Accession Number : ADA306131

Title :   Generalized Linear Elastic Fracture Model for Advanced Materials.

Descriptive Note : Final technical rept. 1 Apr 93-30 Sep 95,

Corporate Author : CLEMSON UNIV SC DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Goree, James G. ; Selvarathinam, Alex S.

PDF Url : ADA306131

Report Date : 30 SEP 1995

Pagination or Media Count : 155

Abstract : The branched crack problem for both an isotropic and anisotropic material is solved using the method of dislocations, and the stress intensity factors and T-stress in front of the branched crack are evaluated numerically. The T-stress based fracture criteria, developed by Cotterell and Rice for a flat crack, is modified by incorporating an experimentally determined critical T-stress value (Tcrit). Based on this Tcrit, a modified T-stress based fracture criteria is proposed. This criteria is applied to the branched crack and the direction of growth of the branched crack is discussed by comparing the theoretically evaluated T-stress values with some available experimentally determined Tcrit values. The solution for the branched crack problem is obtained in terms of a singular integral equation which is solved using three different numerical schemes, the merits of which are discussed. The nature of the stress singularity at the reentrant wedge corner of the branched crack is analyzed and is verified for the isotropic case. It is shown that the T-stress and the stress intensity factors are insensitive to the order of the singularity assumed at the reentrant wedge comer of the branched crack in either an isotropic or anisotropic material. The T-stress for the isotropic case is obtained in terms of applied load, kink length and kink angle. For the anisotropic case the T-stress also depends on the relative stiffness properties of the fibre and matrix. For a uniaxial loading case, by applying the modified T-stress based criteria to the branched crack, it is demonstrated that for a short kink length the kink will turn from its initial direction and realign with the main crack. If the loading is biaxial then the kink growth direction depends strongly on applied transverse stress. (MM)

Descriptors :   *COMPOSITE MATERIALS, *ELASTIC PROPERTIES, *FRACTURE(MECHANICS), *CRACK PROPAGATION, MATHEMATICAL MODELS, ANGLES, STRESS ANALYSIS, TENSILE STRESS, STIFFNESS, MODULUS OF ELASTICITY, THESES, BRITTLENESS, DISLOCATIONS, ANISOTROPY, ISOTROPISM, PERTURBATIONS, INTEGRAL EQUATIONS.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE