Drilling of carbon fiber reinforced polyetheretherketone (CF/PEEK) is prone to burr and delamination damage due to coupled thermal-mechanical effects. A double-angle drill featuring a double-top angle and an outer-edge tip is developed based on cutting-edge decomposition to mitigate such damage. The drilling process of this drill is analyzed, and drilling experiments are conducted on CF/PEEK composites. Results demonstrated that the double-angle drill demonstrated the best cutting performance. In comparison with the traditional twist drill, the double-angle drill reduces the average thrust force and drilling temperature by 45.09% and 10.54%, respectively. This reduction is attributed to the shortened contact length between the cutting edge and chips, as well as the progressive cutting achieved by multiple cutting edges. Moreover, the double-angle drill generated a lower delamination and burr factor, which can be attributed to its independent cutting tips. This design minimizes extrusion and thermal effects during the formation of the machined surface, thereby reducing hole-making damage. This study presents a new methodology for improving the drilling quality of CF/PEEK composite.

The geometry of cutting tools has a critical impact on the hole-making quality of carbon fiber-reinforced polyetheretherketone (CF/PEEK), which in turn significantly influences the mechanical properties and service life of connected components. Based on the cutting-edge decomposition, a double-angle drill with a double-top angle and an outer-edge tip is proposed. A comparative study is performed to evaluate the static tensile performance of drilled thermoplastic CF/PEEK using conventional twist and double-angle drills. The complex strain distribution around the hole edges is examined using the digital image correlation (DIC). The findings indicated that compared with the twist drill, CF/PEEK laminates drilled with the double-angle drill exhibit superior tensile performance, consistent with the lower degree of drilling-induced damage. Furthermore, drilling-induced damage is found to influence the surface strain distribution around the holes. Observed fiber fracture and crack propagation corresponded well with high-strain zones identified via DIC around the hole periphery. These findings provide useful guidance for evaluating machining quality and achieving low-damage drilling of thermoplastic composites.

Fabrication of conductive polymer composites (CPCs) with segregated structure to achieve electromagnetic interference (EMI) shielding while maintaining mechanical properties remains a challenging issue. In this work, high strength polyether-ether ketone (PEEK)/carbon nanotubes (CNTs) composites with segregated conductive networks were facilely fabricated via microwave sintering (MS). The selective heating behavior and temperature distribution during MS were investigated from both macroscopic and microscopic perspectives, revealing a unique heating mechanism. The coated CNTs layer was selectively heated under microwave irradiation, leading to welding of the PEEK matrix. This promoted molecular entanglement across interfaces, improving mechanical properties while maintaining the integrity of the segregated structure. Consequently, PEEK/5 wt% CNTs composites fabricated by MS exhibited excellent conductivity (17.3 S/m) and EMI SE (31.7 dB) in the X-band region, along with a high tensile strength of 81.2 MPa, which was 54.1 % higher than that of CM sample with comparable electrical properties. Finally, this technique was innovatively applied for weld repair of fractured samples. This study provides a novel, economical and energy saving strategy not only for the rapid fabrication of high strength PEEK/CNTs composites with segregated structure, but also for the field of rapid weld repair of polymer materials.

This paper presents a damage identification method based on the Root-Mean-Square of multi-order modal curvature difference (RMS-MCDI). A Warren-type steel truss girder bridge (STGB) was investigated using finite element analysis and impact testing under four damage scenarios. Modal analysis yielded the parameters of the first two vertical bending modes, from which the RMS-MCDI index was constructed. The results show that Damage Index (DI) exhibits pronounced changes at damage locations, enabling accurate detection and localization of damage. The mean peak of DI for the diagonal braces damage exceeds that for chords damage, indicating a stronger effect on the global dynamic characteristics. Under the predefined damage scenarios, the chord members show a larger standard deviation of abrupt changes, that its influence is more confined to the region near the damage. Comparative analysis of DI statistics enables damage identification for steel truss bridge across different operating conditions.

Electromagnetic wave-absorbing materials with lightweight, low-thickness, and good heat dissipation properties are crucial in practical applications. Graphite materials are widely used in heat dissipation and electromagnetic absorption. However, excessive conductivity can worsen impedance matching. In this study, we successfully designed and fabricated weakly oxidized spherical expanded graphite (SEG) materials and corresponding SEG/Polydimethylsiloxane (PMDS) composites through structural and compositional engineering. The SEG/PDMS composites with a 6-wt

Carbon fiber reinforced thermoplastic composites (CFRTP) are increasingly becoming critical lightweight and high-efficiency materials in manufacturing fields such as aerospace and defense technology, owing to their high strength, high modulus, and environmentally friendly recyclability. As a high-performance CFRTP, carbon fiber reinforced polyetheretherketone (CF/PEEK) composites are typically joined with other materials through drilling, where the thrust force is a key parameter affecting hole quality. A novel predictive model for the thrust force in unidirectional CF/PEEK (UD-CF/PEEK) composites was established based on the two-parameter elastic foundation theory and Hertz contact, taking into account tool structure and material characteristics. Experimental validation results showed that the prediction errors for the thrust forces of the chisel edge and the main cutting edge were 1.46% and 8.89%, respectively, and the prediction error for the total thrust force was 6.27%. Furthermore, by investigating the influence of different drilling parameters on the thrust force of UD-CF/PEEK, it was found that at a constant spindle speed, an increase in the feed rate leads to a rising trend in the thrust forces of both the chisel edge and the main cutting edge. This finding provides theoretical guidance for low-damage hole-making in thermoplastic CF/PEEK composites.

For the first time, this paper proposes a new strategy based on crystallinity control in enhancing the flexural strength of drilled carbon fiber reinforced polyetheretherketone (CF/PEEK) composite laminate. The high-positive correlation between the unique crystalline characteristic of the CF/PEEK composite and its flexural strength is introduced into the strategy, and the superposition of pre-heat treatment, intermediate-heat treatment, and post-heat treatment is carried out to increase the crystallinity. The optimal heat treatment temperature of 320 degrees C is identified through in situ X-ray Diffraction (XRD) patterns. The results show that the proposed strategy effectively increased the crystallinity by 21.70%, leading in turn to an increase the flexural strength of the CF/PEEK by 19.56%. The heat treatment compacts the molecular chains, enhancing the intermolecular interactions, which in turn result in increased thrust force in the drilled laminate. Four-point flexural loading experiments of the open-hole laminate reveal that CF/PEEK generates compression and tension failures at the macroscopic level and interlaminar and intralaminar failure at the microscopic level. Finally, the enhancement mechanism is elucidated, in which the transcrystallization of the matrix PEEK caused by heat treatment results in stronger bonding strength between the fiber and matrix, ultimately leading to an improved flexural strength of the drilled CF/PEEK laminate. Highlights Novel strategy enhances CF/PEEK flexural strength via crystallinity control. 21.70% crystallinity increase boosts CF/PEEK flexural strength by 19.56%. Optimal heat treatment at 320 degrees C is identified for CF/PEEK composites. Flexural tests reveal compression, tension, and interlaminar failures in CF/PEEK. Heat treatment fosters crystallization, improving CF/PEEK flexural strength.

In this paper, experimental hole-making tests were conducted on CFRP/Al stacks. The effects of different stacking sequences (CFRP, CFRP/Al, Al/CFRP) on drilling temperature, thrust force, and hole-making quality were studied. The influence of hole-making damage on the residual tensile strength and strain distributions of open-hole laminates were investigated by digital image correlation and mechanical experiments. The results indicate that the drilling temperature and thrust force of laminates can be increased by adding aluminum metal layers in the process of hole-making. Compared with CFRP laminates without aluminum metal layers, the hole-making damage of CFRP/Al lamination at the exit of CFRP holes is less, and the tensile strength of the open-hole CFRP increased by 3.03

2.5D C/SiC composite has been a critical high temperature material for aerospace filed due to its excellent wear, high temperature and oxidation resistance. Understanding the cutting damage behavior is crucial for achieving the high reliability application. This paper presents an in-depth study on damage behavior and material removal mechanism during orthogonal cutting of 2.5D C/SiC composite based on multi-scale modeling and high-speed photography. A three-dimensional numerical micro-macro multi-scale model is established considering the characteristics of the brittle SiC matrix, the isotropic carbon fiber reinforcement, and the pyrolytic carbon (PyC) layer. The orthogonal cutting experiments of 2.5D C/SiC composite with high-speed photography technology is carried out. The results show that the proposed model can accurately predict the microscopic deformation and fracture of the fiber. Meanwhile, surface fiber spring-back phenomenon is found based on high-speed photography, and its mechanism is first explanation based on the stress evolution analysis of the multi-scale model. In addition, it indicates that the increase of the depth of cut has a significant impact on the chip shape evolution, transitioning from powdery, needle-like, to block-like or strip-like shape. The paper covers some new sights for low-damage cutting of 2.5D C/SiC composite materials.

Remelting and remolding characteristics of thermoplastic resin make the carbon fiber-reinforced polyether-ether-ketone (CF/PEEK) composite process unique recyclability and reusability, while thermal characteristics play the crucial mechanism. This paper presents a comprehensive investigation on thermal characteristics of CF/PEEK drilling in terms of the heat transfer mechanism, crystallinity, and hole making performance. Crystallinity is introduced to quantitatively evaluate the change of material performance for CF/PEEK drilling where the crystallinity is positively correlated with tensile strength. Parameter analysis shows that the increased spindle speed leads to the increase of drilling temperature, crystallinity, and slightly deduces the tensile strength of CF/PEEK. The heat transfer curve of CF/PEEK drilling was first obtained and it is found that the heat transfer experiences three stages, namely steady rising, slow falling, and fast falling stage. Crystallinity comparative analysis between the hole wall and chips reveal that heat transfer effect dramatically affects the crystallinity when the drilling temperature exceeds the glass transition temperature (142 °C). Further, high temperature-induced PEEK smearing effect reduces the fiber exposure and surface roughness of hole wall but increases the crack appearance. The work provides important guidance for the high quality drilling of CF/PEEK composites from the point of view of the thermal characteristics.

Thermoplastic carbon fiber reinforced polyetheretherkrtone (CF/PEEK) and thermoset carbon fiber reinforced epoxy (CF/epoxy) composites are being widely applied in aviation and aerospace fields for their excellent performance. To compare the drilling characteristics of two typical carbon fiber reinforced composites under varying feed speeds, drilling experiments were carried out using three different special drills involving twist, brad, and dagger drills. The drilling performance of CF/epoxy and CF/PEEK composites was analyzed in terms of chip morphology, drilling temperature, thrust force, delamination damage, and surface morphology. The results show that CF/PEEK composites produced continuous chips, so that CF/PEEK composites generated higher drilling temperature and thrust force than that of CF/epoxy composites. CF/epoxy composites showed larger delamination damage and poorer machined surface than CF/PEEK composite due to its poor interlaminar toughness. Burrs produced agglomeration and crimping at the hole edges of the CF/PEEK composites due to PEEK resin is softened by heat, matrix plastic deformation. Brad drill revealed fewer burrs and merely a tearing damage at the exit. Dagger drill showed more burrs. The hole wall damage is minimal for brad drill. The results provide guidance for drilling of high quality thermoset and thermoplastic composites.

This 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 degrees C, and the limiting crystallization temperature is 344.5 +/- 0.7 degrees 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 degrees C. Heat-induced PEEK smearing effect improves the surface quality of CF/PEEK drilling.

