Issue 45

C. Huang et alii, Frattura ed Integrità Strutturale, 45 (2018) 108-120; DOI: 10.3221/IGF-ESIS.45.09

FRAC exhibits more complex viscoelastic properties during the creep deformation recovery process after experiencing creep load damage.

Model parameters

Relaxa tion time/s

f V /%

Delay time/s

R

2  /MPa

1  /MPa

1  /MPa·s 332893 417152 556709 343284 234039 456829 402514 215312

2  /MPa·s

0  /MPa·s

a

2 s −

1 s −

c

a/

b/

0

0

591 668 820 670 576 713 708 566

143 156 171 129 107 158 142 108

4996813 3.04E-06 0.00179 3.18 1.13E+09 8456622 8.21E-07 0.00612 4.40 3.11E+09 17987114 5.30E-07 0.00891 6.68 5.78E+09 6904945 5.81E-07 0.00689 5.70 2.22E+09 2871943 3.54E-06 0.00251 3.82 1.61E+09 15366364 6.60E-07 0.00651 5.17 2.35E+09 6006080 1.15E-06 0.00687 5.68 3.98E+09 2431274 3.10E-06 0.00229 3.89 3.38E+09

563 624 679 512 406 641 569 380

34943 54209 105188 53527 26847 97255 42296 22512

0.17 324 0.35 324 0.52 324 0.69 324 0.35 162 0.35 486 0.35 649

Table 2 : Relationship between model parameters of Eqn. (9) with fiber contents and fiber aspect ratio.

Model parameters

Delay time/s

f V /%

2 R

R

a

2 s −

1 s −

2  /MPa

1  /MPa·s

2  /MPa·s a/

0  /MPa·s

b/

c

0

0

114606

0.62 0.96 1.15 0.93 0.61 0.91 0.81 0.66

242 428 593 412 218 369 341 227

4.36E-04 0.97 2.40E-04 2.92 3.17E-05 4.66 1.58E-04 2.56 3.08E-04 0.73 3.45E-04 1.41 1.95E-04 1.67 3.12E-04 0.91

210 4.27E+07 390 584 1.03E+08 448 925 1.51E+08 515 775 9.88E+07 442 544 3.75E+07 356 391 8.90E+07 404 757 7.20E+07 423 502 3.92E+07 342

0.98478 0.97522 0.99166 0.98287 0.98899 0.98453 0.99532 0.98252

0.17 0.35 0.52 0.69 0.35 0.35 0.35

324 318572 324 553520 324 320593 324 99117 162 211117 486 218774 649 113860

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: T

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 a  =  − 



+ 



(18)

2.47 10

f

f

f

116