PEEK Composites Research Articles

Bi-scale interfacial bond behaviors of CCF/PEEK composites by plasma-laser cooperatively assisted 3D printing process

3D printed continuous carbon fiber reinforced PEEK (CCF/PEEK) composites have got much attention because of their excellent mechanical, thermal and chemical performance and the formability of complex structural components. However, there are always two different weak-bond interfaces limiting the application of the composites critically, which are the poor interlayer bond and the weak interface between carbon fibers and PEEK. A plasma-laser cooperatively assisted 3D printing process was utilized to improve the bi-scale interface. After optimizing, the interlaminar shear strength can be improved from 5.78 MPa to 39.05 MPa. After analyzing the failure mode and bi-scale interfacial bond mechanism, it’s found that the laser mainly improves the interlayer bond and crystallinity, while the plasma effectively improves the mechanical modulus by treating the surface of the carbon fibers chemically and physically. The work provides a really novel idea for developing the 3D printed CCF/PEEK composites for further application in aerospace and automotive industries.

Multifunctional performance of carbon nanotubes and graphene nanoplatelets reinforced PEEK composites enabled via FFF additive manufacturing

The study is focused on multifunctional performance of carbon nanotubes (CNT) and Graphene nanoplatelets (GNP) reinforced PEEK composites enabled via fused filament fabrication (FFF) additive manufacturing (AM) utilizing in-house nanoengineered filaments. Thermo-physical, mechanical and wear characteristics of electro-conductive PEEK nanocomposites are reported. The coefficient of thermal expansion (CTE) is found to decrease by 26% and 18% with the incorporation of 5 wt% GNP and 3 wt% CNT into PEEK polymer, respectively. The decrease in CTE provides better dimensional stability to resulting nanocomposite structures. Due to uniform dispersion of CNT and GNP in the PEEK matrix, the crystallization temperature and degree of crystallinity are both increased. The 3D printed PEEK nanocomposites reveal interfacial voids between the beads and intra-bead pores and thus exhibit lower density compared to that of the 3D printed neat PEEK. Young's and storage moduli are found to increase by 20% and 66% for 3 wt% CNT loading and by 23% and 72% for 5 wt% GNP loading respectively. However, the PEEK nanocomposites exhibit similar tensile strength to that of neat PEEK. The coefficient of friction obtained from fretting wear tests is found to decrease by 67% and 56% for 1 wt% CNT and 3 wt% GNP loaded PEEK nanocomposites, respectively and the decrease is attributed to reduced hardness and increased porosity. Multifunctional performance of carbon nanostructures reinforced AM-enabled PEEK composites demonstrated here makes them suitable for a range of applications such as orthopedics, oil and gas, automotive, electronics and space.

Elevated-Temperature Thermal Expansion of PTFE/PEEK Matrix Composite With Random-Oriented Short Carbon Fibers and Graphite Flakes

Abstract A combined experimental and micromechanics investigation is conducted on elevated-temperature thermal expansion of PTFE/PEEK polymer-matrix composite reinforced with randomly oriented short carbon fibers (CF) and graphite flakes (Gr). In the experimental phase of the study, PTFE/PEEK polymer blends with different amounts of PTFE and four-phase CF/Gr/PTFE/PEEK composites with different volume fractions of graphite flakes were made from compression molding. Scanning electron microscopy was performed to evaluate the microstructure of the PTFE/PEEK matrix and the composite, especially the interface, and the size and dispersion of the particles. X-ray diffraction (XRD) was conducted to provide morphological information on the semi-crystalline PTFE/PEEK matrix of the composite. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were carried out to determine transition temperatures and thermomechanical properties of the composite and its constituent phases at the elevated temperature. Thermal expansions of neat PTFE and neat PEEK, the PTFE/PEEK polymer matrix, and the CF/Gr/PTFE/PEEK composite were obtained with a thermal–mechanical analyzer (TMA) in a dilatometric mode. Coefficients of thermal expansion (CTEs) of the PTFE/PEEK matrix and its CF/Gr/PTFE/PEEK composite were then determined from 25 °C up to an elevated temperature 240 °C. To augment the experimental study, micromechanics analyses are also conducted to determine thermal expansion coefficients of the PTFE/PEEK matrix and the CF/GR/PTFE/PEEK composite. The micromechanics solutions elucidate individual roles of different composite constituents, contributions of individual constituent materials’ temperature-dependent thermal and mechanical properties, the importance of composite microstructure and morphology, and the issue of thermal–mechanical coupling on the thermal expansion behavior of the complex CF/Gr/PTFE/PEEK composite at high temperature.

