Carbon Fiber/polyether Ether Ketone Research Articles

A novel model for predicting deformation of thermoplastic composites during heat-pressing process

Carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composites are widely used in the aerospace industry due to their excellent mechanical properties and high-temperature resistance. However, the research on heat-pressing deformation and residual stress during high-temperature and high-pressure heat-pressing processes in CF/PEEK was relatively deficient. In this paper, a framework coupled with crystallization kinetics, micromechanics and thermodynamics was developed to predict the heat-pressing deformations of CF/PEEK and it was conducted by UMAT, DISP and UEXPAN subroutines. Moreover, the predictive model was verified by experiments effectively. Finally, we compared the difference in residual stress distributions between symmetric and asymmetric lay-ups and found that the melting temperature, thickness, angle and sequence of layers have a significant impact on the heat-pressing deformation. This work provided an effective tool for predicting heat-pressing deformations, which is great of significance in the manufacturing and application of CF/PEEK.

Enhanced comprehension of the cross-scale forming mechanism in CF/PEEK resistance welding: Analysis of temperature gradients and meso–microscopic phase transitions

Resistance welding technology is an effective solution for connecting thermoplastic composites. However, limited research on non-uniform distribution of interfacial temperature and complex evolution mechanism of phase-change molding hinders its application. This reliance on traditional experimental and trial-and-error methods severely impedes its development. Therefore, this study employed a novel cross-scale numerical simulation method, being applied for the first time in the field of resistance welding for elucidating the underlying mechanism of joint formation through multi-component phase transformation. The constructed model accurately represented the transient heat transfer of a realistic wire mesh structure in three dimensions, while incorporating complex gradient effects arising from both spatial and temporal variations in heating element temperature due to air interference. Further, melting, flow, and consolidation behavior of the resin matrix in resistance welding of carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composite was investigated herein at a mesoscopic scale. To accomplish this objective, a three-phase flow spatial forming and evolution model for resistance welding was developed at the mesoscopic scale by integrating principles from fluid dynamics. Interestingly, introduction of an air phase reinstated the spatial voids formation and flow in resistance welding, providing robust evidence for the initiation mechanism of internal defects. Moreover, this study revealed variations in the melting mode of PEEK resin across different regions within the weld and highlighted distinct distributions of voids resulting from uneven heat transfer. The interfacial phenomenon and flow diffusion mechanism between components in resistance welding tests were further verified and discussed through analyzing scanning electron microscopy and energy dispersive spectroscopy results. Temporal and spatial correlation in void distribution within the welding zone was observed, which was found to be consistent with simulation results. Specifically, with the progress of the welding process, air near the wire mesh gradually dispersed into the laminate, with significantly more voids at weld seam edges than in central regions. This research methodology based on stepwise scale reduction offers a promising avenue for investigating resistance welding and other connection forming applications, in particular, within the context of engineering underlying logical behavior.

In-situ consolidation of thermoplastic composites by automated fiber placement: Characterization of defects

The emergence of automated manufacturing of composites has not only transformed the manufacturing of optimized and geometrically complex structures but has also expanded the promising prospect of in-situ manufacturing of thermoplastic composites (TPC), where both material placement and consolidation are carried out by automated fiber placement (AFP) equipment, streamlining the process into single step manufacturing. However, the inherent complexities in different aspects of robotic automation, imperfections in the supplied material, and the occurrence of multi-physical phenomena during in-situ consolidation introduce various manufacturing-induced defects. While the defects in thermoset composites (TSC) made by AFP have been widely studied in the past, this study explores the diverse defects at micro and macro scales for TPCs made by AFP, with a focus on carbon-fiber/poly-ether-ether-ketone (CF/PEEK) tapes consolidated using hot gas torch (HGT) heating system. An overview of defects and associated characteristics is presented across three phases: defects in supplied impregnated tapes, defects and limitations in performance of AFP system, and defects in the final in-situ consolidated composite. For the defects subject to studies in the past, the description is limited to a concise review, while those with limited understanding are supported by new empirical observations in this work.

The use of carbon fiber/polyetheretherketone (CF/PEEK) in pedicle screw fixation for spinal neoplasms-potential advantages in postoperative imaging and radiotherapy planning.

