Abstract
Devices for cutting notches of controlled depth in monofils and for manipulating notched specimens under the microscope are described. Chordal and circumferential notches have been cut in nylon moriofils, and the deformation of specimens in the neighborhood of the cracks, when tension (to rupture) is applied, has been examined microscopically. The behavior of the fiber material at the roots of notches is discussed and interpreted in terms of molecular structure and orientation. Breaks observed in flattened monofils that had been notched on an edge, in one case, and centrally punctured, in another, have been interpreted to be of near-brittle character. Analysis of the char acter of a fracture su: face at a notch suggests that two mechanisms are operative in the propagation of a notch or crack to rupture.
Tensile tests made on monofils of various diameters, as well as on circumferentially notched specimens, reveal that breaking strength decreases as the diameter becomes larger. This is taken to imply that the inherent flaw size usually increases with an in crease in specimen volume. From a plot of the breaking loads of monofils having Chordal notches of varying depth, an estimate of the equivalent depth of the inherent flaws is obtained.
Get full access to this article
View all access options for this article.