Carbon Fiber Reinforced PEEK Composites Research Articles

Interfacial crystallization behavior and properties of T1100-grade carbon fiber reinforced PEEK composites

As a semi-crystalline resin, the crystallization behavior of Polyether ether ketone at the interface between carbon fiber and resin matrix profoundly affects the interfacial properties of carbon fiber-reinforced PEEK composite. Therefore, the research on the interfacial crystallization behavior of CF/PEEK composite is of great significance. Aiming at Chinese-made T1100-grade carbon fiber and PEEK resin matrix, the effects of cooling rate and sizing agent on the interfacial crystallization behavior of T1100-grade carbon fiber/PEEK were studied by POM and DSC, and the IFSS was tested by microdebond. The experimental results show that the increase of the cooling rate and the removal of the sizing agent can improve the nucleation ability of PEEK and promote the interfacial crystallization of PEEK. PEEK starts to form transcrystallization, when the nucleus density is increased to about 0.07/μm. The interfacial crystallization behavior has an effect on the interfacial properties. The IFSS increases with increasing cooling rate and removal of sizing agent.

Enhancing the PEEK composites-titanium interface performances through electrochemical treatment in fibre-metal laminates for aerospace applications

In this work, different surface treatments were investigated to improve the adhesion between grade 5 titanium alloy and carbon fibre-reinforced PEEK composites for aerospace applications. Three types of processes were compared: mechanical treatment (MT), carried out by sander with #80 grit sandpaper, chemical treatment, using a silane coupling agent (SIL) and electrochemical treatment, performed by anodic oxidation. The latter was performed by using an ethylene glycol solution composed of 0.5%wt of ammonium fluoride (NH4F) and variable volume content of deionized water: 5%v/v, 20 % v/v, 50 % v/v. The ammonium fluoride content was fixed, while the ethylene glycol percentage depend on the variation of water volume. Two values of electric potential were evaluated: 30V and 50V. Finally, for each potential and water content, three different anodizing times were studied: 10 min, 30 min, and 60 min. Morphology studies were performed through Scanning electron microscopy to evaluate how the anodizing parameters could affect the shape of the nanotubes (NTs) layers. Moreover, short beam shear tests were carried out to evaluate the achieved improvement given by the different surface treatments.

Tribological performance of 3D printed neat and carbon fiber reinforced PEEK composites

This work investigates the tribological behavior of neat and carbon fiber-reinforced polyether-ether-ketone (PEEK) materials processed using the fused filament fabrication (FFF) technique. The reciprocating sliding behavior of printed polymers against stainless steel (SS) under dry and water-lubricated conditions was studied. The running-in behavior and evolution of friction were dependent on the material combination and sliding conditions. PEEK reinforced with 10 wt% carbon fibers was optimal considering tribological performance. Neat PEEK exhibited a combination of abrasive and adhesive wear mechanisms, while composites primarily showed fiber-matrix debonding and delamination during sliding. The outcome of this work has significance in improving the processing design of PEEK-based materials in extrusion-based 3D printing for tribological applications.

Effect of fabrication process on the microstructure and mechanical performance of carbon fiber reinforced PEEK composites via selective laser sintering

Carbon fiber reinforced PEEK (CF/PEEK) composites via selective laser sintering (SLS) are highly promising technologies for the fabrication of polymer-based components with excellent mechanical behavior. In order to further enhance the performance of SLS-CF/PEEK composites, the mixed CF/PEEK powders are designed and CF/PEEK composites are fabricated via SLS under different fabrication process parameters. The effect of laser power, layer thickness, paving speed, fiber weight fraction, and fiber length on the microstructure and mechanical performance along the powder spreading direction is investigated for SLS-CF/PEEK. The results show that the failure strength of 117 MPa is achieved while the layer thickness of 0.08 mm is adopted. Moreover, the fiber weight fraction of 15% is proven to be suited during the fabrication of SLS-CF/PEEK. The maximum failure strength is better than the results of SLS-CF/PEEK with the fiber weight fraction of 10%, and the average elastic modulus reaches 8400 MPa, which is the best result among those published works. In addition, it is found that the correlation between the failure strength and paving speed is non-monotonic, and the higher strength is obtained when the longer carbon fiber is used. Different from the distinct trends in failure strength, the sensitivity of modulus is much less obvious for SLS-CF/PEEK. This work provides guidance for the printing of high-strength CF/PEEK composites.

