applied to the film by a flat-ended shaft of circular cross-section. The effect of substrate deformation on the deflection of the loaded film is taken into account by using a line spring model. For small deflections, an analytical solution is derived, while for large deflections a numerical solution is obtained using the shooting method. The resulting load-shaft displacement relation, which is essential in blister tests, compares favorably with finite element analysis.