应力水平和纤维角度对CGF/PP复合材料蠕变行为的影响及其Burgers模型参数的数值预测
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摘要
采用DMA的Creep模式分别测试了短时间内(15min)聚丙烯(PP)在不同应力水平和温度下的单向拉伸蠕变行为,长时间内(10h)连续玻璃纤维增强聚丙烯(CGF/PP)复合材料单层板在不同应力水平和不同纤维角度上的拉伸蠕变行为。利用Burgers黏弹性模型拟合了蠕变测试数据,构建了相关参数与应力水平和纤维角度的依赖性。结果表明:PP和CGF/PP单层板的蠕变柔量均随应力增大而显著增加,稳态蠕变速率也随之增加,蠕变模量保留率明显下降,PP基体的黏弹性主要决定了CGF/PP单层板在低应力水平下的蠕变行为;30%应力水平下,偏轴拉伸的纤维角度在0°～90°范围内存在拉-剪耦合效应,在45°时最为显著,此时稳态蠕变速率和蠕变变形量最大;利用四元件Burgers黏弹性模型拟合各条件下蠕变曲线得到的数值模型与实验数据具有较好的相关性,相关系数达到0.99,从得到的数值模型可知相关模型参数存在明显的应力和角度依赖关系;利用模型参数的数值拟合公式分别预测10MPa应力下0°纤维方向的蠕变曲线及45°纤维方向上30%应力水平的偏轴蠕变曲线均与实验曲线一致,表明本文得到的数值模型的可靠性。
In this study,the short-term(15 min)tensile creep behaviors of polypropylene(PP)at different temperature and stress levels were examined by DMA creep model test,followed by the characterization on the longterm tensile creep behavior(10 h)continuous glass fiber reinforced polypropylene composites(CGF/PP)at the different stress levels and fiber orientations.The Burgers viscoelastic model was adopted to simulate the materials creep curves and pertinent model parameters associated with the stress levels and fiber orientations were derived.The results show that,with the rise of loaded stress,the creep compliance and steady-state creep rate of PP and unidirectional CGF/PP laminate both increase significantly,and the creep modulus retention rate decrease obviously,demonstrating that the creep behaviors of CGF/PP under low stress levels is dependent on the viscoelastic properties of PP matrix.The tensile-shear coupling effects occur in the loaded angle from 0°to 90°for the off-axis tension with a stress level of 30%,specifically in the 45°where steady-state creep rate and the creep deformation of composites exhibit maximum values.The derived numerical model by means of four element Burgers viscoelastic model to fit the creep curves in different conditions matches well with the experimental data,with a correlation coefficients of 0.99 between them.The numerical clearly illustrated the stress and fiber orientation dependence for the pertinent model parameters.The numerical formula of model parameters was established.The estimated tensile creep curve in the 0°fiber direction at 10 MPa and the estimated off-axis tensile creep curve in the 45°off-axis fiber direction at 30% of stress level are nearly identical with the experimental curve,showing the reliability of the derived numerical model in this paper.
In this study,the short-term(15 min)tensile creep behaviors of polypropylene(PP)at different temperature and stress levels were examined by DMA creep model test,followed by the characterization on the longterm tensile creep behavior(10 h)continuous glass fiber reinforced polypropylene composites(CGF/PP)at the different stress levels and fiber orientations.The Burgers viscoelastic model was adopted to simulate the materials creep curves and pertinent model parameters associated with the stress levels and fiber orientations were derived.The results show that,with the rise of loaded stress,the creep compliance and steady-state creep rate of PP and unidirectional CGF/PP laminate both increase significantly,and the creep modulus retention rate decrease obviously,demonstrating that the creep behaviors of CGF/PP under low stress levels is dependent on the viscoelastic properties of PP matrix.The tensile-shear coupling effects occur in the loaded angle from 0°to 90°for the off-axis tension with a stress level of 30%,specifically in the 45°where steady-state creep rate and the creep deformation of composites exhibit maximum values.The derived numerical model by means of four element Burgers viscoelastic model to fit the creep curves in different conditions matches well with the experimental data,with a correlation coefficients of 0.99 between them.The numerical clearly illustrated the stress and fiber orientation dependence for the pertinent model parameters.The numerical formula of model parameters was established.The estimated tensile creep curve in the 0°fiber direction at 10 MPa and the estimated off-axis tensile creep curve in the 45°off-axis fiber direction at 30% of stress level are nearly identical with the experimental curve,showing the reliability of the derived numerical model in this paper.
引文
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[18]PLUMTREE A,CHENG G X.A fatigue damage para-meter for off-axis unidirectional fibre-reinforced composites[J].International Journal of Fatigue,1999,21(8):849-856.
[19]VARVANI-FARAHANI A,HAFTCHENARI H,PANBE-CHI M.An energy-based fatigue damage parameter for offaxis unidirectional FRP composites[J].Composite Structures,2007,79(3):381-389.
