Condition Assessment of Personal Ballistic Armor Using Fiber Bragg Gratings

"The primary ballistic protection against small arms is based on ceramic with fiber-reinforced composite backing. During normal use, ballistic armor inserts (BAI) made with this material can be damaged. This proposal describes a simple, inexpensive,nondestructive technique to assess the ballistic integrity of the armor system in the field. BAIs instrumented with optical fiber Bragg grating strain sensors will be loaded in bending. A single fiber is capable of carrying hundreds of strain sensorsproviding a nearly continuous visualization of the strain field. The strain field, continuity in the fiber and the grating birefringent response will determine the location, extent and type of damage in the insert. Strain measurement with surface mountedand imbedded fibers will be demonstrated for damaged and undamaged BAIs. Comparing X-rays and measured strain fields of damaged panels will generate qualitative relationships between damage and strain response. The type and extent of damage is thencorrelated to ballistic performance. Finally, fiber egress techniques will be developed. Robust fiber egress is important because the personal ballistic protective vest is handled continuously resulting in the potential to break sensor leads. Limitedballistic tests will be conducted to determine the influence of imbedded optical fibers on ballistic performance. The commercial nonmilitary market for ballistic protection inserts is primarily la