Patents Assigned to The United States of America as represented by the Administrator of the National Aeronautica and Space Administration
  • Patent number: 5994418
    Abstract: A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 .mu.m, a density of about 1 to about 6 pounds/ft.sup.3 and a volume change of 1 to about 20% by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bounded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/ft.sup.3 and a compression strength of about 100 to about 1400 pounds/in.sup.2.
    Type: Grant
    Filed: May 21, 1999
    Date of Patent: November 30, 1999
    Assignees: The United States of America as represented by the Administrator of the National Aeronautica and Space Administration, Unitika, Ltd.
    Inventors: Erik S. Weiser, Terry L. St. Clair, Yoshiaki Echigo, Hisayasu Kaneshiro