1. Dept. of Mechanical, Aerospace and Civil Engineering, Brunel Univ. London, Uxbridge, Middlesex UB8 3PH, U.K.
2. Dept. of Mechanical, Aerospace and Civil Engineering, Brunel Univ. London, Uxbridge, Middlesex UB8 3PH, U.K. (corresponding author).
3. Professor, Centre of Materials and Building Technologies, Univ. of Beira Interior, 6200 Covilhã, Portugal.