The Effect of Fibre Surface Treatment on the Failure of Continuous Carbon Fibre/Epoxy Resin Composites

The failure mechanisms of a composite, consisting of continuous, aligned, high strength, polyacrylonitrile (PAN) based carbon fibre in an epoxy resin, under uniaxial tension, have been studied. In order to study the effect of the interphase/interface strength, six different levels of an electrochemical fibre surface treatment were used. Single tows containing approximately 12,000 treated carbon fibres were impregnated to produce composite rods with a fibre volume fraction of 0.55. Lengths of this impregnated tow were also set in the centre of glass-fibre/epoxy resin composite coupons which were used to study the mechanisms of failure of the embedded tows. Acoustic emission was used to monitor all samples and bundle failure was found to occur after a build-up of sub-critical damage events as previously modelled.¹ Microdebond tests demonstrated an initial increase of interfacial strength which levelled out at the higher levels. In impregnated samples with high surface treatments, catastrophic failure occurred with the crack propagating approximately perpendicular to the fibre direction. However, in samples with lower fibre surface treatments, longitudinal splitting (not accounted for in current models), occurred, meaning that a greater length of composite was involved in the final failure process. Acoustic emission has been shown to have an approximately direct relation with the predicted number of single fibre breaks in composite test-pieces; however, there was no significant difference attributable to the different surface treatments. The hybrid test coupons allow a detailed assessment of the failure mechanisms within the impregnated carbon tow. The failure strains of the embedded tow is some 5% higher than that of unsupported tow. The Weibull modulus is of the same order.     

The Effect of Low Power Nitrogen Plasma Treatment of Carbon Fibres on the Interfacial Shear Strength of Carbon Fibre/Epoxy Composites

Type II (high strength) carbon fibres have been given a low power nitrogen plasma treatment. It is shown that this plasma treatment has no effect on the fibre diameter, no detrimental effect on fibre strength and can significantly improve fibre/resin adhesion. It is proposed that this improvement is due to chemical interaction via amine/epoxy bonding at the edge sites together with the interaction of the epoxy with activated basal planes present on the fibre surface. This improvement is only achieved if the fibres are immersed in resin before being exposed to air. Exposing the treated fibres to air drastically reduces fibre/adhesion due to the adsorption of moisture from the environment. Heating these latter fibres in a vacuum at 130°C for one hour allows some recovery of the interfacial strength. It is also demonstrated that the interfacial shear strength falls dramatically when the nitrogen-containing functional groups are completely removed from the fibre surface.     

The Effect of Low Power Nitrogen Plasma Treatment of Carbon Fibres on the Interfacial Shear Strength of Carbon Fibre/Epoxy Composites

Type II (high strength) carbon fibres have been given a low power nitrogen plasma treatment. It is shown that this plasma treatment has no effect on the fibre diameter, no detrimental effect on fibre strength and can significantly improve fibre/resin adhesion. It is proposed that this improvement is due to chemical interaction via amine/epoxy bonding at the edge sites together with the interaction of the epoxy with activated basal planes present on the fibre surface. This improvement is only achieved if the fibres are immersed in resin before being exposed to air. Exposing the treated fibres to air drastically reduces fibre/adhesion due to the adsorption of moisture from the environment. Heating these latter fibres in a vacuum at 130°C for one hour allows some recovery of the interfacial strength. It is also demonstrated that the interfacial shear strength falls dramatically when the nitrogen-containing functional groups are completely removed from the fibre surface.     

表面处理对碳/酚醛材料层间性能影响的研究

本文分别研究了在有氧与无氧状态下表面处理对碳／酚醛材料界面特性的改善，尤其是在高温环境下的变化。通过扫描电镜(SEM)、电子能谱(XPS)研究了不同状态处理下的碳布，测试了碳／酚醛复合材料的剪切强度。研究表明，在500～600％有氧状态下处理的碳／酚醛材料层间性能最佳。     

The Influence of Alkaline Surface Fibre Treatment on the Impact Properties of Sugar Palm Fibre-Reinforced Epoxy Composites

The aim of this study is to determine the impact properties of sugar palm fibre-reinforced epoxy polymer composite after introduce the alkaline treatment to the fibre. The fibre was treated by alkaline solution with 0.25 M and 0.5 M NaOH solution for 1 hour, 4 hours, and 8 hours soaking time. Hand lay up process was used to prepare the composite specimens with 10% volume fraction. The dimensions of the specimen used to carry out the test were adapted from ASTM D256 for Izod Impact testing. The higher impact strength of treated sugar palm fibre reinforced epoxy composite took place at 0.5 M NaOH solution with 8 hours soaking time, i.e., 60 J/m with improving by 12.85% from untreated composite.     

