Accession Number : ADA189426

Title :   A Continuum Damage Model for Viscoelastic Materials

Descriptive Note : Technical rept.

Corporate Author : TEXAS A AND M UNIV COLLEGE STATION MECHANICS AND MATERIALS CENTER

Personal Author(s) : Weitsman, Y

PDF Url : ADA189426

Report Date : Nov 1987

Pagination or Media Count : 29

Abstract : This paper presents a continuum damage model for viscoelastic materials. Viscoelastic response in the presence of distributed micro-flaws occurs in solid propellants and is likely to be encountered in thermoplastic composites. In contrast to rock and metals, polymeric materials absorb various kinds of solvents, which may damage the polymeric composites in a variety of ways. In the case of water absorption by epoxy-based composites, such damage was noted by several investigators. Damage is expressed by two symmetric, second- rank tensors which are related to the total areas of active and passive micro- cracks within a representative volume element of the multi-fractured material. Viscoelasticity is introduced through scalar-valued internal state variables that represent the internal degrees of freedom associated with the motions of long-chain polymeric molecules. The constitutive relations are established from basic considerations of continuum mechanics and irreversible thermodynamics, with detailed expressions derived for the case of initially isotropic materials. It is shown that damage causes softening of the material moduli as well as changes in material symmetry. The special cases of uni-axial damage under uni-axial stress and the interaction of damage with moisture diffusion are also considered.

Descriptors :   *COMPOSITE MATERIALS, *MATERIALS, *POLYMERS, *SOLID PROPELLANTS, *THERMOPLASTIC RESINS, *VISCOELASTICITY, ABSORPTION, CHAINS, CONTINUUM MECHANICS, CONTRAST, DAMAGE, DEGREES OF FREEDOM, DIFFUSION, EPOXY COMPOSITES, INTERACTIONS, INTERNAL, IRREVERSIBLE PROCESSES, ISOTROPISM, METALS, MODELS, MODULUS OF ELASTICITY, MOISTURE, MOLECULES, RESPONSE, ROCK, SOLVENTS, SYMMETRY, THERMODYNAMICS, VOLUME, WATER

Subject Categories : Plastics
      Ammunition and Explosives

Distribution Statement : APPROVED FOR PUBLIC RELEASE