Issue 45

C. Huang et alii, Frattura ed Integrità Strutturale, 45 (2018) 108-120; DOI: 10.3221/IGF-ESIS.45.09 116 FRAC exhibits more complex viscoelastic properties during the creep deformation recovery process after experiencing creep load damage. f V /% a R Model parameters Relaxa- tion time/s Delay time/s 1  /MPa 1  /MPa·s 2  /MPa 2  /MPa·s a/ 2 s − b/ 1 s − c 0  /MPa·s 0 0 591 332893 143 4996813 3.04E-06 0.00179 3.18 1.13E+09 563 34943 0.17 324 668 417152 156 8456622 8.21E-07 0.00612 4.40 3.11E+09 624 54209 0.35 324 820 556709 171 17987114 5.30E-07 0.00891 6.68 5.78E+09 679 105188 0.52 324 670 343284 129 6904945 5.81E-07 0.00689 5.70 2.22E+09 512 53527 0.69 324 576 234039 107 2871943 3.54E-06 0.00251 3.82 1.61E+09 406 26847 0.35 162 713 456829 158 15366364 6.60E-07 0.00651 5.17 2.35E+09 641 97255 0.35 486 708 402514 142 6006080 1.15E-06 0.00687 5.68 3.98E+09 569 42296 0.35 649 566 215312 108 2431274 3.10E-06 0.00229 3.89 3.38E+09 380 22512 Table 2 : Relationship between model parameters of Eqn. (9) with fiber contents and fiber aspect ratio. f V /% a R Model parameters Delay time/s 2 R 1  /MPa·s 2  /MPa 2  /MPa·s a/ 2 s − b/ 1 s − c 0  /MPa·s 0 0 114606 0.62 242 4.36E-04 0.97 210 4.27E+07 390 0.98478 0.17 324 318572 0.96 428 2.40E-04 2.92 584 1.03E+08 448 0.97522 0.35 324 553520 1.15 593 3.17E-05 4.66 925 1.51E+08 515 0.99166 0.52 324 320593 0.93 412 1.58E-04 2.56 775 9.88E+07 442 0.98287 0.69 324 99117 0.61 218 3.08E-04 0.73 544 3.75E+07 356 0.98899 0.35 162 211117 0.91 369 3.45E-04 1.41 391 8.90E+07 404 0.98453 0.35 486 218774 0.81 341 1.95E-04 1.67 757 7.20E+07 423 0.99532 0.35 649 113860 0.66 227 3.12E-04 0.91 502 3.92E+07 342 0.98252 Table 3 : Relationship between model parameters of Eqn. (10) with fiber contents and fiber aspect FRAC V ISCOELASTIC C ONSTITUTIVE R ELATION he above analysis shows that fiber volume fraction and aspect ratio are important factors, which affect the viscoelastic properties of the AC and the influence of fiber volume fraction and aspect ratio on the model parameters is consistent. Therefore, fiber content characteristic parameter  f (  f = V f  R a ) can be used to represent the combined effects of the fiber volume fraction and fiber aspect ratio. By nonlinear fitting of the experimental data in this paper, the relationship between model parameters of Eqn. (9) and the fiber content characteristic parameters are as follow: 2 1 ( ) 577.8 327.4 149.1 f f f     = + − (14) 2 2 ( ) 142.6 48.4 29.7 f f f     = + − (15) 2 1 ( ) 324331.1 334911.7 172179 f f f     = + − (16) 2 2 ( ) 4267638 17376388 8264399 f f f     = + − (17) 6 6 6 2 ( ) 3.09 10 5.4 10 2.47 10 f f f a    − − − =  −  +  (18) T