Recycled carbon fibers as reinforcements for hybrid PEEK composites with excellent friction and wear performance

Recycling of carbon fibers in polymer matrix provides a new route of developing engineering components for tribological applications, which helps alleviate environment pollution from plastic waste. In the present work, tribological properties PEEK hybrid composite reinforced with recycled carbon fibers (rCFs) were systematically studied and compared to those of virgin carbon fibers (vCFs) reinforced composite with equivalent composition. Comparable friction and wear characteristics were revealed between both PEEK composites, which highlights the validity of replacing vCFs with rCFs in designing polymer tribocomposites. Behind this equivalence in tribo-performance, the synergy between fibers and rigid particles was found to play a crucial role. The later overwhelmed the contribution of different mechanical properties of carbon fibers before and after recycling.

Friction and wear behaviours of self-lubricating peek composites for articulating pin joints

With the rapid development of engineering materials, self-lubricating and high strength composites have become a high demand candidate material for pin joints due to their significant potential in downsizing and weight saving. In this study, bearing bushes made from unfilled polyetheretherketone (PEEK) and PEEK composites were investigated for their tribological performance through two sets of experiments, (i) ball-on-disc dry sliding on CETR UMT, and (ii) pin/bush contact on a purpose built pin joint test rig. Continuous rotation and oscillation of shaft were performed with the pin/bush contact configuration. The contact pressure between the bush and shaft ranged from 20 MPa to 140 MPa and articulation speed from 10 deg/s to 60 deg/s. Wear mechanism was investigated through microscopic observation.

Assessment of (PEEK) Composite as A Dental Implant (in Vitro Physical Properties)

Aim of this study this study was done to evaluate the PEEK and PEEK polymer composite material used as dental implant through physical evaluation including (DSC, FTIR, Wettability, Radioopacity). PEEK composites (PEEK and SiC with selected weight percentage ratios of (0, 1.5%, 3%, 4.5%, 6%), were fabricated using a compounding by melt blending using (Internal Mixer) at 365oC, 5min. technique, The study involved Samples preparation (sheets) shaping and forming into desire shapes according to ASTM standard for physical tests which include DSC, FTIR, Wettability and Radioopacity. The results obtained from the experiments showed that in the DSC test slight increase in the crystallization temperature polymer composite consisting from polyetheretherketone and Silicone Carbide nanofiller implant comparing with pure PEEK, with increase the in the radioopacity of PEEK composite (concentration 1.5%, 3%, 4.5%, 6%), improvement in the wettability value, with no effect in the chemical structure of PEEK composite comparing with the PEEK composite.

A general approach for the study of kink band broadening in fibre composites and layered materials

The progressive non-linear mode of deformation known as steady-state kink band broadening is analysed for fibre composites and layered materials. The mode of deformation is investigated using an analytical, a semi-analytical model and a finite-element model. The semi-analytical model is based on a constitutive model, where independent material behaviour can be given for two constituents. The analytical model assumes rigid fibres and results in a transcendental equation for the kink band broadening state. Both the analytical and semi-analytical model use a Maxwell construction to determine the steady-state, which is done by equating the internal and external work. The influence of size-effects are explored and two case studies are performed; in the first case study the finite element model and semi-analytical model are used upon a carbon fibre-reinforced PEEK composite. The second case study is on a layered composite made from ultra high molecular-weight polyethylene fibres with a kink band developing on ply level.

The Dawn of Thiol-Yne Triazine Triones Thermosets as a New Material Platform Suited for Hard Tissue Repair.

