SEM characterization of the as-grown CMCs.
Representative SEM image of the extended states of superelastic double-helix CMCs.
A series of photos of continuous changes in the coil pitch angle and diameter.
Tensile model of a large-index spring with the ends fixed. Here, is the tensile load, is the torsional moment, is the wire diameter, is the spring radius, and is the pitch angle.
(a) Developed elongation of the spring. (b) Calculation of the polar moment of inertia of the coil cross-section. (c) Spring cross-section with axial load. Here, is the spring length, is the spring elongation, is the initial pitch angle, is the final pitch angle, is the wire radius, is the wire area, and is the tensile load.
The rate of contraction of the spring diameter vs the pitch angle for a single-helix spring with fixed ends. In the inset, curves 1, 2, 3, 4, and 5 correspond to the initial pitch angles of 0°, 5°, 10°, 15°, and 20°, respectively.
The dependence of Poisson’s ratio on the deflection factor of a single-helix spring with fixed ends at . In the inset, curves 1, 2, and 3 correspond to , 0.30, and 0.35, respectively.
Deflection factor vs the coil extension for a single-helix spring with fixed ends. Curves 1, 2, 3, 4, and 5 correspond to the initial pitch angles of 0°, 5°, 10°, 15°, and 20°, respectively.
Spring constant vs the coil elongation for a single-helix CNC. Here, the nanocoil radius , the nanowire diameter and the shear modulus . In (a), the inner diameter is zero, curves 1 and 2 correspond to the coil pitches of 120 and 2000 nm, respectively. In (b), the coil pitch is 2000 nm, curves 3, 4, 5, and 6 correspond to the ratios of 1/6, 1/4, 1/3, and 1/2, respectively.
Tensile load vs the coil elongation for a double-helix CNC. In the inset, the coil number , the initial length , , and , curves 1, 2, 3, and 4 correspond to the elastic moduli of 0.68, 0.70, 0.72, and 0.74 GPa.
Equivalent shear stress-extension diagrams for a single-helix microcoil with its ends fixed. Curves 1, 2, 3, and 4 correspond to the initial pitch angles of 0°, 5°, 10°, and 20°, respectively.
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