A derivative fatigue damage model based on residual strength of composites
-
摘要: 为了研究纤维增强树脂复合材料在疲劳载荷作用下的损伤发展规律,提出了一种基于复合材料剩余强度的归一化衍生疲劳损伤模型。在该模型中,假定累积损伤与应力水平呈线性关系,可以由拉-拉疲劳试验的应力水平的损伤曲线衍生出未试验的应力水平的损伤曲线。对直径为8 mm的碳纤维增强树脂复合材料(CFRP)索材进行了不同应力幅的疲劳试验,并同时采用了文献中玻璃纤维增强树脂复合材料(GFRP)层合板的试验数据验证模型的可靠性,试验结果表明:损伤模型能较好地反映出三阶段的发展规律,衍生的损伤曲线与试验数据拟合出来的损伤曲线偏离度较小。此外,本文还研究了应力水平对复合材料损伤演化的影响,结果表明随着应力水平的增大,损伤曲线相邻阶段的边界变得不明显。Abstract: In order to investigate the damage development regularity of composites subjected to fatigue loading, a normalized derivative damage model based on the residual strength was proposed. In this model, it is assumed that the cumulative damage and stress level have a linear relationship, based on which, the damage curves of untested stress levels can be derived from that of tested stress levels with positive stress ratios. Fatigue tests of 8mm-diameter carbon fiber reinforced polymer (CFRP) composite tendons for different stress situations were conducted, and the experimental data of glass fiber reinforced polymer (GFRP) composite laminates from references were adopted to validate the reliability of the proposed damage model. The experimental results show that the damage model can well reflect the three-stage development law of CFRP composite tendons, and the derived damage curves show a good agreement with the damage curves obtained by fitting the experimental data. Besides, this paper investigates the influence of stress level on the damage evolution of composites. As the stress level increases, the boundaries between adjacent stages of damage curves become unobvious.
-
Key words:
- composite /
- residual strength /
- derivable damage curve /
- fatigue life /
- constant amplitude fatigue test
-
表 1 CFRP复合材料试件的力学性能
Table 1. Mechanical properties of CFRP composite specimens
表 2 本文模型中相关参数值
Table 2. Parameter values of the presented model
Material Stress level $ \sigma $/MPa Nf/cycle a b R2 CFRP tendon ${ {\sigma }_{ {\rm{m} }{\rm{a} }{\rm{x} } }=0.6{\sigma }_{ {\rm{u} } },\sigma }_{{\rm{a}}}=900$ 6 895 0.996 −0.071 0.959 ${ {\sigma }_{ {\rm{m} }{\rm{a} }{\rm{x} } }=0.6{\sigma }_{ {\rm{u} } },\sigma }_{{\rm{a}}}=800$ 7 654 0.868 −0.339 0.902 ${ {\sigma }_{ {\rm{m} }{\rm{a} }{\rm{x} } }=0.6{\sigma }_{ {\rm{u} } },\sigma }_{{\rm{a}}}=600$ 13 758 0.751 −0.614 0.943 ${ {\sigma }_{ {\rm{m} }{\rm{a} }{\rm{x} } }=0.6{\sigma }_{ {\rm{u} } },\sigma }_{{\rm{a}}}=500$ 32 558 0.586 −0.451 0.968 GFRP laminate Ⅰ[1] $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=386,R=0.05 $ 493 0.22487 −2.478 0.999 $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=338,R=0.05 $ 2 471 0.69607 −1.417 0.999 $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=290,R=0.05 $ 14 706 0.63714 −1.096 0.999 $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=241,R=0.05 $ 172 186 0.40554 −1.996 0.999 GFRP laminate Ⅱ[13] $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=174,R=0.1 $ 11 162 0.714 −1.213 0.998 $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=147,R=0.1 $ 44 010 0.637 −1.390 0.997 $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}}=120,R=0.1 $ 377 012 0.582 −1.999 0.989 Notes:${N}_{{\rm{f}}}$—Fatigue life of FRP specimens; $ {\sigma }_{{\rm{m}}{\rm{a}}{\rm{x}}} $—Peak stress of fatigue loading; $ {\sigma }_{{\rm{u}}} $—Ultimate strength of FRP specimens; ${\sigma }_{{\rm{a}}}$—Stress amplitude of fatigue loading; $ R $—Stress ratio; a, b—Relevant parameters of the proposed model; R2—Correlation coefficient. 表 3 对CFRP复合材料拉-拉疲劳试验损伤曲线的预测值与拟合值的比较(