[20]沈观林,胡更开,刘彬.复合材料力学第2版[M].北京:清华大学出版社,2013.SHEN G L,HU G K,LIU B.Mechanics of composite materials:Second edition[M].Beijing:Tsinghua University Press,2013(in Chinese).
[2]方立,周晓东,吴忠泉,等.连续玻璃纤维增强聚丙烯复合板材的性能研究[J].工程塑料应用,2012,40(12):12-15.FANG L,ZHOU X D,WU Z Q,et al.Properties of continuous glass fiber reinforced polypropylene laminates[J].Engineering Plastics Application,2012,40(12):12-15(in Chinese).
[3]DROZDOV A D.Effect of temperature on the vis-coelastic and viscoplastic behavior of polypropylene[J].Mechanics of Time-Dependent Materials,2010,14(4):411-434.
[4]梁军,杜善义.粘弹性复合材料力学性能的细观研究[J].复合材料学报,2001,18(1):97-100.LIANG J,DU S Y.Study of mechanical properties of viscoelastic matrix composite by micro-mechanics[J].Acta Materiae Compositae Sinica,2001,18(1):97-100(in Chinese).
[5]GUEDES R M.Creep and fatigue lifetime prediction of polymer matrix composites based on simple cumulative damage laws[J].Composites Part A:Applied Science&Manufacturing,2008,39(11):1716-1725.
[6]DASARI A,YU Z Z,MAI Y W.Fundamental aspects andrecent progress on wear/scratch damage in polymer nanocomposites[J].Materials Science&Engineering Reports,2009,63(2):31-80.
[7]FLIEGENER S,HOHE J,GUMBSCH P.The creep behavior of long fiber reinforced thermoplastics examined by microstructural simulations[J].Composites Science&Technology,2016,131:1-11.
[8]CHEVALI V S,JANOWSKI G M.Flexural creep of long fiber-reinforced thermoplastic composites:Effect of processing-dependent fiber variables on creep response[J].Composites Part A:Applied Science and Manufacturing,2010,41(9):1253-1262.
[9]KAWAI M,MASUKO Y,SAGAWA T.Off-axis tensile creep rupture of unidirectional CFRP laminates at elevated temperature[J].Composites Part A:Applied Science&Manufacturing,2006,37(2):257-269.
[10]GOERTZEN W K,KESSLER M R.Creep behavior of carbon fiber/epoxy matrix composites[J].Materials Science&Engineering A,2006,421(1):217-225.
[11]刘鹏飞,赵启林,王景全,等.树脂基复合材料蠕变性能研究进展[J].玻璃钢/复合材料,2013(3):109-117.LIU P F,ZHAO Q L,WANG J Q,et al.Research progress in creep property of resin matrix composites[J].Fiber Reinforced Plastics/Composites,2013(3):109-117(in Chinese).
[12]钟轶峰,杨旦旦,周小平,等.聚合物基复合材料有效蠕变响应与单轴拉伸行为的细观力学模拟[J].复合材料学报,2016,33(12):2911-2917.ZHONG Y F,YANG D D,ZHOU X P,et al.Effective creep response and uniaxial tension behavior of polymer matrix composites simulated by mesomechanics[J].Acta Materiae Compositae Sinica,2016,33(12):2911-2917(in Chinese).
[13]中国国家标准化管理委员会.单向纤维增强复合材料拉伸性能的测定:GB/T 1040.5-2008[S].北京:中国标准出版社,2008.Standardization Administration of the People’s Republic of China.Plastics:Determination of tensile properties Part 5:Test conditions for unidirectional fiber-reinforced plastic composites:GB/T 1040.5-2008[S].Beijing:China Standards Press,2008(in Chinese).
[14]GREBOWICZ J,LAU S,WUNDERLICH B.The thermal properties of polypropylene[J].Journal of Polymer Science Polymer Symposia,2010,71(1):19-37.
[15]金日光,华幼卿.高分子物理第3版[M].北京:化学工业出版社,2006.JING R G,HUA Y Q.Polymer physics:Third edition[M].Beijing:Chemical Industry Press,2006(in Chinese).
[16]LIU X,HUANG Y,CONG D,et al.Study on the creep behavior of polypropylene.[J].Polymer Engineering&Science,2009,49(7):1375-1382.
[17]KAWAI M,MASUKO Y.Macro-mechanical model-ing and analysis of the viscoplastic behavior of unidirectional fiberreinforced composites[J].Journal of Composite Materials,2003,37(21):1885-1902.
[18]PLUMTREE A,CHENG G X.A fatigue damage para-meter for off-axis unidirectional fibre-reinforced composites[J].International Journal of Fatigue,1999,21(8):849-856.
[19]VARVANI-FARAHANI A,HAFTCHENARI H,PANBE-CHI M.An energy-based fatigue damage parameter for offaxis unidirectional FRP composites[J].Composite Structures,2007,79(3):381-389.
[20]沈观林,胡更开,刘彬.复合材料力学第2版[M].北京:清华大学出版社,2013.SHEN G L,HU G K,LIU B.Mechanics of composite materials:Second edition[M].Beijing:Tsinghua University Press,2013(in Chinese).