Issue 45

C. Huang et alii, Frattura ed Integrità Strutturale, 45 (2018) 108-120; DOI: 10.3221/IGF-ESIS.45.09 118 2 ( ) 0 1 2 0 ( ) ( ) ( ) 1 ( , ) / ( , ) ( ) ( ) ( ) t f f f f f f f f f a t b t c e d t dt t                 −   − +   = = + +     (31) Unload phase: ( ) ( ) 0 0 0 2 ( 1) ( , )/ ( , ) ( ) t t t f f f f e e d t dt t           − − −   −   = =     (32) Fig. 8 displayed the variation of the creep strain and fiber content characteristic parameter with different loading stress and time, which is derived from Eqn. (29). It can be seen that the creep strain increases with the increase of loading stress and prolonged the load time, while it firstly decreases and then increases with the increase of the fiber content characteristic parameter. It should be noted that when fiber content characteristic parameter is 1.13, the creep strain with different loading stress and the loading time achieved the minimum, at this time the FRAC exhibits good deformation resistance. The variation between the value of creep speed and the fiber content characteristic parameter in the stage of loading, derived from Eqn. (31), is shown in Fig. 9. It can be seen that the creep speed increases with the increase of load stress, while the creep rate firstly decreases and then increases with the increase of fiber content characteristic parameter under the same loading conditions. It should be noted that when fiber content characteristic parameter is 1.13 under different creep load, the rate of creep deformation reaches minimum. It can also be noticed that, the creep rate gradually decreases firstly and then goes to a stable value. Finally, the creep rate increases with the increase of load time. It is worth to mentioning that the above phenomenon is consistent with the three-phase character of the creep curve in the stage of loading from test. Figure 8(a) : Different stress. Figure 8(b) : Different loading time Figure 9 : Relationship between creep speed and  f . Figure 10 : Relationship between creep speed and  f .