Processing parameters for consolidating PEEK/carbon fiber (APC-2) composites

This consolidation of unidirectional APC-2 was studied experimentally to determine the effects of processing parameters (pressure, temperature, and number of layers) on resin flow as measured by the Kozeny constant and the bulk modulus. The Kozeny constant obtained was between 0.0205 and 0.107. It was found to depend on the consolidation pressure, temperature, number of layers, and their interactions at a 99% confidence level. The value of the bulk modulus was found to be between 1.21 MPa (175 psi) and 8.58 MPa (1244 psi). It also was found to depend on the temperature, pressure, number of plies, and their interactions at a 99% confidence level. These results show the critical effects of fiber orientation on resin flow during processing.     

Ultrasonic welding of all-polypropylene composites

In this study, the mechanical properties of ultrasonic welded lap joints of all-polypropylene composite (APPC) were investigated and compared to the interlaminar properties of the composite sheet itself. The process control parameter was welding time: welded samples were prepared with an ultrasonic welding machine in the 0.1–1.0 second time range. In most cases, the shear strength of the welded samples exceeded that of the unwelded APPC. Although it was found that during the ultrasonic welding process, the reinforcing tapes partially melted in the welding zone (WZ), the seam remained strong enough because the heat released and the pressure applied during the welding process further improved the consolidation of the APPC layers. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48799.     

Ultrasonic evaluation of graphite/epoxy composites with different curing conditions

Ultrasonic evaluation of AS4/3501-6 graphite/epoxy composites and Hercules 3501-6 epoxies with different curing conditions has been carried out. A differential scanning calorimeter and a dynamic mechanical analyzer were used to characterize the cure status of these materials. The anisotropic elastic moduli, through-thickness longitudinal wave dispersion and attenuation were measured by different ultrasonic techniques. Effects of curing conditions on the mechanical properties of the composites and corresponding epoxies were discussed.     

Processing and structural optimization of PEEK composites

The objective of this experimental program was to understand how changes in processing conditions affect the morphology and ultimately, the performance of polyetheretherketone (PEEK)-based carbon fiber composites. Based on some initial differential scanning calorimetry (DSC) work, various molding and aging conditions were implemented on compression molded plaques made from PEEK APC-2 prepreg. These conditions included samples that were physically aged, annealed just below the melting point, slow cooled, prepared under low pressure, and under fast cooling. Using DSC, the crystallinity of plaques prepared according to the ICI procedure, low pressure, and physical aging conditions were found to be 31–33 percent, while the slow cooling and annealing conditions resulted in crystallinity of 42 percent, with slow cooling displaying a „shoulder”︁ on the primary melting endotherm. Optical and plasma etching/scanning electron microscopy on faster cooled plaques generally revealed a mixture of isolated and graphite fiber nucleated spherulites, while the slow-cooled condition revealed larger fiber nucleated spherulites exclusively. Fracture toughness and impact delamination as measured by ultrasonic C-scan indicates that slow cooling resulted in the lowest properties, while simultaneously resulting in the highest compression strength, all of which suggests reduced matrix toughness. The annealing condition, which allowed high crystallinity but in a matrix of smaller spherulites, resulted in properties intermediate between slow and fast cooling, suggesting that both spherulite size and degree of crystallinity are important in characterizing these materials. In contrast, physical aging resulted in no degradation in mechanical properties.     

Friction welding joint analysis of dissimilar nanocomposites: PEEK/aluminum to PEEK/titanium

Welding of dissimilar materials is extremely challenging to the researchers. In present work, for the first time, poly(ether ether ketone) (PEEK) based aluminum (Al), titanium (Ti) reinforced nanocomposites with varying reinforcements of 10, 20, 30, and 40 vol% were developed using powder metallurgy technology. Additionally, for the first time, the two dissimilar nanocomposites of PEEK/Al and PEEK/Ti were successfully welded by friction welding (FW) process to produce FW PEEK/Al-PEEK/Ti nanocomposites with equal metallic reinforcements (viz., 10–40 vol% Ti or Al). The nanocomposites were characterized precisely and correlated by physical, microstructural, structural, thermal, and micromechanical tests. Crystallinity being a factor of melting temperature affects significantly the micromechanical characteristics influenced by reinforced particle-concentrations. The FW PEEK/30Al-PEEK/30Ti was found as best material since it showed highest nanohardness (0.652 GPa) and elastic modulus (15.902 GPa) in FW Joint at 40 mN compared to other FW nanocomposites. At the FW joint section, it was discovered that the reinforced particles were being transferred through an interdiffusion mechanism. Mobility of the nanoparticles was influenced by the concentration of the reinforced particles, which further modified the matrix's crystallization behavior and consequently influenced the FW nanocomposites' micromechanical properties. Therefore, the present work has suggested a feasible route for applying thermoplastic nanocomposites in the biomedical and aerospace industries.     

