The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform
Federico Oyedeji Falope - One of the best experts on this subject based on the ideXlab platform.
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mechanical performance and crack pattern analysis of aged Carbon fabric cementitious matrix cfrcm composites
Composite Structures, 2018Co-Authors: Cesare Signorini, Andrea Nobili, Federico Oyedeji FalopeAbstract:Abstract We discuss the effect of environmental exposure on mechanical performance of Impregnated Carbon Fabric Reinforced Cementitious Matrix (CFRCM) composite. Following the recently published ICC-ES AC434 guidelines, mechanical performance of prismatic composite specimens is determined on the basis of tensile uni-axial tests. Exposure to saline and alkaline aqueous solutions is considered at 28- as well as 60-day curing time. Special emphasis is placed on crack pattern evaluation as a mean to gain better insight into matrix/fabric bond quality. To this aim, the evolution of the average crack spacing and of the average crack width is determined as a function of strain for all test environments and curing times. It is found that curing time plays a significant role in mitigating the detrimental effect of aggressive environments. Furthermore, the average crack spacing provides a very reliable measure of matrix/fabric bond degradation at all test stages.
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Impregnated Carbon fabric reinforced cementitious matrix composite for rehabilitation of the finale emilia hospital roofs case study
Journal of Composites for Construction, 2017Co-Authors: Andrea Nobili, Federico Oyedeji FalopeAbstract:AbstractIn this paper, the mechanical performance of concrete beams strengthened by an Impregnated Carbon fabric–reinforced cementitious matrix (CFRCM) composite is investigated. The study is aimed...
Andrea Nobili - One of the best experts on this subject based on the ideXlab platform.
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mechanical performance and crack pattern analysis of aged Carbon fabric cementitious matrix cfrcm composites
Composite Structures, 2018Co-Authors: Cesare Signorini, Andrea Nobili, Federico Oyedeji FalopeAbstract:Abstract We discuss the effect of environmental exposure on mechanical performance of Impregnated Carbon Fabric Reinforced Cementitious Matrix (CFRCM) composite. Following the recently published ICC-ES AC434 guidelines, mechanical performance of prismatic composite specimens is determined on the basis of tensile uni-axial tests. Exposure to saline and alkaline aqueous solutions is considered at 28- as well as 60-day curing time. Special emphasis is placed on crack pattern evaluation as a mean to gain better insight into matrix/fabric bond quality. To this aim, the evolution of the average crack spacing and of the average crack width is determined as a function of strain for all test environments and curing times. It is found that curing time plays a significant role in mitigating the detrimental effect of aggressive environments. Furthermore, the average crack spacing provides a very reliable measure of matrix/fabric bond degradation at all test stages.
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Impregnated Carbon fabric reinforced cementitious matrix composite for rehabilitation of the finale emilia hospital roofs case study
Journal of Composites for Construction, 2017Co-Authors: Andrea Nobili, Federico Oyedeji FalopeAbstract:AbstractIn this paper, the mechanical performance of concrete beams strengthened by an Impregnated Carbon fabric–reinforced cementitious matrix (CFRCM) composite is investigated. The study is aimed...
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on the effect of curing time and environmental exposure on Impregnated Carbon fabric reinforced cementitious matrix cfrcm composite with design considerations
Composites Part B-engineering, 2017Co-Authors: Andrea Nobili, Cesare SignoriniAbstract:Abstract This paper investigates the effect of curing time and aggressive environmental exposure on the mechanical performance of Impregnated Carbon Fabric Reinforced Cementitious Matrix (CFRCM) composite. Following the recently published IIC-ES AC434 guidelines, saltwater, distilled water, alkali and acid resistance are investigated together with freeze-thaw cycles. Mechanical characterization is based on tensile uni-axial tests under deformation control of rectangular-base prismatic specimens. 28- and 60-day curing times are considered for the control environment as well as for saltwater and alkali resistance. Deformation is monitored via digital acquisition. Besides uni-axial tests, experimental results comprise optical and scanning electron microscopy, crack pattern analysis and failure mechanism assessment. Focus is set on the determination of the design limits for the composite system at failure for the tested environments and curing times. In particular, a comparison is drawn with established design criteria already coded for FRP systems, which introduce the concept of safety (or partial) factors. Environmental conversion factors are also defined and calculated on a statistical basis in a twofold manner, as a mean to determine the design strain and strength limits of exposed specimens from the control (unexposed) data. It is found that they provide a convenient method for assessing the composite vulnerability to the aggressive environments at different curing times.
Cesare Signorini - One of the best experts on this subject based on the ideXlab platform.
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mechanical performance and crack pattern analysis of aged Carbon fabric cementitious matrix cfrcm composites
Composite Structures, 2018Co-Authors: Cesare Signorini, Andrea Nobili, Federico Oyedeji FalopeAbstract:Abstract We discuss the effect of environmental exposure on mechanical performance of Impregnated Carbon Fabric Reinforced Cementitious Matrix (CFRCM) composite. Following the recently published ICC-ES AC434 guidelines, mechanical performance of prismatic composite specimens is determined on the basis of tensile uni-axial tests. Exposure to saline and alkaline aqueous solutions is considered at 28- as well as 60-day curing time. Special emphasis is placed on crack pattern evaluation as a mean to gain better insight into matrix/fabric bond quality. To this aim, the evolution of the average crack spacing and of the average crack width is determined as a function of strain for all test environments and curing times. It is found that curing time plays a significant role in mitigating the detrimental effect of aggressive environments. Furthermore, the average crack spacing provides a very reliable measure of matrix/fabric bond degradation at all test stages.
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on the effect of curing time and environmental exposure on Impregnated Carbon fabric reinforced cementitious matrix cfrcm composite with design considerations
Composites Part B-engineering, 2017Co-Authors: Andrea Nobili, Cesare SignoriniAbstract:Abstract This paper investigates the effect of curing time and aggressive environmental exposure on the mechanical performance of Impregnated Carbon Fabric Reinforced Cementitious Matrix (CFRCM) composite. Following the recently published IIC-ES AC434 guidelines, saltwater, distilled water, alkali and acid resistance are investigated together with freeze-thaw cycles. Mechanical characterization is based on tensile uni-axial tests under deformation control of rectangular-base prismatic specimens. 28- and 60-day curing times are considered for the control environment as well as for saltwater and alkali resistance. Deformation is monitored via digital acquisition. Besides uni-axial tests, experimental results comprise optical and scanning electron microscopy, crack pattern analysis and failure mechanism assessment. Focus is set on the determination of the design limits for the composite system at failure for the tested environments and curing times. In particular, a comparison is drawn with established design criteria already coded for FRP systems, which introduce the concept of safety (or partial) factors. Environmental conversion factors are also defined and calculated on a statistical basis in a twofold manner, as a mean to determine the design strain and strength limits of exposed specimens from the control (unexposed) data. It is found that they provide a convenient method for assessing the composite vulnerability to the aggressive environments at different curing times.
Nagi N Mansour - One of the best experts on this subject based on the ideXlab platform.
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competitive kinetic model for the pyrolysis of the phenolic Impregnated Carbon ablator
Aerospace Science and Technology, 2020Co-Authors: Nagi N Mansour, Francesco Panerai, Francisco Torresherrador, Thierry Magin, Joffrey Coheur, Maarten Arnst, Julien BlondeauAbstract:Abstract Carbon/phenolic ablators are successfully used as thermal protection material for spacecraft. Nevertheless, their complex thermal degradation is not yet fully understood, and current pyrolysis models do not reproduce important features of available experimental results. Accurate and robust thermal degradation models are required to optimize design margin policy. We investigate whether the competitive kinetic schemes commonly used to model biomass pyrolysis are appropriate to describe the thermal degradation of Carbon/phenolic composites. In this paper, we apply competitive pyrolysis mechanisms for the thermal degradation of the Carbon/phenolic ablator PICA. Model parameters are then calibrated using a robust two-step methodology: first deterministic optimization is used to obtain the best estimation of the calibration parameters based on the experimental data, then a stochastic Bayesian inference is performed to explore plausible set of solutions taking into account the experimental uncertainties. The proposed calibrated model provides an accurate description of the pyrolysis process at different heating rates. The model shows great flexibility and robustness at a similar computational cost as the traditional devolatilization models. This opens the possibility for more complex mechanisms when more experimental data becomes available.
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a high heating rate pyrolysis model for the phenolic Impregnated Carbon ablator pica based on mass spectroscopy experiments
Journal of Analytical and Applied Pyrolysis, 2019Co-Authors: Jeremie B E Meurisse, Jean Lachaud, Francesco Panerai, Brody K Bessire, Francisco Torresherrador, Julien Blondeau, Thierry Magin, Nagi N MansourAbstract:Abstract A novel model for the pyrolysis of the Phenolic Impregnated Carbon Ablator (PICA) at high heating rate is developed and calibrated based on high fidelity thermal decomposition experiments. The calibration relies on accurate quantification of pyrolysis gases obtained from mass spectroscopy analysis during thermal decomposition at fast heating rates simulating flight conditions. Model calibration is achieved by coupling the Porous material Analysis Toolbox based on OpenFOAM (PATO) with an optimization software (Dakota). A multi-objective genetic algorithm is used to fit the experimental data by optimizing the model parameters for an element and a species-based formulation. The new model captures both the material mass loss and the gaseous species produced during pyrolysis.
