Nanofractography of Composition B Fracture Surfaces With AFM
Abstract
The characteristics of TNT crystals in the fracture surface of Composition B (a melt-cast composition of RDX, TNT and wax) have been studied using atomic force microscopy (AFM). The sub-microscopic size of the TNT crystal component is revealed by the surface structure that is exhibited after mechanical failure. The failure surfaces are produced by subjecting the material to high acceleration in an ultracentrifuge under conditions in which the shear or tensile strength is exceeded. AFM examination of the TNT component fracture surface topography reveals that essentially brittle cleavage has occurred across the very finely-spaced columnar grains. The width of the grains varies narrowly in size between ^ 1 m and ^ 2 m. The height elevations of the inclined and stepped surfaces range in size between ^ 50 nm to ^ 300 nm. Shear-type deformation that has occurred prior to cleavage fracture is evidenced in the lowest magnification images, that is, for the largest AFM scans (8 m and 13.5 m). Specularly cleaved column surfaces alternate with ones containing profuse river patterns identifying the directions of crack growth. The river pattern markings are observed to originate at the boundaries between adjacent columns whereas the average profile angles between adjacent columnar surfaces are within the theoretical limit for dislocations. The smallest, individual, nm-size step heights at the river pattern ledges are smaller than the unit cell dimensions of either allotropic crystal phase of TNT. Such steps, smaller than unit cell dimensions, may relate to the important issue of breaking intramolecular bonds.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2004
- Accession Number
- ADA433490
Entities
People
- J. Sharma
- R. L. Mckenney
- R. W. Armstrong
- T. R. Krawietz
- Y. D. Lanzerotti
Organizations
- United States Army Armament Research, Development and Engineering Center