Development of light weight ballistic armor from fibers-reinforced with benzoxazine alloys

Ballistic impact performance of glass fiber and Kevlar TM fiber reinforced benzoxazine resin and benzoxazine-urethane alloy has been studied against 7.62 mm armor piercing projectiles. Benzoxazine resin which is one kind of phenolic resins was selected to apply as matrix for reinforced fiber due to its outstanding properties, no by-product during polymerization, high thermal stability, excellent mechanical properties, and ability to alloy with various types of resins. In this work, urethane elastomer (PU) is used to enhance toughness of the polybenzoxazine and its effects on the ballistic characteristics. The results reveal that the glass transition temperature (Tg) was found to be about 182oC for glass fiber reinforced benzoxazine resin whereas Tg of KevlarTM fiber reinforced benzoxazine-urethane alloys increased from 184oC to 247oC with the increasing amount of the urethane from 0-40% by weight. The activation energy obtained from Tg of composites increased with increasing amount of urethane fraction. For mechanical properties, flexural strength of glass fiber reinforced benzoxazine resin was about 506 MPa for glass fiber composite and 74-153 MPa for KevlarTM fiber reinforced benzoxazine-urethane alloys at urethane content from 0 to 40% by weight. The result of fire test presented that the hard ballistic armor consisted of 2 panels of glass fiber reinforced benzoxazine resin and 1 panel of KevlarTM fiber reinforced benzoxazine urethane alloy (80/20 BA-a/PU) can resist the penetration 7.62 mm AP projectile (838 ± 15m/s) equivalent to level III of NIJ standard.