全湿热场下碳纤维/环氧树脂复合材料层间剪切强度

针对T700/TR1219B碳纤维/环氧树脂复合材料,在不同湿/热/力耦合条件下进行层间剪切实验,对比分析性能衰减规律,通过峰值力纳米力学模量成像技术定量表征界面尺寸变化,并结合微观断口形貌分析探究湿热损伤机制。结果表明,T700/TR1219B的层间剪切性能受湿、热场影响显著,当吸湿率为2%时,层间剪切强度从原样的72.64 MPa下降到46.92 MPa;随温度的升高,层间剪切性能呈线性递减趋势,降幅约为0.35 MPa/℃;高温高湿环境下层间剪切强度最大降幅达到93%,且温度场造成的损伤效应高于湿度场。微观表征结果表明,吸湿作用是导致界面尺寸增大的主要因素,而高温高湿环境会对纤维、树脂及其界面均造成明显损伤。通过对比分析湿、热单一和耦合作用下T700/TR1219B层间剪切强度的变化规律,建立了全湿热场下层间剪切强度模型。     

三种不同碳纤维的纳米压痕行为

采用Raman光谱对三种不同碳纤维(K223HE、HTA40和T700SC)的微晶尺寸进行了表征,利用纳米压痕技术对三种碳纤维的横向弹性模量和硬度进行了测试,结合Weibull分布函数对碳纤维的横向弹性模量和硬度进行统计分析。结果表明,中间相沥青基碳纤维K223HE的微晶长度最大,为39.43nm±2.63nm,PAN基碳纤维HTA40和T700SC的微晶尺寸基本相同,分别为4.63nm±0.09nm和4.89nm±0.06nm。在纳米压痕载荷-深度曲线上,碳纤维K223HE的残余变形大(75.34nm±17.07nm),压入功恢复率低(65.89%)。碳纤维HTA40、K223HE和T700SC的特征横向弹性模量为19.52GPa、11.99GPa和17.92GPa。三种碳纤维的横向弹性模量的Weibull分布模数分别为25.26、6.85和8.07,说明HTA40碳纤维的性能均匀性最好。碳纤维的纳米压痕行为的差异主要是由碳纤维中微晶的完整性、择优取向性的差异引起的。     

碳纤维复合材料界面结构的形貌与尺寸的表征

为了准确测定碳纤维增强树脂基复合材料界面结构的形貌和尺寸, 本文中介绍了一种原位纳米力学动态模量成像技术, 并采用该方法对碳纤维增强热固性树脂基复合材料进行了测试, 对该技术在界面结构测试上的参数设置、 数据处理方法以及适用性等方面进行了分析。研究表明, 该方法的横向分辨率可以达到纳米尺度, 适于测量界面尺寸在纳米级别的碳纤维复合材料界面形貌与尺寸。对于碳纤维/环氧树脂和碳纤维/双马树脂体系, 界面区的储能模量呈梯度变化, 根据储能模量成像图的统计分析可得到界面的形貌和厚度。所得界面平均厚度在100nm左右, 横截面上界面形貌呈不均匀的“河流状”, 并与碳纤维表面形貌相似。      

全湿热场下碳纤维/环氧树脂复合材料弯曲性能及寿命预测

以碳纤维/环氧树脂（T700/TR1219B）复合材料为研究对象,采用湿度场和温度场单一及耦合的方式,研究了不同湿热环境下其弯曲性能的变化,通过断口形貌和表面粗糙度表征,分析其湿热损伤机制。结果表明:T700/TR1219B复合材料的弯曲性能受湿度场和温度场影响明显,当吸湿率达到2%时,弯曲强度从干态的1 440.60 MPa下降到1 081.07 MPa;随温度的升高弯曲性能呈下降趋势,且在玻璃化转变温度T_g所在温度区间发生陡降,当环境温度为180℃时,弯曲模量和弯曲强度分别下降了71.18%和93.32%;高温高湿环境下弯曲性能陡降的温度区间前移,且性能衰减并非单一湿度场和温度场下衰减量的简单叠加。通过微观形貌分析发现,湿度场主要导致树脂水解脱黏,温度场下树脂形态破坏严重,而湿热耦合场对纤维与树脂均产生较大程度的损伤。考虑湿度场和温度及湿热耦合相关项,建立并验证了全湿热场下剩余弯曲强度模型,结合湿热老化时间、环境当量等参数提出T700/TR1219B复合材料的寿命预测模型。      

聚醚砜对连续碳纤维/聚醚醚酮复合材料性能的影响

以聚醚砜(PES)作为第三组分及活化PES作为连续碳纤维(CCF)的表面改性剂制备CCF/聚醚醚酮(PEEK)复合材料,重点研究CCF/PEEK复合材料的制备工艺方法对其性能的影响.结果表明:PES作为第三组分制备的CCF/PEEK复合材料,当填充16wt％的CCF时,复合材料表面电阻降低到107～109 Ω,出现导电...     

