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Search Publications by: Joy Dunkers (Fed)

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Displaying 76 - 98 of 98

Studying the Buried Interfacial Region With an Immobilized Fluorescence Probe

March 1, 2001
Author(s)
Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, J H. VanZanten, Joy Dunkers, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The properties of a buried epoxy / glass interfacial region were studied by covalently grafting a fluorescent probe to the glass surface. A dimethyl-amino-nitrostilbene (DMANS) fluorophore was tetherred to a triethoxy silane-coupling agent, generating a

Fiber Optic Flow and Cure Sensing for Liquid Composite Molding

February 1, 2001
Author(s)
Joy P. Dunkers, Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, S R. Kueh, J H. VanZanten, S G. Advani, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The Polymer Composites group at the National Institute of Standards and Technology has efforts in both on-line flow and cure sensing for liquid composite molding. For our flow program, a novel fiber optic real time sensor system has been developed that can

The Application of Optical Coherence Tomography to Problems in Polymer Matrix Composites

January 1, 2001
Author(s)
Joy Dunkers, Frederick R. Phelan Jr., D P. Sanders, M J. Everett, William H. Green, Donald L. Hunston, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The Composites Group at the National Institute of Standards and Technology has found optical coherence tomography (OCT) to be a powerful tool for non-destructive characterization of polymer matrix composites. Composites often exhibit superior properties to

Interfacial Response of a Fluorescent Dye Grafted to Glass

October 1, 2000
Author(s)
Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, J H. VanZanten, Joy Dunkers, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The Quality of the fiber/resin interphase region is critical to the final mechanical properties of a composite. By grafting a fluorescent dye to a glass microscope cover slip, a model interphase region can be directly studied. A blue shift and increase in

Imaging of Composite Defects and Damage Using Optical Coherence Tomography

May 1, 2000
Author(s)
Joy Dunkers, M J. Everett, D P. Sanders, Donald L. Hunston
The Composites Group at the National Institute of Standards and Technology has found optical coherence tomography (OCT) to be a powerful tool for non-destructive characterization of polymer matrix composites. Composites can be made more cost competitive by

Long-Period Gratings as Flow Sensors for Liquid-Composite Molding

May 1, 2000
Author(s)
S R. Kueh, Richard~undefined~undefined~undefined~undefined~undefined Parnas, Joy Dunkers, S G. Advanti, P S. Furrows, M E. Jones, T A. Bailey
One of the most important issues in liquid composite molding (LCM) is the complete saturation of the preform by the resin to eliminate voids or dry spots in the structure which could later adversely affect the structural integrity of the part. While there

Interfacial Response of a Fluorescent Dye Grafted to Glass

April 12, 2000
Author(s)
Joy P. Dunkers, Jospeh L. Lenahrt, J Van Zanten, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The properties of an epoxy/glass interfacial region are studied by covalently grafting a fluorescent probe to the glass surface. A dimethylaminonitrostilbene fluorophore is tethered to a triethoxysilane-coupling agent, generating a fluorescently labeled

Imaging of Impact Damage in Composites Using Optical Coherence Tomography

February 1, 2000
Author(s)
Joy Dunkers, D P. Sanders, Donald L. Hunston, M J. Everett
Resistance to impact damage is extremely important for most composites. Such damage can initiate delamination, one of the most common failure modes in composites.. Because this is such an important failure mode, many studies have tried to develop matrix

A Practical Fiber Optic Sensor to Monitor Resin Cure and Interphase Formation

January 1, 2000
Author(s)
Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, J H. VanZanten, Joy Dunkers, Richard~undefined~undefined~undefined~undefined~undefined Parnas
A fluorescent probe, covalently grafted to glass, can be used to study the glass/resin interphase region near the surface. A blue shift in fluorescence during resin cure can be monitored when the grafted dye is immersed in epoxy. The position of the

Immobilizing a Fluorescent Dye Offers Potential to Investigate the Glass/Resin Interface

