perature of 25C (13F). The end of the seal pipe
The work was conducted with ballistic perfor-
terminates into a specially designed plexiglass
ation impact at CRREL. An energy analysis of this
work presented earlier by Hui (1993) shows that
chamber (Fig. 2b). It is equipped with two metal-
the fracture surfaces of fragments produced from
lic holding plates to clamp the composite target
the impact of single-ply and 30-ply plates by 12.7-
test plates at the periphery for normal impact. The
mm (0.5-in.) steel spheres could be related to the
target test chamber is connected to a back-cham-
various mechanisms of energy absorption. How-
ber of the same diameter and length, and also it is
ever, the experimental details and systematic
completely sealed to maintain interior vacuum
microscopic examination were not documented by
when needed. The back-plate of the chamber,
Hui. The purpose of this report is to document
made from plastic, is replaceable after every shot.
those experimental details and the microscopic
The projectile exiting through the back-plate is
analysis. We will also elaborate on the theory of
captured by a sandbox located in the flight path
energy absorption under a penetrating and perfor-
opposite to an opening in the wall. For high vel-
ocity (> 610-m/s, 2000-ft/s) tests the interior of the
ating projectile at greater depth using our experi-
mental data.
gun barrel, seal pipe and the test chamber must
have a very high vacuum pressure, which is
achieved by connecting the pipe interior to a vac-
MATERIALS
uum pump. For low velocity tests no vacuum is
The tests were performed on two batches of
necessary.
Gr/Ep (graphite/epoxy) plates. The first batch
The building is also equipped with a remote
consisted of eight plates each 8-ply thick and was
firing circuit. Red, flashing warning lights are
made of T-300 graphite fiber reinforcement in
located on the outside of the building and all
Fiberite 984 epoxy resin. All fibers were oriented
rooms except the loading room. These warning
in one direction. Size of each plate used for test-
lights, the illuminating lights in the range area,
ing was 12 12 in. (30 30 cm). The second sys-
and door switches on each entrance to the range
tem was a 30-ply AS-4/3502 laminate with a stack-
are integral components of the remote firing cir-
ing sequence of
cuit. The design of the remote firing circuit was
made such that the following three conditions
[(45/02)2 / 9045/02/45]s.
must be met to complete the circuit and fire the
This material was supplied by the U.S. Air Force
gun:
Wright Laboratory, Wright-Patterson Air Force
1. The illuminating lights in the range area must
Base, Dayton, Ohio, in the sizes of 4.5 4.5 in. (11.4
be off.
11.4 cm). The above stacking sequence gives the
2. The red lights must be on and flashing.
laminate a quasi-isotropic property, as opposed to
3. Both doors to the range must be closed.
It is only when those conditions are met that the
the unidirectional (or anisotropic) property of the
remote firing controls in the instrumentation room
batch 1 material.
can be activated.
BALLISTIC TESTS
To make this study compatible and complemen-
Ballistic test facility
The CRREL Terminal Ballistic Facility (TBF) is
tary to the projectile perforation studies that were
shown schematically in Figure 2a and in an as-
being conducted at the Air Force Wright Labora-
sembly photograph in Figure 2b. The entire facil-
tory, 12.7-mm- (0.5-in.-) diam. hardened steel
ity is located in four adjoining rooms: the firing
sphere projectiles were selected for the series of
room, the control and instrumentation room, load-
tests. The firing device has been designed to ride
ing room, and the cold target room. The firing
on two horizontal rails through four Thomson lin-
room is lined with a 20-cm-thick concrete wall. The
room is equipped with a 14.3-mm (9/16-in.) bore,
bearings and the rails, the length of recoil is con-
explosive-powered gun that can be remotely op-
trolled. The firing circuit works through a 42-V DC
erated from the control room. The barrel end and
push type solenoid valve. The valve, mounted
the projectile path are completely sealed with a
beneath the carriage, activates a trigger mechanism
127-mm- (5-in.-) i.d. steel pipe, which passes
through a switching device in the instrumentation
through the wall of the firing room into the target
room. The impact and exit velocities were meas-
room. The target room can be refrigerated to a tem-
ured using light-activated chronograph screens in
2
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