Titanium pedicle screw fixation complicates postoperative care in patients with spinal neoplasms due to postoperative imaging artefacts and dose perturbation. This study aims to measure the benefits of using carbon fiber/polyetheretherketone (CF/PEEK) pedicle fixation compared to titanium in postoperative imaging, radiotherapy planning and delivery for spinal neoplasms treated with conventional external beam radiotherapy with a commercial treatment planning system. The properties of CF/PEEK pedicle fixation systems were compared to titanium in radiotherapy dose planning accuracy and postoperative computed tomography (CT) image quality. Dose profiles through the screw, tulip and longitudinal axis of the screw were acquired with radiochromic films and compared to a collapsed cone algorithm simulation, to measure dose agreement. The image quality of postoperative CTs were compared by defining four regions of interest around the vertebrae and screws in water phantom models and previous planning CTs, and comparing calculated artefact indexes (AIs). CF/PEEK screws have non-inferior dosimetric prediction accuracy up to 50 mm beneath the screw for collapsed-cone algorithm planning systems. There is a statistically significant reduction in the absolute difference between calculated and measured dose at a depth of 2 mm beneath the screw. There is minimal attenuation with CF/PEEK relative to the surrounding dose, extending to 50 mm beneath the screw. There is a statistically significant improvement in CT imaging quality with reduced AIs in CF/PEEK fixation compared to titanium in both model and patient CT plans. CF/PEEK pedicle fixation can provide benefits in postoperative imaging and photon radiotherapy planning and delivery to patients with spinal neoplasms.

Biomechanical Analysis of Mandibular Premolar Restored with Different Custom Post Core

Abstract Objective This study investigated biomechanical behavior of custom post core made of six different materials on the tooth with and without the ferrule under different occlusal load. Materials and Methods Three-dimensional models of mandibular first premolar, with and without ferrule, reconstructed from micro-computed tomography image are restored with different custom post core and zirconia crowns. By using the finite element analysis, von Mises stress shown in MPa was measured under simulated axial and oblique load of 200 [N]. To compare the stress distribution, six different custom post core materials were chosen: zirconia, Ni-Cr alloy, gold alloy, glass fiber-polyether ether ketone, polyether ether ketone, and carbon fiber-polyether ether ketone. Results Custom post cores with a higher modulus of elasticity showed higher measured stress in the posts, but less stress in dentin. Measured stress in custom post core under oblique loading was approximately three times higher compared with axial loading. Stress in custom post core and in dentin under both types of loads was slightly higher in teeth without ferrule effect. Conclusion The use of custom cast post cores made of different alloys is recommended in restoration of endodontically treated teeth, with extensive loss of tooth structure especially in teeth without ferrule effect.

Synergistic enhancement of interfacial adhesion for CF/PEEK composites through carbene chemistry and water‐based self‐catalyzed cross‐linkable PENK‐NH2 sizing agent

AbstractTo address the issue of inadequate interfacial adhesion in carbon fiber/poly ether ether ketone (CF/PEEK) composites, an innovative approach that combines carbene chemistry and sizing treatment was meticulously designed to achieve remarkable synergistic enhancement. Specifically, cyano groups were chemical‐grafted on CF surface via carbene reaction. Meanwhile, a water‐based self‐catalyzed cross‐linkable PENK‐NH2 sizing agent with good storage stability was prepared. Noteworthy, the presence of amino groups as blocking agents of sizing agent significantly accelerated the rate of cyano‐crosslinking, thus effectively avoiding the adverse effects of excessively prolonged cross‐linking period during composites preparation. As a result, robust interaction between cyano‐modified CF and PEEK was established by cross‐linking reaction, along with chemical bonds generated between amino groups of sizing agent and ketone groups in PEEK. The maximum interlaminar shear strength (ILSS) of CF‐CN‐1.5/PEEK composites was 22.0% and 57.0% higher than CF‐1.5/PEEK and CF/PEEK composites. Furthermore, the presence of cyano‐cross‐linked structure endowed interphase with outstanding solvent‐resistance, the mechanical properties of CF composites after solvent treatment were well‐preserved. The strong synergistic interfacial interactions facilitated by chemical bonds in different components provide an effective and fascinating methodology for producing high‐performance CF/composites.Highlights Water‐based self‐catalyzed cross‐linkable PENK‐NH2 sizing agents for CF/PEEK were prepared. NH2 was introduced to avoid the adverse effects of prolonged cyano‐crosslinking. Designed carbenoid motif with cyano group was grafted on CF via carbene chemistry. The interaction between sizing agent and CF was boosted by the cyano‐crosslinking. Mechanical properties of sized composites corroded by solvent were well‐preserved.

Rotating gliding arc plasma: Innovative treatment for adhesion improvement between stainless steel heating elements and thermoplastics in resistance welding of composites

Rotating gliding arc plasma treatment was conducted on a stainless-steel heating element (HE) for the resistance welding of carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composites. The lap shear strength of 51.7 MPa, corresponding to an improvement of 14.63 % compared to that of joints welded using untreated HE, was successfully achieved after the plasma treatment. The results of the surface characterization tests revealed that owing to the cleaning and oxidation effects, the wettability as well as the surface bonding of the HEs were remarkably improved after plasma treatment. Moreover, the reduction of void defects within the welded joints was disclosed via nondestructive inspection of cross-sections, indicating that the enhancement of HE wettability resulted in the improved resin impregnation and void elimination. Besides, according to the fractographic analysis, the main failure mode changed from the HE/PEEK interfacial damage to a CF/matrix interfacial failure, indicating that the HE/matrix interfacial adhesion was highly strengthened after plasma treatment.

Bidirectional-Reinforced Carbon Fiber/Polyether-Ether-Ketone Composite Thin-Walled Pipes via Pultrusion-Winding for On-Orbit Additive Manufacturing.

Benefitting from lightweight, high strength, long life, and green recyclability, continuous fiber reinforced thermoplastic composite (CFTPC) pipes have attracted extensive interest, especially in the on-orbit additive manufacturing of structural components. However, the preparation of CFTPC pipes remains challenging due to the on-orbit limited space and high processing temperature of thermoplastic resin. Here, we report an effective approach for high performance carbon fiber/polyether-ether-ketone (CF/PEEK) thin-walled pipes via bidirectional reinforcement using the pultrusion-winding technique. The continuous fabrication of thin-walled pipes can be achieved, but the limitation by the size of core mold is also broken. The compressive and shear performance of CF/PEEK pipes with different layer designs have been studied based on experiments and simulations. With the increase in axial prepreg tape layer, the resultant CF/PEEK pipes exhibit greatly improved axial compression strength. The finite element analysis indicates that the maximum axial stress is decreased due to the axial enhancement. The flexural strength is greatly proved with pultrusion-winding cycles. The simulation confirms that the circumferential strain is effectively reduced. The high performance of bidirectional reinforced CF/PEEK pipes and the facile controllability of this approach highlight their suitability for utilization in on-orbit manufacturing of large-scale structures.

Carbon fiber–polyetheretherketone-reinforced PVA composites for bone graft applications

Poly(vinyl alcohol) (PVA) is a synthetic, bioinert, semicrystalline, biodegradable, non-toxic and thermoplastic polymer extensively used in the field of biomedical engineering. The weak mechanical properties of PVA, such as low strength and Young’s modulus, limit its application as a bone implant. However, PVA can be reinforced with a suitable material to improve its mechanical properties. Carbon fiber (CF)–polyetheretherketone (PEEK) is a superior thermoplastic synthetic biomaterial with good tensile strength, stiffness, wear properties and X-ray translucence. In this study, CF–PEEK-reinforced PVA composites were prepared by varying the CF–PEEK concentration (0, 0.25, 0.50, 0.75, 1.00, 2.00 and 3.00% w/v) in the PVA matrix (10% w/v) using the solvent-casting method. The physical, chemical, biological and mechanical properties of the prepared PVA–CF–PEEK composites were studied. The environmental scanning electron microscopy micrographs showed agglomeration of CF–PEEK at higher concentrations – that is, 1, 2 and 3% w/v. With the inclusion of CF–PEEK in PVA, the contact angle of the composites was found to increase. The increased hydrophobicity of the samples resulted in reduced swelling and degradation rate. In the hemolysis study, the percentage hemolysis values were found to be <5%, revealing the hemocompatible nature of the developed composites. An increase in in vitro protein adsorption was observed, and cell viability studies showcased the biocompatible nature of the prepared composite samples. Thus, the developed CF–PEEK–PVA polymer composites present great potential for bone graft applications.

Investigation on creep mechanism of CF/PEEK composite material using molecular dynamics

Carbon fiber/Poly ether ether ketone (CF/PEEK) subjects to external loads during service life, high bonding quality of the interface is the key to structural integrity. In order to control the creep slippage of CF/PEEK, explaining the interfacial creep mechanism details are essential. This paper constructs an intercalation model for the CF/PEEK molecular interface and uses molecular dynamics (MD) simulation to demonstrate the evolution mechanism of the interface under different load levels. To verify the effectiveness of the model, the structural morphology, glass-transition temperature, and density of the molecular model were compared with experimental measurements. In terms of interface shear creep, stage Ш creep transitioned from constant to accelerated, the creep curves and corresponding interface microstructure under different stress states were simulated by MD. At the same time, the sliding and debonding processes were explained from an energy perspective. Furthermore, a creep constitutive model was proposed to fit the molecular scale. This study comprehensively interprets the shear creep behavior of the CF/PEEK interface from simulation to constitution.

A PEEK into carbon fiber: A practical guide for high performance composite polymeric implants for orthopaedic oncology

IntroductionThe use of carbon fiber implants in orthopaedic oncology has increased within recent years. The most widely used type of polymer is carbon fiber polyether ether ketone (CF-PEEK). Its radiolucency enables targeted radiotherapy and artifact-free tumor surveillance, which provides major advantages over metallic hardware. We aim to summarize the unique benefits within orthopaedic oncology, clinical pitfalls, and recent advancements. MethodsFour representative patient cases from a single tertiary academic medical center were treated with carbon fiber implants (n = 2 nails, n = 2 plates) from 2021 to 2022. ResultsThere were no adverse events noted during intraoperative implantation or postoperative follow up. All patients reported improvements in pain and no difficulties in ambulation. There were no instances of catastrophic failure or implant loosening. ConclusionCF implants offer a diverse array of advantages regarding its radiolucency, low scatter density, and bioinert profile. Nonetheless, further research is required to understand the long-term surgical outcomes and robustness of CF implants. Multi institutional trials could address important aspects of durability and stability over extended periods, feasibility and ease-of-use for different anatomical sites and bone quality, as well as cost-effectiveness in post-operative imaging, healthcare resource utilization, and revision rates. Providing orthopaedic surgeons with valuable insight will enable thorough clinically supported, informed decision making regarding optimal use of implants.

Thermoplastic composite connecting rods

Engineering carbon fiber thermoplastics have been used in the development and optimization of composite connecting rod(s) with design requirement of bearing 14,000 N and 1 mm maximum deflection. The studies featured engineering thermoplastics- 30 wt percent carbon fiber poly ether ether ketone (C-PEEK) long fiber thermoplastics (LFT) injection over molded in conjunction with 70 wt percent carbon/polyphenylene sulfide (C-PPS) and carbon/poly ether imide (C-PEI) tapes. Over molding of thermoplastic tapes has been investigated in terms of number of tape winding around the small and big end, and different winding patterns within the connecting rod geometry. The design was progressively optimized for the geometry of the connecting rod, i.e., increasing the wall thickness of the small end and width of the center section. The effect of over molded metal bushing with C/PEEK LFT at the bearing surfaces was also investigated. The material and geometry optimization successfully met 14,000 N while several design iterations were necessary to meet the 1 mm deflection limit constraint. Finite element analysis (FEA) was adopted to optimize the increase of the width of the center section width and wall thickness of the small end. The optimized composite connecting rod was estimated to be 78% lighter than the steel incumbent.

Improvement of Interfacial Properties and Bioactivity of CF/PEEK Composites by Rapid Biomineralization of Hydroxyapatite.

The carbon fiber/hydroxyapatite (CF/HA) reinforcement with a three-dimensional flower-like structure was rapidly fabricated with the biomimetic mineralization method to strengthen the interfacial performance and bioactivity of carbon fiber/polyether ether ketone (CF/PEEK) composites. Silk fibroin (SF), which can construct a robust interphase between CF and PEEK, supported an organic template to regulate the growth of inorganic HA. The interfacial properties were markedly enhanced through mechanical interlocking and interface adhesion induced by increasing roughness and surface energy of CF. Besides, the mineralization time was significantly reduced after the addition of cetyltrimethylammonium bromide to the simulated body fluid, and the prepared CF/HA possessed good bioactivity. In this study, the interlaminar shear strength (ILSS) and flexural strength of CF-HA/45/PEEK composites demonstrated an enhancement of 45.9% and 51.2%, respectively, compared to the untreated CF/PEEK composites. It is predicted that this strategy could provide a rapid and convenient route to ameliorate the interfacial performance and bioactivity of CF/PEEK composites simultaneously.

Enhancing fiber-matrix interface in carbon fiber/poly ether ether ketone (CF/PEEK) composites by carbon nanotube reinforcement of crystalline PEEK sizing

Crystalline poly ether ether ketone (PEEK) is an emergent effective sizing agent for carbon fiber (CF) for use in CF/PEEK composites. Soluble PEEK with the ability to recover crystallinity via simple acidification was synthesized and grafted on carbon nanotube for the first time to enhance the effectiveness and thermomechanical integrity of the based sizing, to achieve a higher level of chemical resistance and interfacial enhancement. CNT-filled, acidified-CNT-filled, and PEEK-grafted-CNT-filled sizing compounds were synthesized and coated on to CF. Proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared (FTIR) spectroscopy were used to analyze the products of chemical synthesis, whereas X-ray photoelectron spectroscopy (XPS) was used to assess the grafting reaction. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to assess the morphology of the unsized and sized CF, and a microbond test was used to evaluate the interfacial shear strength (IFSS) of the sizing. As a result, the CF/PEEK composites achieved the highest ever reported IFSS, with values of 101.4 MPa and 103.4 MPa in the acidified-CNT and PEEK-grafted-CNT samples, respectively. It is noted that the PEEK-grafted-CNT sample also exhibited greater solvent resistance due to closer interfacial distance, and an IFSS retention rate of 80%–90% in various polar and non-polar solvents. The successful application of nano-reinforcement in a CF interfacial sizing and the development of the PEEK grafting on CNT possesses an expanded application potential for CF/PEEK composites.

Preparation of MWCNTs/CF/PEEK multi-scale composites with good mechanical and electrical conductivity by a two-step process of AFP and out-of-autoclave tempering

Developing simple and highly automated strategies for manufacturing green, high-performance thermoplastic composite components remains a major challenge. In this paper, multi-walled carbon nanotube (MWCNT) nanofillers are successfully dispersed on the carbon fiber/polyetheretherketone (CF/PEEK) prepreg surface via a simple solution volatilization method. Furthermore, MWCNTs/CF/PEEK multi-scale composites are prepared by the highly automated automatic fiber placement (AFP) in-situ consolidation technology. The in-situ consolidated samples are tempered by an out-of-autoclave (OOA) technique to improve the bonding strength of the MWCNTs with the PEEK substrate. Enhanced adhesion is achieved between the CF and the PEEK substrate by introducing nanofiller modification methods at the interlayer fine-scale. Moreover, the interlocking effect of the nanofiller with the PEEK substrate increases the interlayer strength of the multi-scale composites. Compared to the CF/PEEK composite, the MWCNTs/CF/PEEK multi-scale composite achieved a maximum interlaminar shear strength (ILSS) of 91.49 MPa, i.e., an increase of 25.21%. In addition, due to the excellent electrical conductivity of the nanofillers, the nanofillers form electron channels between the fibers. This increases the conductivity of multi-scale composites by 766% and 323% in the 0° and 90° directions, respectively. This work provides a simple and highly automated method for preparing complex thermoplastic composite components with good mechanical properties and excellent electrical conductivity. Such composites may be employed in aerospace lighting protection.

Thermoplastic Extrusion Additive Manufacturing of High-Performance Carbon Fiber PEEK Lattices

Polyetheretherketone (PEEK) has been the focus of substantial additive manufacturing research for two principal reasons: (a) the mechanical performance approaches that of aluminum at relatively high temperatures for thermoplastics and (b) the potential for qualification in both the aerospace and biomedical industries. Although PEEK provides outstanding strength and thermal stability, printing can be difficult due to the high melting point. Recently, high-temperature soluble support has enabled the printing of lattices and stochastic foams with overhanging features in these high-performance carbon fiber thermoplastics, in which density can be optimized to strike a balance between weight and strength to enhance performance in applications such as custom implants or aerospace structures. Although polymer powder bed fusion has long been capable of the combination of these geometries and materials, material extrusion with high-temperature sacrificial support is dramatically less expensive. This research provides a comprehensive mechanical analysis and CT-scan-based dimensional study of carbon fiber PEEK lattice structures enabled with high-temperature support and including model validation.

Preparing water-based phosphorylated PEEK sizing agent for CF/PEEK interface enhancement

The weak interfacial bonding between fiber and matrix needs to be improved for obtaining good mechanical properties of carbon fiber/polyetheretherketone (CF/PEEK) composites due to the inert nature of both components. Organic sizing is a typical interface improvement method, but it is harmful to both the human and local environment. Here, a two-step process is proposed to modify PEEK for preparing an environmentally friendly water-based sizing agent, involving taking the ketone reduction via NaBH4 and then an esterification reaction with phosphoric acid. This PEEK derivative has good thermal stability, and its dispersion in water is stable for one month. It improves the interface between CF and PEEK by increasing the wettability and surface roughness of CFs, ultimately enhancing the mechanical properties of composites. The two-step process of fabricating the PEEK derivative may have potentials in the industrial application of the polyaryletherketone family.

Optimization of molding process parameters for CF/PEEK composites based on Taguchi method

In this article, nine groups of laminates were prepared according to the Taguchi L9(33) test array to study the influence of three process parameters, including molding pressure, molding temperature, and holding time on the performance of unidirectional carbon fiber/polyetheretherketone (CF/PEEK) laminates. A differential scanning calorimetry test was employed to select a reasonable process parameters range. The transverse tensile strength of the laminates was measured, and the fiber–matrix interfacial bonding behavior of the tested samples was analyzed by scanning electron microscopy. The results showed that the significance of factors to transverse tensile strength were molding temperature, holding time, and molding pressure in sequence. The optimal molding process parameters for CF/PEEK composite laminate were molding temperature of 400°C, molding pressure of 3 MPa, and holding time of 30 min. The optimization results were meaningful for the extension and application of thermoplastic composites.

Thermal analysis of cylindrical molds using thermoplastic composite during robotic fiber placement

Thermoplastic composites have gradually become a hotspot due to its low manufacturing cost and good weld ability. In this study, to realize the placement of the thermoplastic composite material carbon fiber/polyether ether ketone (CF/PEEK), the consolidation roller of the existing thermoplastic composite placement head is optimized. The process simulation analysis of the thermoplastic composite material is carried out. A two-dimensional heat transfer model of the thermoplastic prepreg laying process is established in ANSYS. Transient thermal analysis is carried out using the life and death unit technology. The optimum machining parameters are obtained through analyzing the influence of mold temperature, laying speed, and heating temperature on the temperature field of the first layer in curved surface laying.

Effects of Thermal Cycle and Ultraviolet Radiation on 3D Printed Carbon Fiber/Polyether Ether Ketone Ablator

The extreme heating environment during re-entry requires an efficient heat shield to protect a spacecraft. The current method of manufacturing a heat shield is labor intensive. The application of 3D printing can reduce cost and manufacturing time and improve the quality of a heat shield. A 3D printed carbon fiber/polyether ether ketone (CF/PEEK) composite was proposed as a heat shield material. The aim was to develop a heat shield and the structural member as a single structure while maintaining the necessary recession resistance. Test samples were exposed to thermal cycles and ultraviolet (UV) radiation environment. Subsequently, a tensile test was performed to evaluate the effect of thermal cycle and UV radiation on the mechanical properties. The sample’s recession performance and temperature behavior were evaluated using an arc heated wind tunnel. Exposure to thermal cycle and UV radiation have limited effect on the mechanical properties, recession behavior and temperature behavior of 3D CF/PEEK. Results from the arc heating test showed an expansion of the sample surface and better recession resistance than other existing ablator materials. Overall, 3D CF/PEEK has excellent recession resistance while maintaining mechanical properties when exposed to high temperature, thermal cycle and UV radiation.