AN INEXPENSIVE AND EFFECTIVE METHOD FOR CALCULATING THE STRENGTH OF RANDOMLY REINFORCED FIBER COMPOSITES

Planar randomly reinforced fiber composites (PRRFC) can be made from any combination of a large number of available fibers and matrices. An analytical procedure to determine the strength of PRRFC can serve as an effective and inexpensive means in selecting suitable fiber/matrix combinations for specific designs. It has recently been demonstrated that the well-known laminate theory can be applied to determine the strength of PRRFC. A PRRFC is, in essence, a pseudoisotropic laminate with a large number of ply orientation combinations where the strength is a function of these ply orientation combinations. Laminate theory is used to demonstrate numerically that the minimum strength of a pseudoisotropic laminate is independent of the number of ply orientation combinations. The upper bound on the strength of a pseudoisotropic laminate approaches the lower bound of its strength as the number of ply orientation combinations increases. Since a PRRFC is a pseudoisotropic laminate with a large number of ply orientation combinations and since the maximum strength of the pseudoisotropic laminate approaches its minimum strength as the number of ply orientation combinations increases, it follows that the strength of the PRRFC is equal to the minimum strength of the pseudoisotropic laminate. This establishes the validity for using pseudoisotropic laminate analogy to predict the strength of PRRFC. Laminate theory in conjunction with composite micro- and macromechanics can be used to predict mechanical properties of PRRFC's with any fiber/matrix combination. This procedure can also be used to investigate the effects of processing variables, such as cure temperature and void content, on the PRRFC strength. The pseudoisotropic laminate analogy applies to both fiber/metallic and fiber/nonmetallic matrix composites.

  • Supplemental Notes:
    • This article appeared in a publication Analytical Techniques: A Compilation.
  • Corporate Authors:

    National Aeronautics and Space Administration

    400 Maryland Avenue, SW
    Washington, DC  USA  20546
  • Authors:
    • Chamis, C C
  • Publication Date: 1975-1

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Filing Info

  • Accession Number: 00128508
  • Record Type: Publication
  • Report/Paper Numbers: NASA TD-D-6696
  • Files: TRIS
  • Created Date: Apr 21 1976 12:00AM