Fluid sorption characterization of PEEK matrices and composites

Neat poly(ether-ether-ketone) (PEEK) and carbon fiber reinforced PEEK (APC-2) specimens were prepared using a variety of cooling rates to achieve a range of crystallinities. Amorphous specimens were exposed to a variety of fluids to determine the penetrant types which are able to strongly influence the material. This allowed the estimation of the solubility parameter and hydrogen bonding index for PEEK to be 9.5 and 3.1, respectively. Methylene chloride was used to investigate the kinetics of penetrant sorption. The data demonstrated Case II behavior, with the initial crystallinity having a pronounced effect on both the kinetic and equilibrium data. Accordingly, a model was proposed capable of describing the sorption level and penetration depth as a function of time given the sample crystallinity and sorption temperature. With Case II behavior there was no difference in the sorption kinetics of neat and fiber reinforced PEEK. Finally, the dynamic mechanical properties measured during sorption were found to be dependent on the sorption process.     

Preparation and radiation shielding properties of Gd2O3/PEEK composites

Gd₂O₃/PEEK (poly ether ether ketone) composites were prepared on a twin‐screw extruder by the incorporation of Gd₂O₃ as a shield against X‐ray to PEEK matrix. The influence of Gd₂O₃ addition and surface treatment of the particles with sulfonated PEEK (SPEEK) on the morphology, thermal and mechanical properties of the composites was investigated by SEM, DSC, TGA and tensile tests respectively. DSC results showed that both the crystallization temperature (T_c) and melting temperature (T_m) of the composites decreased compared with pure PEEK at random filler content, which suggested that Gd₂O₃ hindered the process of PEEK nucleation. The tensile modulus of the composites increased with addition of Gd₂O₃ and the strain to break decreased. But the tensile modulus and strength of modified series were always higher than that of unmodified ones at the same filler content. The X‐ray shielding properties of composites apparently improved with the increment of the Gd₂O₃. The X‐ray transmittance (A) of 45% S₄GPEEK reduced greatly by about three to eight times compared with PEEKs in all energy range measured. POLYM. COMPOS., 36:651–659, 2015. © 2014 Society of Plastics Engineers     

Development and characterization of PEEK/carbon nanotube composites

New poly(ether ether ketone) (PEEK) based composites have been fabricated by the incorporation of single-walled carbon nanotubes (SWCNTs) using melt processing. Their structure, morphology, thermal and mechanical properties have been investigated. Scanning electron microscopy observations demonstrated a more uniform distribution of the CNTs for samples prepared following a processing route based on polymer ball milling and CNT dispersion in ethanol media. Thermogravimetric analysis indicated a remarkable improvement in the thermal stability of the matrix by the incorporation of SWCNTs. Differential scanning calorimetry showed a decrease in the crystallization temperature with increasing SWCNT content, whilst no significant changes were observed in the melting of the composites. The crystallite size determined by X-ray diffraction decreased at high SWCNT loading, which is attributed to the spatial limitations on crystal growth by confinement within the CNT network. Dynamic mechanical analysis revealed an increase in the storage moduli, hence in the rigidity of the systems, with increasing SWCNT content. Their addition shifts the glass transition peak to higher temperatures due to the restriction in chain mobility imposed by the CNTs. Higher thermal stability and mechanical strength were found for composites with improved dispersion of the SWCNTs.     