Vibration-assisted cutting (VAC) is an effective way of improving machining quality. Through vibration-assisted cutting experiments, the cutting mechanism of carbon fiber-reinforced polyetheretherketone (CF/PEEK) composites during vibration-assisted cutting and the influencing factors on the quality of machined surfaces were investigated. The effect of cutting-directional vibration-assisted (CDVA) and normal-directional vibration-assisted (NDVA) on cutting force, cutting temperature evolution, chip and surface morphology were analyzed. The experimental results demonstrate that compared with the traditional cutting (TC), the cutting ability of the tool in VAC was enhanced. When the fiber orientation is 0°, 45°, 90° and 135°, the maximum reduction of cutting force in CDVA is 36.48

This is the first investigation on the potential of doubled-sided laser drilling for hole making in Ti6Al4V-C/SiC, a hard-to-machine stacked structure that holds critical significance in high-temperature structural applications. While previous literature reported laser drilling-induced microstructural change in Ti6Al4V and C/SiC single sheets respectively, a comprehensive understanding of the melt pool formation process and its influence on hole morphology/quality is still lacking. The complexity increases when Ti6Al4V is coupled with C/SiC in a stacked structure, highlighting a significant yet understudied knowledge gap in understanding the intricate material interactions at the interface. Here we present a multifaceted study combining novel computational fluid dynamics (CFD) modeling approach with ablation mechanism investigation through advanced microstructure analysis. A hybrid CFD modeling strategy integrating volume of fluid method and level set method has been developed to successfully simulate the evolution of hole shape, recast layer formation, and melt pool flow behaviour in Ti6Al4V-C/SiC. This model provides comprehensive insights into molten pool dynamics under various laser drilling conditions, fostering a fundamental understanding of the mechanism that drives recast layer formation and influencing surface quality. To validate our modeling outcomes, extensive experimental investigations were undertaken across a range of laser drilling conditions. Whenever possible, samples were analysed using advanced materials characterization techniques, including scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction, to elucidate the microstructural evolution within the recast layer and the formation of the heat-affected zone. Whenever possible, the results were also compared with single side drilled Ti6Al4V-C/SiC stacks, Ti6Al4V or C/SiC single sheets (i.e., the benchmark references). Our experimental findings align well with the modeling results, systematically illustrating that doubled-sided laser drilling of the stacked structure outperforms the conventional single-sided laser drilling in terms of hole morphology, surface roughness, and reduced recast layer formation. Despite these promising results, the proposed technology is currently limited to laboratory scales and lacks capacity in manufacturing certain parts with complex geometry. Future outlook has therefore been proposed with potential solution to address these challenges and enable real world applications in future.

Removable joint technology is commonly used in composite laminates for various load-bearing structures. However, existing research primarily focuses on bolted joints, there is relatively limited research on screwed joints in composite materials. This study investigates the influence of connected layer thickness and hole diameter on the tensile behavior of threaded joints in carbon fiber-reinforced polymer (CFRP) laminates. After fabricating different CFRP screwed joint specimens, tensile tests were conducted. The digital image correlation (DIC) technique captured the deformation process. The experiment results indicate a significant increase in load-bearing capacity with the increase in diameter. For instance, joints with an 8 mm diameter exhibited a load-bearing capacity of 10.82 kN. The increase in the connected layer thickness correspondingly enhanced the load-bearing capacity of the joint. The joint with a thickness of 7 mm had the highest load-bearing capacity of 8.83 kN. Besides, with the increase in the thickness of the connected layer, the failure mode transitioned from shear failure in the connected layer to screw pull-out. The tilt angle of the screw during the pull-out process also decreases with the increase in the connected layer thickness. Strain and out-of-plane displacement measurements under ultimate load conditions verify these observations.

为改善碳纤维增强聚醚醚酮复合材料(CF/PEEK)在铣削加工时所产生的毛刺、分层以及表面凹坑等缺陷,采用超声辅助铣削的加工方式分别沿0°、45°、90°、135°四种纤维方向角对CF/PEEK进行实验,并与传统铣削进行对比研究.结果表明:超声辅助铣削与传统铣削相比,切削力更小且加工质量更优.沿90°纤维方向角对试件进行超声辅助铣削,切削力、表面粗糙度和毛刺高度降幅最显著,分别降低了 16.79％、28.9％和71.9％.而且在相同的加工参数下,超声辅助铣削与传统铣削相比,能够有效地改善表面凹坑、分层等表面缺陷.

