Carbon Fiber-reinforced Polyetheretherketone Research Articles

The effect of moulding process parameters on interlaminar properties of CF/PEEK composite laminates

Interlaminar properties are one of the most important indicators of thermoplastic composite quality. A series of laminates with different moulding process parameters were prepared by unidirectional carbon fibre-reinforced polyether ether ketone (CF/PEEK) prepreg to explore the influence of moulding process parameters on the interlaminar properties of CF/PEEK composite laminates. The influence of the three process parameters, moulding pressure, moulding temperature, and holding time on the interlaminar shear strength (ILSS) of [0/90]8 laminates was studied. The interlaminar shear failure modes of specimens under different moulding process parameters were compared, and the correlation between the ILSS and interlaminar shear failure modes was analysed. The results showed that the appropriate moulding pressure was 2 MPa, the proper moulding temperature range was 400–420°C and the holding time should not be less than 20 min. The main failure modes were tensile or compression when the laminates were moulded using proper process parameters; interlaminar shear failure might also appear in those moulded by non-optimised process parameters.

Clinical outcomes of proximal femoral fractures treated with a novel carbon fiber-reinforced polyetheretherketone intramedullary nail

IntroductionWe developed a new carbon fiber-reinforced polyetheretherketone (CFR/PEEK) intramedullary nail for proximal femoral fractures. This study aimed to examine the efficacy and safety of the CFR/PEEK intramedullary nail for use in the treatment of patients with proximal femoral fractures. MethodsThis multicentre single-arm clinical trial enrolled 20 patients (3 men, 17 women; mean age 85.0 years, range 72–95 years) with proximal femoral fractures treated with the CFR/PEEK intramedullary nail. The follow-up period was >4 months. Primary outcomes were union of the bone fracture, time to bone union, bone nonunion, complications, implant failure, and the reoperation rate. Secondary outcomes were fracture reduction success, and clinical scores using the Harris hip score, Barthel index, Vitality index, Mini-Mental State Examination, and Numerical Rating Scale. ResultsAmong the 20 patients with proximal femoral fractures treated with CFR/PEEK intramedullary nails, 19 (95%) were confirmed to display bone union within 3.7 months (range 2.8–10.0 months). One patient was diagnosed as having bone nonunion, although the patient did not complain any pain, and there was no radiological evidence of failure after a follow-up period of >18 months. There were no complications (e.g., cut out, infection, hardware failure), and reoperation was not required. Fracture reduction was good and acceptable in all cases, and the mean tip–apex distance was 13.5 mm (range 9.0–19.1 mm). The results indicated that preoperative activity was maintained (preoperative and postoperative Harris hip scores were 73.2 and 71.0 points, respectively; p = 0.61). ConclusionThere were no adverse reactions or failures related to the CFR/PEEK implant, and it provided satisfactory clinical results and a high union rate. Thus, use of the novel CFR/PEEK intramedullary nail is feasible.

Hybrid composite pedicle screw - finite element modelling with parametric optimization

Abstract As a result of population aging, the number of spine surgeries steadily increases. Metallic pedicle screw systems are commonly used to achieve spinal fusion, and to correct spine misalignments. However, certain disadvantages are linked to these metallic systems: stress shielding can lead to bone degeneration and adjacent disc disease, artefacts prevent precise diagnosis during CT, MRI, or X-ray medical imaging, radiotherapy is complicated due to backscattering, and patient comfort is reduced due to the implant weight. These disadvantages have led to the development of carbon fibre reinforced polyether ether ketone (CF-PEEK) pedicle screws. Carbon fibres improve the structural mechanical properties of the PEEK matrix so that the mechanical requirements of an implant are met. However, with existing CF-PEEK screws the relative motion between screw and bone is increased due to discontinuous fibre reinforcement. Discontinuous fibre reinforced screws complicate precise stiffness control. In this study, a novel screw design consisting of a reinforcing element in the screw centre, and discontinuous short fibre reinforced CF-PEEK in the screw thread and head is presented. By this concept, the stiffness of the pedicle screw can be controlled and tailored by adapting the reinforcing element. This first study concerning hybrid pedicle screws is based upon numerical investigations to optimize hybrid composite screw stability in human bone. Parametric finite element (FE) models of screw and bone were developed. The main purpose of the study was to obtain design recommendations from the optimization, which will be used for future manufacturing of hybrid composite screws. It is further shown that stress shielding could be significantly reduced with this hybrid pedicle screw design as compared to titanium screws, despite the reinforcing element. Additionally, it is confirmed that the worst-case scenario with the highest risk of composite pedicle screw pull-out is shortly after surgery, when osseointegration is still poor. In future studies, mechanical, functional, and visibility tests of the hybrid composite pedicle screw will be conducted.

