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Left panel: several strands of fibrils aligned along in (a) silkworm silk and (b) spider dragline. Right panel: Elements of fibril nanostructure of (a) native silkworm silk double stranded fiber with semicircular cross section and (b) spider dragline with cylindrical cross section. Upper portions in [(a) and (b)]: larger blocks, interprotein -crystallites; smaller beads, intraprotein -sheets; curved lines in-between, helical or random coil structures in amorphous matrix. Thin solid arrows point to the various elements corresponding to model structure in the lower portions of (a) and (b). Silkworm silk in (a) of comprised of interprotein -crystallites, and spider dragline in (b) is comprised of both interprotein -crystallites and intraprotein -sheets in their crystalline regions.
The relation between stress and strain of silkworm silk fibers: the black solid line is the experimental curve, and the red dashed line is the simulation results. A computer-controlled motorized spindle was used to draw fibers from silkworm with 12, 24, and 36 mm/s from the bottom up. Two successive 45 min, heating procedures in 0.5% , and 1% soap solution was adopted in the degumming process. Measurements were performed using an Instron MicroTester (Model 5848; force resolution, 0.5% of indicated load; position resolution ; strain rate is 50%/min), at and the humidity was kept at . The scaling constant in simulation , the corresponding parameters , , and increase with the reeling speed.
The black solid lines denote the stress-strain profile for spider silk under different reeling speeds, see Ref. 14. Stress-strain curves of spider dragline silk (2.5, 10, 25, and 100 mm/s motor-reeled at , from the bottom up) were obtained using an Instron MicroTester (Model 5848; force resolution, 0.5% of indicated load; position resolution ; strain rate is 50%/min), at and the humidity was kept at 55%–60%. The red dashed lines are the computational results, where the scaling constant , the preserved fraction of the intramolecule -sheet , and parameters , and are varied for different reeling speeds.
Threshold value of splitting force vs reeling speed of (a) interprotein -crystallites for silkworm silk; (b) intraprotein -sheets for spider draglines; and (c) interprotein -crystallites for spider draglines.
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