Effect of High Modulus Polyethylene Fibre Surface Treatment on Epoxy Resin Composite Impact Properties

Unidirectional and cross-ply epoxy resin composites have been made using both untreated and plasma treated melt-spun and gel-spun high-modulus polyethylene fibres. Interlaminar shear strength adhesion measurements have been related to high speed flexural strength and impact energy absorption.     

树脂含量对碳布/环氧复合材料力学性能的影响

主要研究了不同树脂含量下，碳布／环氧复合材料的径向拉伸和纬向压缩性能，并初步探讨了树脂含量对复合材料拉伸、压缩性能的影响机理。试验结果表明：树脂含量对复合材料力学性能的影响较大，当树脂质量含量在42％－45％之间时，拉伸、压缩性能较好。     

石墨／碳纤维／聚丙烯高强导热材料的研究

采用聚丙烯、石墨、碳纤维 (CF)制备出满足实际应用要求的高导热、高强度复合材料。实验结果表明 ,石墨和碳纤维在基体中的合理分布能显著提高复合材料的导热性能和力学性能。当聚丙烯和石墨的质量比为 5 0 /5 0时 ,添加 3 .3 3 %的碳纤维 ,其热导率为 2 .1W /(m·K) ,拉伸强度达到 5 1.49MPa。     

A Study of the Interphase Region in Carbon Fibre/Epoxy Composites using Dynamic Mechanical Thermal Analysis

We have examined the effect of fibre addition on the glass transition temperature (T_g) of two epoxy resin systems (an amine cured and an anhydride cured epoxy system) using dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The presence of fibres changes the glass transition temperature (T_g) of an anhydride cured epoxy resin but does not affect that of an amine cured epoxy. The data suggest that two counteracting mechanisms are responsible for these changes: firstly, the presence of fibres causes a restriction of the molecular motion in the resin system, and secondly, the presence of carboxyi and keto-enol groups on the fibre surface inhibit curing of the resin close to the fibre, i.e. in the interphase region. The former increases the T_g and is a long range effect whereas the latter decreases the T_g and is a localised phenomenon. Changes in the dynamic properties of the interphase region are only detected when the samples are loaded in the longitudinal direction and not in the transverse direction where bulk matrix properties dominate. Sizing the fibres before their incorporation into the epoxy resin eliminates the variation in interfacial properties arising from differences in fibre surface chemistry.     

A Study of the Interphase Region in Carbon Fibre/Epoxy Composites using Dynamic Mechanical Thermal Analysis

We have examined the effect of fibre addition on the glass transition temperature (T _g ) of two epoxy resin systems (an amine cured and an anhydride cured epoxy system) using dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The presence of fibres changes the glass transition temperature (T _g ) of an anhydride cured epoxy resin but does not affect that of an amine cured epoxy. The data suggest that two counteracting mechanisms are responsible for these changes: firstly, the presence of fibres causes a restriction of the molecular motion in the resin system, and secondly, the presence of carboxyi and keto-enol groups on the fibre surface inhibit curing of the resin close to the fibre, i.e. in the interphase region. The former increases the T _g and is a long range effect whereas the latter decreases the T _g and is a localised phenomenon. Changes in the dynamic properties of the interphase region are only detected when the samples are loaded in the longitudinal direction and not in the transverse direction where bulk matrix properties dominate. Sizing the fibres before their incorporation into the epoxy resin eliminates the variation in interfacial properties arising from differences in fibre surface chemistry.     

碳纤维布表面处理对酚醛树脂复合材料力学性能的影响

以碳纤维布(CB)为增强相,丁苯橡胶为增韧剂,酚醛树脂(PF)为基体,通过模压成型工艺制得了PF/CB复合材料,研究了CB表面处理方式、丁苯橡胶含量及加工成型温度对PF/CB复合材料的界面结合及力学性能的影响。结果表明,丙酮处理CB、氧化处理CB及加工成型温度的提高都能改善纤维与基体的结合程度,提高界面结合力。但氧化处理CB随着加工成型温度的提高,易断裂,对复合材料的增强作用有所减弱。丁苯橡胶加入量为12%时PF的加工及冲击性能为最佳。     

加捻对T800碳纤维拉伸性能的影响

要通过对日本东丽1700、T800碳纤维复丝拉伸性能的表征主要研究了加捻对,T800碳纤维拉伸性能的影响。研究结果表明：采用浸胶后加捻的方式有助于改善T800碳纤维的拉伸性能,合适的捻度可使其拉伸强度提高5％,断裂延伸率提高10％。并通过对rr800碳纤维干纱加捻的研究基本确定了T800碳纤维的临界捻度为15n／m。     

碳纤维增强环氧树脂基复合材料镀覆预处理技术探讨

简介了碳纤维复合材料(CFRP)材料表面金属化的工艺过程,采用CrO3-H2SO4溶液对CFRP进行蚀刻处理,通过扫描电镜观测经蚀刻处理后的树脂表面的微观形貌,测试了镀层附着力,分析了蚀刻程度与镀层附着力之间的关系。实验表明,CFRP材料镀覆前的适度蚀刻处理对后续的镀层附着力来说至关重要,蚀刻过度或不足都难以获得满意附着力的镀层。     

