This work investigated air plasma effect on the Mode I crack growth resistance of adhesively-bond... more This work investigated air plasma effect on the Mode I crack growth resistance of adhesively-bonded metal-CFRTP dissimilar joints by using aluminum alloy (AA6061) and short-carbon-fiber-reinforced polyamide 66 (CFRPA66) as an example, and the Double Cantilever Beam (DCB) fracture testing as an evaluation method. The results showed that air plasma treatment can improve the fracture resistance of adhesively-bonded AA6061-CFRPA66 dissimilar joints with 140% enhanced Mode I fracture energy in maximum compared to non-treated ones. The quantified fracture energies from size effect method for both non-treated and plasma-treated cases are geometry-independent, whereas this is not true for modified beam theory causing geometry-dependent results. The foregoing improvement was confirmed from the failure surface morphology of plasma-treated specimens, showing fibers peeling off from CFRPA66 surface due to plasma-enhanced bonding between CFRPA66 and adhesive by the formation of covalent bonds at...
Plant-based natural fibers can be used in place of glass in fiber reinforced automotive composite... more Plant-based natural fibers can be used in place of glass in fiber reinforced automotive composites to reduce weight, cost and provide environmental benefits. Current automotive applications use natural fibers in injection molded thermoplastics for interior, non-structural applications. Compression molded natural fiber reinforced thermosets have the opportunity to extend natural fiber composite applications to structural and semi-structural parts and exterior parts realizing further vehicle weight savings. The development of low cost molding and fiber processing techniques for large volumes of natural fibers has helped in understanding the barriers of non-aqueous retting. The retting process has a significant effect on the fiber quality and its processing ability that is related to the natural fiber composite mechanical properties. PNNL has developed a compression molded fiber reinforced composite system of which is the basis for future preforming activities and fiber treatment. We a...
Abstract In this paper, a predictive modeling tool is developed for damage analysis and design of... more Abstract In this paper, a predictive modeling tool is developed for damage analysis and design of hydrogen (H2) storage composite pressure vessels. It integrates micromechanics of matrix cracking into a continuum damage mechanics (CDM) description for damage evolution, and three-dimensional (3D) finite element (FE) modeling of the vessel structural response. At the scale of the composite layer (mesoscale), the temperature-dependent stiffness reduction law in terms of the damage variable for transverse matrix cracking is computed using an Eshelby-Mori-Tanaka approach (EMTA) for the initial composite thermoelastic properties and a self-consistent model for the stiffness reduction as a function of the damage variable. While transverse matrix cracking obeying a damage evolution relation can progressively evolve from an initiation to a saturation state, fiber failure is predicted by a micromechanical fiber rupture criterion that accounts for the fiber strength and matrix stress that can be computed within EMTA. The implementation of this integrated multiscale modeling model into a 3D FE formulation enables damage analysis and design of H2 storage composite pressure vessels. The developed tool is illustrated through 3D damage analyses of a cryogenically compressed H2 storage vessel model subjected to thermomechanical loadings to investigate effects of the helical layer fiber orientation and loading scenario on damage development, vessel integrity and burst pressure.
Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, and Civil Infrastructure 2017, 2017
Fourier transform infrared (FTIR) spectroscopy is an information-rich method that reveals chemica... more Fourier transform infrared (FTIR) spectroscopy is an information-rich method that reveals chemical bonding near the surface of polymer composites. FTIR can be used to verify composite composition, identify chemical contaminants and expose composite moisture content. Polymer matrix changes due to thermal exposure including loss of additives, chain scission, oxidation and changes in crystallinity may also be determined using FTIR spectra. Portable handheld instruments using non-contact reflectance or surface contact attenuated total reflectance (ATR) may be used for nondestructive evaluation (NDE) of thermal aging in polymer and composite materials of in-service components. We report the use of ATR FTIR to track oxidative thermal aging in ethylene-propylene rubber (EPR) and chlorinated polyethylene (CPE) materials used in medium voltage nuclear power plant electrical cable insulation and jacketing. Mechanical property changes of the EPR and CPE materials with thermal degradation for correlation with FTIR data are tracked using indenter modulus (IM) testing. IM is often used as a local NDE metric of cable jacket health. The FTIR-determined carbonyl index was found to increase with IM and may be a valuable NDE metric with advantages over IM for assessing cable remaining useful life.
