Ultrasonic Assessment of Bullet Inflicted Damage in Aramid Laminated Composites

Immersion type ultrasonic C-scan has been performed on Twaron-epoxy (T-E) and Twaron-polypropylene (T-PP) composite laminates impacted by 7.62 mm armor piercing (AP) projectile with different striking velocitiesto assess the bullet inflicted damage area. Square zones of size 72 mm by 72 mm around each impact area are subjected ultrasonic C-scan in pulse echo mode. Ultrasonic features are extracted and processed to estimate the damage area in the laminates due to each impact. The variation in internal damage area is correlated with ballistic properties of composite laminates. It is observed that in the similar range of impact velocity, the damage area is invariably higher in composites made from thermoplastic polypropylene (PP) resin compared to the thermoset epoxy resin. The internal damage area of impacted panel is found to decrease with increase in impact velocity for both the types of resin matrix which corroborated the trend in experimental ballistic curve. The internal damage area, however, increases substantially when shot lodging takes place inside the laminate below ballistic limit or upon excessive yawing.Defence Science Journal, 2012, 62(1), pp.153-158, DOI:http://dx.doi.org/10.14429/dsj.62.146