The identification of a unique set of advanced materials that can bear extraordinary loads for use in bone and tooth repair will inevitably unlock unlimited opportunities for clinical use. Herein, the design of high-performance thermosets is reported based on triazine-trione (TATO) monomers using light-initiated thiol-yne coupling (TYC) chemistry as a polymerization strategy. In comparison to traditional thiol-ene coupling (TEC) systems, TYC chemistry has yielded highly dense networks with unprecedented mechanical properties. The most promising system notes 4.6 GPa in flexural modulus and 160 MPa in flexural strength, an increase of 84% in modulus and 191% in strength when compared to the corresponding TATO system based on TEC chemistry. Remarkably, the mechanical properties exceed those of polylactide (PLA) and challenge poly(ether ether ketone) PEEK and today's methacrylate-based dental resin composites. All the materials display excellent biocompatibility, in vitro, and are successfully: i) molded into medical devices for fracture repair, and ii) used as bone adhesive for fracture fixation and as tooth fillers with the outstanding bond strength that outperform methacrylate systems used today in dental restoration application. Collectively, a new era of advanced TYC materials is unfolded that can fulfill the preconditions as bone fixating implants and for tooth restorations.

Influence of cenosphere on tribological properties of short carbon fiber reinforced PEEK composites

ABSTRACTThis investigation focuses on the effects of cenosphere fillers on tribological properties of carbon fiber reinforced PEEK composites. Dry sliding wear behavior of 15 wt % short carbon fiber (SCF) reinforced PEEK composites filled with 5, 10, 15, and 20 wt % cenosphere was reported in this study, pure PEEK and 15 wt % SCF reinforced PEEK composites were also prepared for comparative analysis. Friction and wear experiments were conducted on a ring‐on‐block apparatus under different loads (100–400 N). The experimental results showed that all the composites exhibited lower coefficient of friction and better wear resistance than the matrix resin under different load conditions. It is noted that 10 wt % of the cenosphere particles filled SCF reinforced PEEK composites show superior tribological properties when compared to the other composites in this study. The morphologies of the worn surface and the fracture surface were analyzed by scanning electron microscopy and the transfer film was observed by optical microscope to understand the dominant wear mechanisms. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47245.

Non-Isothermal Crystallization Kinetics of Short Glass Fiber Reinforced Poly (Ether Ether Ketone) Composites.

Due to its excellent chemical and temperature resistances, short glass fiber reinforced poly (ether ether ketone) composite (SGF/PEEK) is a promising material for application in automotive lightweight. Processing conditions, such as cooling rate, need to be well controlled to obtain the optimal crystallite morphology of PEEK composites. Thus, in this paper, the non-isothermal crystallization kinetics and melting behavior of SGF/PEEK were investigated by differential scanning calorimetry (DSC) at different cooling rates, and the crystallite sizes were evaluated by the X-ray diffraction technique (XRD). Crystallization kinetics models and effective activation energies were evaluated to determine the crystallization parameters of the composites. The results suggest that a lower cooling rate enlarges the size of crystallites and enhances the uniformity of size distribution. The addition of glass fibers improves the nucleation rate owing to heterogeneous nucleation while decreasing the growth rate due to retarded movement of the polymer chain. The combined Avrami-Ozawa equation was shown to describe accurately the non-isothermal crystallization. The absolute value of the crystallization activation energy for SGF/PEEK is lower than that of pure PEEK.

Mechanical properties and cytotoxicity of hierarchical carbon fiber-reinforced poly (ether-ether-ketone) composites used as implant materials

Weak mechanical properties affect the application of PEEK as an implant. Carbon fiber (CFR) reinforcement provides an excellent solution to improve the mechanical strength of PEEK and to provide perfect matching of elastic modulus between CFR-PEEK composites and human bone. To investigate the effect of carbon fiber content on the mechanical, thermal properties and cytotoxicity of CFR reinforced PEEK composites, a series of CFR-PEEK composites with different carbon fiber content (25 wt%, 30 wt%, 35 wt%, 40 wt%) was prepared in this work. Thermal decomposition behavior and melting temperature were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. Subsequently, mechanical properties including bending strength, compressive strength, impact strength and hardness were tested respectively. Afterwards, the fracture morphology of the bending test samples was observed by scanning electron microscopy (SEM). In addition, murine fibroblast L929 cells were adopted for cytotoxicity test by CCK-8 assay in vitro, and the morphology of cells was observed by inverted fluorescence microscope simultaneously, cell compatibility of CFR-PEEK composites was tested.

