The Experts below are selected from a list of 4944 Experts worldwide ranked by ideXlab platform
Vijay Gupta - One of the best experts on this subject based on the ideXlab platform.
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Interface Strength measurement of tungsten coatings on F82H substrates
Journal of Nuclear Materials, 2009Co-Authors: Jaafar A. El-awady, Vijay Gupta, Nasr M. Ghoniem, Shahram SharafatAbstract:In the current work, hot isostatic pressing is adopted to deposit tungsten coatings on F82H substrates. The Interface Strength of the W/F82H samples is measured using the Laser Spallation technique and the microstructure is analyzed to determine the Strength of the coating. Finally, the failure mechanisms of the hot isostatic pressing versus vacuum plasma spraying tungsten coatings and their different failure Strengths are compared. It is concluded that the hot isostatic pressing process ensures a good adhesion for the W/F82H Interface while the vacuum plasma spraying process results in relatively lower failure Strength for the W-coating itself due to the high porosity in the coating.
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Study on the Interface Strength of zirconia coatings by a laser spallation technique
Vacuum, 2004Co-Authors: Akira Kobayashi, Vijay Gupta, Amit Jain, Vassili KireevAbstract:Tensile Strength of Interfaces between zirconia coatings and stainless steel substrates were measured using a laser spallation technique. In this technique, a laser-generated compression stress wave reflects into a tensile wave from the free surface of the coating and pries off its Interface at a critical amplitude. Zirconia coatings were deposited using the gas tunnel-type plasma spraying process which was previously shown to result in denser and harder deposits compared with those produced by conventional spray methods. The Interface Strength was found to increase with a decrease in the spray distance and traverse speed, and with an increase in the traverse number, and coating and substrate thickness. The variation in the measured Strength with these variables could be explained through their effect on controlling the temperature of the particles and that in the interfacial region. Higher temperature in the interfacial region during coating deposition is expected to increase adhesion by enhancing chemical and physical bonding mechanisms. Depending upon the processing conditions used, the tensile Strength for the zirconia/steel Interface system was found to vary anywhere between 206 and 501 MPa.
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Measurement of in situ fiber/matrix Interface Strength in graphite/epoxy composites
Composites Science and Technology, 1998Co-Authors: Allen K. Yu, Vijay GuptaAbstract:Abstract A new experimental strategy for in situ measurement of the fiber/matrix Interface Strength is presented. As-fabricated graphite/epoxy laminates with specially designed grooved islands on their front surfaces were loaded on their rear sides by a 16 to 20 ns long laser-generated pressure pulse. This compressive stress pulse, generated in-line on the rear of one of the surface islands, propagates normal to the plane of the laminate and very quickly attains a steady-state profile of approximately 130 μm after undergoing multiple scattering from individual fibers and laminates. The returning tensile wave from the sample's free surface prises the composite island off by nucleating a subsurface crack. This crack on the local scale comprises several fiber/matrix Interface debonds connected by the intervening matrix. The free-surface velocity causing this damage is recorded by interferometry and related to the far-field composite-scale tensile stress by using a one-dimensional elasto-dynamic analysis. The local fiber/matrix Interface stress concentration corresponding to this overall tensile stress was determined next by using a finite-element simulation that idealized the fiber distribution within the epoxy matrix to be periodic. The Interface tensile Strength was taken as the sum of this stress and the compressive residual stress at the same location, which in turn, was estimated by yet another analysis based on the finite-element procedure. For a graphite/epoxy laminate fabricated from a unidirectional Hercules AS4 graphite fiber tapes pre-impregnated with 450 k cure Hercules 3502 thermosetting epoxy resin, an average fiber/matrix Interface Strength of 210 MPa was estimated.
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Measurement of Interface Strength by the modified laser spallation technique. II. Applications to metal/ceramic Interfaces
Journal of Applied Physics, 1993Co-Authors: Vijay Gupta, J. YuanAbstract:Part II of this series presents applications of the modified laser spallation technique to several Interface systems. For metal/pyrolytic graphite (PG) Interfaces, the tensile Strength of Interfaces between 3‐μm‐thick coatings of Sn, Sb, Cu, Nb, Al, and Cr on a PG substrate were measured in units of MPa to be 18.53, 5.99, 15.46, 41.16, 16.53, and 15.47, respectively. It was found that the Interface fracture mechanisms depend on the elastic‐plastic properties of the coatings, but are independent of the Interface Strength. Interface Strength between diamond, SnO2, and Nb coatings on polycrystalline alumina substrates were measured to be ≳140, 320, and 280 MPa, respectively. It is shown that the brittle fracture takes place at the Interface upon spalling even if the plastic deformation exists within the coatings.
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Calculation, Measurement, and Control of Interface Strength in Composites
Journal of the American Ceramic Society, 1993Co-Authors: Vijay Gupta, Jun Yuan, Doris MartinezAbstract:Strength and energy criteria for Interface delamination are given for composite systems involving anisotropic fibers. The tensile Strength of planar Interfaces is measured with a modified laser spallation experiment involving a laser Doppler displacement interferometer. The technique for achieving desired Interface properties is demonstrated on an Nb/Al 2 O 3 Interface. In the as-deposited state, the Strength is determined to be 0.28 GPa. The Interface Strength is controlled with sputter-deposited Cr and Sb interlayers. The Strength of Nb/Al 2 O 3 Interfaces varies from 0.28 to 0.35 GPa when the Cr layer thickness varies from 1 to 50 A. The Strength is reduced to 0.16 GPa with Sb thickness of 70 A.
Pietro Russo - One of the best experts on this subject based on the ideXlab platform.
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Damage tolerance assessment of the Interface Strength gradation in thermoplastic composites
Composites Part B-engineering, 2017Co-Authors: Luigi Sorrentino, Fabrizio Sarasini, Jacopo Tirillò, Fabienne Touchard, Laurence Chocinski-arnault, David Mellier, Pietro RussoAbstract:Abstract The newly developed hybridization approach for thermoplastic composites, based on the gradation of the interlaminar Interface Strength (IGIS design), was used to prepare polypropylene/glass fibre composites by properly alternating layers of reinforcing fabric with compatibilized and not compatibilized polymeric films. Maleated polypropylene was used to improve the matrix/fibre Interface Strength. The flexural and low-velocity impact characterizations showed that the use of the coupling agent improved the quasi-static flexural properties through the Strengthening of the matrix/fibre Interface, but considerably lowered the low velocity impact resistance of the laminate. The use of the IGIS design, which grades the Interface Strength through the laminate thickness, enabled the fabrication of composites with a favourable combination of flexural properties and impact resistance and proved to be effective in better preserving the integrity of the fibres. The damage after impact has been assessed by means of micro-computed tomography, which elucidated the improving effect of the matrix hybridization on the impact resistance, and acoustic emission analysis, which allowed the identification of the mechanisms responsible for impact energy absorption. The role played by the matrix hybridization sequence was pointed out along with the effective role of IGIS design in the overall mechanical performance of laminates.
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Effects of Interface Strength gradation on impact damage mechanisms in polypropylene/woven glass fabric composites
Composites Part B-engineering, 2016Co-Authors: Simone Boccardi, Luigi Sorrentino, Giorgio Simeoli, Carosena Meola, Giovanni Maria Carlomagno, Pietro RussoAbstract:Abstract The attention of the present work is focused on the behaviour of interlaminar graded Interface Strength (IGIS) laminated structures under impact. IGIS structures are made of layers of a woven glass fabric alternated with compatibilized and not compatibilized polypropylene film layers, symmetrically and asymmetrically arranged with respect to the middle plane. For each configuration some specimens are subjected to impact tests at energies of 6 and 25 J while one specimen is left unloaded. Impacted and not impacted specimens are non-destructively evaluated with lock-in thermography (LT). Results highlight the role played by the stacking sequence in the IGIS laminate and confirm data previously obtained through mechanical characterization.
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mechanical performance optimization through Interface Strength gradation in pp glass fibre reinforced composites
Composites Part B-engineering, 2015Co-Authors: Luigi Sorrentino, Giorgio Simeoli, Salvatore Iannace, Pietro RussoAbstract:Abstract A new design for thermoplastic composites based on the gradation of the interlaminar Interface Strength (IGIS) has been developed with the aim of coupling high impact resistance with high static properties. IGIS laminates have been prepared by properly alternating layers of woven fabric with layers of compatibilized or not compatibilized polymeric films. To prove the new concept, polypropylene (PP) and glass fibres woven fabrics have been used to prepare composites by using the film stacking technique. Maleated PP, able to compatibilize polypropylene with glass fibres, has been used to manage the Interface Strength layer by layer. The flexural and low-velocity impact characterizations have shown that the presence of the coupling agent in conventional composite structures (prepared with fully compatibilized polymeric layers) improves the static flexural properties through the Strengthening of the matrix/fibre Interface but considerably lowers the low velocity impact resistance of the composite, in terms of maximum load before fibre breakage and recovered energy after impact. The use of the IGIS design, that grade the Interface Strength through the laminate thickness, allows to prepare composites with both high flexural properties and high impact resistance, without affecting the balance and type of the reinforcement configuration.
