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Glen Burnie, MD, United States

Djordjevic B.B.,Materials and Sensors Technologies Inc.
International SAMPE Symposium and Exhibition (Proceedings) | Year: 2010

Safe use of composite materials in critical structural applications demands independent structural integrity verification. Traditional ultrasonic non-destructive methods are inappropriate and often misleading when applied to anisotropic and complex composite materials. Complexity of the advanced composite materials structures represents challenges in developing optimized ultrasonic tests that can directly characterize mechanical properties of the material. In advanced technology applications such as aerospace and with industrial emphasis on economics and safety, it is critical to develop and apply new robust and practical ultrasonic nondestructive test (NDT) methods. New guided wave laser ultrasonic sources and small aperture receiving sensors configurations enable testing of advanced composites far beyond conventional ultrasonic capabilities. In contrast to pseudo-imaging methodology such as ultrasonic C-scan, guide wave response to in plane mechanical state of the composite is analyzed and this emerging technology explores the ability of the inhomogeneous, anisotropic composite material to propagate ultrasonic guided waves over a range of distances and part configurations. Appropriate customizing of ultrasonic transduction process enables measurements of material properties and estimate of defect conditions along in-plane sound propagation path. From guided wave acoustic response, one can develop meaningful estimate of material modulus, fatigue damage, thermal damage and sense mechanical defect conditions without need to point-vise scan the complete structure. Source


Djordjevic B.B.,Materials and Sensors Technologies Inc.
Materials Evaluation | Year: 2014

Composite mechanical damage is typically in the form of delaminations or disbonds (laminate-to-laminate or laminate-to-core), broken fibers due to impact, fatigue damage that affects the zone of composite material via micro cracking, fiber delaminations, fiber breaks and overall loss of mechanical modulus. It can be caused by thermal damage from fire, engine bleed air leaks, and prolonged exposure to heat above resin cure temperatures, as well as a combination of environmental effects due to extreme operational conditions. Ultrasonic testing (UT) enables extensive characterization of the composite materials' integrity, and many ultrasonic methodologies are in current use for the inspection of large-scale composites. Challenges for UT of composites are more complex and require better understanding of the ultrasound signal attenuation, ultrasonic signals frequency dependent behavior and consideration of ultrasonic signal modality. UT of composites for optimized operations requires additional consideration of the inspection parameters and a fresh evaluation of applicable UT modes. It is improper to extrapolate metals UT experience to the composite structures. Source


Djordjevic B.B.,Materials and Sensors Technologies Inc.
International Journal of Microstructure and Materials Properties | Year: 2014

Laser ultrasonic sources and guided wave sensing methods, using non-contact transducers or sub-wavelength miniature sensors, are utilised to nondestructively evaluate structural defects or composite material properties. These methods enable in-plane ultrasonic signal testing and very accurate measurements of the ultrasonic directional velocities. Additionally, sensing of the guided wave modes changes, in the geometrically complex composite structures, enables detection of the material structural damage. Experimental data demonstrates reproducibility and feasibility of such tests to sense discontinuity (crack) type defects and characterise micro structural damage in the composite materials. Copyright © 2014 Inderscience Enterprises Ltd. Source


Aissa B.,Materials and Sensors Technologies Inc. | Aissa B.,Ecole Polytechnique de Montreal | Tabet N.,King Fahd University of Petroleum and Minerals | Nedil M.,Laboratoire Of Recherche Telebec En Communications Souterraines | And 4 more authors.
Applied Surface Science | Year: 2012

We report on the electromagnetic (EM) absorption potential and microwave heating capacity of amorphous hydrogenated silicon carbide thin films (a-SiC:H) in the 1-16 GHz frequency domain. a-SiC:H thin films with typical thickness of 1 μm were deposited by plasma enhanced chemical vapor deposition on [1 0 0] undoped silicon substrates, and exhibit a deep EM absorption - up to 96% of the total EM energy irradiation - which is systematically converted into heat. Two-wavelength pyrometer tests show that temperatures exceeding 2000 K can be reached in a very short time, less than 100 s exposure to microwaves, showing a promising potential for specific microwave heating applications. © 2012 Elsevier B.V. All rights reserved. Source


Djordjevic B.B.,Materials and Sensors Technologies Inc.
12th International Conference of the Slovenian Society for Non-Destructive Testing: Application of Contemporary Non-Destructive Testing in Engineering, ICNDT 2013 - Conference Proceedings | Year: 2013

Laser ultrasonic sources and guided wave sensing methods, using sub-wavelength miniature sensors, are utilized to nondestructively evaluate composite materials. These methods enable in-plane characterization of the ultrasonic signals directional velocities. Additionally, sensing of the guided wave modes changes, in the geometrically complex composite structures, enables detection of the material structural damage. Experimental data demonstrates reproducibility and feasibility of such tests to monitor and characterize development of micro structural damage in the composite materials. Source

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