石墨/TinO2n-1复合材料的制备及性能

在常压下,以钛白粉为原料,石墨为还原剂,采用碳热还原法制备了石墨/Ti_nO_2n-1复合材料。采用XRD系统分析了碳热还原过程中钛的价态变化规律;采用XPS、SEM、TEM分析了特定样品的形貌、结构和元素组成。XRD分析结果表明,控制不同的还原条件,可以得到不同n值的石墨/Ti_nO_2n-1复合材料,且还原过程的物相转变顺序为：TiO₂（锐钛型）、TiO₂（金红石型）、Ti₉O₁₇、Ti₈O₁₅、Ti₆O₁₁、Ti₅O₉和Ti₄O₇。在还原温度为1250℃,还原时间为20min,碳钛比为5∶10的条件下所制备的石墨/Ti_nO_2n-1复合材料的电阻率最低,其值为0.1465Ω·cm。吸附/光降解实验表明,石墨/Ti_nO_2n-1复合材料对亚甲基蓝的吸附能力比纯石墨显著增强,吸附去除率为纯石墨的1.40~3.20倍;石墨/Ti_nO_2n-1复合材料对亚甲基蓝具有光催化降解活性,但是其光降解能力低于锐钛型TiO₂;复合材料的催化降解速率常数最大值为0.0047min^-1。     

Material characterization of graphite nanosheet composites

Three sets of expanded graphite‐filled polymers, having three different particle sizes, were reinforced with 1–5% by weight. The structural, mechanical, electrical, and thermal properties of these composites were studied and compared. After dispersion, the particles were reduced to nanometer size through exfoliation, sonication, and high‐shear strain rate mixing, which further breaks and delaminates them. In addition, scanning electron microscope characterizations were performed. The expanded graphite‐filled polymer material could be tailored to be high conducting. Compared with the pure polymer, the polymers filled with 5 wt% expanded graphite have seen a significant reduction in electrical resistivity by orders. The thermal expansion coefficient and water absorption for the weight containing 5 wt% expanded graphite has also been drastically improved, decreasing with the weight percentage of graphite content. Compression and impact tests were conducted. The influence of dispersion on the material behavior was studied. Some fracture modes associated with the layered microstructures of the graphite nanosheets were observed. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

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。     

塑料超声波扫描焊接技术

超声波扫描焊接是连续、高速地超声波焊接在固定超声波焊头或旋转焊头与砧座下方传送的平直工件的方法。该方法适用于至少有一个平面便于焊头接触的硬质热塑性塑料工件。某些织物或薄膜也适用于这种方法。无论是大型的还是小型的热塑性塑料工件都可以超声波扫描焊接。本文简述了超声波扫描焊接原理、分类、接头设计、特点及应用。     

Photografting of argon plasma-treated graphite/PEEK laminate to enhance its adhesion

Graphite/PEEK laminates were treated by argon plasma followed by air aging and then photografting of α- glycidyl ω- acrylate bisphenol A(GABA) to improve their adhesion characteristics. The effects of plasma time and power and photografting time on the epoxy bonded single lap shear joints between graphite/PEEK laminates were investigated. An optimum photografting time was found at which the single lap shear strength was optimized to 37 MPa compared to 28 MPa and 7 MPa obtained with air-aged argon plasma activated and pristine samples, respectively. Argon plasma treatment followed by air aging of graphite/PEEK laminate introduces surface peroxides and hydroperoxides and these when cleaved with ultraviolet (UV) light in the presence of the GABA monomer results in covalent grafting of the latter to PEEK/graphite laminate surface. The epoxy functionality of the GABA monomer then reacts with the epoxy adhesive. X-ray photoelectron spectroscopy (XPS) confirms the appearance of surface peroxides and hydroperoxides on air-aged argon plasma treated samples and disappearance of the same with UV irradiation. With UV irradiation of the air-aged argon plasma treated samples, XPS indicates the appearance of ester groups. Without the grafting monomer, UV irradiation in air cleaves the peroxide and causes oxidation resulting in the formation of surface esters. In the presence of the grafting monomer, UV irradiation results in covalent bonding of the monomer to the peroxide/hydroperoxide through the acrylate functionality resulting in increased concentration of ether linkages as confirmed by our XPS data; the ester functionality present in the grafted monomer caused the appearance of the ester peak in the XPS spectrum.     

Ultrasonic welding of plasticized PLA films

Poly(lactic acid) (PLA) is a commercially available biobased material that has become an ideal material in packaging applications because of its low toxicity along with its environmentally friendly characteristics. Unfortunately, PLA is rigid and brittle. These characteristics impede its wide application. The flexibility of PLA can be improved by plasticization. In addition, welding polymer films is essential in the packaging production. Therefore, the weldability by means of ultrasonic welding of the neat and with polyethylene glycol plasticized PLA films was analyzed in this study. Moreover, the study examines the influence of the material composition on the processing window, that is, the range of welding parameters which could be used to weld films efficiently, and on the weld quality. This research showed that all examined films can be welded by ultrasonic welding. Furthermore, it was discovered that the addition of a plasticizer has a strong influence on the processing window and on the weld quality. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41351.     

