纳米纤维素对碳纤维增强复合材料阻尼性能的影响

Damping properties of carbon fiber reinforced composites modified with cellulose nanofiber

纳米纤维素源自植物纤维,具有较好的力学性能。使用化学预处理结合机械分离法从木浆原材料中提取纳米纤维素,研究机械研磨时间对纤维素结构形态的影响。对得到的纳米纤维素悬浮液进行冷冻干燥处理,可获得结构疏松的三维网状纳米纤维素薄膜。使用水溶性环氧对纳米纤维素进行表面改性,降低纳米纤维素的亲水性,可有效改善纳米纤维素与环氧树脂间的界面结合。将纳米纤维素薄膜加入碳纤维复合材料中,以改善碳纤维增强复合材料阻尼性能,使用动态力学分析法测试损耗因子,评估复合材料的阻尼性能。结果表明:纳米纤维素的加入可以小幅提高碳纤维复合材料的损耗因子,对纳米纤维素进行表面改性后,损耗因子得到进一步提高;随着振幅的增加,纳米纤维素改性复合材料的损耗因子也随之增加。

Cellulose is considered as the most abundant natural polymer from biomass.Cellulose nanofiber(CNF)is derived from natural cellulose.Compared with the other nanomaterials,CNF has the characteristics of low density,large specific surface area and high specific modulus,moreover,it has the advantages of renewable and biodegradable,etc.It is a new type of functional material with outstanding performance and economical practicality.Carbon fiber reinforced polymer composites(CFRPs)have been widely used in recent years due to their low density and high specific strength.However,the damping properties of CFRPs are poor since they have a high sensitivity to damage.In this paper,CNF was used to improve the damping properties of CFRP,which was proposed to provide new ideas and methods for the design and application of CNF in CFRP.A combination of mechanical and chemical methods was used to extract CNF from softwood pulp.The micron-level flocculent fibers were obtained by high-speed shearing treatment,then the impurities were removed by alkali pretreatment.The suspension liquid was grinded by a grinder until the diameters of fibers less than 1μm.The effect of mechanical grinding time on the size of the cellulose product was studied.The obtained CNF suspension liquid was freeze-dried to obtain a three-dimensional networked film with low density and high porosity,which could be added as an interleaf to the CFRP.The hydrophilic characteristics of CNF maked it poorly compatible with the hydrophobic matrix,and the poor interface bonding greatly affected the mechanical properties of CFRP.In this paper,waterborne epoxy(WE)was used to modify the surface of CNF to reduce the hydrophilicity,which could effectively improve the interface between CNF and epoxy resin.The effect of CNF on the damping properties of CFRP was studied.The dynamic mechanical analysis(DMA)method was used to test the loss factor which could evaluate the damping properties of composite laminates.The results show that the addition of CNF films can slightly increase the loss factor of CFRP,because CNF are derived from plant fibers,and their damping properties are better than that of carbon fibers.The viscoelasticity of CNF helps to improve the loss factor of CFRP.In addition,the stick-slip motion occurs between CNF and resin,and friction generates energy consumption,therefore,the damping properties of CFRP were improved.After surface modification,the loss factor is further improved.The stronger interface bonding makes the surface of CNF debonded become rougher,which produces greater interface friction,thereby,the frictional energy consumption is increased.With the increase of amplitude,the loss factor of the cellulose nanofiber modified composite also increases.