We have developed a unique blend of powder injection molding (PIM) feedstock materials in which o... more We have developed a unique blend of powder injection molding (PIM) feedstock materials in which only a small volume fraction of binder (< 8%) is required; the remainder of the mixture consists of the metal powder and a solid aromatic solvent. Because of the nature of the decomposition in the binder system and the relatively small amount used, the binder can be completely removed from the molded component during heat treatment. Here, we present results from an initial study on in-situ titanium alloy formation in near-net shape components manufactured by this novel PIM technique.
The invention is based in part on the discovery that a plastic housing that is lightweight is sur... more The invention is based in part on the discovery that a plastic housing that is lightweight is surprisingly efficient inasmuch as background signals from any gamma radiation are significantly reduced by using a plastic housing instead of a metal housing. A further aspect of the present invention is the profile of the housing as a bi-linear approximation to a parabola resulting in full optical response from any location on the scintillation material to the photomultiplier tube. A yet further aspect of the present invention is that the survey probe is resistant to magnetic fields. A yet further aspect of the present invention is the use of a snap-fit retaining bracket that overcomes the need for multiple screws. 16 figs.
This is the annual report for the Hydrogen Storage Engineering Center of Excellence project as re... more This is the annual report for the Hydrogen Storage Engineering Center of Excellence project as required by DOE EERE's Fuel Cell Technologies Office. We have been provided with a specific format. It describes the work that was done with cryo-sorbent based and chemical-based hydrogen storage materials. Balance of plant components were developed, proof-of-concept testing performed, system costs estimated, and transient models validated as part of this work.
Microsized pore parameters, such as pore size and distance between pores in a series of model EPD... more Microsized pore parameters, such as pore size and distance between pores in a series of model EPDM rubbers, were determined in situ under the pressure of 500 psi using 129Xe nuclear magnetic resonance (NMR) techniques: spin-lattice (T1) and spin-spin (T2) relaxation measurements, pulsed-field gradient (PFG) NMR, and two-dimensional exchange spectroscopy (2D EXSY). The T1/T2 (≫1) ratio for the xenon confined in the pores is larger than that for nonconfined free xenon. This suggests that almost the entire pore surface interacts with xenon atoms like a closed pore. While these pores still connect each other through very narrow diffusion/exchange channels, it is possible to observe the echo decay in PFG-NMR and cross-peaks in 2D EXSY. The results show that both diffusion (Dpore ≈ 2.1 × 10-10 m2/s) and exchange (exchange rate, τexch = a few tens of milliseconds) of xenon between a pore within the material and outer surface are prolonged. The exchange distances (l), which correspond to the xenon gas penetration depth, were estimated to be 70-100 μm based on the measured diffusion coefficients and exchange rate (1/τexch). NMR diffraction analysis reveals that pore size (a) and pore distance (b) are on the order of magnitude of micrometers and tens of micrometers, while the diffusion coefficients of xenon gas in the diffusion channels (Deff) are about 10-8 m2/s. Overall, this study suggests that the pores with a few micrometers connected through very narrow flowing channels with the length of several tens of micrometers are developed 70 to 100 μm below the rubber surface. Furthermore, the overall steady-state diffusion of xenon is slower, approximately 2 orders of magnitudes, than the diffusion in the channel between the pores. The pore and exchange distances correlated with the composition of rubbers showed that the properties of EPDM rubber as a high-pressure gas barrier could be improved by reducing the size of cracks and the depth of gas penetration by the addition of both carbon black and silica fillers.