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the role of Interface Strength on the low velocity impact behaviour of pp glass fibre laminates
Composites Part B-engineering, 2014Co-Authors: Giorgio Simeoli, Luigi Sorrentino, Salvatore Iannace, Domenico Acierno, Carosena Meola, Pietro RussoAbstract:Abstract The low velocity impact behaviour of composites made of polypropylene (PP) as matrix and glass fibre fabric as reinforcement has been investigated. Two PP grades, differing for their melt flow index, have been used as matrix, and maleic anhydride has been used to manage the polymer/glass fibre Interface Strength. Impact tests at four energies (5, 20, 40 and 105 J) have been carried out to evaluate the main dissipation mechanisms occurring in each impact condition and to identify the role of the Interface Strength. Quasi-static flexural tests confirmed that the compatibilizer improves both flexural modulus and Strength, as well as strain at yield. A different performance trend is shown by low velocity impact tests. Not compatibilized samples have exhibited, since the lowest impact energy (5 J), significant energy dissipation resulting from the Interface failure occurring at very low strains, as confirmed by lock-in thermographic analysis. Conversely, compatibilized samples showed no or small damages. As the impact energy increases not compatibilized samples outperformed compatibilized samples by large margins showing better impact resistance. This result has been related to the large energy dissipation occurring at the polymer/fibre Interface. Furthermore, the broad Interface failure and slipping act as crack blocker, preserving the integrity of fibres and allowing for higher load bearing. Managing the Interface Strength can be a viable option to design thermoplastic based composites with improved impact damage tolerance and balanced quasi-static properties.
James A Cornie - One of the best experts on this subject based on the ideXlab platform.
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measurement of Interface Strength by a laser spallation technique
Journal of The Mechanics and Physics of Solids, 1992Co-Authors: Vijay Gupta, A S Argon, David M Parks, James A CornieAbstract:Abstract A laser spallation experiment has been developed to measure the Strength of planar Interfaces between a substrate and a thin coating (in the thickness range of 0.3–3 μm). In this technique a laser pulse of a high enough energy and a pre-determined duration is converted into a pressure pulse of a critical amplitude and width that is sent through the substrate toward the free surface with the coating. The reflected tensile wave from the free surface of the coating pries-off the coating. The critical stress amplitude that accomplishes the removal of the coating is determined from a computer simulation of the process. The simulation itself is verified by means of a piezo-electric crystal probe that is capable of mapping out the profile of the stress pulse generated by the laser pulse. Interface Strength values ranging from 3.7 to 10.5 GPa were determined for the Si/SiC system. For the Interfaces between pyrolytic graphite and SiC coatings an average Strength of 7.2 GPA was measured, while the corresponding Interface Strength between a Pitch-55 type ribbon with a fiber-like morphology and SiC coatings was found to be 0.23 GPa. Intrinsic Strengths of SiC coatings and Si crystal were also determined using this technique. These were, on the average, 8.6 GPa for Si crystals and 11.9 GPa for a SiC coating. Furthermore, the potential of the laser technique to determine the Interface toughness was also demonstrated, provided well-characterizable flaws can be planted on the Interface.
Luigi Sorrentino - One of the best experts on this subject based on the ideXlab platform.
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Damage tolerance assessment of the Interface Strength gradation in thermoplastic composites
Composites Part B-engineering, 2017Co-Authors: Luigi Sorrentino, Fabrizio Sarasini, Jacopo Tirillò, Fabienne Touchard, Laurence Chocinski-arnault, David Mellier, Pietro RussoAbstract:Abstract The newly developed hybridization approach for thermoplastic composites, based on the gradation of the interlaminar Interface Strength (IGIS design), was used to prepare polypropylene/glass fibre composites by properly alternating layers of reinforcing fabric with compatibilized and not compatibilized polymeric films. Maleated polypropylene was used to improve the matrix/fibre Interface Strength. The flexural and low-velocity impact characterizations showed that the use of the coupling agent improved the quasi-static flexural properties through the Strengthening of the matrix/fibre Interface, but considerably lowered the low velocity impact resistance of the laminate. The use of the IGIS design, which grades the Interface Strength through the laminate thickness, enabled the fabrication of composites with a favourable combination of flexural properties and impact resistance and proved to be effective in better preserving the integrity of the fibres. The damage after impact has been assessed by means of micro-computed tomography, which elucidated the improving effect of the matrix hybridization on the impact resistance, and acoustic emission analysis, which allowed the identification of the mechanisms responsible for impact energy absorption. The role played by the matrix hybridization sequence was pointed out along with the effective role of IGIS design in the overall mechanical performance of laminates.
