基于XFEM短纤维聚醚醚酮复合材料结构稳定性数值模拟分析

熔融沉积成型(FDM)制备短纤维增强聚合物复合材料成型技术日趋完善。采用FDM-3D挤压工艺制备了纤维含量为10%的短碳纤维(CF)和玻璃纤维(GF)增强的高性能聚醚醚酮复合材料,通过拉伸实验获取聚醚醚酮(PEEK)、碳纤维聚醚醚酮复合材料(CF/PEEK)以及玻璃纤维聚醚醚酮复合材料(GF/PEEK)试样应力-应变曲线。在此基础上,以单边缺口弯曲断裂试样为对象,基于扩展有限单元法(XFEM)建立三种材料的数值模拟模型,分别讨论了含初始裂纹缺陷和无预制裂纹状况下试样的结构稳定性。结果表明,在相同条件下CF/PEEK复合材料构件先于纯PEEK材料、GF/PEEK复合材料发生结构失效行为,且当构件中存在热裂纹的状况下,CF/PEEK复合材料构件更有可能发生断裂失效。     

模压成型工艺参数对CF/PEEK复合材料Ⅰ型层间断裂韧性的影响

连续碳纤维增强聚醚醚酮(CF/PEEK)复合材料是重要的医疗器械及航空航天热塑性复合材料,可采用模压成型工艺制备层合板及结构,其工艺参数影响复合材料力学性能。本文主要考察了模压成型温度、压力以及降温速率等参数对CF/PEEK复合材料Ⅰ型层间断裂韧性(GIC)的影响规律,并通过扫描电镜表征复合材料撕裂面的微观形貌,分析材料失效模式。较高的模压成型温度可提高基体分子链流动性,适中的成型压力有利于控制树脂不被过多挤出模具,适中的降温速率可降低结晶度并抑制界面粘结强度的损失,均有利于提高CF/PEEK复合材料的GIC。     

连续玻纤聚醚醚酮混杂纱及其织物模压板的研究

目前国内鲜有连续玻纤增强聚醚醚酮(PEEK)的产品,首次尝试用聚醚醚酮与连续玻璃纤维混合制成1种混杂纱,即1种干态预浸料,后续模压而成的复合材料性能也有极大的提高。介绍了使用聚醚醚酮(PEEK)与玻璃纤维混合制成复合纱的生产方式,并对其后续复合材料的模压工艺做了初步的探索。此外,还对聚醚醚酮(PEEK)的市场应用做了简单介绍。     

聚醚醚酮复合材料

聚醚醚酮(PEEK)是一种高性能的半结晶热塑性聚合物,历来用于注塑或挤塑工艺,也可用于复合材料。总部设在英国的PEEK大厂商Victrex公司称,PEEK可用作玻璃纤维、碳纤维或芳纶纤维增强热塑性预浸料的基体,它优良的力学性能和成型加工性能在其可以航空航天、海洋、医疗和工业应用中替代金属和热固性塑料。     

玻璃纤维毡增强聚丙烯在冲压成型中的纤维分布研究

本文研究了玻璃纤维毡增强聚丙烯(GMT)复合材料在流动态冲压成型中玻璃纤维的分布情况,分析了温度、压力等工艺参数对纤维分布的影响,为GMT片材冲压成型复杂形状的产品提供理论指导.     

水悬浮-拉挤法制备长玻纤增强PVC复合材料的研究

本文探索了长玻璃纤维增强PVC(LGF/PVC)复合材料用水悬浮-拉挤成型工艺,针对硬质PVC难加工、易降解的特点,对多种稳定剂进行了试验,并确定选择了有机锡类稳定剂,讨论成型温度等影响成型工艺的各种因素,运用SEM、冲击强度、拉伸强度、弯曲强度等测试技术研究LGF/PVC复合材料的结构和性能。结果表明,水悬浮法制备长玻璃纤维增强PVC复合材料的拉挤成型工艺是可行的,所得的复合材料有十分优良的力学性能。     

GF/PET混纤纱复合材料成型工艺条件与材料性能关系的探讨

复合材料的成型参数可影响复合材料的空隙率,而空隙主又对复合材料的层间剪切强度、弯曲强度等力学性能产生显著影响。本文针对这一点探讨连续玻璃纤维增强涤纤轮混纤纱复合材料的成型工艺条件与复合材料的空隙率及力学性能的关系。     

