碳纤维/聚醚醚酮单向带各向异性导电行为的尺度效应

具有导电各向异性的高分子复合材料(ACPCs)在场发射装置及传感器设计领域具有重要应用。常规的ACPCs很难获得超大导电各向异性系数,且力学性能有限。本文采用碳纤维(CF)宽展、表面浸润与树脂复合一体化超薄热塑性单向带制备方法,制备厚度为0.04 mm和0.1 mm的CF增强聚醚醚酮(CF/PEEK)复合材料单向带,以PEEK纤维为纬线制备CF/PEEK复合材料单向编织布,采用热成型工艺制备CF/PEEK复合材料单向层合板。利用数字万用表和霍尔效应系统测试层合板面内及厚度方向的电阻率和面内的电子迁移率;采用超景深显微镜观察CF/PEEK复合材料单向层合板面内和厚度方向的纤维排列形貌。结果表明,超薄CF/PEEK复合材料单向层合板面内(纤维方向与横向)导电率之比高达377,而面内横向和厚度方向的导电率之比接近1,表明CF/PEEK复合材料获得了良好的横观各向同性;超薄化CF/PEEK复合材料的面内电子迁移行为同样具有巨大的各向异性,这一结果为CF/PEEK复合材料在场发射器件、传感器设计及其灵敏度调控方面提供了实验基础。      

碳纤维增强聚醚醚酮复合材料的形状记忆效应

为推动形状记忆聚合物在空间等极端恶劣环境中的应用,以超薄碳纤维增强聚醚醚酮(Carbon fibers reinforced polyether-ether-ketone,CF/PEEK)预浸料为实验对象,采用薄膜叠层与热压成型工艺制备厚度为0.036 mm超薄预浸料的层合片材,研究了其在热应力驱动下的形状记忆行为。结果表明,在320℃加热-冷却热循环温度场的作用下,CF/PEEK复合材料超薄层合板的初始变形的形状回复率近似可达100%,当变形循环达到100次时,其形状回复率仍然可以保持在90%以上。此外,根据层合板变形的温度与应力-应变关系,解释了CF/PEEK复合材料的热应力驱动变形机制。在此基础上,改变CF/PEEK层合板厚度进行仿真设计,实现了初始状态与深海珊瑚形状、立方体、灯笼草形状之间的变形与回复。利用记忆变形产生的机械夹紧力,完成了硬币抓取实验,验证了CF/PEEK复合材料在主动变形结构应用的可行性。      

聚合物注塑制品的取向研究

概述了聚合物注塑制品的取向机理,取向研究手段.介绍了应用Moldflow软件模拟以及使用偏光显微镜、傅立叶偏光红外光谱仪研究动态注塑制品取向结构的初步结果,指出动态下取向效应明显强于稳态,制品皮层取向产生的光学效应明显强于芯层,红外偏光技术能够较好地对取向态进行定量测试.     

熔体温度对注塑成型iPP制品结晶形态的影响

注塑成型聚丙烯制品的内部结晶形态对制品的最终性能起着至关重要的作用,而结晶形态的形成对成型条件(尤其是熔体温度)有一定依赖性。文中利用偏光显微镜、小角X射线散射和广角X射线衍射等实验方法,详细研究了熔体温度对注塑成型iPP制品结晶形态的影响。研究结果表明,在实验温度范围内,制品厚度方向形态呈现五层皮芯结构,即冷冻层、过渡层、剪切层、β晶层、α球晶层。随着熔体温度提高,皮层厚度减小;结晶度提高,取向度极大值并无明显变化。     

基于导热板的碳纤维增强聚醚醚酮复合材料感应焊接温度调控

研究了碳纤维增强聚醚醚酮(CF/PEEK)复合材料感应焊接中厚度方向及焊接面内的温度分布及调控。基于对温度分布结果的分析,使用导热板结合真空袋压的方式对CF/PEEK进行感应焊接,结合使用合适的功率及加热时间,测试了焊接件的单搭接强度,观测分析了焊接件的断裂形貌。结果表明,导热板对层合板表层和边缘均有良好的散热效果;焊接功率越低,焊接面的加热均匀性增加,但是会延长加热时间。在真空袋中对层合板上表面和两侧添加导热板,在输出功率示数为600时感应焊接300 s,焊接件的单搭接剪切强度达到41.57 MPa。      