碳纳米管/聚合物复合吸波材料性能研究

碳纳米管通过化学气相沉积工艺制备,碳纳米管直径10～30nm,纯度>90%。碳源为乙炔、铁/镍复合催化剂。加入适量的有机溶剂丙酮溶解环氧树脂,然后加入碳纳米管。分别高速搅拌和超声处理30min,加入固化剂乙二胺搅拌均匀,超声10min除去气体后,浇铸在铝板上制成吸波涂层。TEM检测碳纳米管。反射率扫频测量系统HP8757E标量网络分析仪检测吸波性能。碳纳米管和环氧树脂比例为1∶100时,3mm厚吸波层试样吸波峰出现在14 32GHz,吸波峰值R=-10 01dB,吸波频带宽度为2 16GHz(R<8dB)。厚度增加到9mm,在11GHz和17 83GHz出现双吸波峰,最大吸波峰出现在17 83GHz峰值R=-9 04dB,带宽约1GHz(R<8dB)。比例调整为5∶100时,波峰出现在7 91GHz,峰值加大到R=-13 89dB,带宽度达到3 19GHz(R<8dB)。     

碳纤维表面处理对树脂基复合材料力学性能影响研究进展

综述了近期国内在树脂基复合材料用碳纤维表面处理方面的研究进展。其中碳纤维表面处理方法主要包括氧化处理、表面涂层处理、等离子体处理以及超临界流体处理等,对采用这些处理方法后碳纤维增强树脂基复合材料的相关力学性能变化情况进行了总结归纳。     

The Effect of Abrasion Surface Treatment on the Bonding Behavior of Various Carbon Fiber-Reinforced Composites

Abstract

In this paper we show that current abrasion surface preparation practices do not perform equally on all composite surfaces. The effect of abrasion on the adhesive bond strength of various carbon fiber (CF) composites was investigated. Cyanate ester composites were fabricated using a low, a high and an ultra high modulus carbon fiber (T300, M55J, K13C2U). XPS and contact angle measurements showed that the surface energy of all three composites increased due to the removal of contaminants as well as increased in surface roughness. However, the lap shear strength degraded sharply for a number of cases, irrespective of roughness, depending on the fiber used. Composites utilizing lower modulus carbon fibers increased in adhesive bond strength following abrasion in comparison to composites with higher modulus fibers. As the modulus of the fiber and the abrasive grit size increased, the degree of degradation caused by abrasion was shown to increase significantly. Scanning electron microscopy (SEM) and profilometry measurements showed the development of an abrasion-affected zone that was especially prevalent for higher stiffness composites. The failures for the higher modulus specimens were caused by subsurface damage located a few fiber diameters below the abraded surface. However, an alternate technique using atmospheric plasma surface treatment exhibited efficient removal of contaminants while showing no degradation of bond quality when treating these ultra high modulus composites.     

聚丙烯腈基碳纤维抗拉强度的影响因素

提高抗拉强度是碳纤维性能研究的重要目标。讨论并分析了原料、原丝工艺、预氧化工艺、碳化工艺及检测方法等诸多因素对聚丙烯腈基碳纤维抗拉强度的影响。提出了提高碳纤维抗拉强度的建议:聚合原料需精制,纺丝液要精滤;纺丝采用干喷湿纺技术;避免使纤维产生缺陷等。     

碳纤维表面处理技术探讨

介绍了碳纤维的特点及碳纤维表面处理常用方法,采用液相氧化加上阳极氧化的复合表面处理法对碳纤维进行表面氧化处理,然后将表面处理后的碳纤维加捻、并合、再加捻,浸渍于热塑性聚氨脂树脂中,经干燥,制成附着量约为5%的碳纤维复合线;同时用未经表面处理的碳纤维,在同样条件下制成碳纤维复合线进行对比。结果表明:采用缓和的电化学氧化处理和加热处理,能使纤维表面的缺陷得到修复,碳纤维制造过程所形成的物理缺陷得到缓和,使碳纤维的机械强度可在复合材料中起到更大的作用。     

硝酸处理对碳纤维增强环氧树脂复合材料的性能影响

以用浓硝酸处理改性后的碳纤维为增强体,用乙二胺(DBP)为固化剂,邻苯二甲酸二丁酯为增塑剂,以低分子量环氧树脂(E-51)为基体制备碳纤维增强环氧树脂复合材料(CFRP)。SEM测试表明用酸处理碳纤维后,碳纤维表面的极性和粗糙度得到了提升。DMA测试表明储能模量和玻璃化温度都得到了显著提升。控制酸处理时间,可以明显改善碳纤维和环氧树脂之间的结合力,提高复合材料的力学性能。