1. Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093, USA
2. Materials Science and Engineering Graduate Program, University of California, San Diego, La Jolla, California 92093, USA
3. Department of Structural Engineering, University of California, San Diego, La Jolla, California 92093, USA
4. Department of Mechanical Engineering, McGill University, Montreal, Quebec H3A 0C3, Canada