连续纤维增强PPESK树脂基复合材料的界面性能

用SEM观察了复合材料的微观断面结构,用横向拉伸强度和层间剪切强度表征玻璃纤维(GF)、T700碳纤维(CF)、芳纶纤维(F-12)增强PPESK树脂基复合材料的界面性能,研究了界面性能对三种复合材料耐湿热性能的影响.结果表明,T700/PPESK和F-12/PPESK复合材料的界面粘接性能均优于GF/PPESK复合体系.三种纤维复合材料的破坏机理不同:玻璃纤维发生纤维与树脂的界面脱粘破坏,碳纤维复合材料在破坏时,树脂与纤维并没有完全脱粘,破坏发生在树脂内;而芳纶纤维复合材料的破坏总伴随着纤维本身横向的撕裂破坏.三种复合材料体系均具有较低的吸湿率和良好的耐湿热性能,T700/PPESK复合材料在湿热条件下的性能保持率最高.     

基于纳米压痕技术的碳纤维/环氧树脂复合材料各组分原位力学性能测试

基于纳米压痕技术对碳纤维/环氧树脂复合材料各组分的原位硬度、 弹性模量和蠕变性能进行了测试, 实验得到了基体、 纤维和微小厚度界面层的力学性能。结果表明, 从环氧树脂基体到碳纤维过渡过程中, 硬度和弹性模量有明显的梯度变化, 并且纤维和树脂基体的原位弹性模量平均值与其非原位性能有一定的变化, 实验得到纤维的原位弹性模量有所下降, 环氧树脂的弹性模量有所增加。试件制备过程中的机械研磨对其表面产生的残余应力和复合后两种材料的相互影响是组分材料原位性能变化的主要原因。各组分的蠕变性能呈现出明显的差异。     

国产T700级碳纤维/双马来酰亚胺树脂复合材料界面性能

分别以日本东丽T700S和国产T700级碳纤维作为增强体,采用热压罐成型工艺制备了双马来酰亚胺树脂基复合材料。对比研究了两种碳纤维表面物理、化学状态以及复合材料的微观界面性能、层间剪切性能。结果表明,国产T700级碳纤维表面沟槽结构分布较多,表面粗糙度较高,有利于与树脂基体形成更好的物理结合作用。虽然两种碳纤维的含氧官能团相当,但国产T700级碳纤维表面元素氧碳比较高,有利于与基体树脂形成更好的化学结合作用,其界面剪切强度较T700S碳纤维复合材料高约14%,复合材料的层间剪切强度高约19%。     

高刚度环氧树脂与高模碳纤维的界面相容和性能匹配

自行开发了一种高刚度环氧树脂（5182树脂）,研究了5182树脂的增刚机制、耐热性能和力学性能。结果表明,原位生成的酰亚胺刚性链段及增加的多交联位点提高了5182树脂交联网络的刚性,其玻璃化转变温度达228℃,拉伸模量达到4 375 MPa。采用高刚度5182树脂制备了国产BHM3和东丽M40J高模碳纤维增强高刚度环氧树脂复合材料,考察了高模碳纤维/高刚度环氧树脂单丝复合材料的界面黏结性能和断面微观形貌,并评价了高模碳纤维/高刚度环氧树脂单向复合材料的宏观力学性能。结果表明,由于树脂模量的提高及界面破坏区域由碳纤维表面转移到环氧树脂区,高模碳纤维/高刚度环氧树脂复合材料的界面剪切强度最高达106.8 MPa,宏观力学性能优异,尤其弯曲性能和层间剪切强度大幅提高。      

建筑用碳纤维增强环氧树脂复合材料的制备及其性能研究

选择以T700碳纤维为增强相，将碳纤维经浓HNO₃浸渍处理0,40,80,120和160 min后掺入到环氧树脂中，制备了碳纤维增强环氧树脂复合材料。分析了浸渍时间对复合材料微观形貌、力学性能和热稳定性的影响。结果表明，经浓HNO₃浸渍的碳纤维表面粗糙度增大，沟槽数量和深度增加，碳纤维和环氧树脂的结合强度增大；随碳纤维浸渍时间的增大，复合材料的界面剪切强度、层间剪切强度、弯曲强度和弯曲模量均先增大后减小，当浸渍时间为120 min时，复合材料的界面剪切强度和层间剪切强度均达到了最大值，分别为80.2和90.3 MPa,其弯曲强度和弯曲模量也达到了最大值，分别为902.6 MPa和79.3 GPa,且应力-应变最高点增大，弯曲性能提高；在800℃下浓HNO₃浸渍处理120 min的复合材料的残炭率最大为58.2%,热稳定性最佳。     

Nanoscale characterization of natural fibers and their composites using contact-resonance force microscopy

Contact-resonance force microscopy (CR-FM) has been used for the first time to evaluate the mechanical properties of the interphase in natural fiber-reinforced composites and of cell wall layers of natural fibers. With CR-FM, quantitative images of the spatial distribution in nanoscale elastic properties were acquired. The images were calibrated with nanoindentation values. From the modulus images, the average interphase width was found to be (49 ± 5) nm for composite without any treatment, and (139 ± 21) nm for one with a maleic anhydride polypropylene treatment. There was a gradient of modulus across the interphase that ranged between the values of fiber and the polymer. The average values of indentation modulus obtained for different cell wall layers within a fiber were 22.5–28.0 GPa, 17.9–20.2 GPa, and 15.0–15.5 GPa for the S₂ and S₁ layers and the compound middle lamellae, respectively.     

