The creep strain responses of Kevlar 49 fibres and a Kevlar 49 — cement mortar composite board to sustained stresses have been studied over an extended period in excess of four years at ambient temperature. Single filaments of Kevlar 49, 900 mm in length, were stressed in tension in the range 830 to 1830 MPa. The relationship between creep and elapsed time is represented by the power functionAt n whereA is a function of stress andn is a constant. The creep strain in Kevlar 49 was low compared with other polymers. For example after 1000 days at a stress of 1830 MPa the creep strain was 13% of the initial elastic strain and is predicted by the power function to increase to 14.6% after 4000 days. The Kevlar 49 — mortar composite was subjected to bending stresses in the range 6 to 35 MPa and the creep deflection was monitored. The relationship between creep and time could again be represented by the power functionAt n withA dependent on stress andn constant. The creep was similar to that expected from the matrix alone. The ratio of the creep deflection to the initial deflection after 1000 days at a stress of 6.15 MPa (well below the matrix cracking stress) was 1.31 and at 23.5 MPa (well above the matrix cracking stress) was 1.63.
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Walton, P.L., Majumdar, A.J. Creep of Kevlar 49 fibre and a Kevlar 49-cement composite. J Mater Sci 18, 2939–2946 (1983). https://doi.org/10.1007/BF00700774
- Ambient Temperature
- Power Function
- Extended Period
- Elastic Strain