TOP STORY

“Current batteries are too heavy and bulky,” says Vlachos, “and they don't last long enough. There is a tremendous need to develop alternative portable power generation devices for both military and civilian applications.”

The challenge is to devise a way to convert fuel of all types—for example, methanol, natural gas, and military fuels like JP8 and JP10—to energy. “The energy density of fuel is much higher than that of a battery,” says Vlachos, “which means that fuel-based power enables a device to be operated for a longer period of time or over a longer distance than is possible with a battery.”

“Energy is usually produced by combustion,” he continues, “but it's impossible to downsize the combustion process to the micro-scale—the device is so tiny that the flame would destroy it.”

Faced with the challenge of creating a micro-scale device that is robust, safe, and easy to start, the researchers turned to catalysis for the answer.

“The technology we're using is similar to the catalytic converter in a car,” says Vlachos. The complex process involves oxidation of carbon monoxide to carbon dioxide, reduction of nitrogen oxides to nitrogen, and oxidation of hydrocarbons (unburnt fuel) to carbon dioxide and water.

“Catalytic combustion can take advantage of the high surface area-to-volume ratio and the high transport rates characteristic of devices at this small scale,” says Vlachos.

Preliminary devices produced by the team have produced enough energy for a laptop or a cell phone. “We actually ran a student's Game Boy with propane, the same fuel that is used in backyard gas grills,” Vlachos says. A provisional patent has been issued on the technology, and the researchers are now looking both to commercialize the current technology and to expand its capabilities. “We've demonstrated the feasibility of the concept,” says Vlachos, “but we want to explore optimization and commercialization so that the technology can actually be used in civilian and military applications.” He is also interested in going beyond mere power generation to sensing and actuating functions—for example, sensing the presence of a chemical and triggering a mechanical action to change course or mitigate its effects.

Microcatalytic burner in operation

OTHER NEWS

Wool Develops New Theory to Explain Interfaces

By Diane Kukich

Chemical engineering Professor Richard P. Wool has published a seminal paper that documents a new approach to understanding the molecular aspects of adhesion at polymer-polymer interfaces. Appearing in a special issue of French journal Comptes Redus * , Wool's paper presents a theory that successfully unifies a large body of experimental work done on this topic. Polymer-polymer interfaces are important in a number of composites processes, including thermoplastic tow placement and welding. Researchers at UD-CCM have been doing work in this area for more than three decades in an effort to optimize and tailor the properties of advanced composites.

Polymer interface (one side) formed by random walk chains interdiffusing across the weld line at the bottom. The green chains are the connected chains which contribute to weld strength by connecting both sides of the interface; the yellow chains are those chains which have interdiffused but do not contribute to strength since they are not connected to both sides. The red line is the fractal diffusion front, which divides the connected from the non-connected chains in the diffusion gradient

Polymer-polymer interfaces are important in a number of composites processes, including thermoplastic tow placement and welding. Researchers at UD-CCM have been doing work in this area for more than three decades in an effort to optimize and tailor the properties of advanced composites.

“There have been many theories and many experiments by experts throughout the world,” Wool says, “but none of the theories was able to explain the phenomena occurring at all types of interfaces. Each theory was applicable to a specific interface.”

All of the work has centered on developing a basic understanding of the structure and strength of polymer interfaces. “The problem has involved four distinct parts, and over the years international experts have been assembling information about three of them. The missing piece has been the breaking of the bond.”

That piece is no longer missing. With Wool's new theory, known as the Rigidity Percolation Model, researchers can, for the first time, look at entanglement density and predict fracture strength and fracture energy. “We can now look at the molecular structure and predict the strength of the bond without any fitting parameters,” Wool says.

In short, the percolation approach unifies and interrelates the various theories and experiments on a variety of symmetric and asymmetric interfaces by providing a general connectivity relation for structure and strength.

The work has myriad applications, including not only polymer-polymer interfaces but also polymer-solid interfaces and incompatible polymer interfaces, as well as fatigue and fracture of composites, rubber materials, amorphous materials, and carbon nanotubes.