Strength analysis of carbon fiber reinforced PEEK composites with heat resistant sizing agents

Continuous Fiber Reinforced Thermoplastic Composites (CFRTPCs) are known for their demand in high-tech industries due to their excellent mechanical, thermal and chemical performance. However, poor adhesion interaction between carbon fiber (CF) and high-performance polymers such as PEEK tend to influence the mechanical modulus of the composite parts in a negative way. In the current work, a number of PAA-based sizing agents modified with various fillers were used for CF surface treatment in order to improve adhesion. Thus, the wettability of the sizing agents was studied, as well as the free surface energy using the Owens-Wendt method. The calculated energy values were used to determine the work of adhesion between the sizing agents and PEEK. The adhesive connection between the CF treated with the sizing agents and PEEK was examined by the single fiber pull-out testing. Furthermore, the most promising samples were used for CF, on the basis of which towpreg composites samples were obtained to study its physico-mechanical properties. Results suggested that the values of the strength characteristics of the composites are comparable to the values measured for composites based on commercially available materials.

Progress in the Preparation Process and Application of Carbon Fiber Reinforced PEEK Composites

Due to their outstanding overall performances, carbon fiber/poly(ether-ether-ketone) (CF/PEEK) composites have attracted a lot of interest recently. High-performance CF/PEEK composites have many advantages such as high strength, good toughness, and high service temperature, which have been widely used in various high-precision fields. This paper reviews the research progress of the CF/PEEK composite molding process and its applications in view of the research hotspots in recent years, laying the foundation for the research on the preparation technology and industrial application of the material. CF/PEEK molding process mainly includes injection molding, press molding, filament winding, 3D Printing, and automated fiber placement (AFP). Different processing methods and material ratios result in CF/PEEK materials with different mechanical properties. Since CF/PEEK has its own unique advantages over traditional metal materials in terms of mechanical properties, corrosion resistance, and density, CF/PEEK materials can be used to replace metal materials in many applications, such as aviation and aerospace, biomedical field and automotive part.

Enhanced adhesion between PEEK and stainless-steel mesh in resistance welding of CF/PEEK composites by various surface treatments

In order to improve the interfacial adhesion of stainless-steel mesh reinforced poly(ether-ether-ketone) (SSM/PEEK) heating elements (HEs) used in the resistance welding process for continuous carbon fiber reinforced PEEK composites (CF/PEEK composites), three kinds of surface treatments, sandblasting, aryl diazonium grafting and silane grafting, were adopted on SSM surfaces. The functional groups were grafted successfully according to the Fourier Transform Infrared (FTIR) results and Energy Dispersive Spectrometer (EDS) results, and the surface morphologies of SSM changed significantly after different treatments. Although the tensile performances of sandblasted stainless-steel (SS) wire and sandblasted SSM were distinctly reduced, the lap shear strength (LSS) of joints with sandblasted SSM still slightly improved. Besides, the interfacial shear strength (IFSS) increased from 28 MPa for untreated SSM to 34 MPa for diazonium grafted SSM and 38 MPa for silane grafted SSM. Furthermore, the LSS results were in agreement with this trend, representing a 9% improvement for joints with diazonium grafted SSM and a 23% improvement for joints with silane grafted SSM compared with untreated CF/PEEK joints. After comparison, silane grafting was the most suitable surface modification for resistance-welded CF/PEEK joints. The interfacial bonding mechanism of CF/PEEK joints with silane grafted SSM was compared with that of untreated CF/PEEK joints, suggesting that the mechanical interlocking contributed to improved interfacial bonding.

