The objective of this research is to analyze theoretically and experimentally the nonlinear material characteristics, structural responses and optimization of motor cycle helmets and other protective devices. It will be conducted in conjunction with a parallel study, which will be funded by the Air Force Office of Scientific Research, on the generic experimental and theoretical analyses of impacted crushable shells. This particular research will start with two major thrusts involving the impact responses of crushable half cylindrical/semi-circular shells and the development of a model which simulates a human head. These two research thrusts will be combined during the third year for the optimization study. The two principal investigators are highly respected researchers in their respective fields of impact mechanics, which includes head injury studies, and structural mechanics.