Dr. Louis J. Ghosn Profile

Dr. Louis J. Ghosn

at NASA Glenn Research Ctr

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Author

Publications (4)

Proceedings Article | 26 April 2007 Paper

A combined NDE/FEA approach to evaluate the structural response of a metal foam

Louis Ghosn, Ali Abdul-Aziz, Sai Raj, Richard Rauser

Proceedings Volume 6526, 65262U (2007) https://doi.org/10.1117/12.715215

KEYWORDS: Foam, Metals, 3D modeling, Finite element methods, Solids, 3D image processing, Computed tomography, X-ray computed tomography, Aerospace engineering, Nondestructive evaluation

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Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

Proceedings Article | 19 May 2005 Paper

Structural assessment of metal foam using combined NDE and FEA

Louis Ghosn, Ali Abdul-Aziz, Philippe Young, Richard Rauser

Proceedings Volume 5767, (2005) https://doi.org/10.1117/12.601753

KEYWORDS: Foam, Metals, 3D modeling, Finite element methods, Solids, 3D image processing, Nondestructive evaluation, Computed tomography, X-ray computed tomography, Aerospace engineering

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Proceedings Article | 20 July 2004 Paper

A combined NDE-fatigue testing and three-dimensional image processing study of a SiC/SiC composite system

Ali Abdul-Aziz, Louis Ghosn, George Baaklini, Richard Rauser, John Zima

Proceedings Volume 5393, (2004) https://doi.org/10.1117/12.538241

KEYWORDS: Composites, Computed tomography, Nondestructive evaluation, 3D image processing, Image processing, Silicon carbide, 3D modeling, X-ray computed tomography, Ceramics, Coating

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Non destructive evaluation (NDE) is a critical technology for improving the quality of a component in a cost-sparing production environment. NDE detects variations in a material or a component without altering or damaging the test piece. Using these techniques to improve the production process requires characterization of the faults and their influence on the component performance. This task depends on the material properties and on the complexity of the component geometry. Hence, the NDE technique is applied to study the structural durability of ceramic matrix composite materials used in gas turbine engine applications. Matrix voids are common anomalies generated during the melt infiltration process. The effects of these matrix porosities are usually associated with a reduction in the initial overall composite stiffness and an increase in the thermal conductivity of the component. Furthermore, since the role of the matrix as well as the coating is to protect the fibers from the harsh engine environments, the current design approach is to limit the design stress level of CMC components to always be below the first matrix cracking stress. In this study, the effect of matrix porosity on the matrix cracking stress is evaluated using a combined fatigue tensile testing, NDE, and 3 D image processing approach. Computed Tomography (CT) is utilized as the NDE technique to characterize the initial matrix porosity’s locations and sizes in various CMC test specimens. The three dimensional volume rendering approach is exercised to construct the 3 D volume of the specimen based on the geometric modeling of the specimen's CT results using image analysis and geometric modeling software. The same scanned specimens are then fatigue tested to various maximum loads and temperatures to depict the matrix cracking locations in relation to the initial damage. The specimen are then re-scanned and checked for further anomalies and obvious changes in the damage state. Finally, rendered volumes of the gauge region of the specimen is generated and observed to check damage progression with increasing cycles. Observations and critical findings related to this material are reported.

Proceedings Article | 1 August 2003 Paper

Combined NDE/finite element technique to study the effects of matrix porosity in the behavior of ceramic matrix composites

Ali Abdul-Aziz, Louis Ghosn, George Baaklini, Ramakrishna Bhatt

Proceedings Volume 5046, (2003) https://doi.org/10.1117/12.484775

KEYWORDS: Computed tomography, 3D modeling, Finite element methods, Composites, Ceramics, 3D image processing, Nondestructive evaluation, Coating, X-ray computed tomography, Roads

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