Tribological behaviour of high performance polymers and polymer composites at elevated temperature

Abstract In this work, the tribological properties of three different high-performance polymers have been investigated at different temperature regimes. In addition, wear behaviour of PEEK composites (reinforced with different TiO 2 content) has also been studied and compared at different temperatures. SEM cross-sectional analysis of the transfer film layers (TFLs) on steel counterparts was carried out to understand the formation of TFLs. Further, the thickness and distribution of TFLs were measured using nanoindentation as well as possible structural changes of the materials by Fourier transformed infrared (FTIR) technique. Based on experimental investigation, it was concluded that the development of transfer film and wear performance of polymeric materials, can be greatly affected by materials' brittle-ductile transition behaviour, depending on the temperature tested.

Bending property and fracture behavior of continuous glass fiber-reinforced PEEK composites fabricated by the wrapped yarn method

The purpose of this study was to investigate bending properties and fracture behavior of the unidirectional continuous glass fiber-reinforced poly(ether ether ketone) composites based on the wrapped yarn method and to obtain an optimum fabrication condition. The composite plates were fabricated at different processing conditions, and their bending properties and fracture behaviors were investigated in terms of thermal, morphology, and fracture characterizations. The results indicate that the cooling rate lightly affected the bending performance; however, both molding temperature and holding time had a significant effect on the bending performance. Specifically, increasing the molding temperature or the holding time was conductive to reducing the delamination.

Multiscale enhancement behavior of nano‐silica modified CF/PEEK composites prepared by wet powder impregnation

The mechanical performance of modified multiscale carbon fiber (CF) reinforced poly(ether‐ether‐ketone) (PEEK) composites is improved through wet powder impregnation. The complex PEEK suspension is prepared by mixing nano‐silica and PEEK powders in water homogeneously. The CFs are pulled through the complex PEEK suspension, and the modified multiscale PEEK prepregs and composites are prepared by a series of drying and consolidation process. The increasing energy storage, decreasing tan δmax and the area under the tan δ curve in the dynamic mechanical tests indicate strong interface interactions of modified multiscale CF/PEEK composites. The interlaminar shear strength increases by 15.6% from 72.2 to 83.5 MPa for 2.5 wt% nano‐silica addition, showing significant improvement in resisting the delamination damage. Besides, the same addition makes the flexural strength and modulus increase by 13.9 and 8.6%, respectively. The modified multiscale CF/PEEK composites exhibit higher flexural strength and modulus at elevated temperature than the pristine composites. Furthermore, the enhancement mechanisms for the modified multiscale CF/PEEK composites are proposed and illustrated, which contributes to future research on multiscale enhancement for conventional composites. POLYM. COMPOS., 40:1187–1197, 2019. © 2018 Society of Plastics Engineers

Modelling and analysis of four wheel rim by using PEEK composites

Modelling and analysis of four wheel rim by using PEEK composites

Wear Behavior of PEEK Matrix Composites: A Review

The aim of the present study is to conduct a focused review on the wear behavior of PEEK composites. The selection conditions for this article were: research papers focused on the mechanical behavior of PEEK composites. Results showed the addition of reinforcement into PEEK to improve the wear behavior although some of those fillers can increase the weakness of the composite. Further, the inclusion of carbon fiber increased considerably the mechanical strength of PEEK composites. Indeed, the chemical composition, microstructure and properties of the fillers can affect the wear performance of PEEK composites. This exposes a great challenge in this field leading to novel development to increase the mechanical strength of PEEK composites. A potential reinforcement has to be manufactured to improve the mechanical strength. Alternative way could be to carry out a surface treatment in the particles in order to increase the adhesion between matrix and filler.

Taguchi Technique for Dry Sliding Wear Behavior of PEEK Composite Materials

In today’s industrial scenario, use of polymer composite materials for tribological applications have been increasing. In this regard, a study on polymer composite materials was carried out. The tribological behavior of PEEK composites, including different types and amounts of filler materials was examined. Effects of operating parameters such as sliding velocity, pressure and time on tribological performance of PEEK composite materials were studied. Wear tests were performed on a pin-on-disc set up using plan of experiments based on Taguchi’s technique. Analysis of variance has been carried out to establish the relative significance of the individual factors on wear performance. An empirical relation between wear and operating parameters were established for all composite materials using linear regression analysis. The sliding velocity, pressure and test duration plays an important role on tribological performance of PEEK composite materials by influencing the temperature of contact area. It was observed that PEEK reinforced with CF, PTFE and graphite could effectively improve the tribological performance.

