Paper 1

(cited 312 times, by January 2002)

J.W. HUTCHINSON, Z. SUO, MIXED-MODE CRACKING IN LAYERED MATERIALS. ADVANCES IN APPLIED MECHANICS, 29, 63-191 (1992).

Paper 2

(cited 243 times, by January 2002)

Z. SUO, C.M. KUO, D.M. BARNETT, J.R. WILLIS, FRACTURE-MECHANICS FOR PIEZOELECTRIC CERAMICS. JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, 40, 739-765 (1992).

Abstract: WE STUDY cracks either in piezoelectrics, or on interfaces between piezoelectrics and other materials such as metal electrodes or polymers matrices. The projected applications include ferroelectric actuators operating statically or cyclically, over the major portion of the samples, in the linear regime of the constitutive curve, but the elevated field around defects causes the materials to undergo hyteresis locally. The fracture mechanics viewpoint is adopted-that is, except for a region localized at the crack tip, the materials are taken to be linearly pieozelectric. The problem thus breaks into two subproblems: (i) determining the macroscopic field regarding the crack tip as a physically structureless point, and (ii) considering the hysteresis and other irreversible processes near the crack tip at a relevant microscopic level. The first subproblem, which prompts a phenomenological fracture theory, receives a thorough investigation in this paper. Griffith's energy accounting is extended to include energy change due to both deformation and polarization. Four modes of square root singularities are identified at the tip of a crack in a homogeneous piezoelectic. A new type of singularity is discovered around interface crack tips. Specifically, the singularities in general form two pairs: r-1/2 +/- i-epsilon and r-1/2 +/- kappa, where epsilon and kappa are real numbers depending on the constitutive constants. Also solved is a class of boundary value problems involving many cracks on the interface between half-spaces. Fracture mechanics are established for ferroelectric ceramics under small-scale hysteresis conditions, which facilitates the experiment study of fracture resistance and fatigue crack growth under combined mechanical and electrical loading. Both poled and unpoled ferroelectric ceramics are discussed.