January 1, 2000
Author(s)
Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, J H. VanZanten, Joy Dunkers, C G. Zimba, C A. James, S K. Pollack, Richard~undefined~undefined~undefined~undefined~undefined Parnas
Silane coupling agents are commonly applied to glass fibers to promote fiber/resin adhesion and enhance durability in composite parts. In this study, a coupling agent layer on glass was doped with trace levels of the dimethylaminonitrostilbene (DMANS)

The Effect of Processing on Interfacial Shear Properties of Composite Materials

January 1, 2000
Author(s)
Walter G. McDonough, Joy P. Dunkers, Gale A. Holmes, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The objective of our research was to extend the use of the single fiber fragmentation test to include fast reacting resin systems and to determine the effect of gelation time on interfacial shear properties. To do this work, we developed a processing

Numerical Prediction of Permeability Using a Lattice Boltzmann Method and Optical Coherence Tomography

September 23, 1999
Author(s)
Frederick R. Phelan Jr., Joy Dunkers, C G. Zimba, Kathleen M. Flynn, Richard~undefined~undefined~undefined~undefined~undefined Parnas, R C. Peterson, X Li, J G. Fujimoto
A rapid, non-destructive technique called optical coherence tomography (OCT) is used to image the microstructure of an epoxy/e-glass composite. The raw OCT data is processed and converted to a binary image, and then input into a lattice Boltzmann

A Fiber Optic Sensor for Composite Cure Monitoring

March 1, 1999
Author(s)
Joseph~undefined~undefined~undefined~undefined~undefined Lenhart, J H. Van Zanten, Joy Dunkers, C G. Zimba, C A. James, S K. Pollack, Richard~undefined~undefined~undefined~undefined~undefined Parnas
The fiber/resin interface is critical to the final mechanical properties of a composite part. The extent f cure and cross-link density affect the resin structure in this interfacial region. In addition, the type of coupling agent coating the fiber, the

Characterization of Composite Microstructure and Damage Using Optical Coherence Tomography

January 1, 1999
Author(s)
Joy Dunkers, C G. Zimba, Kathleen M. Flynn, Donald L. Hunston, R Prasankumar, X Li, J G. Fujimoto
Optical coherence tomography (OCT) is a non-destructive and non-contact technique that images microstructure within scattering media. In this work, the versatility of OCT for non-destructive evaluation is demonstrated through imaging of composite

Microstructural Characterization for Polymer Composites

January 1, 1999
Author(s)
Richard~undefined~undefined~undefined~undefined~undefined Parnas, Donald L. Hunston, Joy Dunkers, Gale A. Holmes
Characterization of composite microstructure is a crucial area since such features plays a major role in processability, performance, damage tolerance, and service life. Moreover, as the reinforcement geometries available are becoming more complex, the

Optical Coherence Tomography of Glass Reinforced Polymer Composites

January 1, 1999
Author(s)
Joy Dunkers, Richard~undefined~undefined~undefined~undefined~undefined Parnas, C G. Zimba, R C. Peterson, Kathleen M. Flynn, J G. Fujimoto, B E. Bouma
Optical coherence tomography (OCT) is a non-destructive and non-contact technique to image microstructure within scattering media. The application of OCT to highly scattering materials such as polymer composites is especially challenging. In this work, OCT

Monitoring Composites with Optical Fiber Sensor Systems

April 26, 1998
Author(s)
Richard~undefined~undefined~undefined~undefined~undefined Parnas, Joy Dunkers, R A. Neff
An inexpensive optical fiber has been interfaced with high-speed fluorescence and near infrared spectrometers to provide real-time monitoring of fast-reacting systems. Cure monitoring measurements were conducted in high volume fraction, glass reinforced

Evaluation of Dental Adhesion and Durability by Means of the Microbond Test

February 25, 1998
Author(s)
Joseph M. Antonucci, Walter G. McDonough, Joy P. Dunkers
The phenomenon of interfacial of interphase adhesion is a critical factor in determining the strength and durability of multiphase dental materials. For example, the clinical performance of acrylic polymer based dental composites depends to a large extent