TOP STORY

Previously, the addition of magnetic components to composites came with a price. “Magnetic materials are ‘lossier' than dielectric materials,” Xiao explains, “which means that they absorb more energy. When energy is absorbed, the signal transmitted is poorer.”

“We now have a new technology to mitigate lossiness,” he continues. “With nanostructures, we can solve the problem.” He and his research team are using two platforms to address the issue.

The first is the development of an effective technique to deform iron particles into thin flakes that confer good magnetic properties on the composite. The flakes are only a few hundred nanometers thick but a few hundred microns in length and width, so they have a high aspect ratio.

“Deforming the iron particles into flakes results in good high-frequency properties—in the radio to microwave range, which is suitable for communications applications,” Xiao says.

In an effort led by CCM Assistant Director Shridhar Yarlagadda, the flakes were mixed with a styrene-based liquid resin and aligned during the extrusion process. Test results confirmed a significant degree of alignment and showed that good permeability and permittivity measurements could be achieved with small losses when the loading fraction of Fe flakes was below 30 percent.

A second project, initiated more recently with CCM Associate Scientist Joe Dietzel, is focused on using an electrospinning process to make polymer panels with integrally embedded very long, very thin nanowires.

“Our preliminary data on this process show incredible results,” says Xiao, “but we still need to do more work to confirm them. The potential is there for these materials to have a tremendous impact.”

OTHER NEWS

The purpose of the Student Poster Session was to highlight composite materials research conducted by both undergraduate and graduate students. Posters were judged for the level quality? of research as well as presentation. Twenty-six posters were presented at the session.

Lim, who is advised by Prof. John W. Gillespie Jr., earned her bachelor's degree in mechanical engineering at the University of Southern California.

Her doctoral research . sponsored by the Army Research Office in collaboration with our CCM's colleagues at Tuskegee University , focuses on the modeling and characterization of shear-thickening fluids (STF) as a field - responsive material.

“Over the past four years, STF-infused fabrics have been proven by Dr. Wagner's research group and Dr. Wetzel of ARL to outperform neat fabrics under various threats, including spike, stab, and low-velocity projectile,” Lim says.

“Given a plain woven fabric with discrete domains of STF, we want to know two things: How long does it take the STF to thicken? and What are the properties of the post-transitioned STF?”

To answer these questions, a new approach, using the compression-shear split-Hopkinson pressure bar (CS-SHPB) experimental technique, has been developed to determine the stress-strain behavior of a viscous fluid under dynamic compression-induced shear as a function of strain rate. Lim's poster addresses the questions above using this technique approach .

Although she received a small cash prize for winning the poster contest, Lim feels that she took away far more than money. “It was all-around a really good experience for me,” she says. “The ASC meeting attracts top researchers in composites, and it was great to have the opportunity to speak with them and get their feedback on my work.”

“My advisor sends me to at least one or two conferences every year,” she continues. “I think every grad student should have this experience.”

“There were a lot of quality posters at the ASC meeting,” Gillespie says, “but I'm not surprised that Amanda won. She is an excellent student who is making significant contributions to our understanding of STF materials .” ”.

UDaily Story:

Published 4:37 p.m., Oct. 4, 2006
UD scientists use carbon nanotubes to detect defects in composite materials
Two University of Delaware researchers have discovered a means to detect and identify damage within advanced composite materials by using a network of tiny carbon nanotubes, which act in much the same manner as human nerves. Full Story in UDaily

UD Civil and Environmental Engineering Faculty Positions Open

The Department of Civil and Environmental Engineering invites applications for two tenure-track faculty positions starting Fall 2007. Please click here for more information.

CCM would like to welcome 3F, LLC, Raleigh, NC, and Ashland Performance Materials, Dublin, OH, to our University-Industry Consortium. We also wish to thank CASE Engineering, Newark, DE, Daikin America, Inc., Orangeburg, NY, Green Tweed & Company, Kulpsville, PA, and Martin Marietta, Raleigh, NC, for their ongoing support, and for continuing to participate in consortium activities. To learn more about our Industry-University Consortium, please visit

http://www.ccm.udel.edu/Consortium/members.html .

