SCALE EFFECTS ON COUPLED WAVE PROPAGATION IN SINGLE WALLED CARBON NANOTUBES

Abstract

THIS PAPER PRESENTS THE EFFECT OF NONLOCAL SCALING PARAMETER ON THE COUPLED I.E., AXIAL, FLEXURAL, SHEAR AND CONTRACTION, WAVE PROPAGATION IN SINGLE-WALLED CARBON NANOTUBES (SWCNTS). THE AXIAL AND TRANSVERSE MOTION OF SWCNT IS MODELED BASED ON FIRST ORDER SHEAR DEFORMATION THEORY (FSDT) AND THICKNESS CONTRACTION. THE GOVERNING EQUATIONS ARE DERIVED BASED ON NONLOCAL CONSTITUTIVE RELATIONS AND THE WAVE DISPERSION ANALYSIS IS ALSO CARRIED OUT. THE STUDIES SHOW THAT THE NONLOCAL SCALE PARAMETER INTRODUCES CERTAIN BAND GAP REGION IN ALL WAVE MODES WHERE NO WAVE PROPAGATION OCCURS. THIS IS MANIFESTED IN THE WAVENUMBER PLOTS AS THE REGION WHERE THE WAVENUMBER TENDS TO INFINITE OR WAVE SPEED TENDS TO ZERO. THE FREQUENCY AT WHICH THIS PHENOMENON OCCURS IS CALLED THE {\IT ESCAPE FREQUENCY}. EXPLICIT EXPRESSIONS ARE DERIVED FOR CUT-OFF AND ESCAPE FREQUENCIES OF ALL WAVES IN SWCNT. IT IS ALSO SHOWN THAT THE CUT-OFF FREQUENCIES OF SHEAR AND CONTRACTION MODE ARE INDEPENDENT OF THE NONLOCAL SCALE PARAMETER.  THE RESULTS PROVIDED IN THIS ARTICLE ARE NEW AND ARE USEFUL GUIDANCE FOR THE STUDY AND DESIGN OF THE NEXT GENERATION OF NANODEVICES THAT MAKE USE OF THE WAVE PROPAGATION PROPERTIES OF SINGLE-WALLED CARBON NANOTUBES.