PEEK/CCF复材增材制造多重分形谱表面形貌评定方法

随着航空事业的发展，增材制造(AM)被用于连续碳纤维增强聚醚醚酮(PEEK/CCF)复材的成型制造中，其中AM工艺参数对PEEK/CCF复材加工形貌有较大影响。基于此提出了一种基于多重分形谱表面形貌评定方法，通过PEEK/CCF复合材料在AM中的成型速度(v)、成型厚度(s)、成型角度(θ)与加工表面粗糙度和表面形貌之间的关系设计了单因素试验，研究了PEEK/CCF复合材料在AM中的v,s,θ与表面形貌之间的关系，结合成型材料表面多重分形谱的方式，评定AM中所选工艺参数对表面形貌的影响，得到了加工表面粗糙度和表面形貌随v,s,θ的变化特点。结果表明，v,s对材料表面形貌有明显影响，θ对表面形貌影响较小，通过试验验证了PEEK/CCF复合材料表面形貌有较好的分形特征，多重分形谱谱差ΔD(α)表征表面波峰波谷的占比，其值越大，材料表面形貌越复杂，分形谱的宽度Δα表征表面起伏程度，定性表征了形貌特征，最终工艺参数组合为v=20 mm/s,s=0.2 mm,θ=30°。     

玻璃纤维增强APA6复合材料的研究及应用进展

玻璃纤维增强阴离子开环聚合尼龙6(APA6)复合材料因其优良性能被广泛应用于汽车、船舶、轨道交通、机械制造等领域,其主要包括短玻璃纤维增强APA6复合材料、连续玻璃纤维增强APA6复合材料和填料改性玻璃纤维增强APA6复合材料。本文综述了玻璃纤维增强APA6复合材料的研究及应用进展,主要介绍三类玻璃纤维增强APA6复合材料的成型工艺、力学性能和相关产业的应用情况。     

红外加热缠绕成型工艺参数对CF/PEEK复合材料层间剪切性能的影响

为获得层间粘结性能优异的连续碳纤维增强聚醚醚酮复合材料(CF/PEEK)缠绕成型制品,以粉末浸渍法制备的CF/PEEK单向带为原料,采用自制的高功率红外加热热塑性复合材料缠绕成型设备,进行缠绕成型工艺的研究。以层间剪切强度(ILSS)作为评价缠绕制品性能的主要依据,分别研究了缠绕成型过程中的送料张力、下压辊压力、缠绕速率、加热温度、预热时间和冷却速率等关键工艺参数对CF/PEEK环制品性能的影响。实验结果表明,成型温度为410℃,预热为40 min,送料张力为8 kg,下压辊气缸压力为0.30 MPa,芯模转速为6 r/min,缓慢冷却条件下制得的缠绕制品性能最优,层间剪切强度达到(82.29±1.27) MPa,并据此制备出了CF/PEEK缠绕管道。     

Preparation and properties of poly(ether ether ketone) composites reinforced by modified wollastonite grafting with silaneterminated poly(ether ether ketone) oligomers

Silane-terminated poly(ether ether ketone) oligomers were synthesized and grafted onto wollastonite (W) particles. The prepared grafted-wollastonite particles (g-W) were then incorporated into PEEK matrix via melt processing. Properties of the PEEK composites were investigated using differential scanning calorimetry (DSC), universal tester and rheometer. The researchers found the mechanical properties of the PEEK/g-W composites were markedly enhanced, complex viscosity of the PEEK/g-W composites increased, and both the peak crystallization temperature (T _c ) and crystalline fraction (χ _c ) of the PEEK composites with g-W were significant higher compared with those of the PEEK composites with W. It is our belief that these results are due to the strong interaction between the grafted-wollastonite particles and the PEEK matrix.     

