The PC samples show very localized damage and absorbed almost 500 J prior to penetration
(ballistic velocity). All the PVC samples showed little or no indication of damage up to the
threshold of ballistic penetration. The projectile simply bounced off, leaving a small indentation
up to the ballistic limit. The ballistic limit was around 120 m/s, corresponding to approximately
120 J, at which multiple radial cracks were observed, as shown in the figure. The change in the
effect of exposure as the ballistic limit increased slightly (from 122 to 130 m/s) can be attributed
to the surface hardening of the 200-hour UV exposed samples.
To summarize, we have observed that:
The UV exposure added a skin-like feature to a few microns of the surface of the PVC
samples. The samples were quite thick, so the effect of exposure was minimal.
There was severe discoloration of the samples after the 20-hour and 200-hour UV
exposures.
The low-velocity impact response was minimally influenced by the UV exposure. There
was no radial cracking, and all PVC samples showed local indentation and a small bulge
on the back face. The tests showed a peak load of about 2530 kN and about 30 J of
energy absorbed.
The higher-velocity tests indicated that the PVC had a ballistic limit of 122130 m/s,
which caused radial cracks growing from the impact location. Up to 120 m/s, no
indications of damage were seen; the projectile simply bounced off. The UV exposure
increased the ballistic limit due to surface hardening.
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