Low-velocity impact test
Low-velocity impact (LVI) tests were conducted to evaluate damage initiation of the PVC.
For comparison, a few representative samples of polycarbonate (PC, also referred to as Lexan)
were included, using a PC sheet of equivalent thickness to the PVC. The equipment used to
conduct the tests is an instrumented Instron 8250-drop tower, as shown in Figure 20. The basic
principle of operation is to drop a tup of known weight from a set height onto the test sample. The
maximum load and maximum energy absorbed by the test sample and the damage to the sample
is assessed.
Pneumatic
release
51.59-lb
drop weight
9892-lbf
load cell
0.625-in
hemispherical
tup
Figure 20. Instrumented drop-weight, low-velocity impact test.
For the PVC control, PVC 20-hour UV exposed, PVC 200-hour UV exposed, and PC
samples, the drop height and mass where held constant at 39.37 in. (100 cm) and 51.59 lb (23.4
kg), respectively. A 9892-lb (44-kN) load cell along with a 0.625-in.- (15.875-mm-) diameter
hemispherical tup (impactor) was used (Fig. 20). The specimen fixture is composed of two
aluminum plates, with 3-in.-diameter holes, bolted together with the specimen residing in
between (Fig. 21). The load and energy curves for the PVC control, PVC 20-hour UV exposed,
PVC 200-hour UV exposed, and PC samples are shown in Figure 22. The front and back face
deformations for each specimen tested are shown in Figures 2326. The depth of indentation
from plastic deformation under low-velocity impact was quantified and shown in Figure 27. The
indentation percentage is calculated as the ratio of the penetration depth to the nominal specimen
thickness. The PC specimen exhibited the highest depth of penetration (38.7%), followed by the
PVC control (28.3%), PVC 20-hour (27.6%), and the PVC 200-hour (23.5%) specimens.
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