Polyetheretherketone (PEEK): Processing-structure and properties studies for a matrix in high performance composites

The processing, structure and properties of polyetheretherketone (PEEK) semicrystalline thermoplastic as matrix polymer for high performance composites has been investigated in this work. In processing PEEK samples with different crystallinities, a specially designed mold capable of cooling the polymer in excess of 115°C/s from its melt temperature was constructed. In addition, during processing studies, a reaction of PEEK in the presence of copper was discovered. Analysis of the samples in terms of their crystallinity values also provided a new method for measuring crystallinity of the matrix in the composite. Crystallization of low crystalline samples at room temperature in the presence of methylene chloride was also confirmed for the first time with polarized microscopy. However, at the same time, the excellent hygrothermal resistance of PEEK was also confirmed. Finally, dynamic mechanical and stress-strain experiments with samples of different crystallinities elucidated the dependence of these properties to crystallinity. However, this study also elucidated that under normal processing conditions for high performance composites, PEEK properties may not be strongly affected by different levels of crystallinity.     

Kinetics of strain-induced crystallization during injection molding of short fiber composites of poly(ether ether ketone)

Crystallization kinetics of short glass and carbon fiber composites of poly(ether ether ketone) (PEEK) under melt-strain conditions have been obtained for the first time, using in-situ wide angle X-ray scattering, and have been correlated to a model based on the Avrami equation in order to enable minimization of the processing time for injection molding of these materials. It has been demonstrated that increased flow rate of the melt in the mold and, consequently, increased shear rate accelerates the crystallization process of PEEK composites, analogous to similar trends observed previously in PEEK resin. Short glass fiber composites of PEEK crystallize slower than the resin under identical processing conditions, while short carbon fiber composites crystallize faster than the resin, except at the highest mold temperatures and the lowest flow rates. A model based on the Avrami equation has been proposed to fit the kinetics data obtained experimentally. The Avrami coefficient has been calculated and Arrhenius plots have been used to predict the crystallization kinetics at temperatures lower than those at which experimental data have been obtained here. Fiber orientation, flexural elastic modulus, and flexural fracture toughness of the composites have also been evaluated.     

High performance thermoplastic composites: Study on the mechanical,thermal, and electrical resistivity properties of carbon fiber‐reinforced polyetheretherketone and polyethersulphone

High temperature processing thermoplastic polymers, polyetheretherketone (PEEK) and polyethersulphone (PES), were melt blended with carbon fibers (CFs) to make composites. These composites were investigated for their mechanical, thermal, and electrical properties. Mechanical properties that are expressed in terms of storage modulus, loss, and damping were enhanced with the addition of CFs. Thermal properties were determined by DSC and TGA. These methods help to understand the effects of fiber content and fiber–matrix adhesion in the composites. Composites were also tested for their electrical and thermal conductivity because CFs leave the composites thermally and electrically conductive. CFs enhanced the crystallinity of the PEEK appreciably that in turn influenced thermal conductivity, electrical resistivity, and the stiffness of PEEK/CF (composites of PEEK with CFs). PES/CF (composites of PES with CF) shows a different behavior due to the amorphous nature of PES. The work involves one filler and two different matrices, and so it provides an interesting comparison of how matrix morphology can influence the properties of composites. POLYM. COMPOS. 28:785–796, 2007. © 2007 Society of Plastics Engineers.     

Effects of thermal history on mechanical behavior of PEEK and its short-fiber composites

The effect of crystallinity differences induced by mold wall temperature and annealing on mechanical behavior is evaluated for poly(etheretherketone) (PEEK) resin and its composites. The systems investigated were neat PEEK, glass fiber (GF) reinforced PEEK, and carbon fiber (CF) reinforced PEEK. Both composite systems were reinforced with 10, 20, and 30 wt% fiber. The degree of crystallinity (X_c) of PEEK was found to increase by processing at higher mold temperatures, by annealing, and by fiber length reductions, which appears to indicate the ability of short fibers to nucleate the crystallization of PEEK under favorable thermal conditions. Improvements in Young's modulus and strength together with ductility reductions are generally obtained as crystallinity increases in both neat PEEK and its composites. The contribution of crystallinity to mechanical behavior is significant only for neat PEEK and PEEK reinforced by 10% fiber. SEM micrographs reveal that this is due to a change in failure mode. When PEEK is reinforced by carbon fibers or by 20–30% glass fibers, a macroscopic brittle mode of failure is observed irrespective of matrix crystallinity, and mechanical behavior is principally determined by the nature and content of the reinforcing fibers.     

聚醚醚酮复合材料摩擦学性能研究现状

介绍聚醚醚酮(PEEK)的基本物理化学性能,评述粒子填充、纤维增强、有机-无机共混和等离子处理PEEK复合材料的摩擦磨损性能研究进展,指出今后应加强对多因素协同作用下PEEK复合材料磨损机理、开展PEEK复合材料微观摩擦学及生物摩擦学方面的研究。     

Blends of semicrystalline and amorphous polymeric matrices for high performance composites

The compatibility and crystallization behavior of blends of semicrystalline and amorphous polymers, traditionally used as matrices of high performance composites, has been studied. The analysis has been focused on blends of semicrystalline poly(etheretherketone) (PEEK) with amorphous poly(etherimide) (PEI) prepared by melt mixing. Differential scanning calorimetry and thermogravimetric analysis have been used to analyze the influence of blend constituents and processing conditions on the compatibility, on the crystallization kinetics and on the final crystalline content. An Avrami model has been applied to the crystallization of PEEK in a PEEK/PEI 50/50 blend and the results have been compared with the behavior of the neat PEEK resin. The results of the characterization can be applied to predict the behavior of such blends when processed as matrix of composites or when used in the “amorphous bonding” procedure.     

碱液中晶须增强PEEK复合材料的摩擦磨损性能

研究了不同含量PTW增强PEEK复合材料在碱液中的摩擦磨损性能,并与经典的CF增强PEEK复合材料对比,借助于SEM分析了磨损面和对偶面微观形貌,探讨了相关机理。结果表明,干摩擦时15%(质量)PTW增强PTFE/PEEK复合材料耐磨性是相同含量CF增强时的10.5倍。在碱液中,CF增加了PTFE/PEEK复合材料的摩擦系数、降低了其耐磨性能,而PTW可以进一步降低PTFE/PEEK复合材料的摩擦系数、明显地提高其耐磨性能。含5%PTW可提高PTFE/PEEK复合材料碱液中耐磨性2.36倍。碱液阻止了对偶面转移膜的形成,犁削和磨粒磨损是CF增强PEEK复合材料碱液中的主要磨损机制,而隧道状晶体结构和细微尺寸的纤维态形貌使得PTW在碱液中仍具有显微增强耐磨作用。     

Experimental characterization of processing-performance relationships of resistance welded graphite/polyetheretherketone composite joints

A study to investigate fusion bonding (welding) of AS4 graphite/polyetheretherketone (PEEK) thermoplastic composites is presented. Processing studies are conducted for resistance welding preconsolidated AS4/PEEK laminates in both unidirectional and quasi-isotropic configurations using PEEK and polyetherimide (PEI) film at the joint interface. All bonding was done under a constant displacement process. The influence of processing time, initially applied consolidation pressure, and the rate of heat generation on weld performance is examined through lap shear and Mode I interlaminar fracture toughness testing. A rapid increase in strength with processing time that asymptotically approaches the compression molded baseline is measured. Weld times for quasi-isotropic lap shear coupons are significantly shorter than those with a unidirectional lay-up. Variation of the initially applied consolidation pressure is shown to have little influence on the lap shear strength of PEEK film welded lap joints. A discussion of the mechanisms allowing void formation during the welding process is given. Bond strength test results are correlated with ultrasonic C-scans of the weld regions.     

PEEK抗静电复合材料的研究

制备了聚醚醚酮/炭黑(PEEK/CB)、聚醚醚酮/碳纤维(PEEK/CF)抗静电复合材料。结果表明,在PEEK/CB复合体系中,炭黑渗滤区含量为3%⁵%,较低的炭黑含量确保了复合材料优异的力学性能;在PEEK/CF复合体系中,碳纤维渗滤区含量为15%5%,较低的炭黑含量确保了复合材料优异的力学性能;在PEEK/CF复合体系中,碳纤维渗滤区含量为15%²0%;扫描电镜(SEM)结果证明:炭黑在PEEK基体中达到纳米级分散,形成空间导电网络结构,这种结构提高了复合材料的抗静电性能。