“An enormous amount of work has been done on interfaces by an enormous number of internationally renowned people,” says Wool. “This theory condenses and simplifies that work. Of all the papers I've published over the years, this is the one that I expect to have the greatest impact.”

“Richard's work resolves longstanding conflicts in our understanding of the molecular aspects of adhesion at polymer-polymer interfaces,” says UD-CCM Director Jack Gillespie. “It will be of great value to us in refining composites manufacturing processes as well as to other groups interested in adhesion and advanced composites.”

* R. P. Wool, C. R. Chimie 9, 25-44 (2006)

CCM Hosts Potential Young Engineers

By Diane Kukich

On February 28, 2006 , a group of CCM grad students contributed to the Center's educational mission by hosting Explorer Post 88 for a series of lab demos and a facilities tour. Part of the Boy Scouts of America's “Learning for Life” subsidiary career education program for young men and women ages 14 to 20, the Explorers are organized into posts, with each focusing on a different career field. Post 88's area of interest is engineering. Sponsored by ATK-Elkton, the group is co-advised by Rod Don, an avionics software engineer at ATK. The company is a member of CCM's Industrial Consortium, and Don is an alumnus and former staff member of the Center.

Preparation of a complex mold for the manufacture of a composite part

The budding engineers had the opportunity to observe the molding of a Comanche helicopter part using CCM's 2Phase rapid reformable tooling system. They also viewed several demonstrations, including the Center's thermal camera, the robotic process used to place fibers in metal-matrix composites, an application of the shear-thickening fluid (STF) technology, and testing of glass-fiber and carbon-fiber beams for comparison of strength and stiffness.

The event was organized by graduate student Solange Amoroux, with Justin Clews providing an introduction to composites. Graduate student Amanda Lim and Research Associate Hope Deffor conducted the lab demonstrations. “We're very grateful to CCM for organizing the tour and lab activities,” says Don. “The kids loved all of it, but the thermal camera and the shear-thickening fluid technology were especially popular. They had the chance to test their strength by trying to push an ice pick through Kevlar impregnated with STF.” “ATK certainly enjoys its ongoing partnership with the Center,” he continues, “and that affiliation enabled us to provide these young men and women with insight into what engineering is all about.”

Stab demonstration on shear-thickening fluid impregnated Kevlar®

Liquid Body Armor Technology Licensed by UD

1:22 p.m., Feb. 24, 2006--A new technology developed by a University of Delaware researcher to improve ballistic fabrics and protective armor products is now being commercialized. Armor Holdings Inc., a leading manufacturer of security products and vehicle armor systems, announced Friday, Feb. 24, that it has been selected as an exclusive licensee by the UD Technology Corp. (UDTC). The unique shear thickening fluid technology has been under active development for the last five years at the UD Center for Composite Materials by Norman Wagner, Alvin B. and Julia O. Stiles Professor of Chemical Engineering, in cooperation with Eric Wetzel of the U.S. Army Research Laboratory's Weapons and Materials Research Directorate, a UD alumnus. Shear thickening fluid can be intercalated into conventional ballistic fabrics or other materials used in armor applications, allowing them to remain flexible under normal wear but simultaneously becoming resistant to penetration when struck by a spike, knife or high velocity projectile or fragment by effectively spreading the energy of the impact over a larger area.

Norman Wagner, Alvin B. and Julia O. Stiles Professor of Chemical Engineering Photo and article courtesy of UDaily

Tony Russell, chief technology officer for Armor Holdings, said the new technology “has the potential to unlock entirely new and better solutions that will leapfrog to the next generation of armor and other lifesaving equipment.” He added that researchers at both UD and with the Army “have done an outstanding job of creating the core technology and demonstrating its advantages.”

CONSORTIUM

JOB OPPORTUNITIES

Boeing Philadelphia has numerous intern openings for Mechanical, Electrical and Comp. Science majors. The job details and info on how to apply is provided in the links below. The first link is for Electrical and Comp. Science and the second for Civil, Mechanical, Aerospace, Aeronautical, Material and Process.

• Intern - Student Engineer Electrical or Computing
• Intern - Student Engineer Mech, Struct, Test, System, M&P

NEW PUBLICATIONS

Journals

Denli, H., J. Q. Sun, and T-W. Chou, “Minimization of Acoustic Radiation from Thick Multilayered Sandwich Beams,” AIAA Journal , 43 (11), pp. 2337-2341, 2005.

Gillespie, Jr., J. W., B. A. Gama, C. E. Chicanowski, and J. R. Xiao, “Interlaminar Shear Strength of Plain Weave S2-Glass/SC 79 Composites Subjected to Out-of-Plane High Strain Rate Compressive Loadings,” Composite Science and Technology , 65 (11-12), pp. 1891-1908, 2005.

Li C. Y. and T. W. Chou, “Modeling of Heat Capacities of Multi-Walled Carbon Nanotubes by Molecular Structural Mechanics,” Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing , 409 (1-2), pp. 140-144, November 15, 2005.

Li, C. Y., R. S. Ruoff, and T. W. Chou, “Modeling of Carbon Nanotube Clamping in Tensile Tests,” Composites Science and Technology , 65 (15-16), pp. 2407-2415, December 2005.

Mahdi, S., B. A. Gama, S. Yarlagadda, and J. W. Gillespie, Jr., “Structural Repair of Composite Structural Armor, ” Journal of Composite Materials , 39 , (19), pp. 1695-1717, 2005.

Thielemans, W. and R. P. Wool, “Kraft Lignin as Fiber Treatment for Natural Fiber-Reinforced Composites,” Polymer Composites , 26 (5), pp. 695-705, October 2005.

Thielemans, W., I. M. McAninch, V. Barron, et al., “Impure Carbon Nanotubes as Reinforcements for Acrylated Epoxidized Soy Oil Composites,” Journal of Applied Polymer Science , 98 (3), pp. 1325-1338, November 5, 2005.

Thielemans, W. and R. P. Wool, “Butyrated Kraft Lignin as Compatibilizing Agent for Natural Fiber Reinforced Thermoset Composites,” Composites Part A-Applied Science and Manufacturing , 35 (3), pp. 327-338, 2005.

Xiao, J. R., B. A. Gama, and J. W. Gillespie, Jr., “An Analytical Molecular Structural Mechanics Model for the Mechanical Properties of Carbon Nanotubes,” International Journal of Solids and Structures , 42 (11-12), pp. 3075-3092, 2005.

Zhou, F., S. G. Advani, and E. D. Wetzel, “Characterization of the Viscous Behavior of Compacted Ceramic Particles under Shear and Pressure Loads,” International Journal of Applied Mechanics and Engineering , 10 (3), pp. 505, 2005.

Zhou, F., S. G. Advani, and E. D. Wetzel, “Slow Drag in Polydisperse Granular Mixtures under Pressure, Physical Review E , 71 , pp. 125506, 2005.

Duan, Y., M. Keefe, T. Bogetti, and B. Powers, “Finite Element Modeling of Transverse Impact on a Ballistic Fabric,” International Journal of Mechanical Sciences , 48 , pp. 33-43, 2006.

Duan, Y., M. Keefe, T. Bogetti, B. Cheeseman, and B. Powers, “A Numerical Investigation of the Influence of Friction on Energy Absorption by a High-Strength Fabric Subjected to Ballistic Impact,” International Journal of Impact Engineering , 32 , pp. 1299-1312, 2006.

Lu, J., S. Knot, and R. P. Wool, “New Sheet Molding Compound Resins from Soybean Oil, I. Synthesis and Characterization,” Polymer , 46 (1), pp. 71-80, January 6, 2005.

Lu, J. and R. P. Wool, “Novel Thermosetting Resins for SMC Applications from Linseed Oil: Synthesis, Characterization and Properties,” Journal of Applied Polymer Science , 99 (5), pp. 2481-2588, March 5, 2006.

Wool, R. P., “Adhesion at Polymer-Polymer Interfaces: A Rigidity Percolation Approach,” Comptes Rendus Chimie , 9 (1), pp. 25-44, January 2006.

Xiao, J. R., S. L. Lopatnikov, B. A. Gama, and J. W. Gillespie, Jr., “Nanomechanics on the Deformation of Single- and Multi-Walled Carbon Nanotubes under Radial Pressure,” Materials Science and Engineering, A , 416 (1-2), pp. 192-204, 2006.