AWE and PNNL are engaged in a technical collaboration investigating techniques to enhance continu... more AWE and PNNL are engaged in a technical collaboration investigating techniques to enhance continuity of knowledge over Treaty Accountable Items, with emphasis on a verified nuclear weapons dismantlement process. Tamper Indicating Enclosures (TIE) will likely be deployed as part of a chain of custody regime to indicate an unauthorised attempt to access a Treaty Accountable Item, or secure authenticated monitoring equipment. In 2011, the collaboration presented a paper at the INMM annual conference held in Palm Desert, CA titled “Passive Tamper Indicating Enclosures Incorporating Embedded Optical Fibre”, which discussed the concept of integrating optical fibres into TIEs for use as a passive tamper indicating mechanism. This paper provides an update on the Fibre Optic based TIE and introduces a second passive TIE concept based on the use of Poly(Methyl MethAcrylate) (PMMA). Concepts relating to deployment, tamper indication, and unique identification will be discussed.
Safe and efficient hydrogen storage and distribution are key attributes to realizing hydrogen as ... more Safe and efficient hydrogen storage and distribution are key attributes to realizing hydrogen as an alternative energy carrier to traditional fossil fuels. To this end, cryogenic liquid and cryo-compressed gaseous hydrogen are considered high energy density alternatives to ambient temperature gas. However, these alternatives have significant material demands to overcome extreme temperature (20 K) and pressure (700 bar) as well as hydrogen effects. Austenitic stainless steels are widely used for cryogenic pressure vessels owing to relatively high ductility even at 4 K. However, the influence of hydrogen on mechanical properties at cryogenic temperatures has rarely been studied. In this study, the tensile properties of 304L austenitic stainless steel with internal hydrogen were evaluated at 20 K, 77 K, and 113 K. Test specimens were saturated with internal hydrogen to concentration of 140 wtppm in a high pressure environment at elevated temperature, a process called thermal prechargin...
This work investigated air plasma effect on the Mode I crack growth resistance of adhesively-bond... more This work investigated air plasma effect on the Mode I crack growth resistance of adhesively-bonded metal-CFRTP dissimilar joints by using aluminum alloy (AA6061) and short-carbon-fiber-reinforced polyamide 66 (CFRPA66) as an example, and the Double Cantilever Beam (DCB) fracture testing as an evaluation method. The results showed that air plasma treatment can improve the fracture resistance of adhesively-bonded AA6061-CFRPA66 dissimilar joints with 140% enhanced Mode I fracture energy in maximum compared to non-treated ones. The quantified fracture energies from size effect method for both non-treated and plasma-treated cases are geometry-independent, whereas this is not true for modified beam theory causing geometry-dependent results. The foregoing improvement was confirmed from the failure surface morphology of plasma-treated specimens, showing fibers peeling off from CFRPA66 surface due to plasma-enhanced bonding between CFRPA66 and adhesive by the formation of covalent bonds at...
Plant-based natural fibers can be used in place of glass in fiber reinforced automotive composite... more Plant-based natural fibers can be used in place of glass in fiber reinforced automotive composites to reduce weight, cost and provide environmental benefits. Current automotive applications use natural fibers in injection molded thermoplastics for interior, non-structural applications. Compression molded natural fiber reinforced thermosets have the opportunity to extend natural fiber composite applications to structural and semi-structural parts and exterior parts realizing further vehicle weight savings. The development of low cost molding and fiber processing techniques for large volumes of natural fibers has helped in understanding the barriers of non-aqueous retting. The retting process has a significant effect on the fiber quality and its processing ability that is related to the natural fiber composite mechanical properties. PNNL has developed a compression molded fiber reinforced composite system of which is the basis for future preforming activities and fiber treatment. We a...
