Issue 45

C. Huang et alii, Frattura ed Integrità Strutturale, 45 (2018) 108-120; DOI: 10.3221/IGF-ESIS.45.09 114 that the creep strain–time curve of modified Burgers model is closer to the test curve in the stages of decelerating creep and stable creep, and the modified Burgers model can better describe deceleration and constant velocity creep deformation characteristics of FRAC. The fitting curve of the new model almost coincides with the measured test curve. The present model greatly increases the fitting accuracy and can describe the viscoelastic deformation characteristics of the whole creep process of FRAC very well. f V /% a R Test rheology time /s Calculation rheology time /s 2 R Burgers model Modified Burgers model Five units and eight parameters model/s Burgers model Modified Burgers model Five units and eight parameters model 0 0 1450 / / 1320 0.99912 0.99930 0.99975 0.17 324 7500 / / 7332 0.99815 0.99930 0.99966 0.35 324 10200 / / 10996 0.99540 0.99926 0.99988 0.52 324 7200 / / 7739 0.99923 0.99958 0.99996 0.69 324 3200 / / 2986 0.99913 0.99925 0.99984 0.35 162 5500 / / 6045 0.99936 0.99951 0.99987 0.35 486 9000 / / 8532 0.99746 0.99924 0.99990 0.35 649 8000 / / 7501 0.99118 0.99905 0.99981 Table 1 : Relationship between model index with fiber content and fiber aspect. Figure 6(a) : Fiber volume ratio. Figure 6(b) : Fiber aspect ratio. Figure 7(a) : Burgers model. Figure 7(b) : Modified Burgers model.