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Effects of Interface Strength gradation on impact damage mechanisms in polypropylene/woven glass fabric composites
Composites Part B-engineering, 2016Co-Authors: Simone Boccardi, Luigi Sorrentino, Giorgio Simeoli, Carosena Meola, Giovanni Maria Carlomagno, Pietro RussoAbstract:Abstract The attention of the present work is focused on the behaviour of interlaminar graded Interface Strength (IGIS) laminated structures under impact. IGIS structures are made of layers of a woven glass fabric alternated with compatibilized and not compatibilized polypropylene film layers, symmetrically and asymmetrically arranged with respect to the middle plane. For each configuration some specimens are subjected to impact tests at energies of 6 and 25 J while one specimen is left unloaded. Impacted and not impacted specimens are non-destructively evaluated with lock-in thermography (LT). Results highlight the role played by the stacking sequence in the IGIS laminate and confirm data previously obtained through mechanical characterization.
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mechanical performance optimization through Interface Strength gradation in pp glass fibre reinforced composites
Composites Part B-engineering, 2015Co-Authors: Luigi Sorrentino, Giorgio Simeoli, Salvatore Iannace, Pietro RussoAbstract:Abstract A new design for thermoplastic composites based on the gradation of the interlaminar Interface Strength (IGIS) has been developed with the aim of coupling high impact resistance with high static properties. IGIS laminates have been prepared by properly alternating layers of woven fabric with layers of compatibilized or not compatibilized polymeric films. To prove the new concept, polypropylene (PP) and glass fibres woven fabrics have been used to prepare composites by using the film stacking technique. Maleated PP, able to compatibilize polypropylene with glass fibres, has been used to manage the Interface Strength layer by layer. The flexural and low-velocity impact characterizations have shown that the presence of the coupling agent in conventional composite structures (prepared with fully compatibilized polymeric layers) improves the static flexural properties through the Strengthening of the matrix/fibre Interface but considerably lowers the low velocity impact resistance of the composite, in terms of maximum load before fibre breakage and recovered energy after impact. The use of the IGIS design, that grade the Interface Strength through the laminate thickness, allows to prepare composites with both high flexural properties and high impact resistance, without affecting the balance and type of the reinforcement configuration.
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the role of Interface Strength on the low velocity impact behaviour of pp glass fibre laminates
Composites Part B-engineering, 2014Co-Authors: Giorgio Simeoli, Luigi Sorrentino, Salvatore Iannace, Domenico Acierno, Carosena Meola, Pietro RussoAbstract:Abstract The low velocity impact behaviour of composites made of polypropylene (PP) as matrix and glass fibre fabric as reinforcement has been investigated. Two PP grades, differing for their melt flow index, have been used as matrix, and maleic anhydride has been used to manage the polymer/glass fibre Interface Strength. Impact tests at four energies (5, 20, 40 and 105 J) have been carried out to evaluate the main dissipation mechanisms occurring in each impact condition and to identify the role of the Interface Strength. Quasi-static flexural tests confirmed that the compatibilizer improves both flexural modulus and Strength, as well as strain at yield. A different performance trend is shown by low velocity impact tests. Not compatibilized samples have exhibited, since the lowest impact energy (5 J), significant energy dissipation resulting from the Interface failure occurring at very low strains, as confirmed by lock-in thermographic analysis. Conversely, compatibilized samples showed no or small damages. As the impact energy increases not compatibilized samples outperformed compatibilized samples by large margins showing better impact resistance. This result has been related to the large energy dissipation occurring at the polymer/fibre Interface. Furthermore, the broad Interface failure and slipping act as crack blocker, preserving the integrity of fibres and allowing for higher load bearing. Managing the Interface Strength can be a viable option to design thermoplastic based composites with improved impact damage tolerance and balanced quasi-static properties.
Gerald A Miller - One of the best experts on this subject based on the ideXlab platform.
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influence of matric suction on geotextile reinforcement marginal soil Interface Strength
Geotextiles and Geomembranes, 2014Co-Authors: Danial Esmaili, Kianoosh Hatami, Gerald A MillerAbstract:Abstract This paper presents descriptions and results of multi-scale pullout and Interface shear tests on a woven polypropylene (PP) geotextile reinforcement material in a marginal quality soil. A main objective of these tests was to develop a moisture reduction factor (MRF) for the pullout resistance equation in the currently available design guidelines. The tests were carried out at different overburden pressure and gravimetric water content (GWC) values. The differences in the soil-geotextile Interface Strength among the cases with different GWC values were used to determine the corresponding MRF values. Results of the study indicate that the reinforcement Interface Strength and pullout resistance could decrease significantly as a result of the loss in the matric suction (e.g. by 42% between the cases of 2% dry and 2% wet of the soil optimum moisture content). It is concluded that wetting of the soil-geotextile Interface during construction or service life of a reinforced soil structure can measurably reduce the Interface Strength and pullout resistance of the geotextile reinforcement which needs to be accounted for in design. Results of the study will be also useful to estimate the difference in the pullout capacity of geotextile reinforcement in a marginal soil when placed at different GWC values during construction. The methodology described in the paper could be used to expand the database of MRF results to include a wider range of soil types and geotextile reinforcement for practical applications.