1. Institute of Lightweight Structures and Aerospace Engineering, Vienna University of Technology, Gusshausstr. 27-29, A-1040 Vienna, Austria
2. Institute of Mechanics, Montanuniversitat Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria
3. Institute of Lightweight Structures and Aerospace Engineering, Vienna University of Technology, A-1040 Vienna, Austria