Proceedings

Bonnaillie, L. M. and R. P. Wool, “Thermosetting Foam with a High Bio-Based Content from Acrylated Epoxidized Soybean Oil and Carbon Dioxide,” 20 th ASC Technical Meeting , Philadelphia , PA , September 7-9, 2005.

Duan, Y. M. Keefe, T. A. Bogetti, and B. Powers, “Modeling Ballistic Impact of a Lead Projectile onto a Flexible Fabric Laminate,” American Society of Composites (ACS) 20 th Annual Technical Conference , (paper # 13), Drexel University, Philadelphia, PA, September 7-9, 2005.

Ishiguro, K., S. S. Sangari, and J. C. Seferis, “The Influence on Mechanical Properties of Epoxy Foam Matrix Structural Differentiations,” Society for the Advancement of Materials and Process Engineering (SAMPE) Fall Technical Conference 2005, Seattle , WA , October 21 – November 3, 2005.

Killgore, J. P., S. S. Sangari, T. Jensen, and J. C. Seferis, “B-Stage Control of Swellling in Layered Silicate Epoxy Polynanomers,” Society for the Advancement of Materials and Process Engineering (SAMPE) Fall Technical Conference 2005 , Seattle , WA , October 21 – November 3, 2005.

Lu, L., S. S. Sangari, and J. C. Seferis, “Effect of Processing and Interface Morphology on Carbon Fiber Modified Interlayer toughened Polynanomatrix Composites,” Society for the Advancement of Materials and Process Engineering (SAMPE) Fall Technical Conference, 2005, Seattle, WA, October 21 – November 3, 2005.

McAninch, I. M. and R. P. Wool, “Aggregation Behavior in Carbon Nanotube/Modified Soy Oil Composites,” 20 th ASC Technical Meeting , Philadelphia , PA , September 7-9, 2005.

Tierney, J. J., S. Andersen, S. Yarlagadda , J. W. Gillespie, Jr., E. Hyland, D. Crayon, a. Littlefield, J. Tzeng, and L. Burton, “Optimal Design of Cylindrical Steel/Composite Hybrid Structures for Gun Barrel Applications,”, SAMPE Symposium , Long Beach, CA, 2005.

Wool, R. P., “Bio-Based Composites Research,” SAMPE, Seattle , WA , 2005.

Wool, R. P., “Bio-Based Polymers and Composites,” GCE05 , DC, 2005.

Zhu, L. and R. P. Wool, “Acrylate Rubber-Organoclay Hybrid Nanocomposites from Renewable Resources, 20 th ASC Technical Meeting , Philadelphia , PA , September 7-9, 2005.

Zhu, L. and R. P. Wool, “Biodegradable Elastomers from Plant Oils, 20 th ACS Annual Meeting , Washington, DC, August 28 – September 1, 2005

Book Chapters

Wool, R. P., Polymer Diffusion: Reptation and Interdigitation , Handbook of Adhesion, 2 nd Edition, D. E. Packham , Ed., Wiley, New York, 341, 2005.

Wool, R. P., Polymer –Polymer Adhesion: Incompatible Interfaces , Handbook of Adhesion, 2 nd Edition, D. E. Packham , Ed., Wiley, New York, 344, 2005.

Wool, R. P., Polymer –Polymer Adhesion Models , Handbook of Adhesion, 2 nd Edition, D. E. Packham, Ed., Wiley, New York, 347, 2005.

Wool, R. P., Polymer –Polymer Adhesion: Molecular Weight Dependence , Handbook of Adhesion, 2 nd Edition, D. E. Packham, Ed., Wiley, New York, 350, 2005.

Wool, R. P., Polymer –Polymer Adhesion: Weld Strength , Handbook of Adhesion, 2 nd Edition, D. E. Packham, Ed., Wiley, New York, 353, 2005.

Books

 Wool, R. P., Bio-Based Polymers and Composites , with X. S. Sun, Elsevier Press, Burlington, MA, 620 pages, ISBN-13:978-0-12-763952-9, 2005.

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