考虑氧化损伤的陶瓷基复合材料弹性模量多尺度预测模型

分析了化学气相渗透(CVI)工艺制备的陶瓷基复合材料的氧化损伤演化规律,基于基体的微裂纹分布规律及界面、纤维、基体等组分氧化历程,建立了考虑温度、氧化时间影响的纤维和单胞两个尺度的弹性模量预测模型。预测结果表明,碳纤维(C_f)/SiC和SiC纤维(SiC_f)/SiC复合材料的拉伸弹性模量随氧化温度升高和氧化时间的增长,下降趋势越明显。通过复合材料高温氧化后的力学性能试验,验证了弹性性能预测模型的正确性:BN界面的SiC_f/SiC材料在1000℃不同时间氧化后预测结果与试验结果误差不超过2%;PyC界面的C_f/SiC在700℃不同时间氧化后预测结果与试验结果误差不超过7%。      

碳纤维增强聚醚砜的工艺、性能和断裂形貌研究

本文介绍了连续碳纤维增强聚醚砜复合材料(CF/PES)的制造工艺与性能.阐述了一种改进的连续纤维增强热塑性复合材料预浸料的制造方法,给出了CF/PES复合材料的最佳模压成型工艺条件,制得了低孔隙率、高机械性能的复合材料.最后,分析了CF/PES的断裂模式和断口形貌.     

Cooling rate influences in carbon fibre/PEEK composites. Part 1. Crystallinity and interface adhesion

The effect of cooling rate on the fibre–matrix interface adhesion for a carbon fibre/semicrystalline polyetheretherketone (PEEK) composite was characterised based on the fibre fragmentation, fibre pullout and short beam shear tests. The interface adhesion was correlated to the degree of crystallinity and the crystalline morphology, as well as the bulk mechanical properties of neat PEEK resin, all of which were in turn controlled by cooling rate. It was shown that the interface bond strength decreased with increasing cooling rate; the tensile strength and elastic modulus of PEEK resin decreased, while the ductility increased with increasing cooling rate through its dominant effect on crystallinity and spherullite size. The improvement of crystalline perfection and flattened lamella chains with high crystallinity at the interphase region were mainly responsible for the strong interface bond in composites processed at a low cooling rate. The interphase failure was characterised by brittle debonding in slow-cooled composites, whereas the amorphous PEEK-rich interphase introduced in fast cooled specimens failed in a ductile manner with extensive plastic yielding.     

Tensile Fracture Behavior of Carbon Fiber/Al Composites Produced by the Liquid Extrusion Infiltration Technique

Strength of Materials - The liquid extrusion infiltration technique was used to fabricate two 2D CF/Al composites with T700 and T300 carbon fiber fabrics. Microstructure examination demonstrated...     

Carbon fiber/ceramic matrix composites: processing,oxidation and mechanical properties

Ceramic matrix composites (CMC) have been considered in the last two decades to be alternative materials for highly demanding thermo-structural applications. Pre-ceramic polymers offer significant advantages for manufacturing these composites by the polymer impregnation method. In the present work, carbon fiber/silicon oxycarbide (C/SiC _x O _y ) composites were obtained by controlled pyrolysis of carbon fiber/bridge polysilsesquioxane composites (COMPOSITE 1) followed by infiltration/pyrolysis cycles with a polycyclic silicone network. The polysilsesquioxane showed high wettability and adhesion on the carbon fiber surface. An improvement of the thermo-oxidation resistance and a reduction of the porosity as a function of the number of polycyclic silicone infiltration cycles were observed. An extra improvement in the thermo-oxidation protection was found when the C/SiC _x O _y composite was coated with a poly(phenylsilsesquioxane) layer (COMPOSITE 2). Shear properties for the composites showed a dependence on the nature of the matrix. The average in-plane shear strength and the shear modulus were 44.2 ± 1.9 MPa and 2.2 ± 0.5 GPa for the polymeric matrix composite (COMPOSITE 1), respectively. For the ceramic matrix composite (COMPOSITE 2) the values were 14.2 ± 4.1 MPa and 15.0 ± 2.0 GPa, respectively. The properties of the latter composite were also governed by the microstructure of the ceramic matrix.