Carbon fiber-reinforced PEEK in implant dentistry: A scoping review on the finite element method

Objective : The aim of the present study was to perform an integrative systematic review on the stress distribution assessed by finite element analysis on dental implants or abutments composed of carbon fiber-reinforced PEEK composites. Method: An electronic search was performed on PUBMED and ScienceDirect using a combination of the following search terms: PEEK, Polyetheretherketone, FEA, FEM, Finite element, Stress, Dental implant and Dental abutment. Results: The findings reported mechanical properties and the stress distribution through implant and abutment composed of PEEK and its fiber-reinforced composites. Unfilled PEEK revealed low values of elastic modulus and strength that negatively affected the stress distribution through the abutment and implant towards to the bone tisues. The incorporation of 30% carbon fibers increased the elastic modulus and strength of the PEEK-matrix composites although some studies reported no statistic differences in stress magnitude when compared to unfilled PEEK. However, an increase in short carbon fibers up to 60% revealed an enhancement on the stress distribution through abutment and implants towards to the bone tissues. PEEK veneering onto titanium core structures can also be a strategy to control the stress distribution at the implant-to-bone interface. Conclusions: The stiffness and strength of PEEK-matrix composites can be increased by the improvement of the carbon fibers’ network. Thus, the content, shape, dimensions, and chemical composition of fibers are key factors to improve the stress distribution through abutment and implants composed of PEEK-matrix composites.

Influence of repass treatment on carbon fibre-reinforced PEEK composites manufactured using laser-assisted automatic tape placement

Laser-assisted automated tape placement (LATP) in-situ consolidation of thermoplastic composites offers an efficient solution for production of large, high performance composite structures. The present work investigates laser repass treatment as a method of enhancing surface roughness and mechanical properties of LATP processed CF/PEEK laminates. Three laminate stacking sequences were studied, viz. [0°]16, [−45°/0°/45°/90°]2s and [±45°]4s. Four repass treatments were performed, including single, double, perpendicular and tool-side repasses. The effect of these repasses on interlaminar shear strength (ILSS), open-hole compression (OHC), in-plane shear (IPS), density, fibre volume fraction, void content and surface roughness was investigated. Surface roughness tests confirmed the improvement of the surface finish due to repass treatment. However, insignificant differences in ILSS values were observed across all repass treatments, but a single laser repass did appear to improve the OHC and IPS performance. Autoclave treated samples were used as a benchmark to compare with LATP processed laminate properties.

Strong Interface Construction of Carbon Fiber-reinforced PEEK Composites: An Efficient Method for Modifying Carbon Fiber with Crystalline PEEK.

In order to improve the poor solvent resistance and poor temperature resistance caused by traditional sizing agents, crystalline poly(ether ether ketone) (PEEK) is introduced to the interfacial phases of carbon fiber (CF) reinforced PEEK composites by a soluble precursor named PEEK-1,3-dioxolane. By changing the soluble precursor molecular weight and concentration in the sizing solution, the content of PEEK coated on the CF fiber surface can be controlled and the different interfacial properties of the PEEK composites can be obtained. The results shows that, with this method, crystalline PEEK can be completely coated on the CF surface, and the interfacial shear strength of the PEEK composites increases from 43.42 to 83.13 MPa. Due to none of any soluble compounds in the PEEK composites, the interfacial layer is well preserved under organic solvents and hygrothermal conditions, and the interfacial shear strength (IFSS) of the PEEK composites maintained above 85.4% and 90.44%, respectively. Scanning electron microscope clarifies that the mechanism of interface enhancement comes from a better wetting of crystalline PEEK on the fiber surface. Additionally, the sizing system of this investagation has the potential commercial value because of no toxic reagent (such as 2,4,5-trichloro-1-hydroxy-benzene or concentrated sulfuric acid) is required during sizing.

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.

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.

Pitch-Based Carbon Fibre-Reinforced PEEK Composites: Optimization of Interphase Properties by Water-Based Treatments and Self-Assembly

This work addresses the challenging fibre-matrix compatibilization and interface adhesion improvement of poly(etheretherketone) (PEEK) composites reinforced with pitch-based carbon fibre. An innovative and environmentally friendly method, inspired both by supramolecular “layer-by-layer” (LBL) assembly and by the composition of adhesive proteins in mussels was designed to modify the carbon fibre surface and improve the composites transverse properties by supramolecular interactions. The results proved that few sensitive carbon surfaces can be selectively modified by stable polyelectrolyte complexes and catechol amine polymer partners dispersed in water in such a way that a sizing treatment can be applied by techniques as simple as immersion or spraying procedure. It was shown that the combination of these solutions self-organized to form thin deposits containing compatibilization and/or crystallization promoter partners, thought transcrystallinity, onto carbon surface. This approach is an innovative and environmentally-friendly method which improves fibre-matrix interface quality in terms of compatibilization, adhesion and mechanical properties.

Air DBD plasma treatment on three-dimensional braided carbon fiber-reinforced PEEK composites for enhancement of in vitro bioactivity

Surface treatment for bio-inert PEEK and its composites is required to broaden their applications in biomedical fields. In this work, a dielectric barrier discharge (DBD) plasma treatment in ambient air was performed on the surface of a three-dimensional braided carbon fiber-reinforced PEEK (C3D/PEEK) composite. The changes in surface chemistry and topography after DBD treatment were examined using water contact angle measurement, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Apatite formation on the DBD-treated C3D/PEEK composite was assessed using SEM after immersion in a simulated body fluid (SBF) to determine its in vitro bioactivity. It was shown that DBD plasma treatment led to a significant decrease in water contact angle, an increase in roughness and the creation of new oxygen related functional groups on C3D/PEEK composite. These changes were found to result in a significant improvement in its in vitro bioactivity. The results presented here clearly indicate that DBD plasma treatment in air is capable of modifying the surface of C3D/PEEK composite such that the treated surface changes from bio-inert to bioactive.

Preparation of three-dimensional braided carbon fiber-reinforced PEEK composites for potential load-bearing bone fixations. Part I. Mechanical properties and cytocompatibility

In this study, we focused on fabrication and characterization of three-dimensional carbon fiber-reinforced polyetheretherketone (C3-D/PEEK) composites for orthopedic applications. We found that pre-heating of 3-D fabrics before hot-pressing could eliminate pores in the composites prepared by 3-D co-braiding and hot-pressing techniques. The manufacturing process and the processing variables were studied and optimum parameters were obtained. Moreover, the carbon fibers were surface treated by the anodic oxidization and its effect on mechanical properties of the composites was determined. Preliminary cell studies with mouse osteoblast cells were also performed to examine the cytocompatibility of the composites. Feasibility of the C3-D/PEEK composites as load-bearing bone fixation materials was evaluated. Results suggest that the C3-D/PEEK composites show good promising as load-bearing bone fixations.

Friction and wear of PEEK composites in vacuum environment

The sliding performance of PEEK composites was investigated in vacuum environment. Tests were performed with carbon fibre reinforced PEEK composites filled with PTFE, and MoS 2 or graphite as further solid lubricant. Polymer samples were tested in a pin-on-disc configuration continuously sliding against CrNi-steel. Depending on sliding speed and temperature, the MoS 2 filled composites showed high wear resistance and friction coefficients as low as PVD coatings.

Interfacial studies on the ozone and air‐oxidation‐modified carbon fiber reinforced PEEK composites

AbstractIn this work, ozone modification method and air‐oxidationwere used for the surface treatment of polyacrylonitrile(PAN)‐based carbon fiber. The surface characteristics of carbon fibers were characterized by XPS. The interfacial properties of carbon fiber‐reinforced (polyetheretherketone) PEEK (CF/PEEK) composites were investigated by means of the single fiber pull‐out tests. As a result, it was found that IFSS (interfacial shear strength) values of the composites with ozone‐treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PEEKcomposites was comparativelyinvestigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PEEK matrix. Thus the wear resistance was significantly improved. Copyright © 2009 John Wiley & Sons, Ltd.

