The peel test is a commonly used testing method for adhesive strength evaluation. The test involves peeling a pressure sensitive tape away from a substrate and measuring the peel force that is applied to rupture the adhesive bond. In the present study, the mechanics of the peel test is analyzed based on a cohesive zone model. Cohesive failure is assumed to prevail in the vicinity of the peel front, that is, the adhesive fails not by debonding from the adherends but by splitting of the adhesive itself. Generally, the failure of the adhesive is accompanied with a process of cavitation and fibrillation. Therefore, the cohesive zone is modeled as a continuous fibrillated region. A Maxwell model is employed to characterize the viscoelastic behavior of the adhesive. The governing equation and boundary conditions that describe the mechanics of the peel test are derived. Numerical results are obtained under steady state conditions. The model predicts the peel force in terms of the peel rate, the peel angle, the nature of the adhesive, and the properties of the backing and the substrate. The traction distribution on the substrate surface is found to depend on various test parameters. Finally, finite element analysis is performed using the commercial software package ABAQUS. The results from FEA are compared with those from the mathematical method to evaluate the validity of the present model. The effective range of the present model is found to be related to the ratio of the critical fibril length to the extent of the cohesive zone. Given the nature of the adhesive as well as the properties of the backing and the substrate, the proposed model is able to predict the peel force and the traction distribution in terms of the peel rate and the peel angle, and thus provides a measure of the strength of the adhesive bond.

The peel test is a commonly used testing method for adhesive strength evaluation. The test involves peeling a pressure sensitive tape away from a substrate and measuring the peel force that is applied to rupture the adhesive bond. In the present study, the mechanics of the peel test is analyzed based on a cohesive zone model. Cohesive failure is assumed to prevail in the vicinity of the peel front, that is, the adhesive fails not by debonding from the adherends but by splitting of the adhesive itself. Generally, the failure of the adhesive is accompanied with a process of cavitation and fibrillation. Therefore, the cohesive zone is modeled as a continuous fibrillated region. A Maxwell model is employed to characterize the viscoelastic behavior of the adhesive. The governing equation and boundary conditions that describe the mechanics of the peel test are derived. Numerical results are obtained under steady state conditions. The model predicts the peel force in terms of the peel rate, the peel angle, the nature of the adhesive, and the properties of the backing and the substrate. The traction distribution on the substrate surface is found to depend on various test parameters. Finally, finite element analysis is performed using the commercial software package ABAQUS. The results from FEA are compared with those from the mathematical method to evaluate the validity of the present model. The effective range of the present model is found to be related to the ratio of the critical fibril length to the extent of the cohesive zone. Given the nature of the adhesive as well as the properties of the backing and the substrate, the proposed model is able to predict the peel force and the traction distribution in terms of the peel rate and the peel angle, and thus provides a measure of the strength of the adhesive bond.

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In this study, complex rolling technology is adopted to produce aluminum/copper clad metals . The aluminum alloy A1050 and the copper C1100 are used. The experimental plan : the roughness (RCu=3.5£gm¡ARAl=6.45£gm)¡A(RCu=1.0£gm¡ARAl =2.15£gm)¡A(RCu=0.35£gm¡ARAl=0.8£gm) the thickness ratio(tAl:tCu=3:1)¡A(tAl:tCu =2:2)¡A(tAl:tCu=1:3) reduction 60% and 70% are set. It shows that the influence of the thickness is more significant than the roughness on the curvature according to the experimental results. And the results of peeling tests show that the peeling strength for the reduction 70% is larger than that for 60%. And peel strength with the second time rolling is larger than that with only once. The average peeling strength of the specimen in the rolling direction is larger than that in the perpendicular direction. From the micro Vickers hardness tests , it is known that the larger of the reduction of copper is, the larger the micro Vickers hardness between the interface of the sheets is .

