A History of Research and a Review of Recent Developments

Penetration into soil, stone and rock 163
Figure 7.19 Penetration data for a projectile entering Thirsty Canyon tuff (from
Amini and Anderson, ref. 7.31).
expensive, so the possibility of using commercially available cheap polymers
was investigated.
In analysing the mechanics the authors made use of the empirical equations
given in the 1972 report by Young [7.4]. Most analytical methods are aimed
for simplicity at homogeneous materials, where the projectile cross sections
are orders of magnitude greater than the size of the aggregate. This simplification
does not apply to aggregates bonded by a low-elasticity matrix of polymer
with sand filler, particularly when the projectile sections are similar in dimension
to the size of the aggregate, and when the projectile strikes the matrix at an
oblique angle.
Anderson et al. reported a series of tests, in which hardened steel core
projectiles, 7.62 mm diameter, 33.3 mm long, were fired at various mixes of
polymer and rock aggregate. Since impact trajectory through the composite
was not straight, it was necessary to distinguish between the total length of