$ {\sigma }_{{\rm{a}}} $ =800 MPa)Table 3. Comparison of predicted results and fitting results of tension-tention fatigue damage curve for CFRP composite (
$ {\sigma }_{{\rm{a}}} $ =800 MPa)n/Nf Prediction of
900-500 MPaPrediction of
900-600 MPaDamage
curveDeviation
(900-500 MPa)/ %Deviation
(900-600 MPa)/ %0.1959 0.2358 0.2185 0.2292 2.89 4.70 0.2613 0.2982 0.2793 0.2897 2.97 3.57 0.3266 0.3585 0.3380 0.3467 3.40 2.50 0.3919 0.4173 0.3952 0.4013 3.99 1.52 0.5879 0.5895 0.5624 0.5577 5.70 0.84 0.7839 0.7638 0.7336 0.7194 6.17 1.97 0.9145 0.8905 0.8636 0.8509 4.65 1.49 0.9861 0.9747 0.9601 0.9577 1.77 0.25 Notes:n—Number of cycles that have been performed; Prediction of 900-500 MPa is the fatigue damage prediction D(x) derived from damage curves of 900 MPa and 500 MPa; Deviation (900-500 MPa) is the deviation between the fitting value and the prediction value derived from damage curves of 900 MPa and 500 MPa. 表 4 对CFRP复合材料拉-拉疲劳试验损伤曲线的预测值与拟合值的比较(
$ {\sigma }_{{\rm{a}}} $ =600 MPa)Table 4. Comparison of predicted results and fitting results of tension-tention fatigue damage curve for CFRP composite (
$ {\sigma }_{{\rm{a}}} $ =600 MPa)n/Nf Prediction of
900-500 MPaPrediction of
800-500 MPaDamage
curveDeviation
(900-500 MPa)/ %Deviation
(800-500 MPa)/ %0.2181 0.3389 0.3365 0.2852 18.84 18.00 0.3271 0.4321 0.4281 0.3706 16.60 15.53 0.4361 0.5144 0.5079 0.4446 15.70 14.25 0.5815 0.6163 0.6058 0.5354 15.11 13.16 0.6542 0.6664 0.6540 0.5807 14.76 12.63 0.7433 0.7295 0.7152 0.6397 14.04 11.81 0.8722 0.8310 0.8164 0.7439 11.70 9.75 0.9813 0.9524 0.9457 0.9029 5.48 4.74 表 5 对CFRP复合材料拉-拉疲劳试验损伤曲线的预测值与拟合值的比较(
$ {\sigma }_{{\rm{a}}} $ =338 MPa)Table 5. Comparison of predicted results and fitting results of tension-tention fatigue damage curve for CFRP composite (
$ {\sigma }_{{\rm{a}}} $ =338 MPa)n/Nf Prediction of
386-241 MPaPrediction of
386-290 MPaDamage
curveDeviation
(386-241 MPa)/ %Deviation
(386-290 MPa)/ %0.2 0.4743 0.4071 0.2572 84.42 58.28 0.4 0.4462 0.4368 0.3472 28.52 25.83 0.6 0.3957 0.4401 0.4028 1.75 9.26 0.8 0.3571 0.4544 0.4641 23.07 2.11 0.9 0.3579 0.4851 0.5228 31.54 7.21 表 6 对CFRP复合材料拉-拉疲劳试验损伤曲线的预测值与拟合值的比较(
$ {\sigma }_{{\rm{a}}} $ =290 MPa)Table 6. Comparison of predicted results and fitting results of tension-tention fatigue damage curve for CFRP composite (
$ {\sigma }_{{\rm{a}}} $ =290 MPa)n/Nf Prediction of
386-241 MPaPrediction of
338-241 MPaDamage
curveDeviation
(386-241 MPa)/ %Deviation
(338-241 MPa)/ %0.2 0.4323 0.3235 0.3001 44.08 7.82 0.4 0.4280 0.3779 0.4093 4.56 7.66 0.6 0.3964 0.4000 0.4851 18.28 17.55 0.8 0.3738 0.4278 0.5688 34.29 24.78 0.9 0.3833 0.4666 0.6394 40.05 27.03 表 7 对CFRP复合材料拉-拉疲劳试验损伤曲线的预测值与拟合值的比较(
$ {\sigma }_{{\rm{a}}} $ =147 MPa)Table 7. Comparison of predicted results and fitting results of tension-tention fatigue damage curve for CFRP composite (
$ {\sigma }_{{\rm{a}}} $ =147 MPa)n/Nf Prediction of
174-147 MPaDamage
curveDeviation
(174-147 MPa)/ %0.1242 0.2189 0.2280 3.99 0.3854 0.3419 0.3690 7.34 0.6416 0.3932 0.4369 9.98 0.7822 0.4257 0.4786 11.05 0.9012 0.4800 0.5437 11.71 0.9271 0.5021 0.5691 11.77 -
[1] BROUNTMAN L J, SAHU S. A new theory to predict cumulative fatigue damage in fiber glass reinforced plastics[J]. ASTM STP 497,1972:170-188. [2] BRUNBAUER J, ARBEITER F, STELZER S, et al. Stiffness based fatigue characterisation of CFRP[J]. Advanced Materials Research,2014,891-892:166-171. doi: 10.4028/www.scientific.net/AMR.891-892.166 [3] LLOBET J, MAIMÍ P, MAYUGO J A, et al. A fatigue damage and residual strength model for unidirectional carbon/epoxy composites under on-axis tension-tension loadings[J]. International Journal of