The challenge of demolding during the cast molding process of silicone hydrogel contact lenses can be addressed with the application of hydrophobic coatings on the surface of lens mold. In particular, the adhesion between silicone hydrogel and silicate substrates was minimized by applying silane modification on the surface of silicate substrates. Peel tests were conducted to measure the adhesive strengths between silicone hydrogel and surface modified glass substrates. Water contact angle measurement and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the surface properties of silane treated glass substrates.Silicone hydrogel was obtained by curing macromer mixture under UV for 6 minutes, with UV intensity of 95.0 mW/cm2. The obtained silicone hydrogel had a modulus of 0.87±0.09 MPa, within the same range of commercial contact lenses. And the hydrogel with a UV curing time of 6 minutes was unable to be peeled off from clean glass substrates. The effects of silane type and concentration on coating effectiveness were investigated and the most effective types of silane were found to be triethoxyphenylsilane (TEPhS) and octyltriethoxysilane (OTES), with an optimal concentration of 5 wt%. The peel strength between silicone hydrogel and silicate substrates was reduced to below 15.5 N/m with the application of TEPhS and OTES coatings. However, these silane coatings were not durable enough. Silane coupling agents need to be reapplied before each curing process of silicone hydrogel. / Thesis / Master of Applied Science (MASc)

When bonds between copper and printed circuit board laminates are subjected to impulsive forces, the need arises to characterize fracture energies corresponding to related, high-speed failure events. Work (or energy) is required to create new surface area—with associated dissipation events—during fracture, and this energy (for a given material system) is dependent on the speed of crack propagation, the locus of failure, and the temperature of the bond when it is broken. Since the 90° peel test has been widely employed in quasi-static fracture testing of film adhesion for printed circuit board applications, this test was first used as a basis to which other test results could be compared. A test fixture was designed and built for quasi-static peel testing that accommodated peeling at different angles and temperatures. A similar test was then desirable for the direct comparison of dynamic fracture events to those quasi-static results. The “loop peel test” was thus developed to mimic the common 90° peel test and to quantify the time- and temperature-dependent fracture energies of peel specimens during low-velocity impact. This test has been successfully used to determine the apparent critical strain energy release rate of copper/epoxy bonds for low-velocity impact conditions (1-10 m/s), for a case of near-interfacial failure. The falling wedge test has also been adapted to estimate the apparent critical strain energy release rate at similar fracture conditions. Four types of printed circuit boards have been analyzed with the above impact test methods as well as with their corresponding quasi-static tests, and the fracture energies measured with the impact tests have been compared to those obtained using quasi-static tests. Fracture energies of the material systems considered were dependent on time (speed of fracture), temperature, and the amount of moisture migration, as determined via humidity conditioning parameters. / Master of Science

