【作者】 李刚；

【导师】 杨小平；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2008， 博士

【摘要】 碳纤维/环氧树脂基复合材料的增韧方法是先进复合材料研究发展的重要方向,其历程已经从第二代复合材料的热塑性工程塑料物理共混增韧环氧树脂基体,发展到热塑性工程塑料颗粒或溶剂法膜层间增韧的第三代复合材料。物理共混方法存在的问题是复合材料成型加工困难,而后者未解决层间增韧与树脂基体流动性、渗透性和浸润性之间的矛盾。为此提出纳米纤维膜层间增韧碳纤维/环氧树脂复合材料的新方法,利用电纺纳米纤维的直径小、高孔隙率和大比表面积等特性,实现热塑性工程塑料改性复合材料的增韧效果与工艺适应性的统一。1.以N,N′-二甲基乙酰胺（DMAC）/丙酮为混合溶剂,采用静电纺丝工艺制备了聚砜（PSF）纳米纤维膜。增加混合溶剂中丙酮比例和纺丝溶液浓度有利于得到单一形貌的聚砜纳米纤维膜。增加纺丝电压,纳米纤维直径变小,而降低纺丝液流速,可以避免串珠形貌的形成。2.基于碳纤维的导电性,通过静电纺丝直接将聚砜纳米纤维膜接收于碳纤维/环氧树脂预浸布上,建立了一种层间增韧的新方法,采用纳米纤维膜层间增韧碳纤维/环氧树脂基复合材料,实现增韧复合材料的目的。所用聚砜纳米纤维膜是由无规取向的纳米纤维组成,根据其特殊结构,建立了纳米纤维膜的非均相相分离模型,即在环氧树脂固化过程中,聚砜沿着纳米纤维的方向发生“原位”相分离,聚砜微球呈现无规取向分布的“海岛”结构,而且贯穿于整个复合材料层间。在纳米纤维膜含量为5 wt%时,增韧复合材料的G_ⅠC和G_ⅡC分别增加了181%和177%,高于同等含量的溶剂法膜增韧复合材料。DMTA测试表明,与溶剂法膜相比,纳米纤维膜与环氧树脂基体的相容性更好。3.采用差示扫描量热法（DSC）和近红外光谱（NIR）研究了环氧树脂基体、5wt%聚砜纳米纤维膜和溶剂法膜增韧环氧树脂的等温固化反应动力学。比较了聚砜纳米纤维膜和溶剂法膜增韧环氧树脂的基本动力学参数,表明环氧基团转化率和固化反应速率的变化趋势一致。在固化反应初期,聚砜纳米纤维膜增韧体系的反应速率高于溶剂法膜增韧体系和树脂基体,而聚砜纳米纤维膜和溶剂法膜增韧体系的最终转化率却低于树脂基体,通过NIR测试得到的一级胺的变化趋势,解释了其固化反应机理。4.采用混酸氧化处理的碳纳米管（CNTs）,通过静电纺丝制备了聚砜（PSF）/碳纳米管（CNTs）杂化的纳米纤维膜。研究了PSF/CNTs的纳米纤维膜增韧增强环氧树脂基体的拉伸、冲击和耐热性能,结果表明碳纳米管含量为3 wt%的PSF/CNTs纳米纤维膜增韧增强环氧树脂的拉伸强度提高12%,冲击强度提高10%,玻璃化转变温度提高4℃。增韧增强的协同效应归因于非均相相分离的聚砜微球和分散于树脂基体或热塑性塑料微球的不同位置碳纳米管的共同作用。更多还原

【Abstract】 Toughening methods of carbon fiber/epoxy composite are the important target of advanced composite development.In the second generation composite,thermoplastics have been used to toughen epoxy matrix by physical blending.However,composite fibrication was difficult due to the high viscosity of blending systems.In the third generation composite, thermoplastic particles or films prepared by solvent method have been used in the interlaminar toughening composite.However,among these methods some limitations still existed in practical utility,such as the low fluidity of polysulfone（PSF） and permeability of resin matrix etc.Therefore,we suggested a novel method to toughen the composites using electrospun PSF nanofibrous membranes.Unique properties of nanofibrous membranes, such as small diameter,large porosity and high specific surface area, allowed the nanofibers being easily impregnated by epoxy matrix to increase the compatibility,resulting in easy dissolution into matrix.1.Polysulfone nanofibrous membranes were prepared by electrospinning of PSF solutions in mixtures of N,N’-dimethylacetamide（DMAC） and acetone.Increasing the acetone amount and the polymer concentration was beneficial to produce electrospun nanofibrous membranes with uniform morphology.Raising the applied voltage tented to produce smaller diameters of the electrospun nanofibers,while applying a lower flow rate was favorable to avoid bead-fiber morphology.2.A novel approach for toughening carbon fiber/epoxy composite using electrospun PSF nanofibrous membranes was performed.As-received membranes were composed of nanofibers with random orientation,and were directly electrospun onto layers of carbon fiber/epoxy prepregs to toughen the composites.According to the random dispersed nanofibers on the membranes,the inhomogeneous phase separation of polysulfone,which was generated in-situ along the nanofibers direction during the curing of epoxy matrix,was proposed.PSF spheres exhibited random alignment in "sea-island" morphology and presented uniform dispersion through the composite interlayers.Mode I and II inteflaminar fracture toughness(G_ⅠC & G_ⅡC) of 5 wt%PSF nanofibrous membranes toughened composite increased by 181%and 177%,which were higher than those of 5 wt%PSF films toughened composite.DMTA tests revealed good compatibility between nanofibrous membranes and epoxy matrix.3.The isothermal curing kinetics of epoxy matrix,5 wt%PSF nanofibrous membranes and films toughened epoxy resins were investigated by Differential Scanning Caliorimetry（DSC） and Near Infra-red Spectroscopy（NIR）.The fundamental kinetic parameters were compared,and the conversion of epoxide group and the curing rate exhibited identical variations.At the initial curing stage,the curing rate of PSF nanofibrous membranes toughened epoxy resin was faster than that of PSF films toughened epoxy resin and epoxy matrix,whereas the final conversion degree of PSF nanofibrous membranes and films toughened epoxy resins was lower than that of epoxy matrix.The curing mechanism could be explained by the variation of primary amine from NIR testing.4.Electrospun nanofibrous membranes of PSF/CNTs hybrid were prepared by using CNTs treated with the mixture of H₂SO₄ and HNO₃.The tensile,impact and thermal properties of nanofibrous membranes toughened and reinforced epoxy matrixes were investigated.When the content of nanofibrous membranes was 3 wt%,the tensile strength and impact strength of toughened and reinforced epoxy matrixes were increased by 12%and 10%,respectively,and the glass transition temperature（T_g） was enhanced by 4℃.The synergism effects of toughening and reinforcing were due to PSF spheres from the inhomogeneous phase separation and CNTs at different sites in epoxy matrix or PSF spheres.更多还原