The second cleavage ([S.sub.b]) has a close superficial resemblance to [S.sub.a] in being a spaced, smooth fracture cleavage with lithons ranging in width between 0.25 and 1.0 cm.
At two localities south of Moncton, these thick mudstone intervals carry two fracture cleavages that are almost perpendicular to each other, and perpendicular to bedding.
Both are fracture cleavages with lithons 0.25-1.5 cm wide, as at Weldon Creek, but without the specularite-vivianite that is seen there.
The early cleavages described here are fracture cleavages with evidence of shear, rather than true 'slaty' cleavages or their precursors.
Wood penetration and fracture cleavage adhesion were examined solely as a function of blend ratio.
The adhesive rheology, wood penetration, and fracture cleavage properties are reported in this paper, while cure and morphological properties will be discussed in a future paper.
Like all adhesion tests, fracture cleavage has certain advantages and disadvantages.
With no toughener, the brittle epoxy exhibited no bond thickness effects in mode-I fracture cleavage; whereas polysulfide-induced plasticity produced a strong bond thickness effect in crack initiation energy (Takatani and Sasaki 1980).
We mention this because neat pMDI forms extremely thin bonds, and is thus affected by bond thickness effects in fracture cleavage testing.