The advantages of carbon fiber based orthopedic devices in patients who have to undergo radiotherapy.

Background and Objectives:The modern approach to primary and secondary muscular skeletal tumors is multidisciplinary. The right combination of chemotherapy, surgery and radiotherapy (RT) makes obtaining local and distant disease more likely. When surgery is indicated, radiotherapy often has a fundamental role as an adjuvant treatment; however, the titanium alloy instrumentations interfere with Radiotherapy setting, decreasing its effectiveness. It is common opinion that carbon fiber-reinforced devices are convenient in case of adjuvant RT in muscular skeletal oncology. The aim of the study is to support this intuition with experimental data, verifying the more accurate estimation of the delivered dose during RT, comparing Carbon Fiber-Reinforced PEEK (CFRP) plates with titanium-alloy orthopedic devices in order to evaluate their effects on target volume identification and dose distribution for radiation treatment.Methods:Phantoms were then irradiated with a linear accelerator Varian 2100 C/D with photon beams of 6 and 15 MV energies. Absorbed dose in the point of interest was verified by EBT3 gafchromic films above and below the two materials. Images from CT simulations were also analyzed in terms of Hounsfield numbers in patients with titanium and carbon fiber orthopedic implants in the spine or in the femur.Results:For a 6 MV photon beam, the doses measured just under the titanium-alloy plate were less than approximately 20% of the value calculated by the TPS. For a 15 MV beam energy, these differences were slightly lower. Using CFRP plate, the difference between measured and calculated doses was within ±3% for both energies, which was comparable with the statistical uncertainties. In the cases of simulated treatment of humerus titanium implants, the difference varies in range ± 10% with hot spot of + 10% and cold spot of -15%.Conclusions:The use of CFRP for orthopedic devices and implants provides a valuable advantage in identifying the target due to the reduction of artifacts. Clear imaging of the soft tissues surrounding the bone is useful and reduces the discrepancies between calculated/delivered and measured doses, generating a more homogeneous dose distribution. Furthermore, there is a significant benefit in detecting the state of disease in CT imaging during the follow-up of treated patients. In-vivo studies are encouraged to verify whether a more effective radiotherapy leads to a decrease in local recurrence and local progression. (www.actabiomedica.com)

Influence of bionic non-smooth surface texture on tribological characteristics of carbon-fiber-reinforced polyetheretherketone under seawater lubrication

Abstract To explore anti-wear characteristics for valve pair, the influences of smooth and non-smooth surfaces on tribological properties of the carbon-fiber-reinforced polyetheretherketone (CFRPEEK) coupled with stainless steel 316L were investigated under natural seawater lubrication. The results show that the specimen with ellipsoidal pits has the best frictional performance, followed by the specimen with triangular pits, and the specimen with hemispherical pits is the worst. Microscope observation analysis showed that the reasonable non-smooth surface can reduce adhesion wear and improved the stability of friction system as compared to smooth surface. Results also indicated that the reasonable non-smooth unit can effectively store seawater and debris, and produce hydrodynamic lubrication effect, which surface shows the excellent tribological properties.

Plate-related results of opening wedge high tibial osteotomy with a carbon fiber reinforced poly-ether-ether-ketone (CF-PEEK) plate fixation: a retrospective case series of 346 knees

BackgroundWhile open wedge high tibial osteotomy (owHTO) is an established standard procedure to treat medial osteoarthritis of the knee in combination with varus deformity, it bears the risk of postoperative hardware failures and lateral cortical hinge fractures. This in turn can lead to an accelerated osteoarthritis, non-union, or a loss of correction accuracy. The purpose of the study was to evaluate the radiologic outcomes of owHTO with a carbon fiber reinforced poly-ether-ether-ketone (CF-PEEK) plate fixation in patients with medial osteoarthritis and varus deformity.MethodsThree hundred twenty-four consecutive patients (346 knees) who were treated with owHTO using the PEEKPower HTO plate were included in this retrospective study; 89.9% of the patients were overweight or obese. Patients were followed by conventional radiographs over a 12-month period. Typical plate-related results such as the time and quality of gap healing as well as the correction accuracy were analyzed. Furthermore, the number of lateral cortex fractures was determined.ResultsBony consolidation was observed after a mean gap healing time of 4.0 ± 1.7 months independent on the patients’ weight (p = 0.2302). With increasing gap sizes, bony healing was significantly prolonged (p < 0.001). Additionally, patients with greater gap sizes had a significantly increased risk for a lateral cortex fracture (p = 0.0041). However, none of the patients had a non-union 1 year postoperative. A hinge fracture occurred in 30% of patients. Hinge fractures with Takeuchi grades I and II increased the gap healing time compared to no fracture (p = 0.0069 and p = 0.0002, respectively), but only 1.2% of patients with hinge fracture had a clinical relevant loss of correction ≥ 3 mm. No implant failures were found.ConclusionsOpen wedge HTO using the PEEKPower HTO plate for patients with medial osteoarthritis of the knee in combination with tibial varus deformity leads to excellent bony consolidation also in cases with a hinge fracture, a gap size > 12 mm as well as for severely obese patients.

Distribution Performance Analysis and Experimental Research on the Port Plate Pairs of Low Speed High Torque Seawater Hydraulic Motor

The current research of seawater hydraulic motor mainly focused on piston motor and vane motor, but seldom regarded low speed high torque seawater hydraulic motor. Low speed high torque seawater hydraulic motor as a kind of energy conversion device and actuator plays an important role in seawater hydraulic transmission system. However, the physical and chemical properties of seawater, such as low viscosity, high causticity and poor lubrication, result in numerous problems. In this paper, the flow distribution characteristics of port plate pairs for the seawater hydraulic motor are investigated, and the leakage flow and power loss models of port plate pairs are established. Numerical simulations are carried out to examine the effects of water film, inlet pressure and rotating speed on the pressure distribution and leakage flow. And the friction and wear tests of port plate pairs are also carried out. Moreover, the test system of the seawater hydraulic motor is constructed and the performance of prototype with no-load or loading is conducted. The results indicate that the clearance of port plate pairs and inlet pressure have a significant effect on distribution characteristics, but the effect of rotating speed is not very obvious. The experimental results show that the minimum error rate can be maintained within 0.3% by the proposed flow model and the counter materials of 316L against carbon-fiber-reinforced polyetheretherketone (CFRPEEK) are suitable for the port plate pairs of seawater hydraulic motor. Finally, based on the seawater hydraulic experiment platform, the volumetric efficiency of no-load and loading are obtained that the maximum can achieve 94.71% and 90.14%, respectively. This research work may improve the flow distribution performance, lubrication and the friction and wear properties, enhance energy converting efficiency of port plate pair and provide theoretical and technical support for the design of high-performance water hydraulic components.

Low-velocity impact response of friction riveted joints for aircraft application

In this paper, the sensitivity of carbon fiber reinforced polyether-ether-ketone (CF-PEEK) friction riveted joints to impact damage was assessed as well as the damage propagation during fatigue and quasi-static mechanical testing. The joints were impacted with energies between 5 J and 30 J at room temperature and the impact damage was evaluated through microscopy and ultrasonic C-scan. Two damage types were identified: barely-visible impact damage with mainly shear-driven damage in the first plies of the composite and visible impact damage with delamination and premature failure of the rivet-composite interface owing to peel stresses upon the impact event. The joint strength and fatigue life were not compromised by the barely-visible impact damage, while a 40% decrease of quasi-static strength and lower fatigue resistance were achieved for visible impact damage. Despite altered fatigue behavior of impacted joints, damage accumulated towards fatigue was not critical to the joint mechanical integrity, confirmed by the residual strength of up to 96% after 106 cycles for 20 J impacts.

The Treatment of Proximal Humerus Fracture Using Internal Fixation with Fixed-angle Plates.

Implants made of various types of material can be used for the internal fixation of fractures. Carbon fiber reinforced polyetheretherketone (CFR-PEEK) is a radiolucent material that may have advantageous handling properties compared with titanium implants. Seventy-six patients with proximal humerus fractures requiring surgery were randomized to receive a fixed-angle plate made out of either titanium or CFR- PEEK. To measure the functional outcome, the DASH score (Disabilities of Arm, Shoulder, and Hand; primary endpoint), the Simple Shoulder Test (SST), and the Oxford Shoulder Score (OSS) were determined in 63 patients at 6 weeks, 12 weeks, and 6 months after surgery, accompanied at each time point by radiological evaluation. Both groups displayed improvement in DASH scores 6 months after surgery (CFR-PEEK: 27.5 ± 20.5; titanium: 28.5 ± 17.9; p = 0.82). Sensitivity analysis with multiple imputations confirmed this result (27.4 ± 19.2 versus 28.5 ± 16.6). The OSS and SST scores were likewise improved in both groups. All patients displayed full bony consolidation 12 weeks after surgery. In no case was material failure, secondary dislocation, or screw perforation seen. No difference was seen in the maintenance of postoperative reposition between the CFR-PEEK group and the titanium group. The internal fixation of proximal humerus fractures with either CFR-PEEK or titanium led to clinical improvement 6 months after surgery. No clinical or radiological difference in outcomes was seen between the two groups. Because of the study design, however, the equivalence of the two interventions was not con- clusively demonstrated; a non-inferiority study would have been needed for this purpose.

Effect of Different Framework Materials in Implant-Supported Fixed Mandibular Prostheses: A Finite Element Analysis.

To evaluate the biomechanical behaviors of different framework materials in implant-supported fixed mandibular prostheses using three-dimensional (3D) finite element analysis. A model of a severely resorbed edentulous mandible was obtained from a tomography database. Morse taper-connection implants and multi-unit abutments were cut with an electro-erosion machine and scanned using a 3D scanner. The implants were positioned on the model at the bone level and distributed equally to support a fixed complete prosthesis. The simulations were divided into six groups according to the framework material: titanium (Ti); cobalt-chromium (Co-Cr); zirconia (ZrO2); polyether ether ketone (PEEK); carbon fiber-reinforced polyether ether ketone (CFR-PEEK); and polymethyl methacrylate (PMMA). The resultant load applied was obtained from the masseter, temporal, lateral, and medial pterygoid muscles. The principal stresses and von Mises equivalent stresses were analyzed and compared among the framework materials, and the results were described both quantitatively and qualitatively. PEEK and PMMA frameworks showed the highest total deformation values, showing decreases of von Mises stresses in the frameworks, implants, and abutments, but with a high tensile stress in the trabecular bone that achieved critical values. CFR-PEEK frameworks achieved their failure limit, whereas the ZrO2, Co-Cr, and Ti frameworks exhibited principal stresses in the bone region within physiologic limits. From a biomechanical point of view, the Ti, Co-Cr, and ZrO2 frameworks demonstrated the most favorable outcomes.

Pre-Inscribed Laser Surface Pattering for Increased Joining Strength in Laser Fusion Bonding of CFRP and Zinc-Coated Steel

In this study, we present improved fusion-bonding strength results between carbon fiber-reinforced polyetheretherketone (CFR-PEEK) and zinc-coated steel through the introduction of pre-inscribed laser surface patterns. Optimized laser welding parameters, including laser power, focal position, pitch, number of passes, and clamping pressure, are presented along with parameters for producing the rectangular laser patterns. It was found that for the optimized parameters, the tensile shear strength of the welded samples is improved by as much as 100% when pre-inscribed laser patterns are present. Detailed SEM images of the fractured fusion welded joint samples after the tensile shear test are presented for analysis. The tight bonding between the polymer matrix and the zinc-coated steel inside the formed grooves is found to be the main reason behind the increased tensile shear strength. A comparison of the tensile shear loads for various joining methods is also presented and discussed.

Effect of insert material on forces on quadriceps, collateral ligament, and patellar tendon after rotating platform mobile-bearing total knee arthroplasty

There is a gradual increase in the number of patients for total knee arthroplasty (TKA), and TKA demonstrates reliable clinical outcomes. The orthopaedic biomaterials community continuously attempted over the past decades to improve the longevity of UHMWPE in TKA by using various improved technologies. Polyetheretherketone (PEEK) and carbon fiber reinforced-PEEK(CFR-PEEK) are suggested as potential tibial insert materials to replace UHMWPE in some applications. The aim of this study involves evaluating the biomechanical effects of UHMWPE and CFR-PEEK tibial materials on mobile-bearing TKA. The finite element (FE) model was obtained by conducting computed tomography and magnetic resonance imaging. The FE investigation included three types of loading conditions corresponding to the loads used in the experiments for FE model validation and model predictions under deep-knee bend loading conditions. We investigated forces on quadriceps, collateral ligament and patellar tendon with UHMWPE and CCFR-PEEK tibial insert materials under the deep-knee-bend condition. Quadriceps force decreased with flexion for CFR-PEEK when compared to that for UHMWPE. A similar trend was observed in terms of the patellar tendon force. An opposite trend was observed in the collateral ligament. Medial collateral ligament force in the CFR-PEEK exceeded that in the UHMWPE, and lateral collateral ligament force in the UHMWPE exceeded that in the CFR-PEEK. The CFR-PEEK represents an alternative insert material given its superior biomechanical effect after mobile-bearing total knee arthroplasty. However, a balance between the medial and lateral ligaments is considered as an important factor in the CFR-PEEK tibial insert due to its opposite biomechanical effect.

Biomechanical Effect of UHMWPE and CFR-PEEK Insert on Tibial Component in Unicompartmental Knee Replacement in Different Varus and Valgus Alignments.

The current study aims to analyze the biomechanical effects of ultra-high molecular weight polyethylene (UHMWPE) and carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) inserts, in varus/valgus alignment, for a tibial component, from 9° varus to 9° valgus, in unicompartmental knee replacement (UKR). The effects on bone stress, collateral ligament force, and contact stress on other compartments were evaluated under gait cycle conditions, by using a validated finite element model. In the UHMWPE model, the von Mises’ stress on the cortical bone region significantly increased as the tibial tray was in valgus >6°, which might increase the risk of residual pain, and when in valgus >3° for CFR-PEEK. The contact stress on other UHMWPE compartments decreased in valgus and increased in varus, as compared to the neutral position. In CFR-PEEK, it increased in valgus and decreased in varus. The forces on medial collateral ligaments increased in valgus, when compared to the neutral position in UHMWPE and CFR-PEEK. The results indicate that UKR with UHMWPE showed positive biomechanical outputs under neutral and 3° varus conditions. UKR with CFR-PEEK showed positive biomechanical outputs for up to 6° varus alignments. The valgus alignment should be avoided.

Biomechanical Study of a Novel, Expandable, Non-Metallic and Radiolucent CF/PEEK Vertebral Body Replacement (VBR).

Vertebral body replacement is well-established to stabilize vertebral injuries due to trauma or cancer. Spinal implants are mainly manufactured by metallic alloys; which leads to artifacts in radiological diagnostics; as well as in radiotherapy. The purpose of this study was to evaluate the biomechanical data of a novel carbon fiber reinforced polyetheretherketone (CF/PEEK) vertebral body replacement (VBR). Six thoracolumbar specimens were tested in a six degrees of freedom spine tester. In all tested specimens CF/PEEK pedicle screws were used. Two different rods (CF/PEEK versus titanium) with/without cross connectors and two different VBRs (CF/PEEK prototype versus titanium) were tested. In lateral bending and flexion/extension; range of motion (ROM) was significantly reduced in all instrumented states. In axial rotation; the CF/PEEK combination (rods and VBR) resulted in the highest ROM; whereas titanium rods with titanium VBR resulted in the lowest ROM. Two cross connectors reduced ROM in axial rotation for all instrumentations independently of VBR or rod material. All instrumented states in all planes of motion showed a significantly reduced ROM. No significant differences were detected between the VBR materials in all planes of motion. Less rigid CF/PEEK rods in combination with the CF/PEEK VBR without cross connectors showed the smallest reduction in ROM. Independently of VBR and rod material; two cross connectors significantly reduced ROM in axial rotation. Compared to titanium rods; the use of CF/PEEK rods results in higher ROM. The stiffness of rod material has more influence on the ROM than the stiffness of VBR material.

Tribological Performance of CF-PEEK Sliding against 17-4PH Stainless Steel with Various Cermet Coatings for Water Hydraulic Piston Pump Application

To improve the abrasion resistance performance of the critical tribopairs within water hydraulic piston pumps, tribological characteristics of the stainless steel 17-4PH and 17-4PH coated with Cr3C2-NiCr, WC-10Co-4Cr, Cr2O3 and Al2O3-13%TiO2 sliding against carbon fiber reinforced polyetheretherketone (CF-PEEK) composite under water-lubricated condition were experimentally studied using a pin-on-ring test bench with different working conditions. It has been demonstrated by the experimental results that the tribological behaviors of CF-PEEK/cermet coatings tribipairs were better than that of CF-PEEK/17-4PH tribopair under water lubrication. However, the Cr3C2-NiCr coating could be damaged under high rotational speed. Due to the reaction film produced by the Al2O3-13%TiO2 and water, the CF-PEEK/Al2O3-13%TiO2 material combination exhibits more excellent tribological behaviors than other tribopairs lubricated with water, and could preferentially be used in water hydraulic piston pumps.

First Clinical Experience with a Carbon Fibre Reinforced PEEK Composite Plating System for Anterior Cervical Discectomy and Fusion.

Carbon fibre reinforced polyether ether ketone (CFR-PEEK) is a suitable material to replace metal implants in orthopaedic surgery. The radiolucency of CFR-PEEK allows an optimal visualisation of the bone and soft tissue structures. We aimed to assess the performance and radiological and clinical outcomes of anterior cervical discectomy and fusion (ACDF) with CFR-PEEK anterior cervical plating (ACP) under first use clinical conditions. We retrospectively studied the prospectively-collected data of 42 patients who underwent ACDF with CFR-PEEK ACP between 2011 and 2016. We assessed clinical outcome (Odom’s criteria, complications) and radiological parameters (global and segmental cervical lordosis, Bridwell score for fusion, adjacent segment degeneration) preoperatively, immediately post-operatively, and after a 12-month follow-up period. Patients’ satisfaction was excellent, good, fair, and poor in 12, 19, 3, and 1 patients, respectively. Two patients developed dysphagia. No hardware failure occurred. Compared with preoperative radiographs, we observed a gain of global cervical lordosis and segmental lordosis (7.4 ± 10.1 and 5.6 ± 7.1 degrees, respectively) at the 12-month follow-up. Bridwell IF grades I, II, and III were observed in 22, 6, and 7 patients, respectively. The 12-month adjacent segment degeneration-free and adjacent segment disease-free survival rates were 93.1% and 96.3%, respectively. We observed a dysphagia rate of 5.7% and a reoperation rate of 4.8%. In conclusion, CFR-PEEK ACP shows positive outcomes in terms of implant safety, restoration of cervical lordosis, and functional recovery, and is suitable for ACDF.

Biomechanical behavior of an implant system of carbon fiber-reinforced polyether ether ketone (PEEK) bars with different designs: finite elements analysis

We used finite elements analysis to assess the biomechanical behavior of lower protocol bars made of Polyether Ether Ketone (PEEK) reinforced by carbon fiber, with different designs on All-on-four® system, subjected to physiological occlusal loads. The models were built to have an I-shaped or an inverse T-shaped section. We also assessed the stress distribution on the peri implant bone, implants, prosthetic intermediates, prosthetic intermediate screws, and prosthetic screws. In the simulations, strength peaks were similar for both inverse T and I shaped models; however, the I-shaped bars showed larger resistance in comparison with the inverse T shape. Since it is a new material in dentistry, further research is necessary for a better assessment of PEEK's mechanical and clinical performance.

Investigation of the fiber-matrix interaction in carbon fiber-reinforced polyether ether ketone by cyclic single fiber push-out and push-back tests

ABSTRACTTo characterize the fiber-matrix interaction of carbon fiber-reinforced polyether ether ketone, a high-performance thermoplastic composite material, micromechanical cyclic single fiber push-out and push-back tests were performed. A new type of successive push-out behavior was observed in addition to the well-known abrupt fiber push-out. To determine the interfacial fracture toughness from the successive push-out load-displacement curves, an advanced energy-based method was developed. It was found that the two different types of push-out correspond to two different values of interfacial fracture toughness. Thermal expansion measurements indicate that residual thermal stress within the investigated sample induces the two different push-out behaviors. The findings suggest that the fiber-matrix interaction might be one reason for the considerable impact of thermal stress on interface dominated macroscopic parameters.

Prediction of Wear on Tibial Inserts Made of UHMWPE, PEEK, and CFR-PEEK in Total Knee Arthroplasty Using Finite-Element Analysis

The wear of tibial inserts in total knee arthroplasty (TKA) remains a major limitation of longevity. However, wear tests are expensive and time-consuming. Computational wear prediction using a finite-element (FE) model followed by validation through comparison with experimental data is effective for assessing new prosthetic designs or materials prior to functional testing and surgical implementation. In this study, the kinematics, volumetric wear, and wear depth of tibial inserts made of different materials (ultrahigh-molecular weight polyethylene (UHMWPE), polyetheretherketone (PEEK), and carbon fiber-reinforced PEEK (CFR–PEEK)) in TKA were evaluated by employing FE models and analysis. The differences among the materials were evaluated using adaptive wear modeling to predict the wear depth, volumetric wear, and kinematics under a gait loading condition. The volumetric wear and wear depth of the CFR–PEEK decreased by 87.4% and 61.3%, respectively, compared with those of the UHMWPE, whereas the PEEK exhibited increased volumetric wear and wear depth. These results suggest that CFR–PEEK is a good alternative to UHMWPE as a promising and suitable material for tibial inserts used in TKA. However, orthopedic research should be performed to evaluate the threshold conditions and appropriate applications for the newly developed and introduced biomaterial.

The Influence of Clamping Pressure on Joint Formation and Mechanical Performance of Ti6Al4V/CF-PEEK Friction-Riveted Joints.

This work aims at investigating the influence of pre-set clamping pressure on the joint formation and mechanical strength of overlapping direct-friction-riveted joints. A pneumatic fixture device was developed for this work, with clamping pressure varying from 0.2 MPa to 0.6 MPa. A case study on overlapping joints using Ti6Al4V rivets and woven carbon fiber-reinforced polyether-ether-ketone (CF-PEEK) parts were produced. Digital image correlation and microscopy revealed the expected compressive behavior of the clamping system and the continuous pressure release upon the joining process owing to the rivet plastic deformation and the polymer squeezing flow. Two preferential paths of material flow were identified through the alternate replacement of the upper and lower composite parts by a poly-methyl-methacrylate (PMMA) plate—the composite upward and squeezing flow between the parts which induced their separation. The ultimate lap shear forces up to 6580 ± 383 N were achieved for the direct-friction-riveted CF-PEEK overlap joints. The formation of a gap to accommodate squeezed polymer between the composite parts during the process had no influence on the joint mechanical performance. The increase in the clamping pressure for joints produced with a low friction force did not affect the joint-anchoring efficiency and consequently the joint strength. On the other hand, the combined effect of a high-friction force and clamping pressure induced the inverted bell shape of the plastically deformed rivet tip, a lower anchoring efficiency, and the delamination of the composite, all of which decrease the mechanical strength by 31%. Therefore, the higher the friction force and clamping pressure, the more defects would be generated in the composite parts and the more changes in the shape of the plastically deformed rivet tip, leading to a lower level of quasi-static mechanical performance. All the joints failed by initial bearing of the composite and final rivet pull-out. The findings of this work can contribute to further improvement of the clamping design for industrial application.