Scanning Electron Microscopy as Related to the Study of High-Speed Fiber Impact
Final technical rept.
ARMY NATICK LABS MA CLOTHING AND PERSONAL LIFE SUPPORT EQUIPMENT LAB
Pagination or Media Count:
Scanning electron microscopy of the morphology of nylon impacted at very high speeds, including ballistic speeds, shows a large amount of plastic deformation and melting of the broken fiber ends. In attempts to produce fibers for specialty applications, manufacturers have produced organic fibers with moduli equal to or greater than that of glass and heat resistance far greater than that of nylon. The initial products of this type showed a typically brittle fracture because of their low ductility but in addition showed a tendency to split longitudinally. The better products show this splitting to a more marked degree until it reaches a state best described as fibrillation. This process is thought to be of considerable importance because it tends to minimize premature brittle failure, and considerable energy is absorbed in creation of the many subsurfaces. The potential for high strength in these new aromatic polymers is probably due to extended polymer chains which are broken more nearly in unison during extension. However, the realization of these high strengths with such low elongation fibers depends upon the process of fibrillation to prevent premature catastrophic failure. The strength of the aromatic polyamide Fiber B is 23 grams denier 400,000 psi as contrasted with 10 g d 150,000 psi for the strongest nylon tire cord previously available and approximately 200 gd 4,000, 000 psi for the theoretical value calculated on the basis of all primary bonds breaking at once.
- Laminates and Composite Materials