Made available in DSpace on 2017-07-21T20:42:46Z (GMT). No. of bitstreams: 1 Danielle M Ferreira Madeira.pdf: 2830948 bytes, checksum: b0683133449a7aa9574bf79758c203d4 (MD5) Previous issue date: 2013-02-27 / The objective of this work was to study the surface adhesion of polyethylene on the liquid paper board. By using surface characterization, the chemical and physical interactions between the paper board and polyethylene were studied. Paper board samples were laminated with low density polyethylene with an extruder, in order to evaluate the adhesion forces of the following samples: 1) Paper board coating with different latex composition; 2) paper board bottom layer (brown side) with surface sizing (starch) and, 3) paper board bottom layer (brown side) without surface sizing (starch). It was also evaluated in the extruded samples treated with flame the polyethylene adhesion. The following analyses were used in other to characterize the paper board surface: 1) Contact angle analysis for surface energy determination, 2) Confocal laser scanning microscopy for surface roughness analysis and, 3) FTIR spectroscopy Attenuated Total Reflectance (ATR) to evaluate differences in the functional groups. The characterization results were correlated with the increase of polyethylene adhesion forces on the paper board surface. It was observed that flame treatment on the paper board surface increased the surface tension, thus increasing the adhesion forces of the polyethylene. In comparison to the styrene-butadiene latex, the styrene acrylic latex, which contains polar groups in its composition, improved the adhesion forces of the polyethylene with the paper board top layer (white side). For the paper board bottom layer (brown side) with no surface sizing, the polyethylene adhesion was superior when compared to the sized paper board. It can be explained by the increase on the surface smoothness of the paper which may interfere on the polyethylene adhesion. The flame treatment may have caused the oxidation of functional groups on the surface of the paper board, resulting in the surface tension increase and, consequently, increasing the polyethylene adhesion. The surface tension has shown to be an excellent indicator for polyethylene adhesion due to its linear correlation with polyethylene adhesion forces. On the other hand, it has not been observed difference on surface roughness on the studied samples. The FTIR-ATR technique has not been sensitive for the detection of chemical differences among the samples treated with and without flame. However, this technique can be used to verify the latex composition in the paper board coating. The Peel Test Method (180º) which is used to evaluate the adhesion force, presents more reliable results than the manual delamination test that depends on the analyst. / O objetivo deste trabalho foi estudar a adesão de polietileno à superfície do papel cartão utilizado na produção da embalagem Longa Vida. Através de técnicas de caracterização de superfície foram verificadas as interações químicas e físicas existentes entre o papel cartão e o polietileno. Amostras de papel cartão foram laminadas com polietileno de baixa densidade em uma extrusora para avaliar a força de adesão nas seguintes amostras: 1) “coating” do papel cartão com diferentes látex na composição da tinta de revestimento. 2) base do papel cartão (lado marrom) com colagem superficial com amido. 3) base do papel cartão (lado marrom) sem colagem superficial com amido. Nas amostras extrusadas também foi avaliada a adesão de polietileno quando a superfície do papel cartão foi tratada com chama. Análise do ângulo de contato para obtenção da energia superficial, microscopia confocal a laser, para verificar efeitos na rugosidade superficial, e análise de infravermelho (ATR – reflectância total atenuada), para avaliar diferenças dos grupos funcionais, foram também utilizadas para a caracterização da superfície do papel cartão. O resultado da caracterização foi correlacionado com aumento das forças de adesão de polietileno à superfície do papel cartão. Para os casos estudados, observou-se que o tratamento de superfície feito com chama no papel cartão aumentou a energia superficial, elevando assim a força de adesão ao polietileno. O uso de látex estireno-acrílico, que apresenta grupos polares na composição, também propiciou melhor adesão de polietileno na cobertura (lado branco do papel cartão) comparado ao látex estireno-butadieno. Para a base do papel cartão (lado marrom) sem a colagem superficial, a adesão de polietileno se mostrou superior à condição com colagem, pois esta gera maior nivelamento da superfície, deixando a base do papel cartão mais lisa, dificultando assim a adesão de polietileno. Os tratamentos de superfície com chama podem ter causado a oxidação da superfície do papel cartão, gerando assim um aumento de grupos polares na superfície, aumentando a energia superficial da mesma e, consequentemente, melhorado a adesão de polietileno. A energia superficial pode ser vista como um excelente indicativo para adesão de polietileno, pois se verificou uma correlação linear onde quanto maior a energia superficial do papel cartão, maior a força de adesão ao polietileno. Por outro lado, a rugosidade superficial não mostrou diferenças entre as amostras estudadas. A técnica de infravermelho (ATR) não foi sensível para detectar diferenças químicas entre os tratamentos com e sem chama. No entanto, esta técnica pode ser utilizada para verificar a composição, quanto ao tipo de látex, usado na tinta de revestimento do papel cartão. O método Peel Test em 1800, usado para avaliar a força de adesão, apresenta resultados mais confiáveis do que somente a avaliação através da delaminação manual, que depende muito do analista e sua percepção.

This thesis deals with numerical simulation of a peel test with an Aluminium foil and Low Density Poly-Ethylene (LDPE) laminate. This work investigates the effects of the substrate thickness and studies the influences of interfacial strength and fracture energy of the cohesive zone between the Aluminium and LDPE. This study evaluates the proper guidelines for defining cohesive properties. A numerical cohesive zone model was created in ABAQUS. Continuum tensile tests were performed to extract LDPE material properties. The aluminium properties were found in literature. After acquiring material parameters, the simulation continued with studying the effects of changing interfacial strength, geometric parameters and fracture energy. The results were obtained in the form of root rotations and the force displacement response was studied carefully. It was validated by comparison to the traction separation curve.