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multidimensional material response simulations of a full scale tiled ablative heatshield
Aerospace Science and Technology, 2018Co-Authors: Jeremie B E Meurisse, Jean Lachaud, Francesco Panerai, Chun Tang, Nagi N MansourAbstract:Abstract The Mars Science Laboratory (MSL) was protected during Mars atmospheric entry by a 4.5 meter diameter heatshield, which was constructed by assembling 113 thermal tiles made of NASA's flagship porous ablative material, Phenolic Impregnated Carbon Ablator (PICA). Analysis and certification of the tiles thickness were based on a one-dimensional model of the PICA response to the entry aerothermal environment. This work provides a detailed three-dimensional heat and mass transfer analysis of the full-scale MSL tiled heatshield. One-dimensional and three-dimensional material response models are compared at different locations of the heatshield. The three-dimensional analysis is made possible by the use of the Porous material Analysis Toolbox based on OpenFOAM (PATO) to simulate the material response. PATO solves the conservation equations of solid mass, gas mass, gas momentum and total energy, using a volume-averaged formulation that includes production of gases from the decomposition of polymeric matrix. Boundary conditions at the heatshield forebody surface were interpolated in time and space from the aerothermal environment computed with the Data Parallel Line Relaxation (DPLR) code at discrete points of the MSL trajectory. A mesh consisting of two million cells was created in Pointwise, and the material response was performed using 840 processors on NASA's Pleiades supercomputer. The present work constitutes the first demonstration of a three-dimensional material response simulation of a full-scale ablative heatshield with tiled interfaces. It is found that three-dimensional effects are pronounced at the heatshield outer flank, where maximum heating and heat loads occur for laminar flows.
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detailed analysis of species production from the pyrolysis of the phenolic Impregnated Carbon ablator
Journal of Analytical and Applied Pyrolysis, 2016Co-Authors: Hsiwu Wong, Jean Lachaud, Francesco Panerai, Jay Peck, James Assif, Nagi N MansourAbstract:Abstract Many modern materials that are being developed to protect space vehicles entering planetary atmospheres use phenolic Impregnated Carbon fiber substrates as the basic material architecture. To mitigate the heat flux into the material, the decomposition of phenolic phase generates protective gases that blow into the boundary layer and help shield the material. The goal of this paper is to measure the decomposition products of cross-linked phenolic as used in the NASA's Phenolic Impregnated Carbon Ablator (PICA). A custom batch reactor was designed to quantitatively determine detailed species production from the pyrolysis of PICA. A step-wise heating procedure using 50 K increments from room temperature up to 1250 K was followed. An initial PICA mass of 100 mg was loaded in the reactor, and the mass loss was measured after each 50 K step. Species production after each step was quantified using gas-chromatography techniques. The quantitative molar yields of pyrolysis products as a function of reaction temperature are compared to those from resole phenol-formaldehyde resin pyrolysis reported in the literature. The differences in product distributions between PICA pyrolysis and resole phenol-formaldehyde pyrolysis confirm that the decomposition products are sensitive to the composition of the material and the cross-linking process. These results indicate that characterizations need to be performed for all variations of phenolic-matrix based ablators. Such information is also critical for the development of next generation material response models.
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flow tube oxidation experiments on the Carbon preform of a phenolic Impregnated Carbon ablator
Journal of Thermophysics and Heat Transfer, 2014Co-Authors: Francesco Panerai, Nagi N Mansour, Alexandre Martin, Steven Sepka, Jean LachaudAbstract:Oxidation experiments on the Carbon preform of a phenolic-Impregnated Carbon ablator were performed in a flow-tube reactor facility, at temperatures between 700 and 1300 K, under dry air gas at pressures between 1.6×103 and 6.0×104 Pa. Mass loss, volumetric recession and density changes were measured at different test conditions. An analysis of the diffusion/reaction competition within the porous material, based on the Thiele number, allows identification of low temperature and low-pressure conditions to be dominated by in-depth volume oxidation. Experiments above 1000 K were found at transition conditions, where diffusion and reaction occur at similar scales. The microscopic oxidation behavior of the fibers was characterized by scanning electron microscopy and energy dispersive x-ray analysis. The material was found to oxidize at specific sites, forming a pitting pattern distributed over the surface of the fibers. Calcium- and oxygen-rich residues from the oxidation reactions were observed at several lo...
Chongwu Zhou - One of the best experts on this subject based on the ideXlab platform.
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red phosphorus Impregnated Carbon nanofibers for sodium ion batteries and liquefaction of red phosphorus
Nature Communications, 2020Co-Authors: Cheng Jian-xin, Tom Nilges, Mingrui Chen, Teng Li, Kai He, Zhen Li, Chongwu ZhouAbstract:Red phosphorus offers a high theoretical sodium capacity and has been considered as a candidate anode for sodium-ion batteries. Similar to silicon anodes for lithium-ion batteries, the electrochemical performance of red phosphorus is plagued by the large volume variation upon sodiation. Here we perform in situ transmission electron microscopy analysis of the synthesized red-phosphorus-Impregnated Carbon nanofibers with the corresponding chemo-mechanical simulation, revealing that, the sodiated red phosphorus becomes softened with a “liquid-like” mechanical behaviour and gains superior malleability and deformability against pulverization. The encapsulation strategy of the synthesized red-phosphorus-Impregnated Carbon nanofibers has been proven to be an effective method to minimize the side reactions of red phosphorus in sodium-ion batteries, demonstrating stable electrochemical cycling. Our study provides a valid guide towards high-performance red-phosphorus-based anodes for sodium-ion batteries. Red phosphorus is a promising anode for Na-ion batteries but suffers from large volume change upon cycling. Here the authors show a red-phosphorus-Impregnated Carbon nanofiber design in which the sodiated red phosphorus is featured by a “liquid-like” behavior and ultra-stable electrochemical performance is realized.