碳纤维增强铝合金层合板(CARALL)是一种较新的纤维金属层压材料.为研究CARALL层合板的螺栓连接性能,采用热压罐固化成型工艺制备试件,对其螺栓连接结构进行准静态拉伸试验.对接头在承受准静态拉伸载荷时的失效过程进行了讨论,失效模式涵盖铝合金塑性变形、碳纤维断裂和界面分层.针对CARALL各层的不同材料成分分别建立失效模型,并采用VUMAT子程序实现了基于三维Hashin失效准则对CFRP层的渐进损伤分析.试验与有限元预测的极限载荷相对误差为8.9％,且所提出的模型能较准确预测试件发生分层失效的位置,证明了该模型能够有效地预测碳纤维增强铝合金层合板单钉螺栓连接结构的力学性能.

To detect rail top surface defects, NdFeB toroidal permanent magnets were firstly used to excite the rail detection area, and the magnetic excitation direction was perpendicular to the rail direction. So that, the magnetic circuit can be analyzed, and the model was verified by finite element simulation. Secondly, the artificial rectangular defect samples were machined on the top surface of the rail, and the magnetic field data acquisition system was developed and equipped on the inspection vehicle. With that, a linear array which consisted of three-dimensional hall sensors was designed to detect the magnetic leakage field signal from the defect samples. Finally, the features of the leakage field signal in each dimension were extracted. And then, the length, width, and depth of the defects were predicted using BP neural network algorithm. The results indicate that the method can improve the excitation efficiency, and the average absolute errors of prediction for defect length, width, and depth were 1.43 mm, 1.01 mm, and 0.63 mm respectively.

Tool geometry can significantly influence hole quality during drilling of CFRP laminates, which has impact on mechanical properties. In this paper, drilling experiments with different drill bit geometries (twist, brad and dagger drill) are carried out on carbon fiber reinforced polyetheretherketone (CF/PEEK) composites. The influence of tool geometry on drilling temperature, thrust force, and hole-making quality are analyzed. The effect of machining-induced damage on the tensile properties of CF/PEEK composites with machined hole are investigated. The strain distributions around the holes were measured using digital image correlation (DIC). The results indicate that PEEK is softened by heat, the matrix is plastically deformed, and the edge burrs of the hole are curled and agglomerated. The best hole-making quality is obtained by brad drill. Compared to the tensile strength of undrilled laminates, the tensile strength of the laminates drilled with brad, dagger and twist drills decreases by 51.47%, 53.99% and 56.09%, respectively. The strain distribution of open-hole laminates with different machining-induced damage shows obvious difference. The fracture mode of matrix cracking, fiber splitting, delamination, fiber pull-out and debonding are mainly observed. The research results in this paper can provide reference for the optimization of CF/PEEK composites drilling process.

Here, we designed a flexible, highly adaptive, self-Standing photoelectrochemical (PEC) aptasensor for Aflatoxin B1 (AFB1) detection based on BiOBr/TiO2 hierarchical nanofiber membranes (NFM) with a 3D pinecone-like structure by integrating sol-gel electrospinning with the successive ionic layer adsorption and reaction (SILAR) method. The uniformly deposited BiOBr nanosheets could not only enlarge the surface area but also expand the light absorption range of TiO2 NFM. Owing to the pinecone-like and hierarchical structure, the photogenerated carriers of BiOBr/TiO2 NFM could be separated quickly and efficiently, which was contributed to obtain a larger and more stable photocurrent intensity. The photocurrent intensity of 6-BiOBr/TiO2 NFM was 12.1 times of pristine TiO2 NFM and 3.4 times of pure BiOBr, respectively. The constructed flexible and selfStanding PEC aptasensor has achieved AFB1 detection in tomato samples with good repeatability, specificity and sensitivity. Under the optimized conditions, a wide linear range (0.001-400 ng mL-1) and a detection limit of 0.12 pg mL-1 (S/N = 3) were obtained for AFB1 determination. This design principle provided a neo-idea for development of flexible and self-Standing PEC aptasensor.