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Toward higher-performing space vehicles
XuM is proving particularly useful in two other Lehigh-NASA projects.
In a collaboration with GSFC's Powell,
Wojciech Misiolek, director of Lehigh's
Institute for Metal Forming, is seeking to disperse boron nanoribbons in aluminum matrix composites to improve the strength and stiffness of the composites and thus reduce the weight of the composite structures. The materials are used in aerospace applications, and NASA hopes Misiolek's work leads to lighter, stronger space vehicles with improved thermal stability and fuel efficiency.
"We believe that nanoribbons, because of their size and ability to disperse, will function as a strengthening agent for aluminum matrix systems," says Misiolek, who collaborates with experts in Europe, Australia, New Zealand and Brazil.
"At present, aluminum matrix composites dispersed with microscale powders of silicon carbide or alumina are used in the automotive and aerospace industries. We're hoping to improve the mechanical properties of these composites by 30 percent with nanoribbons of boron."
In a second project, nanoparticles of silica and rubber are demonstrating the potential to increase the interlaminar fracture toughness of carbon-fiber composites, which are also used in aerospace applications.
Ray Pearson, director of Lehigh's
Center for Polymer Science and Engineering, studies toughening mechanisms in thermosetting resins used in composites. Low interlaminar fracture toughness has been the "Achilles' heel" in fiber composites, says Pearson, because resin-rich regions between plies enable flaws and cracks to travel unimpeded by fibers.
Engineers have long used microscale particles of rubber to toughen the matrix of composite materials and to improve the interlaminar fracture toughness, says Pearson. A consensus was formed in the 1990s that 200-nm was the optimal particle size and that decreasing that size would decrease the particles' effectiveness as toughening agents. Pearson, working with the international chemicals giant Arkema Inc., has recorded a five-fold increase of interlaminar fracture toughness in an epoxy resin containing a tri-block copolymer that selfassembles into 40-nm rubber nanoparticles. Additional improvements are obtained when a few percent of 20-nm particles of nanosilica are added to the nano-rubber.
"We are continuing to investigate why these nanoparticles are more effective toughening agents than their microscale counterparts," says Pearson. "We're particularly interested in finding out what kind of mechanisms the nanoparticles are triggering. What we've seen so far is a lot of ductility occurring, because of the presence of rubber nanoparticles, in a material that would otherwise be brittle."
In other projects, materials scientists led by
Prof. Richard Vinci are seeking to control the mechanical properties of thin film materials exposed to the extreme cold of space. Electrical engineers are developing sensor arrays to monitor space environments, and are also studying methods of protecting sensitive equipment on spacecraft from the ultraviolet rays of the sun and the lethal radiation emitted by some planets. Engineers and physicists are studying new ways of dispersing and sorting carbon nanotubes.
Minding the future
The relationship between Lehigh and NASA dates to the early 1970s, when the space agency asked
Joseph Goldstein, former vice president for research at Lehigh, to study meteorites and moon rocks.
In 1983,
Mohamed El-Aasser, Lehigh provost and professor of chemical engineering, helped design a reactor that, in zero gravity aboard the Challenger STS-6, synthesized the first products ever made in space – polystyrene latex microspheres for calibrating microscopic objects.
In 2005, seniors in Lehigh's failure-analysis class became the first college students in the U.S. to be asked by NASA to
evaluate debris from the Columbia space shuttle.
As part of the current Lehigh-NASA partnership, five Lehigh undergraduates are doing summer internships at GSFC. NASA is also sponsoring two teams of students in Lehigh's
Integrated Product Development (IPD) program. One team is designing a boom that will stabilize a spacecraft against the earth's gravity. The second is helping to design a special vacuum chamber that will simulate the environments on the moon and on Mars as they pertain to dust migration and charging. Both teams are supervised by former NASA astronaut
Terry Hart, a member of Lehigh's Class of 1968 and an adjunct professor of mechanical engineering and mechanics at the university.
Mindful of the need to inspire future engineers and scientists, Lehigh faculty and students lead projects at two nearby NASA Explorer Schools – Harrison-Morton Middle School in Allentown, Pa., and Broughal Middle School in Bethlehem, Pa. The outreach efforts at these and other schools are led by Henry Odi, executive director for
academic outreach at Lehigh, and Andrea Harmer, CAMN director of Web-based education.
Lehigh is furnishing Broughal Middle School with GIS (Geographic Information Systems) technology, satellite images and remote sensing. Broughal students have toured Lehigh's microscopy labs, and will learn to use Lehigh's microscopes remotely.
Students at Harrison-Morton are not waiting for official approval to commence their own exploration of space. With help from Lehigh, which has leveraged a grant from NSF's
STEM (Science, Technology, Educational and Mathematics) program, the middle school has built a
lifelike Martian landscape in its basement. In their technology classroom on the second floor, eighth-graders learn the basics of computer programming from Lehigh students and professors. Then, like real engineers at mission control, the students guide the robots across the rocky "Mars Yard" terrain two floors below and direct them to fetch rocks to analyze.