Fatigue,2017,103:508-515. doi: 10.1016/j.ijfatigue.2017.06.026 [4] RAFIEE R. Stochastic fatigue analysis of glass fiber reinforced polymer pipes[J]. Composite Structures,2017,167:96-102. doi: 10.1016/j.compstruct.2017.01.068 [5] STOJKOVIĆ N, FOLIĆ R, PASTERNAK H. Mathematical model for the prediction of strength degradation of composites subjected to constant amplitude fatigue[J]. International Journal of Fatigue,2017,103:478-487. doi: 10.1016/j.ijfatigue.2017.06.032 [6] YANG J N, LIU M D. Residual strength degradation model and theory of periodic proof tests for graphite epoxy laminates[J]. Journal of Composite Materials,1977,11:176-203. doi: 10.1177/002199837701100205 [7] CHOU P C, CORMAN R. Residual strength in fatigue based on the strength-life equal rank assumption[J]. Journal of Composite Materials,1978,12(2):177-194. doi: 10.1177/002199837801200206 [8] REVUELTA D, CUARTERO J, MIRAVETE A, et al. A new approach to fatigue analysis in composites based on residual strength degradation[J]. Composite Structures,2000,48(1-3):183-186. doi: 10.1016/S0263-8223(99)00093-8 [9] CAI D, YIN J, LIU R. Experimental and analytical investigation into the stress performance of composite anchors for CFRP tendons[J]. Composites Part B: Engineering,2015,79:530-534. doi: 10.1016/j.compositesb.2015.05.014 [10] WHITWORTH H A. Evaluation of the residual strength degradation in composite laminates under fatigue loading[J]. Composite Structures,2000,48(4):261-264. doi: 10.1016/S0263-8223(99)00113-0 [11] CREMONA C. Probabilistic approach for cable residual strength assessment[J]. Engineering Structures,2003,25(3):377-384. doi: 10.1016/S0141-0296(02)00173-6 [12] PHILIPPIDIS T P, PASSIPOULARIDIS V A. Residual strength after fatigue in composites: Theory vs. experiment[J]. International Journal of Fatigue,2007,29(12):2104-2116. doi: 10.1016/j.ijfatigue.2007.01.019 [13] POST N L, CAIN J, MCDONALD K J, et al. Residual strength prediction of composite materials: Random spectrum loading[J]. Engineering Fracture Mechanics,2008,75(9):2707-2724. doi: 10.1016/j.engfracmech.2007.03.002 [14] REIFSNIDER K L, HENNEKE E G, et al. Damage mechanics and NDE of composite laminates[J]. Mechanics of Compo-site Materials, 1983: 399-420. [15] YAO W X, HIMMEL N. A new cumulative fatigue damage model for fibre-reinforced plastics[J]. Composites Science and Technology,2000,60(1):59-64. doi: 10.1016/S0266-3538(99)00100-1 [16] 中华人民共和国国家质量监督检验检疫总局. 结构工程用纤维增强复合材料筋规范: GB/T26743-2011[S], 北京: 中国标准出版社, 2011.General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. Standard for fiber reinforced composite materials used in structural engineering: GB/ T26743—2011[S]. Beijing: China Standards Press, 2011(in Chinese). [17] American Society for Testing and Materials. Standard test method for tensile properties of polymer matrix composite materials[S]. West Conshohocken: ASTM, 2017. [18] American Society for Testing and Materials. Standard test method for tension-tension fatigue of polymer matrix composite materials[S]. West Conshohocken: ASTM, 2012. [19] OWEN M J, HOWE R J. The accumulation of damage in a glass-reinforced plastic under tensile and fatigue loading[J]. Journal of Physics D: Applied Physics,1972,5(9):1637-1649. doi: 10.1088/0022-3727/5/9/319 [20] 邱爽, 周金宇. 不同应力水平对碳纤维复合材料疲劳剩余刚度的影响[J]. 航空材料学报, 2018, 38(2):110-117. doi: 10.11868/j.issn.1005-5053.2017.000076QIU S, ZHOU J Y. Effects of different fatigue stress levels on residual stiffness of carbon fiber composites[J]. Journal of Aeronautical Materials,2018,38(2):110-117(in Chinese). doi: 10.11868/j.issn.1005-5053.2017.000076