Abstract In this paper, a predictive modeling tool is developed for damage analysis and design of... more Abstract In this paper, a predictive modeling tool is developed for damage analysis and design of hydrogen (H2) storage composite pressure vessels. It integrates micromechanics of matrix cracking into a continuum damage mechanics (CDM) description for damage evolution, and three-dimensional (3D) finite element (FE) modeling of the vessel structural response. At the scale of the composite layer (mesoscale), the temperature-dependent stiffness reduction law in terms of the damage variable for transverse matrix cracking is computed using an Eshelby-Mori-Tanaka approach (EMTA) for the initial composite thermoelastic properties and a self-consistent model for the stiffness reduction as a function of the damage variable. While transverse matrix cracking obeying a damage evolution relation can progressively evolve from an initiation to a saturation state, fiber failure is predicted by a micromechanical fiber rupture criterion that accounts for the fiber strength and matrix stress that can be computed within EMTA. The implementation of this integrated multiscale modeling model into a 3D FE formulation enables damage analysis and design of H2 storage composite pressure vessels. The developed tool is illustrated through 3D damage analyses of a cryogenically compressed H2 storage vessel model subjected to thermomechanical loadings to investigate effects of the helical layer fiber orientation and loading scenario on damage development, vessel integrity and burst pressure.
Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, and Civil Infrastructure 2017, 2017
Fourier transform infrared (FTIR) spectroscopy is an information-rich method that reveals chemica... more Fourier transform infrared (FTIR) spectroscopy is an information-rich method that reveals chemical bonding near the surface of polymer composites. FTIR can be used to verify composite composition, identify chemical contaminants and expose composite moisture content. Polymer matrix changes due to thermal exposure including loss of additives, chain scission, oxidation and changes in crystallinity may also be determined using FTIR spectra. Portable handheld instruments using non-contact reflectance or surface contact attenuated total reflectance (ATR) may be used for nondestructive evaluation (NDE) of thermal aging in polymer and composite materials of in-service components. We report the use of ATR FTIR to track oxidative thermal aging in ethylene-propylene rubber (EPR) and chlorinated polyethylene (CPE) materials used in medium voltage nuclear power plant electrical cable insulation and jacketing. Mechanical property changes of the EPR and CPE materials with thermal degradation for correlation with FTIR data are tracked using indenter modulus (IM) testing. IM is often used as a local NDE metric of cable jacket health. The FTIR-determined carbonyl index was found to increase with IM and may be a valuable NDE metric with advantages over IM for assessing cable remaining useful life.
We have developed a unique blend of powder injection molding (PIM) feedstock materials in which o... more We have developed a unique blend of powder injection molding (PIM) feedstock materials in which only a small volume fraction of binder (< 8%) is required; the remainder of the mixture consists of the metal powder and a solid aromatic solvent. Because of the nature of the decomposition in the binder system and the relatively small amount used, the binder can be completely removed from the molded component during heat treatment. Here, we present results from an initial study on in-situ titanium alloy formation in near-net shape components manufactured by this novel PIM technique.
The invention is based in part on the discovery that a plastic housing that is lightweight is sur... more The invention is based in part on the discovery that a plastic housing that is lightweight is surprisingly efficient inasmuch as background signals from any gamma radiation are significantly reduced by using a plastic housing instead of a metal housing. A further aspect of the present invention is the profile of the housing as a bi-linear approximation to a parabola resulting in full optical response from any location on the scintillation material to the photomultiplier tube. A yet further aspect of the present invention is that the survey probe is resistant to magnetic fields. A yet further aspect of the present invention is the use of a snap-fit retaining bracket that overcomes the need for multiple screws. 16 figs.
This is the annual report for the Hydrogen Storage Engineering Center of Excellence project as re... more This is the annual report for the Hydrogen Storage Engineering Center of Excellence project as required by DOE EERE's Fuel Cell Technologies Office. We have been provided with a specific format. It describes the work that was done with cryo-sorbent based and chemical-based hydrogen storage materials. Balance of plant components were developed, proof-of-concept testing performed, system costs estimated, and transient models validated as part of this work.
