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To ensure the aperture consistency of the stepped hole in the drilling of braided carbon fiber reinforced polyether ether ketone (BCF/PEEK) and PEEK stacks, a step variation parameter method is proposed to obtain the optimum process parameters in this study. Initially, the lay-up sequence is determined by analyzing diameter differences in drilled sequences of BCF/PEEK and PEEK stacks. Concurrently, hole-wall surface morphology and damage are observed under traditional drilling conditions to define stepped hole phenomena. Subsequently, optimum step position is identified by analyzing diameter differences at various positions with variable parameters. Moreover, the influence weight of drilling parameters on diameter difference is assessed using Taguchi orthogonal array. An optimization process scheme is proposed for minimum diameter difference control. Results suggest spindle speed of 2000 r/min and feed rate of 40 mm/min for BCF/PEEK, and 5000 r/min and 30 mm/min for PEEK are optimum parameters. This method holds promise for achieving consistent apertures in other laminated composites during drilling. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of different thermal aggressions (resulting in the decomposition of the thermoplastic matrix) on thermal degradation and residual tensile mechanical behavior of hybrid carbon/glass fibers reinforced PolyEther Ether Ketone (PEEK) laminates. The specimens are exposed to isothermal (from melting temperature to decomposition temperature by means of a furnace) and anisothermal conditions (116 kW/m2 and 1150 ℃ kerosene flame by means of a burner bench) respectively. The mechanical tests are further conducted to evaluate the residual tensile properties at Room Temperature (RT). When the laminates are exposed to flame, the microscopic observation reveals the heterogeneous thermally induced damages, compared with the isothermal case. A significant reduction in the axial stiffness (−35 %) and axial strength (−90 %) occurs after a 900 s flame exposure, as the structural integrity of laminate is significantly affected, compared with virgin specimens. By means of a three-region modeling, the importance of different damage regions for a post-fire laminate under mechanical loading is quantified and it is possible to further predict the residual mechanical properties with different flame exposure time. [ABSTRACT FROM AUTHOR]

[Display omitted] • The developed model separately considers the individual contribution of the PEEK matrix and the fiber reinforcement. • Relaxation parameters are obtained by the standard relaxation test of the PEEK matrix. • Volume-fraction and temperature controlled strain concentration parameters are determined by RVE simulations and composite experiments. • Transverse and oblique tensile relaxations of composites are well predicted from 25 °C to 200 °C. Due to super toughness and good repairability, the fiber reinforced polyether ether ketone (PEEK) composites are promising to replace metals in the primary-load bearing structures for the next generation aircraft. However, at the high service temperature close to or even above the glass transition temperature of PEEK, composite properties strongly depend on the loading temperature and time, bringing great challenges to their applications. How to evaluate their temperature/time dependent properties over a wide temperature range is the key issue in both the structure design and the process design. This study proposes a multiscale viscoelastic constitutive model for the composites to separately consider the individual contribution of the intrinsic matrix properties and the fiber induced strain concentration. The generalized Maxwell model for the PEEK viscoelastic properties was extended to a three-dimensional case by the genetic integration method. Based on the bottom-up approach, the isotropic viscoelastic matrix and the anisotropic linear elastic reinforcement were considered to construct a multiscale model of the fiber reinforced PEEK composites. To verify the developed model, the unidirectional carbon fiber reinforced PEEK composite samples were fabricated and tested. By the PEEK matrix relaxation tests, the composite transverse tensile tests and the representative volume element (RVE) simulations, the model parameters were calibrated step by step. Good agreements among the experimental results, the RVE simulations, and the model predictions under different tensile states over a wide temperature range (25–200 °C), proved that this model could be used to predict and to design the relaxation behaviors of the fiber reinforced PEEK composites. [ABSTRACT FROM AUTHOR]

The introduction of new materials and manufacturing technologies has significantly improved soft magnetic composites (SMCs) applications, with unique 3D shapes, reduced weight, and lower energy losses, material waste, and manufacturing costs. However, coating materials and existing iron powder insulation techniques limit the applicability of SMCs. This study used an organic polyether ether ketone (PEEK) coating to insulate iron particles using a more effective technique. The prepared SMCs comprised several volume concentrations of iron and PEEK, which were evaluated based on their magnetic, electric, and physical properties. Their magnetic properties were studied at various temperature ranges, considering the operating temperature limits for different applications. A mass magnetization saturation value of 236.2 emu/g was achieved at 348.15 K for a 6.2 g/ c m 3 sample. Furthermore, lighter and energy-efficient brushless direct current (BLDC) motors featuring SMC cores were manufactured and compared with a laminated core-based motor. The developed SMC motors (93 %) were approximately 9.90 % more efficient than the laminated core-based motors (83.1 %), while the core losses of SMC core (<1 %) were approximately 5.50 % less than those of the laminated core (6.50 %). [ABSTRACT FROM AUTHOR]

The mechanical behavior of polymer-metal structure (PMCS) made by Friction Assisted Joining is investigated. Al-Mg Alloy and polyetheretherketone (PEEK) were adopted. Laser texturing was performed on the aluminum substrate to enhance the strength of the joints. A campaign of experimental tests was conducted by varying the energy supplied during the joining process. During the heating and the cooling phases, the thermal history and temperature gradients were monitored by means of an IR camera. Single lap shear tests were conducted to determine the mechanical behavior of the joints. Morphological analysis and fracture surface analysis were performed by means of Optical Microscopy and Scanning Electron Microscopy to evaluate the material flow produced under different processing conditions as well as the mean features of the joints. The highest strength joints were achieved after a heating time of 25 s to which corresponded an supplied energy of 3.5 kJ, which led to a maximum and average temperature (reached by the upper aluminum surface during the joining process) of 390 °C and 350 °C, respectively. Under such conditions, the maximum shear force of 6.9 kN and an average shear strength of 47 MPa were achieved corresponding to a joint efficiency of 83%. [ABSTRACT FROM AUTHOR]

The present investigation aimed to determine the influence of the texturing strategy on the mechanical behavior of metal-polymer hybrid joints made by friction-assisted joining. An experimental campaign was conducted on AA7075 aluminum alloy and PolyEther Ether Ketone (PEEK). Laser texturing was performed on the aluminum surface before joining to improve the mechanical interlock between the substrates. Different laser texturing conditions were used by varying the number of scans and the distance between consecutive laser tracks. Microscopic analysis was conducted on the treated samples to determine the main geometrical characteristics. Single-lap shear tests were performed to determine the mechanical behavior of the produced connections. Fracture surface analysis was also performed to establish the main failure mechanisms. According to the achieved results, the laser texturing strategy significantly influenced the mechanical behavior of the joints, the peak force, the absorbed energy, and the failure mode. The density of the laser texturing affected the stress on the aluminum protrusions and the mechanical behavior. Adopting a higher number of scans improved the mechanical interlock and, consequently, the mechanical behavior of the joints. [ABSTRACT FROM AUTHOR]

In this paper, the effects of FDM parameters (nozzle temperature, platform temperature, layer thickness, and printing speed) as well as annealing temperature on the mechanical properties of poly(ether ether ketone) (PEEK) were investigated through orthogonal experiments. And the tribological properties of PEEK were also studied before and after annealing. Results show that nozzle temperature and printing speed were main factors affecting the mechanical properties of PEEK, which was optimized to be 440 ℃ and 40 mm/s, respectively. The mechanical strength of PEEK was increased with increasing annealing temperature and reached the maximum at 300 ℃ with the sacrifice of elongation at break, and the ultimate tensile, flexural and compressive strength was increased by 36%, 54% and 21%, respectively. As for the tribo-properties, there appeared a minimum wear rate(1.37 × 10−6mm3/Nm) in 200 °C annealed PEEK when tested in parallel manner, combined influences of annealing and filament orientation were revealed, and appropriate annealing temperature was found to help enhance the formation of uniform and homogeneous transfer films on the counter steel surfaces. [ABSTRACT FROM AUTHOR]

Polyether-ether-ketone (PEEK) nanocomposites with different amount of CNT (i.e. 3 %, 5 %, 10 % by weight) have been produced in the form of filaments and successively 3D printed via fused filament fabrication. Different analytical models, based on rule of mixture and mechanical percolation have been applied to evaluate the elastic modulus and the ultimate tensile strength of PEEK-CNT composites. From the comparison of the predicted mechanical properties with those obtained experimentally the combination of Takayanagi I and Takayanagi II models, based on mechanical percolation, allows to compute the elastic modulus trend of the composites with an error less than 10 %. The ultimate tensile strength Takayanagi model well represents the behaviour found experimentally, with predicted values being slightly higher than the measured ones (error < 11 %). The analytical models cannot be applied to predict the mechanical behaviour of 3D printed parts because it is shown that mechanical properties of additive manufactured composites are deeply influenced by the sum of mechanical percolative behaviour and the interphase strength among 3D printed layers. [ABSTRACT FROM AUTHOR]

The exceptional mechanical properties of Polyether-ether-ketone(PEEK) polymers make them ideal candidates for interlayer toughening of carbon fibre/epoxy composites. Herein, ultra-thin PEEK films with a thickness of 8 μ m , 18 μ m and 25 μ m were used for interlayer toughening of an aerospace-grade carbon fibre/epoxy composite. The mode-I and mode-II fracture behaviour of the interleaved laminates were investigated, with the fracture mechanisms being investigated. The surfaces of the PEEK films were treated by a UV-irradiation technique to enhance their intrinsically low surface activities. This significantly increased the adhesion at the interface between the PEEK interlayers and the composite matrix. A topography analysis on the fracture surfaces revealed extensive damage of the PEEK interlayers during the fracture process of the laminates. Owing to the exceptional properties of the PEEK films, significant enhancements in the mode-I and mode-II fracture properties of the laminates were obtained, i.e. the mode-I and mode-II fracture energies were significantly increased by 227% and 441%, respectively. Overall, the UV-treated PEEK films proved superior effectivenesses for laminate toughening when compared to the other state-of-the-art interlayer materials. [ABSTRACT FROM AUTHOR]

• 66 wt% carbon fiber reinforced PEEK composite with strong interface was prepared. • The composite has ultra-high specific strengths exceeding majority of polymer or metal matrix composites. • The wear rate of composite is 1–2 orders of magnitude lower than materials with lubricating particles. • Excellent properties are attributed to high-mass carbon fibers and self-lubricating of composite. • A new idea is provided for the application of high-strength resin-based composite. It remains challenging to incorporate high-content fibers in fiber-reinforced polymer matrix composites to significantly enhance their mechanical properties. This work prepared polyether ether ketone (PEEK) matrix composite reinforced with 66 wt% carbon fibers with 0°/90° prepreg layer by compression molding, with aim to further increase the carbon fibers content in PEEK-based composites to improve the mechanical and wear properties at different temperatures, especially high temperature. The composite exhibits tensile and flexural strength of both exceeding 1000 MPa at room temperature, 810 ± 10 MPa and 521 ± 12 MPa at 200 °C and 458 ± 22 MPa and 290 ± 18 MPa at 300 °C, respectively. Especially at 300 °C, the composite demonstrates specific strength of 290 MPa/(g/cm3), which is superior to many magnesium or aluminum alloys (18–86 MPa/(g/cm3)). Further, the composite has a lower wear rate (5.47–12.80 × 10−7 mm3/Nm) at 200 °C by 1–2 orders of magnitude that of some materials with lubricating particles, and the wear surface is dominated by mild adhesive wear instead of abrasive wear at room temperature. The ultra-high mechanical and friction wear properties are attributed to the high content of staggered 90° carbon fibers, great interface bonding between the fibers and PEEK matrix, and self-lubricating effect of fibers and PEEK particles in the composite. This opens up a new performance level and provides a new idea for high-temperature applications of high-strength fiber-reinforced resin matrix composites. [ABSTRACT FROM AUTHOR]

This paper address the challenges in using traditional film inserts specific to hot gas torch (HGT) assisted and in-situ consolidated automated fibre placement (AFP) manufactured double cantilever beam (DCB) and end notched flexure (ENF) specimens using carbon fibre (CF) reinforced polyetheretherketone (PEEK) prepregs. Traditional films suffer from thermal degradation, wrinkling and distortion under the consolidation roller. In this study, steel shim inserts with different thicknesses (25 and 50 µm) were used to manufacture the DCB and ENF specimens for fracture toughness evaluation. The processing parameters for in-situ consolidation were selected based on prior optimisation studies on short beam tests. In-situ consolidated specimens suffer from high void content which can affect the mechanical properties. Hence, optical micrography was used to investigate on the void contents in the manufactured specimens. Microhardness measurement is proposed as an AFP manufacturing quality assessment tool for DCB and ENF specimens which were taken from different regions of composite laminates. A manufacturing methodology for producing high quality DCB and ENF specimens by hot gas torch assisted in-situ consolidation using AFP is proposed in this paper that provide comparable results with those specimens manufactured using traditional methods. [ABSTRACT FROM AUTHOR]

In this study, the energy dissipation behavior of short carbon fiber reinforced polyether-ether-ketone (SCFR-PEEK) subjected to fatigue loading is investigated. A new model is established to rapidly predict the fatigue limit and S-N curve for SCFR-PEEK by combining thermodynamic laws and fatigue damage mechanisms. An infrared camera is used during the fatigue tests to monitor the evolution of the temperature distribution of the specimen. The energy dissipated during the fatigue test is calculated by solving local thermodynamic differential equations based on the variation in surface temperature of the specimen. Based on thermodynamic laws and the fatigue damage characteristics of SCFR-PEEK, the different sources of intrinsic dissipation are analyzed and classified to determine their correlation to fatigue damage. The intrinsic dissipation contributing to fatigue damage is extracted and used to estimate the fatigue properties of SCFR-PEEK. The model predictions show a satisfactory agreement with the results of traditional fatigue tests, with a goodness of fit of 0.964. [ABSTRACT FROM AUTHOR]

The influence of in-plane fiber waviness defects on the compressive properties of quasi-isotropic (QI) carbon polyether-ether-ketone (C/PEEK) composites was investigated experimentally. Specimens with localized waviness were manufactured using a stamp forming process resulting into laminates featuring multiple wavy plies, i.e. from one to three wavy 0 ° plies in a 24-ply QI composite and a range of maximum waviness angle between 23 ° to 60 °. No significant influence of the waviness was found on the global laminate stiffness. Compression tests coupled with high-speed camera monitoring were performed to study the failure process. It was confirmed that the waviness defects act as a trigger for the initiation of damage, predominantly by the kinking mechanism, resulting into an early failure and significantly lower ultimate strength than the baseline when loading in 0 ° direction. Furthermore, it was found that all specimens with waviness and with the same layup have a similar strength, indicating that the maximum waviness angle within the range studied in this work did not significantly influence the ultimate compressive strength. However, the presence of waviness in multiple plies clearly affected the strength. It was found that the ultimate compressive strength decreased proportionally to the percentage of plies oriented in the loading direction that is wavy. [ABSTRACT FROM AUTHOR]

As having high heat resistance, excellent mechanical and tribological properties, Polyether-Ether-Ketone (PEEK) is widely used in aerospace, rail transit, etc. The short basalt fiber (BF) reinforced PEEK composites were fabricated to further improve the mechanical and tribological properties. With increasing BF content, the surface roughness of composites increases, while the friction coefficient decreases gradually, attributing to a certain lubricating friction film formed on the part surface. With a BF content of 25 wt%, the specific wear rate of the composites reaches the lowest value of 5.28 × 10−7m3/N·m, which is an order of magnitude lower than that of neat PEEK. Simultaneously, good ultimate tensile strength and the elongation at break were achieved, reaching 150 MPa and 31% respectively. Thermal and rheological behaviors of the composites were also investigated through differential scanning calorimetric (DSC) and rotating rheological testing to understand the effect of BF on the crystallization performance and flow abilities of PEEK composites. [ABSTRACT FROM AUTHOR]

• Polymer composite materials were reinforced by organic and/or inorganic fibers and formulated by various fillers. • Composite materials have an excellent mechanical and thermal properties. • Composite materials have a best abrasion resistance and exceptional electric insulation. Herein, in the present review we developed and investigated a comprehensive review of advanced composite materials based on thermoplastic polymers, elastomer polymers and thermosetting polymers. These advanced composite materials were reinforced by organic and/or inorganic fibers and formulated using various fillers such as organic, mineral and metallic. Further, we present the development and the synthesis of several macromolecular matrices namely polycarbonate, polyhexamethylene sebacic, polyether sulfone, polyether ether ketone, polyether ketone ketone, polyether imide, polyethylene terephthalate, phenoplasts, epoxy resin and polyurethane. The advantage of composite materials formulating is to have excellent mechanical performances, high thermal resistance, good fire behavior, high impact resistance, best abrasion resistance, exceptional electric insulation and good rigidity. Then, composite materials formulation were examined and discussed in detail. [ABSTRACT FROM AUTHOR]

• Based on the characteristics of CF/PEEK, a new manufacturing process is proposed for CF/PEEK sandwich structure. • A novel in-suit hot-pressing connection technology is proposed for the connection between the panel and the truss core. • The FE model provide a way for designers to study the low-velocity impact response of FRP sandwich structures. The composite sandwich structures, as a representative of lightweight and high-strength structures, exhibit extraordinary engineering application potential. However, the weak connection between panel and core limits their application. This paper focuses on investigating the panel-core connection and impact properties of the carbon fiber reinforced polyether ether ketone (CF/PEEK) sandwich structure with truss core. An in-suit hot-pressing connection technology distinguishing from traditional brazing (for metal materials) and bonding (for thermosetting composites) methods is proposed for connecting panels and truss cores. The low velocity impact test were carried out to investigate the impact response and failure modes of the CF/PEEK sandwich structures. The finite element (FE) model is established to predict the structural response under low velocity impact loading. The impact response of the structure is analyzed using experimental and simulation results, which are affected by relative density of core, impact energy and impact site. Besides, parametric analyses on impactor diameter and unit cell number was carried out. This work provides guidance for studying the impact performance of composite sandwich structures. [ABSTRACT FROM AUTHOR]

• Impact and Failure analysis of a complex PEEK/Ceramic/Gelatin composite system. • Behind the Armor Trauma. • Large 3-dimensional coupled thermo-elasto-plastic deformations. • Sensitivity Analysis. • Effect of reduced versus full integration rule. A ceramic-based armor system must arrest bullet penetration and dissipate a large amount of impact energy. Taking the total linear momentum transferred to the wearer of a ceramic armor as a measure of the behind-armor ballistic/blunt trauma (BABT), we study the effect on the BABT of adding a thin polyether-ether-ketone (PEEK) layer on the face of a Silicon Carbide (SiC) ceramic target impacted at normal incidence by a full metal jacket bullet traveling at a low velocity. A human torso is simulated by a block of ballistic gelatin. Three-dimensional non-linear large deformations of the system are numerically analyzed using the commercial finite element software ABAQUS/Explicit with the full integration rule to evaluate elemental matrices. Sensitivity tests are conducted with random samples generated by the Latin Hypercube Sampling technique to delineate the influence of the static yield stress, strain hardening, Young's modulus and the mass density of the PEEK layer as well as of the shear modulus, the mass density and the maximum hydrostatic tensile stress of the ceramic on the BABT. It is found that reducing the acoustic mismatch between the PEEK and the ceramic increased the plastic energy dissipated in the ceramic. For normal impact at 180 m/s of a bullet having kinetic energy of 130 J, the 2 mm thick surface layer decreased the total peak normal force, the normal impulse transmitted, and the maximum pressure transferred from the SiC target to the gelatin layer by 19%, 18% and 32%, respectively. Simulations using a reduced integration rule significantly under-predict the final kinetic energy and the back face displacement of the bullet as compared to those using the full integration rule. For the 2 mm thick PEEK layer located on the top, the middle and the bottom of the SiC plate, the back face displacement is the least for the layer located in the middle but the BABT increased. [ABSTRACT FROM AUTHOR]