Seven empirical equations were developed for the prediction of seal strength for medical device trays. A new methodology was developed and used for identifying burst and peel locations and comparing burst pressure and peel force. Multiple linear regression was used to fit 76 models, selecting the best models based on the Akaike Information Criterion (AIC) and adjusted R2 (R2 adj) value of each model. The selected models have R2 adj and prediction R2 (R2 pred) values of .83 to .94. Factors investigated for the peel force response were sealing pressure (3 levels), dwell time (3 levels), sealing temperature (3 levels), and adhesive. Additional factors investigated for the burst pressure response were restraining plate gap, and tray volume, height, length-to-width ratio and area. Polyethylene terephthalate-glycol (PETG) trays with Tyvek 1073B lids and two popular water-based adhesives were used. Trays were selected to yield three levels of area and three levels of length-to-width ratio, defining nine package configurations. Packages for burst testing were sealed under a fractional factorial design with 27 treatments. Packages for peel testing were sealed under a 17-point face-centered central composite design. Packages were tested using peel testing following the ASTM F88-07 standard and restrained burst testing with three gap distances following the ASTM F2054-00 standard. All possible subsets of the factors were evaluated, with the best models selected based on AIC value. Equations were developed to predict peak and average peel force based on sealing process parameters (R2 pred =.94 and .92), burst pressure based on tray and sealing parameters and gap (R2 pred =.94), and four peel force responses based on burst pressure and gap (R2 pred =.83 to .86). Models were validated through cross-validation, using the prediction error sum of squares (PRESS) statistic. The R2 pred was calculated to estimate the predictive ability of each model.

The polymer laminated sheet metal (PLSM) is a layered material which involves a sheet metal substrate, a thin polymer film and an adhesive layer between the film and the substrate. The adhesion properties between the bonded materials are among the most important issues in PLSM forming operations. In this thesis, the main focus has been devoted to characterizing and improving the adhesion properties of the PLSM system for forming applications. Metallic surface roughness evolution and residual stress development in polymer adherends are two consequences of the plastic deformation of the PLSMs. In chapter 2, the effect of these factors on interfacial adhesion strength between metallic substrate and polymer adherend (polymer film with a thin uniform pressure-sensitive adhesive layer on one side) is investigated by devising a new experimental methodology. This methodology is based on two different protocols for preparation of peel sample, one involving pre-straining in uniaxial tension of the metallic substrate prior to lamination and the other involving post-lamination pre-straining of the PLSM. In chapter 3, the peel test results of two different types of PLSMs at different peel speeds are analyzed with two different approaches common in cohesive zone modeling in the literature, namely linear elastic stiffness approach and critical maximum stress approach. The modeling results revealed the significance of the peel speed in determining the interface strength between the adhesive and metallic substrate. In chapter 4, two mechanical treatment techniques of grinding and knurling are implemented to alter the metallic substrate surface roughness before lamination. Peel strength of these samples are investigated at different peel speeds and at different peel loading directions with respect to the grinding and knurling directions. / Thesis / Doctor of Philosophy (PhD) / The polymer laminated sheet metal (PLSM) is a layered material which involves a sheet metal substrate, a thin polymer film and an adhesive layer between the film and the substrate. In this thesis, the main focus has been devoted to characterizing and improving the adhesion properties of the PLSM system for forming applications. A new experimental methodology has been devised for analyzing the effects of deformation-induced surface roughness of metallic substrate and deformation-induced residual stress in polymer adherends on interfacial peel properties of PLSMs. A novel interpretation of the results obtained from rate-independent cohesive zone modeling of peel test has revealed the significance of peel speed in determining the interface strength between the adhesive and the metallic substrate. In another part of this thesis, the effects of two substrate surface alteration techniques, grinding and knurling, on peel properties of PLSMs have been studied.