NEW PUBLICATIONS

Conference Proceedings

Lim, A. S., B. A. Gama, S. L. Lopatnikov, and J. W. Gillespie, Jr., “Post Transition Characterization of a Shear-Thickening Fluid (STF) via Compression-Shear Split Hopkinson Pressure Bar (CS-SHPB) Technique,” 21 st Annual Technical Conference, American Society for Composites, Dearborn, MI, September 17-20, 2006.  

Xiao, J. R. and J. W. Gillespie, Jr., “A Phenomenological Failure Criterion for Composite Laminates under Interlaminar Shear and Compression,” 21 st Annual Technical Conference, American Society for Composites, Dearborn , MI , September 17-20, 2006.  

Doherty, S. P., M. Takemori, J. M. Deitzel, D. Heider, J. W. Gillespie, Jr., A. Shah, and A. Giaya, “Thermal Degradation of Carbon Fiber/Cyanate Ester Resin Composites Filled with Clay Silicate Nanoparticles,” Thermoset Resin Formulators Association Annual Meeting, Montreal Quebec, Canada, September 12, 2006. 

Li, C. and T-W. Chou, “Charge Distributions on Single-Walled Carbon Nanotubes by an Atomistic Moment Method,” Proceedings of the American Society of Composites- 21 st Technical Conference , Dearborn , MI , September 17-20, 2006. 

Invited Talks/Presentation

Journals

Xiao, J. R. and J. W. Gillespie, Jr., “Nonlinear Deformation and Progressive Failure of Multi-walled Carbon Nanotubes under Internal Radial Pressure,” Physical Review B , 74 , 155404, October 2006.  

Thostenson, E. T. and T-W. Chou, “Carbon Nanotube Networks: Sensing of Distributed Strain and Damage for Life Prediction and Self-Healing,” Advanced Materials , available on-line: http://dx.doi.org/10.1002/adma.200600977 , 2006.  

Thostenson, E. T. and T-W. Chou, “Processing-Structure-Multi-Functional Property Relationship in Carbon Nanotube/Epoxy Composites,” Carbon , 44 (14) 2869-3148, 2006.  

Egres, R. G., F. Nettesheim, and N. J. Wagner, “Theo-SANS Investigation of Acicular-Precipitated Calcium Carbonate Colloidal Suspensions Through the Shear Thickening Transition,” Rheology , 50 (5), pp. 685-709, 2006.  

Suwanwatana, W., and J. W. Gillespie, Jr., “Influence of Particle Size on Hysteresis Heating Behavior of Nickel Particulate Polymer Films,” Composites Science and Technology , available on-line: http://dx.doi.org/10.1016/j.compscitech.2006.02.033 .

Gazonas, G. A., D. S. Weile, R. Wildman, and A. Mohan, “Genetic Algorithm Optimization of Phononic Bandgap Structures,” International Journal of Solids and Structures, 43 , pp. 5851-5866, 2006. 

Li, C. and T-W. Chou, “ Charge-Induced Strains in Single-Walled Carbon Nanotubes,” Nanotechnology , 17 , pp. 4624-4628, 2006.

Li, C. and T-W. Chou, “ Electrostatic Charge Distribution On Single-Walled Carbon Nanotubes,” A pplied Physics Letters , 89 , pp. 063103, 2006.

Li, C. and T-W. Chou, “ Multiscale Modeling of Compressive Behavior of Carbon Nanotube/Polymer Composites,” Composites Science and Technology , 66 , pp. 2409-2414, 2006.

Li, and T-W. Chou, “Elastic Wave Velocities in Single-Walled Carbon Nanotubes,”  Physical Review B, 73 , 245407, 2006.

Li, C. and T-W. Chou, “Atomistic Modeling ofCarbon Nanotube-based Mechanical Sensors,” Journal of Intelligent Materials Systems and Structures 17 , 247-254, 2006.

Li, C. and T-W. Chou, “Static and Dynamic Properties of Single-walled Boron Nitride Nanotubes,” Journal of Nanoscience and Nanotechnology , 6 (1) pp. 54-60, 2006.

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