Microsized pore parameters, such as pore size and distance between pores in a series of model EPD... more Microsized pore parameters, such as pore size and distance between pores in a series of model EPDM rubbers, were determined in situ under the pressure of 500 psi using 129Xe nuclear magnetic resonance (NMR) techniques: spin-lattice (T1) and spin-spin (T2) relaxation measurements, pulsed-field gradient (PFG) NMR, and two-dimensional exchange spectroscopy (2D EXSY). The T1/T2 (≫1) ratio for the xenon confined in the pores is larger than that for nonconfined free xenon. This suggests that almost the entire pore surface interacts with xenon atoms like a closed pore. While these pores still connect each other through very narrow diffusion/exchange channels, it is possible to observe the echo decay in PFG-NMR and cross-peaks in 2D EXSY. The results show that both diffusion (Dpore ≈ 2.1 × 10-10 m2/s) and exchange (exchange rate, τexch = a few tens of milliseconds) of xenon between a pore within the material and outer surface are prolonged. The exchange distances (l), which correspond to the xenon gas penetration depth, were estimated to be 70-100 μm based on the measured diffusion coefficients and exchange rate (1/τexch). NMR diffraction analysis reveals that pore size (a) and pore distance (b) are on the order of magnitude of micrometers and tens of micrometers, while the diffusion coefficients of xenon gas in the diffusion channels (Deff) are about 10-8 m2/s. Overall, this study suggests that the pores with a few micrometers connected through very narrow flowing channels with the length of several tens of micrometers are developed 70 to 100 μm below the rubber surface. Furthermore, the overall steady-state diffusion of xenon is slower, approximately 2 orders of magnitudes, than the diffusion in the channel between the pores. The pore and exchange distances correlated with the composition of rubbers showed that the properties of EPDM rubber as a high-pressure gas barrier could be improved by reducing the size of cracks and the depth of gas penetration by the addition of both carbon black and silica fillers.
AWE and PNNL are engaged in a technical collaboration investigating techniques to enhance continu... more AWE and PNNL are engaged in a technical collaboration investigating techniques to enhance continuity of knowledge over Treaty Accountable Items, with emphasis on a verified nuclear weapons dismantlement process. Tamper Indicating Enclosures (TIE) will likely be deployed as part of a chain of custody regime to indicate an unauthorised attempt to access a Treaty Accountable Item, or secure authenticated monitoring equipment. In 2011, the collaboration presented a paper at the INMM annual conference held in Palm Desert, CA titled “Passive Tamper Indicating Enclosures Incorporating Embedded Optical Fibre”, which discussed the concept of integrating optical fibres into TIEs for use as a passive tamper indicating mechanism. This paper provides an update on the Fibre Optic based TIE and introduces a second passive TIE concept based on the use of Poly(Methyl MethAcrylate) (PMMA). Concepts relating to deployment, tamper indication, and unique identification will be discussed.
Safe and efficient hydrogen storage and distribution are key attributes to realizing hydrogen as ... more Safe and efficient hydrogen storage and distribution are key attributes to realizing hydrogen as an alternative energy carrier to traditional fossil fuels. To this end, cryogenic liquid and cryo-compressed gaseous hydrogen are considered high energy density alternatives to ambient temperature gas. However, these alternatives have significant material demands to overcome extreme temperature (20 K) and pressure (700 bar) as well as hydrogen effects. Austenitic stainless steels are widely used for cryogenic pressure vessels owing to relatively high ductility even at 4 K. However, the influence of hydrogen on mechanical properties at cryogenic temperatures has rarely been studied. In this study, the tensile properties of 304L austenitic stainless steel with internal hydrogen were evaluated at 20 K, 77 K, and 113 K. Test specimens were saturated with internal hydrogen to concentration of 140 wtppm in a high pressure environment at elevated temperature, a process called thermal prechargin...
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