Influence of weathering and gamma irradiation on the mechanical and ballistic behavior of UHMWPE composite armor

Fiber reinforced polymeric-matrix composites have been extensively applied to various structural components successfully replacing many conventional materials, especially in land, sea, air and aerospace vehicles and in sporting goods. Since World War II, polymeric materials have been used in military applications, especially as ballistic armor. Due to their great capacity for absorbing the kinetic energy of projectiles, ultrahigh molecular weight polyethylene (UHMWPE) fibers are presently used in composite armors for personnel and vehicle protection. However, polymers are liable to degrade when subjected to environmental agents such as sunlight, rain, radiation, etc. The aim of the present work was to use accelerated tests, short exposures to weather and gamma radiation, to study the influence of aging agents on the mechanical and ballistic performance of a UHMWPE composite armor. Composite panels were submitted to ballistic tests using 9 mm caliber projectiles. The mechanical and ballistic characteristics of composite were related to macromolecular modifications induced in the polymer by the environment through physicochemical testing. Exposure to environmental agents induces changes in the UHMWPE macromolecular chains, altering the mechanical properties and the ballistic behavior of the composite. The use of accelerated tests may be an adequate way to predict the effects of environmental agents on the performance of ballistic armor. These results are presented and discussed.