Vol. 19, No. 21

Feb. 24, 2000

Composites team focuses on world’s largest aircraft

The Department of Mechanical Engineering has received a grant increment for this year from the U.S. Air Force Office of Scientific Research (AFOSR) for $349,986, to continue its work in the planning and development of what could become the world’s largest aircraft, the Global Range Transport (GRT). This Advanced Composite Materials Research for the New World Vistas grant is the third installment in the initial three-year, $1.4 million research grant to UD. According to principal investigator Jack R. Vinson, H. Fletcher Brown Professor of Mechanical and Aerospace Engineering, the GRT, destined for operation by the year 2020, will be designed to meet future defensive and humanitarian needs of the U.S. military in the world of ever-changing allies and potential enemies. The concept of the GRT evolved from a U.S. Air Force (USAF) study in 1998 that focused on the possible role of the Air Force over the next 50 years. “It’s clear that we have no idea who our friends or enemies will be during the next 50 years,” Vinson said. “The Air Force decided it needed a global range transport that could be flown out of the United States with the capability of flying anywhere in the world.” The upside to this concept, according to Vinson, is that if you have the capability to reach any point in the world, you do not have to rely totally on having military bases in every part of the world. The success of the GRT will depend greatly on finding the correct blending of the very latest technological innovations in aircraft construction and design. “This research involves all the basic structural, material and manufacturing aspects of the fuselage,” Vinson said. “It also will involve advanced composite materials using sandwich construction and liquid injection molding.” Tentative plans call for a 20-foot-wide cargo space, similar in area to two, 10-foot-wide traffic lanes found on many American highways. This flying highway will be used to transport all manner of vehicles, including tanks and other heavy equipment that must conform to the minimum 14-foot clearance height of bridges and overpasses on interstate highways. The research on the use of sandwich construction with liquid injection molding for the fuselage incorporates the work of nine professors at five universities. In addition to his duties as principal investigator, Vinson is looking at the role of structural analysis and structural optimization (design) in determining the minimum weight for the GRT structures. “It looks like we will be using advanced composite materials in a sandwich construction with an advanced architectural design,” Vinson said. “The sandwich construction would have one type of material on the plane’s outer surface, another on the inside of the sandwich wall construction with a special light weight core.” Liquid injection involves placing fibers as laminates or in various woven or braided configurations as preforms. It may also include placing a foam core for the sandwich construction. Then a polymer is shot into the mold at the proper temperature and pressure to infiltrate the liquid among these fibers and foam where it will then harden or cure as the matrix material. Suresh G. Advani, mechanical engineering, is working on developing the primary methods of liquid injection molding and the computer simulation of the manufacturing process. “We need to know how much material will be needed and how to get the desired properties of these materials as well as knowing how to place the fibers as reinforcers,” Vinson said. “Dr. Advani will be using computer program to aid his research.” Tsu-Wei Chou, mechanical engineering, is working to determine whether to use continuous fiber laminate composites or textile composites, such as woven, braided or three-dimensional composites, to arrive at the optimum structural design for the super transport. Jian Q. Sun, mechanical engineering, is looking at ways to suppress structural noise and vibration in the GRT. “In modern aerospace engineering, the plane is usually built before someone thinks about noise problems and when conventional soundproofing methods are used, they just add weight,” Vinson said. “With sandwich construction, we may be able to suppress noise and vibration by choosing the proper core space material while at the same time making use of its attendant thermal insulation and structural properties as well.” Joining the UD researchers is Ole T. Thomsen, on sabbatical from Aalborg University in Denmark. Thomsen is working on structural analysis and optimization, using computational methods he developed earlier. Other universities involved in the project include the University of Cincinnati, where two professors are involved with finite element and alternative analysis methods. At the University of Missouri, a professor will be examining thermal stress problems since the structure will undergo fairly severe temperature changes. A Georgia Tech professor will be examining buckling and stability problems, while a researcher at Ohio State University will be focusing on testing with a special emphasis on the structural behavior of the aircraft. Vinson said the research program grant also involves a number of graduate students. With researchers now in the last year of the original three-year grant, Vinson and his colleagues are in the process of submitting a proposal for a second, three-year grant from the AFOSR. Vinson said he believes that the intense research considerations undertaken by the project contributors is a positive demonstration of the ability of researchers at five separate universities to function as a cohesive unit. The research has resulted in 24 papers to date, and there have been three sessions on sandwich construction at each of the previous two annual meetings of the American Society of Mechanical Engineers (ASME). Indicative of how rapidly the research is moving is the fact that six sessions on composite sandwich construction are scheduled for this year’s ASME November meeting in Atlanta. Vinson, who joined the UD faculty in 1964, chaired the then Department of Mechanical and Aerospace Engineering from 1965-79. He founded the Center for Composite Materials in 1974 and served as its first director. Vinson is a fellow in the ASME and the American Institute of Aeronautic and Astronautics. He also is editor-in-chief of the Journal of Sandwich Structure and Materials, and past president of the American Society for Composites. The author of six textbooks and 175 research papers, Vinson’s latest book, The Behavior of Sandwich Structure of Isotropic and Composite Materials, is one of only two books in print on that subject. Enthusiastic about the growing acceptance of composite sandwich construction worldwide, Vinson said he is not surprised that the University was chosen to contribute to the GRT research project. “The interest in composites is worldwide, with attention being given by academic institutions, industry and governments,” Vinson said. “I would like to think that Delaware is one of the top universities in this field and that we are a leader in the area of composite sandwich construction.” –Jerry Rhodes Birthday honor A symposium honoring the 70th birthdays of Jack R. Vinson, H. Fletcher Brown Professor of Mechanical and Aerospace Engineering, and Charles W. Bert of the University of Oklahoma, who serves on the Advisory Committee to the Dean of Engineering at UD, was held at the November 1999 International Mechanical Engineering Conference and Exposition in Nashville. The two-day symposium consisted of 10 sessions each day and included 32 presentations of research papers. In addition, a banquet honoring Vinson and Bert was held, where they were presented with plaques, clocks and pens. Both honorees have spent much of their careers in composite materials and their use in structures.