纤维含量对注塑制品残余应力影响的数值模拟

采用短纤维增强尼龙6复合材料,对带有半圆形缺口平板制件的注塑成型过程进行了模拟。以制件半圆形缺口附件的5个单元为研究对象,分别获得了不同位置上纤维取向和制件脱模时应力沿厚度方向上的变化,深入讨论了模具外形、纤维含量变化对纤维取向以及残余应力的影响。研究结果表明,随着纤维含量的增加,纤维间相互作用系数Ci减小,取向程度升高,皮层取向厚度减小,芯层取向厚度增加;纤维含量越高,制品冷却时沿厚度方向的压力幅值越大,残余应力沿厚度分布幅值也越大;制件形状的改变,影响了熔体流经此处的流动状态,同时也影响了缺口附件纤维取向以及残余应力。     

CF/PEEK复合材料界面层结构与性能关系研究

本文根据聚醚醚酮(PEEK)在碳纤维表面形式的横晶层的结构特征分析,建立了CF/FEEK复合材料界面层微观力学性能的理论方程,计算了界面层的杨氏模量.通过超声浸渍法测量复合材料的力学性能验证了计算结果,证明所进行的分析合理.计算结果表明,PEEK界面横晶层在垂直于纤维方向的杨氏模量E_r随PEEK结晶度的增大,或随横晶中PEEK晶片长度的增大而增大,并随晶片厚度的增大而减小.该界面层的上述模量值始终高于界面层附近球晶的模量值E_s,两者之间的比值E_T/E_s;依赖于横晶及球晶中的晶片长度b、厚度c和宽度a.由于界面层的模量高于非界面层的模量,当复合材料中纤维表面形成横晶时,复合材料将有较高的刚性.     

超薄微注塑等规聚丙烯制品形态结构及注射速度的影响分析

针对100μm和200μm厚的2种超薄微制品,采用单因素实验,对等规聚丙烯微注塑制品的形态结构进行研究,并分析注射速度对超薄微注塑制品形态结构的影响。研究结果表明,超薄微注塑制品中呈现出2种典型的形态结构,200μm微制品厚度方向呈现出纯剪切层的无芯结构,剪切层内为明显的Shish-Kebab结构;100μm厚微制品内部形态为含大比例柱晶结构的皮芯结构;广角X射线衍射结果显示无芯结构内形态沿流动方向呈现高度取向,且β晶含量微弱。含柱晶层皮芯结构的取向也较明显,且结构中有明显β晶存在。注射速度对超薄微注塑制品的形态结构、结晶度和取向度都有重要的影响,存在临界注射速度,当注射速度小于该临界速度时,制品内部结晶度、取向度随着注射速度的提高而提高。     

剪切载荷下温度和应变率对碳纤维增强聚醚醚酮复合材料强化行为的影响

碳纤维增强聚醚醚酮(CF/PEEK)是一种高性能热塑性复合材料,在航空航天领域有着广阔的应用前景。由于PEEK具有温度和应变率相关的非线性行为,导致CF/PEEK复合材料在基体主导的面内剪切方向也有类似的力学行为。本文在不同的温度和应变率下对CF/PEEK复合材料试件进行了剪切实验,将应力-应变曲线分为线性与非线性部分,发现温度和应变率对CF/PEEK复合材料的屈服应力有着较大的影响。随着温度从20℃升高到130℃屈服应力下降了66%左右,下降速度先快后慢,随着应变率从10?5 s?1提高到0.1 s?1屈服应力均匀增大了35%左右。将所得规律拟合背应力经验公式,修改了经典的热塑性复合材料本构模型的屈服函数。并编写VUMAT用户子程序对CF/PEEK复合材料剪切实验进行数值分析,与实验结果对比发现非线性阶段的剪切应力-应变关系及屈服点的剪切应力吻合良好,但是由于纤维和PEEK基体的浸润性较差,导致CF/PEEK复合材料内部存在孔隙缺陷,影响了CF/PEEK复合材料的初始剪切弹性行为,导致加载初始阶段存在偏差。      

新系列耐热增强塑料

美国Wilson-Fiberfil International公司介绍了两个新的增强塑料系列。其一是聚醚醚酮(PEEK)高性能注塑材料,热变形温度超过600°F。J_(1105)/_(CF)/_(30)是含有30％碳纤维的增强PEEK,在264磅/时~2的负荷下,热变形温度是610°F。J_(1105)/_(30)是含30％玻璃纤维的增强PEEK,热变形温度亦可达594°F。不增强的PEEK的热变形温度是320°F。该公司介绍说,这一新系列的增强     

