抄録
This study was carried out in a serial research on spider thread. The thread is supposed to consist of three layers, outer coat resistant to water, middle layer with oriented micro-fibers and inner core with soft substance. It is desirable to observe its longitudinal and perpendicular cross-sections directly to confirm its hierarchical structure. This paper aims to tear natural and synthetic fibers with diameters 20 to 100μm and observe their micro structures in a simple manner, while the final goal is to inspect those of structures of more fine fibers with diameter of a few micrometers like spider thread. It was shown that 1. several natural fibers such as horse mane, human hair, rabbit fur, fox tail grass etc. and synthetic fibers of aramid and nylon were torn and their hierarchical structures were observed easily through a SEM and 2. the forces required to tear fibers along their longitudinal directions were measured by a laboratory-made tearing machine and their fracture toughness were calculated on the basis of the fracture mechanics.
