Carbon Fiber-reinforced Polyetheretherketone Research Articles

Thermal-force coupling simulation of carbon fibre-reinforced poly-ether-ether-ketone thermoplastic composites during the laser-assisted automated tape placement process

To reveal the thermal-force coupling characteristics of the laser in-situ consolidation (ISC) of carbon fibre-reinforced poly-ether-ether-ketone (CF/PEEK) composites, a two-dimensional transient thermal-force model of CF/PEEK composites was constructed using COMSOL Multiphysics finite element simulation software to calculate the temperature history and the thermal stress variation of CF/PEEK composites during the laser-assisted automated tape placement (LATP) process. The results show that the temperature field formed on the surface of each layer by the laser spot during LATP is stable, and the temperature gradient at the front of the spot movement direction is higher than that at the back edge. The maximum stresses in the laminate occur on both sides of the first CF/PEEK layer and the stresses are unevenly distributed along the length and thickness directions of the lay-up. The composite material on both sides of the laminate tends to ‘shrink’ compared to its original position.

Experimental investigation on effect of tool geometry on thermal and crystallization characteristics in drilling of carbon fiber reinforced PEEK composite

AbstractThis paper comprehensively investigated the effect of the tool geometries on heat transfer and special crystallization characteristics in the drilling of carbon fiber‐reinforced polyetheretherketone (CF/PEEK) composite for the first time. Three tools with different geometries (twist, brad, and dagger drill) are carried out on CF/PEEK drilling experiments, and temperature, as well as crystallinity and surface roughness, are introduced to make a comparative evaluation on the effect of the tool geometries. The results show that the drilling temperature is determined by the contact length of the profile between the drill and the material. Correspondingly, better surface quality with lower surface roughness and smoother surface is obtained by using a twist drill due to the heat‐induced PEEK smearing effect. Further, in situ XRD and differential scanning calorimeter (DSC) were used to characterize the crystallization characteristics where crystal phase transformation at different temperatures was measured. The occurring temperature of the strongest crystallization characteristics for CF/PEEK is basically not affected by tool geometries, all at 300°C, and the limiting crystallization temperature is 344.5 ± 0.7°C. The crystallinity is found to be affected by drilling temperature and cooling rate and gradually decreases along the heat transfer direction. This work provides a new sight into the improvement of CF/PEEK drilling.Highlights The effect of tool geometries on thermal and crystallization for CF/PEEK is provided. In situ XRD and DSC are used to characterize crystallization characteristics. The drilling temperature and cooling rate are both determinants of crystallinity. The limiting crystallization temperature of the CF/PEEK composite is 344.5 ± 0.7°C. Heat‐induced PEEK smearing effect improves the surface quality of CF/PEEK drilling.

Inflammatory tissue response in human soft tissue is caused by a higher particle load near carbon fiber-reinforced PEEK compared to titanium plates

Titanium as the leading implant material in locked plating is challenged by polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK), which became the focus of interest of researchers and manufacturers in recent years. However, data on human tissue response to these new implant materials are rare.Osteosynthesis plates and peri‑implant soft tissue samples of 16 healed proximal humerus fractures were examined (n = 8 CFR-PEEK, n = 8 titanium). Soft tissue was analyzed by immunohistochemistry and µCT. The entrapped foreign bodies were further examined for their material composition by FTIR. To gain insight into their origin and formation mechanism, explanted and new plates were evaluated by SEM, EDX, profilometry and HR-CT.In the peri‑implant soft tissue of the CFR-PEEK plates, an inflammatory tissue reaction was detected. Tissues contained foreign bodies, which could be identified as tantalum wires, carbon fiber fragments and PEEK particles. Titanium particles were also found in the peri‑implant soft tissue of the titanium plates but showed a less intense surrounding tissue inflammation in immunohistochemistry. The surface of explanted CFR-PEEK plates was rougher and showed exposed and broken carbon fibers as well as protruding and deformed tantalum wires, especially in used screw holes, whereas scratches were identified on the titanium plate surfaces.Particles were present in the peri‑implant soft tissue neighboring both implant materials and could be clearly assigned to the plate material. Particles from both plate materials caused detectable tissue inflammation, with more inflammatory cells found in soft tissue over CFR-PEEK plates than over titanium plates. Statement of significanceOsteosynthesis plates are ubiquitously used in various medical specialties for the reconstruction of bone fractures and defects and are therefore indispensable for trauma surgeons, ENT specialists and many others. The leading implant material are metals such as titanium, but recently implants made of polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK) have become increasingly popular. However, little is known about human tissue reaction and particle generation related to these new implant types. To clarify this question, 16 osteosynthesis plates (n = 8 titanium and n = 8 CFR-PEEK) and the overlying soft tissue were analyzed regarding particle occurrence and tissue inflammation. Tissue inflammation is clinically relevant for the development of scar tissue, which is discussed to cause movement restrictions and thus contributes significantly to patient outcome.

Grinding performance investigation of multidirectional CF/PEEK composites—A comparative with unidirectional CF/PEEK

AbstractTo distinguish the grinding performance of the multidirectional (MD) and unidirectional (UD) carbon fiber‐reinforced thermoplastic (CFRTP) composites, MD and UD carbon fiber‐reinforced poly‐etherether‐ketone (CF/PEEK) composites were employed in this study. Different ply stacking sequences and process parameters were set for grinding experiments. Subsequently, the surface morphologies and roughness were observed and measured. Experimental results indicated that the variations of grinding forces with grinding parameters of MD‐CF/PEEK and UD‐CF/PEEK were consistent. However, the heat transfer mechanism and the effects of grinding parameters on the maximum grinding temperatures were different between the two composites. The grinding forces and temperatures of MD‐CF/PEEK were slightly lower than UD‐CF/PEEK, and MD‐CF/PEEK reached better surface quality under the same parameters, indicating that the grinding performance of MD‐CF/PEEK was not the simple superposition of UD‐CF/PEEK. In addition, the chip formation and material removal mechanism of CF/PEEK were investigated. The grinding performance of MD‐CF/PEEK was primarily dependent on the θ elements of laminate while the grinding performance of UD‐CF/PEEK was closely related to the fiber orientation angles during grinding. This study established a more in‐depth understanding into the grinding performance of MD‐CF/PEEK and provided technical guidance for high‐quality grinding of CFRTP.Highlights The grinding performance of the multidirectional (MD) and unidirectional (UD) carbon fiber‐reinforced poly‐etherether‐ketone (CF/PEEK) is compared. The grinding forces and temperatures of MD‐CF/PEEK are slightly lower than that of UD‐CF/PEEK, and the MD‐CF/PEEK reach a better surface quality under the same grinding parameters. The grinding performance of MD‐CF/PEEK is primarily dependent on the θ elements of laminate, and the change of layering order is not a critical factor. The grinding performance of UD‐CF/PEEK is closely related to the fiber orientation angles during the grinding process. The surface quality of MD‐CFRTP can be effectively improved by reducing the grinding depth and feed speed, and increasing the grinding wheel speed.

Investigation on grinding temperature characteristics of CF/PEEK and material removal mechanism under temperature treatments

Carbon fiber reinforced thermoplastic (CFRTP) composites grinding temperatures could even exceed the glass transition temperature (Tg) of the material due to heat accumulation, combined with the unknown material removal mechanism, resulting in machining defects. To investigate the grinding temperature distribution and maximum temperatures of carbon fiber-reinforced poly-ether-ether-ketone (CF/PEEK) composites, as a typical kind of CFRTP, an analytical temperature model considering the anisotropy was proposed based on the moving heat source theory, verified by the experimental results measured by the infrared camera. Further, the material removal mechanism under temperature treatments (below and above Tg) was also studied. In high temperatures (above Tg), there were many defects on surfaces after grinding, including resin smearing, severe deflection, fiber distortion, and grinding wheel clogging. Therefore, to reduce the grinding temperature below Tg, the vortex tube cooling-assisted grinding method was proposed in the research. The proposed method could reduce the grinding temperature in the grinding area, suppress resin smearing, improve the surface quality, enhance the elastic modulus and nano-hardness of the workpiece, and reduce the clogging of grinding wheels. This study provided a better understanding of the CF/PEEK grinding temperature characteristics and suggested a method to improve the grinding quality.

MIS technique for separation surgery in lumbar spine metastatic disease.

Around 40% of cancer patients present with spinal metastases (SM), the lumbar spine being the second most involved site (15%-30%) after the thoracic (60%-80%). Since the development of separation surgery, minimally invasive surgery (MIS) has increasingly been applied to approach SM, mirroring benefits yielded in the degenerative realm. Moreover, preoperative embolization potentially enhances local control for certain radioresistant histologies. Carbon fiber-reinforced PEEK hardware reduces image artifact, facilitating more accurate follow-up and radiotherapeutic planning. Additionally, short-segment cement-augmented constructs may be beneficial to decrease surgical morbidity and operative risk in this population. The authors present a lumbar spinal metastasis treated with MIS techniques. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23222.

Enhanced mechanical and tribological properties of 3D printed short carbon fiber reinforced polyether ether ketone composites

AbstractMaterial extrusion additive manufacturing provides an effective solution for fabrication of highly customized polyether ether ketone (PEEK) composite parts with any complex shape. Nevertheless, compared with conventional methods, the mechanical strength of 3D printed carbon fiber reinforced PEEK (CF/PEEK) composites is unsatisfactory due to the weak interface bonding strength and high voids content induced by the temperature difference. To overcome this challenge, a temperature‐control 3D printer was used to investigate the effects of ambient temperature and annealing temperature on the microstructure, crystallization behavior and mechanical properties of 3D printed parts. Moreover, the tribological properties of parts printed at different ambient temperature were also studied under various contact pressure. Experimental results showed that the ambient temperature and annealing treatment directly affected the interfacial bonding (fiber/matrix, filament/filament, layer/layer), crystallinity of printed samples, thus affecting their mechanical and tribological properties. The CF/PEEK parts printed at high ambient temperature of 200°C exhibited outstanding mechanical and tribological properties. This study has positive significance for promoting the application of 3D printed PEEK composites in the field of structural load‐bearing and friction materials.Highlights Structure–property relationships for 3D printed CF/PEEK composites. The ambient temperature strongly affects the thermal and microstructural properties Interaction between crystallization and molecular interface diffusion. Interfacial bonding and crystallinity determine the mechanical properties. Tribological properties are highly dependent on applied pressures.

Experimental Study on Tribological Properties of Coated Surface and Textured Surface under Seawater Lubrication Conditions

In order to improve the tribological properties of the flow distribution pair of the seawater axial piston pump, SAF2507 super duplex stainless steel and carbon-fiber-reinforced polyetheretherketone (CF/PEEK) were selected as the matching materials. The surface coating treatment and surface texture treatment were carried out on the flow distribution pair, and the friction and wear test were carried out by MMD-5A. In order to fully understand the friction and wear properties of the surface coating flow distribution pair and the surface texture flow distribution pair, and analyze the friction and wear mechanism, the data of the friction coefficient, wear loss, and wear surface morphology were obtained in the experiment. The results show that the coating surface has little difference in the test, the texture surface significantly reduces the friction coefficient, and the wear scar density is significantly reduced. Adding texture to the surface of the lower sample is better than adding it to the surface of the upper sample. The research results are helpful in improving the tribological performance of the flow distribution pair of the seawater axial piston pump.

Optical properties optimization of carbon fiber reinforced thermoplastic tapes by micro surface texturing for enhanced laser heating efficiency and in-situ consolidation quality during AFP process

The laser-assisted automated fiber placement (L-AFP) process of carbon fiber-reinforced thermoplastic composites suffers from insufficient heating efficiency and in-situ consolidation quality caused by significant reflection on the tape surface. Here, we propose a novel strategy to increase the heating efficiency by refocusing the reflected light, initially scattered to the environment and wasted, onto the tapes for multiple and full absorptions. The method for laser concentration is first validated through light-tracing simulation. Then, three kinds of tapes with different micro textures on the surface are prepared by the hot-embossing process. The transverse V-grooved texture tapes and flat surface tapes absorb 25% more laser energy than the longitudinal V-grooved and commercial tapes due to the reduction in transverse scattering angle from 180° to 2.72°. This leads to a temperature increase of 130 °C at the nip point during the L-AFP process at the lay-down rate of 500 mm/s with 1 kW laser power. Improved in-situ consolidation quality leads to a significant increase in the flexural and shear strength of L-AFP-prepared carbon fiber reinforced polyetheretherketone (CF/PEEK) laminates, with a reduction in porosity to around 2%.

Investigation of an Optimal Material Addition Rate for Energy Consumption and Dimensional Accuracy in Fused Filament Fabrication of CFR-PEEK.

The material addition rate (MAR) of fused filament fabrication (FFF) is an indicator of process efficiency varied by process parameter settings, which affects energy consumption and part quality in FFF. This study aims to identify the optimal MAR of FFF using carbon-fiber-reinforced polyether-ether-ketone (CFR-PEEK) by considering a trade-off between energy consumption and the dimensional accuracy of FFF outputs. A design of experiments considering two main process parameters is planned to print three sample types through FFF for CFR-PEEK. Then, the MAR (i.e., deposited material volume per build time) of FFF is obtained to derive individual regression models of energy consumption and the dimensional accuracy measured for each sample type. Furthermore, a trade-off between energy consumption and dimensional accuracy on the MAR is formulated to derive an optimal MAR for each sample type. The results show that FFF for CFR-PEEK has a trade-off between energy consumption and dimensional accuracy; there exists a specific MAR that maximizes the overall performance of energy consumption and dimensional accuracy for each sample type. The optimal MAR is the highest for the small volume sample, whereas it becomes the lowest for the vertical build orientation sample. This study suggests that the optimal MAR should be flexibly adjusted based on a fabricated part. The findings from this study also address the fact that decision-making for optimal FFF operations needs a transition from the identification of specific process parameter settings to the management of a proper process efficiency level in FFF.

Joint interface optimization of all-CFRTP composite honeycomb prepared by ultrasonic multi-spot welding

An all carbon fiber reinforced polyetheretherketone (CF/PEEK) composite honeycomb is prepared by the multi-spot ultrasonic welding in this work. The interfacial responses and flat compression failure behaviors of the honeycomb are firstly analyzed. It is found that ultrasonic welding has both positive and negative effects on honeycomb performance. High-frequency vibration results in fiber waviness, which is beneficial to elevating both the bending resistance of the joints and the compression strength of the honeycomb. However, melted EDs also lead to resin-rich areas at the interface. Based on the findings, the multiwall carbon nanotubes/PEEK (MWCNTs/PEEK) energy directors are developed, providing new insights on optimizing the properties of the interface. The experimental results indicate that the interfacial node tensile strength is enhanced by 400 % (1267 kPa) with the MWCNTs content increasing to 7.5 wt%, and the optimized CF/PEEK honeycomb shows more superior specific energy absorption and specific compressive strength than those of the commercial light-weight honeycombs. Moreover, the joint failure behaviors are investigated thoroughly. The addition of MWCNTs is found to induce fiber bridging between the cell walls and facilitate stress transfer through the joint interface. The optimized ultrasonic welding method provides a new opportunity for efficient and volume manufacturing of carbon fiber reinforced composite honeycombs without dimension limitation and large mold costs.

Biomechanical Analysis of One-Piece Post and Cores in Different Materials: Can High-Performance Polymers Be an Option?

The aim of this finite element analysis was to evaluate the stress distribution along a premolar's root dentin, its post, and post luting agent when materials with different elastic modulus are used to fabricate one-piece post-and-cores in 2 different design. Two 3D virtual models (for cylindrical and conical post designs) of a mandibular premolar restored with one-piece post-and-core restorations were obtained by using a software. A total of eight post-and-core materials (polyether-ether-ketone (PEEK), polyether-ketone-ketone (PEKK), glass fiber-reinforced polyether-ether-ketone (GFR-PEEK), carbon fiber-reinforced polyether-ether-ketone (CFR-PEEK), gold-palladium alloy (Au-Pd), titanium (Ti), zirconia (Zi) and chromium-nickel (Cr-Ni)) were tested. Maxiumum principals stress (MPS) in the post, post luting agent, and root dentin were determined. A load of 150 N was applied to the buccal cusp in linguo-labial direction at an angle of 45° oblique to the longitudinal axis of the crown. The highest MPS value in post structure was observed with Cr-Ni material for both post designs. Similarly, the highest MPS value in the post luting agent was observed for Cr-Ni, the material with the highest elastic modulus. However, in the root dentin, the highest value was observed in PEEK, the material with the lowest elastic modulus. Post material and design influenced the stress concentration in the post, post luting agent, and root dentin. The stress at root dentin was slightly higher for polymeric materials. Cylindrical post design revealed lower stresses than conical post design at root dentin for all post-and-core materials tested.

Exploring Advanced Functionalities of Carbon Fiber-Graded PEEK Composites as Bone Fixation Plates Using Finite Element Analysis.

This study aims to address the challenges associated with conventional metallic bone fixation plates in biomechanical applications, such as stainless steel and titanium alloys, including stress shielding, allergic reactions, corrosion resistance, and interference with medical imaging. The use of materials with a low elastic modulus is regarded as an effective approach to overcome these problems. In this study, the impact of different types of chopped carbon fiber-reinforced polyether ether ketone (CCF/PEEK) functionally graded material (FGM) bone plates on stress shielding under static and instantaneous dynamic loading was explored using finite element analysis (FEA). The FGM bone plate models were established using ABAQUS and the user's subroutine USDFLD and VUSDFLD, and each model was established with an equivalent overall elastic modulus and distinctive distributions. The results revealed that all FGM bone plates exhibited lower stress shielding effects compared to metal bone plates. Particularly, the FGM plate with an elastic modulus gradually increased from the centre to both sides and provided maximum stress stimulation and the most uniform stress distribution within the fractured area. These findings offer crucial insights for designing implantable medical devices that possess enhanced mechanical adaptability.

A novel thermoplastic water-soluble sizing agent for the interfacial enhancement of carbon fiber/polyether ether ketone composites

Recently reported novel water-soluble polyether ether ketone (PEEK) derivative sizing agents have garnered considerable attention for improving interfacial bonding of carbon fiber-reinforced PEEK (CF/PEEK) composites. However, their extensive application is somewhat limited due to two drawbacks: the use of hazardous organic solvents in production and the retention of emulsifiers in sizing dispersion systems. Herein, an extremely hydrophilic sulfonated PEEK with a cardo group (S-PEEK-WC) was synthesized and used to prepare a water-soluble sizing agent. The S-PEEK-WC exhibits excellent thermal stability, with a 5 % decomposition temperature of 446.5 °C, and its aqueous solution remains stable for over six months. A robust interphase was also constructed in the CF/PEEK composites through multiple physicochemical interactions. Compared with the de-sized CF/PEEK composites, the interlaminar shear strength, flexural strength and interfacial shear strength of the CF2/PEEK composites improved by 57.9 %, 56.3 % and 44.8 %, respectively. This approach may shed some light on the development of a valid and environmentally friendly method for preparing water-soluble sizing agents of polyaryletherketone.

Construction of a layer-by-layer self-assembled rosemarinic acid delivery system on the surface of CFRPEEK implants for enhanced anti-inflammatory and osseointegration activities.

Carbon fiber-reinforced polyether ether ketone (CFRPEEK) implants have attracted widespread attention in the field of clinical bone defect repair. However, the surface bioinertness confines the application of CFRPEEK implants. Inspired by the study of rosmarinic acid (RA)-promoted osteogenic differentiation, a self-assembly surface modification method based on electrostatic interactions, involving deposition of sodium carboxymethyl cellulose/chitosan and rosmarinic acid layer by layer on the surface of poly-L-lysine modified hydroxy CFRPEEK (SCPP/CC5@RA), is proposed to introduce RA on the surface of CFRPEEK for bioactivation. After layer-by-layer self-assembly (LBL), the surface of SCPP/CC5@RA exhibits weak electrophoresis (11.43 eV), suitable hydrophilicity, and bioactivity. The results of in vitro studies indicate that the RA release behavior of SCPP/CC5@RA effectively regulates the immune-inflammatory response and promotes the differentiation of osteoblasts. The rapid release of RA (0.17 μg mL-1) in the initial stage can downregulate the secretion of inflammation-related cytokines and significantly reduce oxidative stress levels; the sustained release of RA (0.06 μg mL-1) in the late stage can upregulate the expression of osteogenesis-related genes and induce mineralization of osteoblasts. Moreover, the rabbit tibia defect model demonstrates that the LBL technique can enhance the osseointegration of CFRPEEK implants. Compared with the control group, the bone trabecular thickness of the SCPP/CC5@RA group increases by 1.36 times, and the maximum pushing force increases by 2.67 times. In summary, this study provides a promising LBL based RA delivery system for the development of a dual-functional CFRPEEK implant in the field of bone implant biomaterials.

Effect of fiber content on mechanical properties of carbon fiber-reinforced polyether-ether-ketone composites prepared using screw extrusion-based online mixing 3D printing

The mechanical properties of carbon fiber-reinforced polyether-ether-ketone (CF/PEEK) composites are closely related to the fiber content. However, the low fiber content (typically below 20 wt%) that can be prepared by current material extrusion limits the application of the composites. In this work, CF/PEEK composites with up to 50 wt% carbon fiber content were manufactured using a custom-made screw extrusion-based online mixing 3D printhead. The impact of fiber loading on the rheological and flow characteristics of the composites was thoroughly examined initially. Subsequently, the influence of fiber content on the crystallinity and mechanical behavior of 3D-printed parts before and after annealing was further explored. The results indicated that adding CF and annealing significantly enhanced the strength and modulus of the 3D-printed composites within a fiber content range of 10 wt% to 40 wt%, compared to those of pure PEEK. At 40 wt% CF, the tensile and flexural strengths of the samples reached their maximum values at 135.9 MPa and 251.2 MPa, respectively, which were enhanced by 94% and 111% compared to those of the unannealed pure PEEK specimens. Also, these properties are the highest values achieved in 3D-printed short CF/PEEK composites. The mechanical properties of composites are affected by various factors such as fiber content, crystallinity, and internal pore defects when the fiber content is less than 20 wt%. However, when the fiber content exceeds 20 wt%, the influence of crystallinity on the mechanical properties becomes less significant. This study further explores the potential application of CF/PEEK composites and provides a novel approach for composite preparation.

Development and Evaluation of an MRI Artifact-Free Aneurysm Clip.

The digital subtraction angiography is still the gold standard in the follow-up after aneurysm surgery, although it remains a repeating invasive technique with accumulating X-ray exposure. An alternative magnetic resonance angiography has the disadvantage of metal-related artifacts. A metal-free aneurysm clip could overcome this problem. Recent advances in manufacturing technologies of fiber-reinforced plastics might allow developing a prototype of a metal-free clip. The prototype was formed out of carbon fiber-reinforced polyetheretherketone (CF-PEEK) in accordance with the standard clip design. In vivo and in vitro studies were performed to analyze the central nervous system biocompatibility. The prototype was tested in a phantom in a 3 T MRI scanner and microtomography scanner. For in vivo assessment, the left renal artery of rats was either ligated with a suture, clipped with a regular titanium clip or with the CF-PEEK prototype clip. The animals underwent standard MRI sequences and magnetic resonance angiography and assessment by a blinded neuroradiologist. Phantom studies showed no signs of artifacts. The prototype showed a reliable clamping and reopening after clip application, although the clamping force was reduced. In vivo studies showed a successful occlusion of the renal artery in all cases in the magnetic resonance angiography. Clip artifacts were statistically significant reduced in the prototype group (P < .01). CF-PEEK showed no signs of impaired biocompatibility compared with the titanium samples in vitro and in vivo. Former attempts of metal-free aneurysm clips did not meet the criteria of the standard clip design. In this study, the practicability of this new CF-PEEK artifact-free aneurysm clip has been proven. The further fabrication developments should overcome the problem of a reduced clamping force in the future. After clinical approval, it will improve the magnetic resonance image quality and might help to reduce the amount of digital subtraction angiography in the follow-up.

Advancing spacecraft demisability through a novel composite bolt joint system: a step toward sustainable and safe space environments

AbstractFrom the recent awareness of the booming number of space debris and their derived worldwide re-entry event threat originating from the use of high survivability components, complementary mitigation measures must be taken for future orbital elements. In this direction, the implementation of a design for demise at an early stage of spacecraft conception allows a progressive and effective solution. As part of a collaborative effort launched by École Polytechnique Fédérale de Lausanne and the European Space Agency, we focus on the evaluation of polymer composite bolts as the main structural satellite panel fastening systems to improve the overall spacecraft demisability during its destructive re-entry into the atmosphere as compared to baseline critical systems, while maintaining equivalent mission-relevant properties. Two carbon fiber-reinforced polyetheretherketone (PEEK) designs were compared to a stainless steel baseline in terms of static properties at room temperature, dynamic properties over a temperature range, as well as demise capability by static re-entry simulation testing. The results led us to identify a promising short CF/PEEK composite bolt design.

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.

The Influence of Titanium-coated Poryetheretherketone Cages in Fusion Status after Posterior Lumbar Interbody Fusion with Cortical Bone Trajectory Screw Fixation

Posterior lumbar interbody fusion (PLIF) with cortical bone trajectory (CBT) screw fixation (CBT-PLIF) shows potential for reducing adjacent segmental disease. Previously, our investigations revealed a relatively lower fusion rate with the use of carbon fiber-reinforced polyetheretherketone (CP) cages in CBT-PLIF compared with traditional pedicle screw fixation (PS-PLIF) using CP cages. This study aims to evaluate whether the implementation of titanium-coated polyetheretherketone (TP) cages can enhance fusion outcomes in CBT-PLIF. A retrospective analysis was conducted on 68 consecutive patients who underwent CBT-PLIF with TP cages (TP group) and 89 patients who underwent CBT-PLIF with CP cages (CP group). Fusion status was assessed using computed tomography at 1 year postoperatively and dynamic plain radiographs at 2 years postoperatively. No statistically significant differences in fusion rates were observed at 1 and 2 years postoperatively between the TP group (86.8% and 89.7%, respectively) and the CP group (77.5% and 88.8%, respectively). Notably, the CP group exhibited a significant improvement in fusion rate from 1 to 2 years postoperatively (P= 0.002), while no significant improvement was observed in the TP group. Examination of temporal changes in fusion rates reveals that only the TP group achieved a peak fusion rate 1 year postoperatively. This implies that TP cages may enhance the fusion process even after CBT-PLIF. Nevertheless, the definitive efficacy of TP cages for CBT-PLIF remains uncertain in the context of overall fusion rates.