碳纤维-AlN/聚醚醚酮复合材料的制备与性能

以聚醚醚酮(PEEK)为基体树脂、碳纤维(CF)和氮化铝(AlN)为填料,通过模压成型的方法制备了抗静电耐热型CF-AlN/PEEK复合材料。采用高阻计、导热系数测定仪、热失重、差示扫描量热仪和SEM研究了CF-AlN/PEEK复合材料的抗静电性能、热性能、力学性能以及降温速率对复合材料性能的影响,并探讨了后期热处理对力学性能的影响。结果表明:当CF和AlN的质量分数均为10%时,CF-AlN/PEEK复合材料的性能较优,其表面电阻率达到108 Ω,比PEEK的表面电阻率提高了6个数量级;导热系数为0.418 W·(m·K)-1,初始分解温度高达573℃;拉伸强度提高了40.4%;降温速率越低,复合材料的熔点越高;后期热处理会影响CF-AlN/PEEK复合材料的力学性能,在270℃下热处理2 h,其拉伸强度可达146 MPa,表明在生产过程中,加工温度是影响复合材料性能的因素之一。      

Self-reinforced poly(ethylene terephthalate) composites by hot consolidation of Bi-component PET yarns

Self-reinforced polymer composites or all-polymer composites have been developed to replace traditional glass-fibre-reinforced plastics (GFRP) with good lightweight, mechanical and interfacial properties and enhanced recyclability. Poly(ethylene terephthalate) (PET) is one of the most attractive polymers to be used in these fully recyclable all-polymer composites, in terms of cost and properties. In this work, unidirectional all-PET composites were prepared from skin–core structured bi-component PET multifilament yarns by a combined process of filament winding and hot-pressing. During hot-pressing, the thermoplastic copolyester skin or sheath layers were selectively melted to weld high-strength polyester cores together creating an all-PET composite. Physical properties of the resulting composites including thickness, density and void content were reported. The effect of processing parameters, i.e. consolidation temperature and pressure on mechanical properties and morphology was investigated in order to balance good interfacial adhesion with residual tensile properties of the composite.     

PEEK复合材料用碳纤维上浆剂研究进展EI北大核心CSCD

热塑性聚醚醚酮(PEEK)复合材料具有优异的断裂韧性、抗冲击性能、耐疲劳性能,广泛应用于航空航天领域。上浆剂作为碳纤维的核心配套产品,对复合材料界面有重要影响。受分解温度限制,传统热固性碳纤维上浆剂难以满足PEEK复合材料使用,制约高性能PEEK复合材料的研制和应用,因此研制匹配PEEK复合材料的碳纤维上浆剂具有重要意义。本文分析了PEEK复合材料界面特性及上浆剂作用机理;重点介绍了改性PEEK、聚酰亚胺前驱体、聚醚酰亚胺等类型上浆剂的研究进展和成果,并对不同体系上浆剂进行分析总结;最后对PEEK复合材料用碳纤维上浆剂的研制提出建议,对上浆剂绿色环保多功能化趋势进行了展望。     

The mechanical properties of insert-molded poly (ether imide) (PEI)/C fiber poly (ether ether ketone)(PEEK) composites

The mechanical properties of insert-molded poly(ether imide) (PEI)/carbon fiber poly(etheretherketone) (CF PEEK) have been examined. Bimaterial composite specimens were constructed by injecting CF PEEK into a mold containing one-half of a PEI tensile specimen. These PEI/CF PEEK composites retained much of their strength and dimensional integrity at temperatures as high as 200°C. Variations in test speed had little affect on breaking strains or stiffness. For two grades of PEI examined, properties were independent of the molecular weight of the PEI. Ultimate properties and fracture surfaces suggested good adhesion between the PEI and CF PEEK, possibly aided by miscibility between the two materials. The PEI/CF PEEK bimaterial composites behaved similarly to PC/CF PEEK specimens, but exhibited higher breaking stresses and moduli, both at room and elevated temperatures.     

Hybrid effect of nanoparticles with carbon fibers on the mechanical and wear properties of polymer composites

Polyetheretherketone (PEEK) composites reinforced with carbon fibers (CFs) and nano-ZrO₂ particles were prepared by incorporating nanoparticles into PEEK/CF composites via twin-screw extrusion. The effects of nanoparticles on the mechanical and wear properties of the PEEK/CF composites were studied. The results showed that the incorporation of nano-ZrO₂ particles with carbon fiber could effectively enhance the tensile properties of the composites. The tensile strength and Young’s modulus of the composites increased with the increasing nano-ZrO₂ content. The enhancement effect of the particle was more significant in the hybrid reinforced composites. The compounding of the two fillers also remarkably improved the wear resistance of the composites under water condition especially under high pressures. It was revealed that the excellent wear resistance of the PEEK/CF/ZrO₂ composites was due to a synergy effect between the nano-ZrO₂ particles and CF. CF carried the majority of load during sliding process and prevented severe wear to the matrix. The incorporation of nano-ZrO₂ effectively inhibited the CF failures through reducing the stress concentration on the carbon fibers interface and the shear stress between two sliding surfaces. It was also indicated that the wear rates of the hybrid composites decreased with the increasing applied load and sliding distance under water lubrication. And low friction coefficient and low wear rate could be achieved at high sliding velocity.     

改性处理对热塑性聚合物基复合材料性能的影响

研究了冷却方式及改性处理对玻纤增强热塑性聚合物复合材料性能的影响.采用模压工艺制备复合材料,研究冷却方式、偶联剂处理及等离子改性处理对玻纤增强聚丙烯力学性能的影响,并通过DSC分析复合体系结晶性能的变化规律.结果表明:采用同加热板一起冷却的复合材料结晶性能较好,材料的拉伸性能最高;改性处理在一定程度上改善了材料的界面结...     

Influence of cooling rate on interlaminar fracture properties of unidirectional commingled CF/PEEK composites

The influence of cooling rates on the mechanical property profile (transverse flexure properties and modes-I and -II interlaminar fracture toughness) has been investigated for unidirectional commingled CF/PEEK composites. A laboratory hot press with a steel mould was used to process the composites at 400°C for 60 min, at an applied pressure of 1 MPa. Cooling rates from fast (quenching in oil) to slow (hot press cooling) were achieved at ambient pressure. The results indicate that different matrix morphology was found at different cooling conditions, although deconsolidation occurred in the CF/PEEK composites during cooling. When the cooling rate was shifted from slow to fast, consolidation quality of the CF/PEEK composites was improved. The resulting effect of the consolidation quality and cooling rates on the mechanical property profile of commingled CF/PEEK composites is presented. It was found that the effect of the cooling rate on the mechanical property profile of the commingled CF/PEEK composites could not be isolated from the consolidation quality.     

Mechanical properties of palmyra/glass fiber hybrid composites

Use of eco friendly composites gains attraction due to its lightweight and moderate strength in the recent years. Palmyra fiber is a natural fiber obtained from Palmyra (Borassus flabellifer) tree. Mechanical properties of randomly mixed short fiber composites are studied and optimum fiber length and wt% are estimated. This paper deals with the properties of (randomly mixed) palmyra fiber, glass fiber hybrid composites. Two types of specimens are prepared, one by mixing the palmyra and glass fiber and the other by sandwiching palmyra fiber between the glass fiber mats. Composite plates are prepared for different palmyra/glass fiber weight ratio. Rooflite resin is used as matrix. Tensile, impact, shear and bending properties are studied. The mechanical properties of the composites are improved due to the addition of glass fiber along with palmyra fiber in the matrix. The glass fiber skin–palmyra fiber core construction exhibits better mechanical properties than dispersed construction. Moisture absorption studies are conducted and the results are presented as a function of square root of time. Addition of glass fiber with palmyra fiber in the matrix decreases the moisture absorption of the composites.     

Enhanced electrical conductivity of polypyrrole/polypyrrole coated short nylon fiber/natural rubber composites prepared by in situ polymerization in latex

In this paper we report the characterization and properties of conductive elastomeric composites of polypyrrole (PPy) and PPy coated short Nylon-6 fiber (F-PPy) based on natural rubber (NR) prepared by in situ polymerization method. PPy/NR blends were prepared by polymerizing pyrrole in NR latex using anhydrous ferric chloride as oxidizing agent, p-toluene sulphonic acid as dopant and vulcastab VL as stabilizer. PPy/F-PPy/NR composites were prepared as above in presence of short nylon fiber. The products were coagulated out, dried, compounded on a two roll mill and moulded. The cure pattern, DC electrical conductivity, morphology, mechanical properties, thermal degradation parameters and microwave characteristics of the resulting composites were studied. Incorporation of PPy to elastomer retards the cure reaction whereas addition of fiber accelerates the cure reaction. DC conductivity up to 6.25 × 10⁻² was attained for NR/PPy/F-PPy system. The composites containing F-PPy exhibited better mechanical properties compared to NR/PPy systems. The absolute value of the dielectric permittivity, AC conductivity and absorption coefficient of the conducting composites prepared were found to be much greater than the gum vulcanizate. PPy and F-PPy were found to decrease the dielectric heating coefficient and skin depth significantly.