Influence of processing conditions on bending property of continuous carbon fiber reinforced PEEK composites

The purpose of this study is to achieve an optimum fabrication condition for the continuous carbon fiber reinforced PEEK matrix composites based on a micro-braiding fabrication method. The composite plates were fabricated at three processing temperatures (380, 410 and 440 °C) and three holding times (20, 40 and 60 min), respectively, with a total number of nine different fabrication conditions, and their bending properties were investigated in terms of thermal and fracture characterizations. As a result, the bending performance of the fabricated composites was significantly affected at the 440 °C temperature. Although no significant change in the bending performance was seen at the 380 and 410 °C with all the holding times, the thermal and fracture characterizations implied a degradation of the PEEK matrix property during the fabrication process. In order to avoid the matrix degradation and the decrease of mechanical properties, a lower fabrication temperature with a shorter holding time should be recommended for the carbon/PEEK composites fabricated by the micro-braiding method.

Study on tribological behaviour of plasma-treated PEEK and its composites

In this paper, neat PEEK, PEEK-8%PTFE and PEEK-10%PTFE-10%graphite-10% carbon fibre have been treated by plasma to improve their tribological behaviour. The treatment gas was argon, and five different treatment parameters were selected. The range of plasma treatment time was 1.0–5.0 min, the range of voltage was 0.8–1.3 kV. Tribological experiments of sliding PEEK and its composites against a steel ring showed that the sliding friction coefficient μ, and the specific wear rate w̄ s decreased significantly, especially for the PEEK/steel rubbing pair. The mean friction coefficient μ dropped from 0.42 to 0.23 and the mean specific wear rate w̄ 5 dropped from ≈ 10 −5 to ≈ 10 −6 (mm 3N −1m −1), i.e. a one order of magnitude decrease. It is also shown that μ, and w 5 for different plasma treatments have different values. In general, a certain type of plasma treatment has been found to have the best results for all three specimens. The highest selected voltage of the equipment was 1.3 kV and the shortest treatment time was 1.0 min for this treatment. With scanning electron microscopy of polymeric wear debris it has been found that the wear mechanisms were different for treated and untreated specimens. Fourier transform reflection IR spectroscopic analysis of worn pin surfaces showed that the thermal degradations for treated and untreated specimens were also different. Differential scanning calorimetry analysis of worn pin top sections also showed that the crystallinity for treated specimen was smaller than that for untreated specimen. It is concluded that the improvement of tribological behaviour of PEEK and its composites after plasma surface treatment is due to cross-linking of PEEK and improvement of the interface strength of carbon fibre reinforced PEEK composites. The plasma treatment for polymers and their composites has potential application prospects.

Failure mechanisms in continuous carbon-fibre reinforced PEEK composites

The fracture behaviour of unidirectional carbon-fibre/poly(ether ether ketone) (PEEK) composites has been studied over the temperature range −60 to +100°C. Double cantilever beam tests were carried out for crack propagation parallel to the fibre direction, with the fracture plane either parallel (specimen DCB1) or perpendicular (specimen DCB2) to the plane of the pre-preg tapes. Stable crack propagation in the composite requires stable drawing of the PEEK matrix, and both depend similarly on strain rate and temperature. The fracture toughness can be related quantitatively to the failure mechanisms inferred from the fracture surface. The primary contribution is from matrix deformation and this is related to the energy of rupture of the unreinforced polymer, taking into account the volume of plastically deformed polymer seen on the fracture surface. Secondary contributions are from fibre bridging and the formation of large fibre bundles, which also increase the amount of matrix deformation. These are caused by misalignment of fibres with respect to the primary crack and are most important for the DCB2 geometry.