Comparative study of the effects of nano‐sized and micro‐sized CF and PTFE on the thermal and tribological properties of PEEK composites

The tribological characteristics of PEEK composites fretting against GCr 15 steel were investigated by a SRV‐IV oscillating reciprocating ball‐on‐disk tribometer. In order to clarify the effect of type and size of fillers on the properties of PEEK composites, nano‐sized and micro‐sized CF and PTFE fillers were added to the PEEK matrix. The thermal conductivity, hardness, and fretting wear properties of PEEK composites reinforced by CF or PTFE were comparatively studied. The results showed that the type and size of the fillers have an important effect on both the friction coefficient and wear rate, by affecting their thermal conductivity, hardness, as well as the surface areas of their transfer films. In comparison, the effect on improving the tribological properties of micro‐sized CF was superior to that of nano‐sized CF, while the effect of nano‐sized PTFE was superior to that of micro‐sized PTFE. Considering the acceptable friction coefficient and wear rate of the composite under the fretting wear test, it seemed that 4% nCF, 20% mCF, 2% nPTFE and 10% mPTFE were desired additive proportions. And it also can be found that during the fretting wear test, the abrasive and adhesive wear resulted in accumulative debris at the contacting surface. The transfer films made of debris were formed on the counterfaces.

Enhanced interfacial interactions of carbon fiber reinforced PEEK composites by regulating PEI and graphene oxide complex sizing at the interface

The interfacial interactions and bonding of carbon fiber (CF) reinforced poly(ether-ether-ketone) (PEEK) composites is improved by applying polyether imide (PEI) and graphene oxide (GO) complex sizing at different ratios at the interface. The thermally stable polyether imide (PEI) and graphene oxide (GO) complex sizing is prepared and then coated on carbon fiber surfaces homogeneously. The sizing layer forms on the fiber surfaces, and multiple GO sheets are introduced successfully surrounding the carbon fibers. The surface morphologies of carbon fibers change distinctly with different GO contents. The interfacial shear strength (IFSS) increases from 43.4 MPa for bare fiber reinforced PEEK composites to 49.4 MPa for composites reinforced by carbon fibers coated with PEI only. However, a significant improvement is achieved when GO sheets are introduced to the CF surfaces, making the IFSS grow up to 63.4 MPa. Furthermore, the dynamic mechanical tests show that the normalized damping area results of carbon fibers coated with complex sizing decrease remarkably by about 50%. DMA results, interlaminar shear strength (ILSS) test and flexural test results are in agreement with each other, suggesting better interface bonding of composites by applying PEI and GO complex sizing. Besides, the interfacial interaction mechanism in modified composites is proposed. The enhanced interfacial performance is caused by the positive effect of complex interface layer.

Study on mechanical properties of unidirectional continuous carbon fiber‐reinforced PEEK composites fabricated by the wrapped yarn method

The purpose of this study was to investigate the mechanical properties of unidirectional continuous carbon fiber‐reinforced PEEK (CCF/PEEK) composites via the wrapped yarn method and to obtain optimum fabrication conditions. The composite plates were fabricated at different processing conditions and their mechanical properties (i.e., tensile, bending and short beam shear strength performance) were investigated in terms of thermal and fracture morphology characterizations. As the molding temperature and molding time increased, the mechanical properties of the composites enhanced due to the improved impregnation of the fibers, although there was potential matrix degradation. Moreover, slow cooling rate had little effect on the mechanical properties of the composites. Therefore, to obtain a combination of excellent mechanical properties and high production efficiency, a relatively high molding temperature, sufficient molding time and moderate cooling rate were optimal for the CCF/PEEK fabricated by the wrapped yarn method. POLYM. COMPOS., 40:56–69, 2019. © 2017 Society of Plastics Engineers