Ultrasonic properties of polystyrene-based composites

In this study, first the pure polystyrenes (PS) with different molecular weights (350 × 10³ and 500 × 10³) have been modified by the chemical modification with succinic anhydride (SA), maleic anhydride (MA), and phthalic anhydride (PhA) and then the polystyrene based composites (CPS) prepared by addition of modified polystyrenes (MPS) into pure PS (with the molecular weight of 230 × 10³) in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. Ultrasonic measurements were performed on PS/MPS blends of different weight percent of MPSs by use of pulse echo method with 5-MHz frequency at room temperature. Elastic properties namely; longitudinal modulus (L), Young's modulus (E), bulk modulus (K) and shear modulus (G), Poisson's ratio (μ), and acoustic impedance (Z) were calculated from the ultrasonic velocities values measured and densities values obtained experimentally. Atomic force microscopy (AFM) has been used for determining the microstructure of composites. The variations of these parameters with increasing MPSs weight percentage content in PS/MPS from 10 to 30 have been discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

用于聚合物检测的PEEK超声缓冲杆性能测试分析

借用缓冲杆来实现熔融态聚合物的超声检测是一种行之有效的方法,但缓冲杆的材料会影响最终的检测效果,通过实验测量了聚醚醚铜(PEEK)的声阻抗、声衰减系数、声速等参数,在不同测试温度下测试了PEEK缓冲的超声回波信号衰减情况,通过仿真分析了缓冲杆直径、长度对回波信噪比的影响情况。综合上述的结果得出,PEEK缓冲杆适合用于≤160℃环境下的聚合物检测,具有较低的声衰减、较高的声透射率和信噪比。     

High performance polymer composites on PEEK reinforced with aluminum oxide

A study on high performance poly(ether‐ether‐ketone) (PEEK) composites prepared by incorporating aluminum oxide (Al₂O₃), 0 to 50 wt % by hot compaction at 15 MPa and 350°C was described. Density, thermogravimetric analysis/differential scanning calorimetry, and scanning electron microscopy (SEM) were employed to evaluate their density, thermal stability, crystallinity, and morphology. Experimental density was found higher than theoretical density, which indicates that composite samples are sound. It was found that the addition of micron sized (< 15 μm) Al₂O₃ increased the peak crystallization temperature by 12°C when compared with neat PEEK with insignificant increase in melting temperature. Half‐time of crystallization is reduced from 2.05 min for the neat PEEK to 1.08 min for PEEK incorporated with 30 wt % Al₂O₃ because of the strong nucleation effect of Al₂O₃. The thermal stability of composites in air atmosphere was increased by 26°C. However, thermal stability in nitrogen atmosphere decreases at lower concentration of Al₂O₃ but increases above 20 wt % of Al₂O₃. Uniform dispersion of Al₂O₃ particles was observed in PEEK polymer matrix by SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4623–4631, 2006     

Effect of dispersion on graphite nanosheet composites

By intercalating and exfoliating natural graphite flakes, expanded graphite was obtained and used as the additive for making composites. The expanded graphite was composed of partly connected graphite nanosheets. Three types of composites were made, representing three levels of dispersing the graphite nanosheets. The first was the impregnation of epoxy resin to the expanded graphite by resin transfer molding. No dispersion was applied, and the expanded graphite can retain its original shape. The second was the use of a high‐power sonication to break apart the expanded graphite. The thickness of the sonicated expanded graphite was reduced to about 100 times. The third method was to use a high‐shear strain rate to separate the graphite nanosheets from the expanded graphite and to disperse them into the resin. The thickness range of the graphite nanosheets was 20–50 nm, about 100 times thinner than the sonicated ones. Compression and impact tests were conducted. The influence of dispersion on the material behavior was studied. Some fracture modes associated with the layered microstructures of the graphite nanosheets were observed. A simple model was used to study the stress transfer and frictional energy consumption of the pullout of the nanosheet. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers