1. Composite Materials Research Laboratory, Univ. at Buffalo, State Univ. of New York, Buffalo, NY 14260-4400; formerly, Box 1430, School of Civil Engineering, Harbin Institute of Technology, 66 West Dazhi St., Nangang District, Harbin 150006, P.R. China.
2. Composite Materials Research Laboratory, Univ. at Buffalo, State Univ. of New York, Buffalo, NY 14260-4400 (corresponding author).