1. Research Assistant, Dept. of Plastics, Fraunhofer Institute for Structural Durability and System Reliability (LBF), Schloßgartenstr. 6, D-64289 Darmstadt, Germany (corresponding author).
2. Professor, State Key Laboratory for Strength and Vibration of Mechanical Studies, Xi’an Jiaotong Univ., No. 28, Xianning West Rd., Xi’an 710049, P.R. China.
3. Professor, Institut für Mechanik (IFME), Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, D-39106 Magdeburg, Germany.
4. Research Assistant, Dept. of Structural Durability, Fraunhofer Institute for Structural Durability and System Reliability (LBF), Bartningstr. 47, D-64289 Darmstadt, Germany.