Accession Number : ADA334876

Title :   Elastothermodynamic Damping in Composite and Cracked Media

Descriptive Note : Final rept.

Corporate Author : AIR FORCE RESEARCH LAB BOLLING AFB DC

Personal Author(s) : Bishop, Joseph E.

PDF Url : ADA334876

Report Date : DEC 1995

Pagination or Media Count : 165

Abstract : When a composite material is subjected to a stress field, different regions undergo different temperature fluctuations due to the well-known thermoelastic effect. As a result irreversible heat conduction occurs, and entropy is produced which is manifested as a conversion of mechanical energy into heat. Moreover, the changes in temperature produce a thermal strain that is out of phase with the stress, thus converting mechanical energy into heat, i.e. work is lost. We define this process as elastothermodynamic damping. Herein, using the linear one-way coupled theory of elastothermodynamic relaxation, the elastothermodynamic damping of composite and cracked media is examined. Two equivalent descriptions of elastothermodynamic damping are first established: (1) the mechanical description and (2) the entropic description. An integral-transform technique is then developed to solve for the temperature field of a general composite medium with arbitrary heat generation. With this solution, a general expression for the damping of the composite material is derived.

Descriptors :   *THERMODYNAMICS, *COMPOSITE MATERIALS, *CRACKS, *ELASTIC PROPERTIES, *DAMPING, STRESSES, COUPLING(INTERACTION), LINEAR SYSTEMS, MECHANICAL PROPERTIES, THESES, THERMAL CONDUCTIVITY, HEAT, THERMAL STRESSES, ENTROPY, MECHANICAL ENERGY, THERMOELASTICITY.

Subject Categories : Laminates and Composite Materials
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE