1. Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250
2. Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250;
3. Protective Equipment Division, U.S Army Aberdeen Test Center, Aberdeen, MD 21001
4. Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD 21250
5. Department of Mechanics, Shanghai University, Shanghai 200444, China;
6. Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai 200072, China
7. Department of Mechanics, Shanghai University, Shanghai 200444, China;
8. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195;
9. Department of Endodontics, Prosthodontics, and Operative Dentistry, Dental School, University of Maryland, Baltimore, MD 21201 e-mail: