Strength of covalent crystals under multiaxial loading

P. Rehak, M. Cerny and J. Pokluda

Ab initio study of crystals with diamond structure subjected to multiaxial loading is performed for the particular case of superposition of uniaxial tensile (and compressive) and transverse biaxial stresses. A typical example of such multiaxial loading is a stress induced by the matrix/reinforcement incompatibility strain on the reinforcing single crystal nanofiber in a composite material. The fibers are subjected to triaxial loading even in case of the remote (purely uniaxial) tension of the composite. Despite this fact, only a few studies were devoted to a coupling of various stress tensor components.
In this work, we study the elastic constants and the theoretical strength of diamond crystal structures (C, Si) as functions of the superimposed transverse biaxial stresses. A plane-wave pseudo-potential code Abinit is employed for calculation of stresses.

Keywords:
Theoretical strength, multiaxial loading, covalent crystals

D3 Materials Modeling on all Length Scales
D31 Ab-initio based modelling, designing new materials with electronic structure calculations
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