Fiber Debonding Research Articles

Bonding properties of composite interface composed of concrete/magnesium phosphate cement-based ECC/CFRP plate

To prevent premature debonding of fiber reinforced polymer (FRP) from concrete surface and achieve rapid repair of flexural members, magnesium phosphate cement-based ECC (MPC-ECC) with many advantages of early strength, multi-cracking and steady-state cracking was combined with carbon fiber reinforced polymer (CFRP) to explore the feasibility of strengthening flexural members. The bonding properties of the concrete/MPC-ECC/CFRP composite interface were investigated in this study. Results showed that the higher composite interface bearing capacity can be obtained by using the MPC-ECC as a binder compared to the use of epoxy resin adhesive, which can reach 15.9 kN. In addition, it was found that a good bonding between the high-pressure water gun treated concrete and the MPC-ECC was obtained, which could ensure that the concrete/MPC-ECC interface does not fail before the MPC-ECC/CFRP interface fails. Compared with the concrete/CFRP interface, the maximum effective bond length, slip value of CFRP, and energy consumption of the concrete/MPC-ECC/CFRP composite interface are greatly improved, all of which increase with the increase of MPC-ECC thickness. Furthermore, the composite interface has obvious residual stress in the failure stage, which can avoid the sudden failure of specimens. However, the increase of curing age from 7 days to 28 days does not significantly improve the bonding performance, which reflects that the bond strength of the composite interface mainly develops within 7 days, that is, possessing good early strength characteristics.

Reducing Cf/SiC composite damages through collaborative control of laser ablating depth and grinding modes

Cf/SiC composites are regarded as difficult-to-machine aerospace materials. A low-damage surface machining of Cf/SiC composite by laser-ablating assisted grinding (LAAG) was conducted, and investigated the effects of laser-ablating depth and grinding modes on surface/subsurface damages. The results showed that ablated material depth reached 420 μm after 1200 times scanning, while the effective ablating rate was inhibited by the depth. Compared with down grinding, the grinding forces and temperatures were substantially higher in up grinding, with a maximum increase of 123.5 % and 140 % in normal and tangential grinding forces, respectively; however, micro brittle fracture and ductile removal were remarkably enhanced in normal and transverse fibers, and surface macroscopic damage has been suppressed; subsurface damage remained insignificant, mainly exhibited in internal micro cracks and minor interfacial debonding. It was attributed to cutting characteristics of up grinding. Furthermore, as grinding depth increased, the material removal behavior underwent a brittle-ductile transition and the surface roughness grew accordingly. Moreover, a laser scanning angle of 0° and up grinding facilitated the occurrence of longitudinal fiber debonding, producing larger sized fiber bundle chips. Combining up grinding with 90° scanning angle at low grinding depth was an effective method to improve the surface quality of Cf/SiC composite.

Experimental characterization on fracture behavior of UHPMC under small-scale sample tensile testing: Acoustic emission monitoring and digital image correlation

Manufactured sand (MS) was used to partially replace the traditional quartz sand (QS) to prepare a novel ultra-high-performance manufactured sand concrete (UHPMC). To better understand the fracture damage mechanism of UHPMC, small-scale sample tensile tests were conducted to investigate the tensile behavior of three types of UHPMC (low strain hardening, low strain softening and high strain softening). Acoustic emission (AE) and digital image correlation (DIC) are employed simultaneously to monitor and assess the damage characteristics of UHPMC. The results indicate that the classical AE characteristic parameters (ringing counts, duration and b-value) provide a satisfactory result in identifying the feature stages of low strain hardening and high strain softening. Based on the Gaussian mixture model (GMM) and support vector machine (SVM), an automatic probability classification algorithm has been developed that achieves the quantitative categorization of three UHPMC cracking types (shear or tensile cracks). Among them, tensile damage is dominant during the entire loading process, whereas shear damage, including aggregate dislocation and fiber debonding and pullout, accumulates during the hardening and softening stages. DIC visualization and AE source localization complement each other in identifying crack distribution, contributing to further revealing the tensile damage mechanism of UHPMC. The results obtained in this study can provide data and theoretical support for fracture damage characterization and health monitoring of ultra-high-performance concrete materials under tensile conditions.

Revealing damage evolution and ablation behavior of SiC/SiC ceramic matrix composites by picosecond laser high-efficiency ablation

The picosecond laser was utilized to fabricate the slanting microholes efficiently on SiC/SiC ceramic matrix composites. The machining damage, material oxidation, and temperature field were mainly analyzed through static and in-situ detections. The damage evolution and ablation behavior of SiC/SiC composites were qualitatively and quantitatively revealed. The results showed that the lowest peak temperature of the slanting microhole was 282.6 °C. The heat accumulation effect and thermal stress that was tensile stress in nature present caused recasts, microcracks, fiber fracture, fiber debonding, and fiber stripping. Fibers and matrix underwent slight oxidation, forming SiO2 recasts through the phase transition. The pulse energy, frequency, and inclination angle regularly affected the quantity, size, and distribution of microcracks, material removal rate (MRR), and hole wall roughness. The maximum MRR was about 2.5 mm3/s, corresponding to the minimum time was 0.9 s. The circularly polarized picosecond laser could process parallel striped laser-induced periodic surface structures (LIPSS) on the hole wall.

Investigation of the Mechanical Behaviors and Damage Mechanism of C/C Composites Impacted by High-Velocity Jets.

Carbon/Carbon (C/C) composites exhibit excellent mechanical properties at high temperatures, making them widely used in aerospace, such as the leading edges of spaceplane wings and the nose cones of hypersonic aircraft. However, damage caused by rain erosion to C/C composites affects their mechanical properties and poses significant challenges during operational service periods. A jet impingement test platform was employed to conduct single and multiple water-jet erosion tests on three-dimensional orthogonal C/C composite materials and to investigate the residual mechanical properties of the specimens after jet impact. The damage was characterized using optical microscopy, scanning electron microscopy, and X-ray computed tomography. The results showed that the damage types of the C/C composite materials under water-jet impingement included fiber bundle fracturing, delamination, and debonding. The extent of erosion damage was positively correlated with the jet velocity and diameter. The changes in the multi-jet damage indicated a cumulative expansion process, and z-directional fiber bundles exhibited superior resistance to jet impact damage propagation. The results of the three-point bending tests showed that the greater the initial impact damage, the lower the residual mechanical properties of the materials, and the residual strength of the specimen suddenly decreased when damage occurred at the back of the specimen.

Biaxial fatigue failure of short glass fiber reinforced polyamide 6,6: An in-depth investigation of stiffness drop and microstructural evolution

In the automotive industry, short glass fiber-reinforced thermoplastics are widely used under the hood and subjected to dynamic vibrations of the engine in multiple directions resulting in fatigue failure. Under fatigue loading, a significant portion of the strain energy is stored within the material, while the remaining portion is lost due to internal frictions and the damage occurrence. Internal friction results in heat generation, which in turn causes an increase in external temperature. This increase in temperature leads to thermal degradation of the polymer. Investigations on the cause of the stiffness drop are not widely available in the literature. Therefore, this study explores the source of the stiffness drop under biaxial fatigue loading of a polyamide 6,6 reinforced with 30 wt. % short glass fibers (PA66GF30) and distinguishes the contributions of thermal degradation and damage accumulation. The thermal evolution of the specimens was captured by means of thermography. In addition, the digital image correlation (DIC) technique was used to measure the in situ strain field during the fatigue. Despite the temperature stabilization being observed around the 10,000th cycle, the reduction in the stiffness continued until failure which was attributed to the mechanical damage accumulation and cyclic creep during the fatigue tests. Dynamic mechanical analyses (DMA) were carried out to quantify the stiffness drop with the varying temperature. From the results, it is seen that the damage accumulation and cyclic creep during the fatigue tests were responsible for the major part of the stiffness drop. Finally, scanning electron microscopy (SEM) inspection of the fracture surface was performed to identify fatigue damage mechanisms. Four unique features associated with the fatigue damage were identified: (1) debonding of fibers from the matrix, (2) polymer matrix crazing, and (3) cavitation and porosities, (4) pull out fiber ends and break on the fiber.

Effect of adding reinforcing phase to the interface and matrix on the interlaminar shear properties of multilayer-structured composites

Currently, poor mechanical properties limit the application of composite, especially the interlaminar shear strength (ILSS). Herein, this work employed a simple atomization deposition and co-blending method to introduce reinforcing phase on the interface and in the matrix, and then the unique multilayer-structured composites were fabricated by the technology of layer-by-layer assembly and hot-pressing. Benefiting from the presence of mechanical interlocking, hydrogen bonding, and van der Waals forces, the MXene on the interface and inside the matrix can both improve the ILSS of the composite. Specifically, when 0.5 wt% MXene nanosheets are deposited on the interface, the ILSS of the composite is increased by 21.41 %, and when 2 wt% MXene nanosheets are further introduced into the epoxy, the ILSS of the composite is improved by 55.58 %, reaching 59.96 MPa. Moreover, the ILSS of the composites shows good mechanical stability even after 30 days of storage. Besides, the failure modes of the composite were investigated, mainly including fiber debonding, matrix fracture and fiber breakage. This work adopts a facile and effective approach to prepare composites with excellent shear performance, which can provide more possibilities for the development of composites with high mechanical properties.

Fabrication and mechanical properties of TiC coated short carbon fiber reinforced Ti5Si3–TiC composites

Ti5Si3-based composites reinforced with TiC-coated Cf and TiC particulate (TiC@Cf/Ti5Si3–TiC) were fabricated by spark plasma sintering. The performance of the TiC@Cf/Ti5Si3–TiC composite was comprehensively evaluated by investigating its mechanical properties at room temperature, as well as the thermal shock resistance, oxidation resistance and flexural strength at high temperatures. By employing optimal process parameters obtained through response surface methodology, the TiC@Cf/Ti5Si3–TiC composite exhibited a maximum room-temperature fracture toughness of 9.32 ± 1.05 MPa m1/2, which represented a significant increase of 261.2% and 23.1% compared to monolithic Ti5Si3 and TiC@Cf/Ti5Si3 composite, respectively. The flexural strength of the TiC@Cf/Ti5Si3–TiC composite measured at room temperature, 1000 °C, and after quenching from 1200 °C was 531 ± 61 MPa, 299 ± 43 MPa, and 138.4 ± 15 MPa, achieving an improvement of 221.8%, 128.2%, and 295.4% compared to monolithic Ti5Si3. The incorporation of TiC particulates appeared to mitigate the fiber-matrix interfacial reaction more effectively than that observed in the TiC@Cf/Ti5Si3 composite previously investigated. Consequently, the reinforcing mechanism of fiber pulling-out and debonding, crack blocking, deflection, and bridging was fully operational at heightened sintering temperatures. These essential factors play a vital role in remarkably enhancing the mechanical properties of the TiC@Cf/Ti5Si3–TiC composite.

Additive manufacturing of high-performance CCF/SiC composites under dual protection

In this work, chopped carbon fibre reinforced silicon carbide (CCF/SiC) composites were fabricated by selective laser sintering (SLS) combined with reaction melt infiltration (RMI), using the SiC interface and pyrolytic carbon layer as a dual protection to protect the CCF from the erosion of molten silicon. The pyrolytic carbon layer encapsulates the CCF@SiC and the outer carbon preferentially reacts with silicon to form a β-SiC layer, which hinders the reaction of liquid silicon to CCF. Moreover, the fine-crystal β-SiC generated by the Si–C reaction optimizes the microstructure and enhances the mechanical performance of CCF/SiC composites. The CCF under the dual protection maintains its original high strength and high modulus, and the toughness of the CCF/SiC composites is significantly improved through the fibre debonding and fibre pull-out mechanism. The bending strength and toughness of CCF/SiC composites are 265.2 MPa and 3.5 MPa m1/2, respectively. The insights gained from this study contribute to a better understanding of microstructural engineering in SLS&RMI-fabricated CCF/SiC composites. This paves the way for future breakthroughs in composite material design and low-cost manufacturing for extreme environments.

Energy release rate for steady-state fiber debonding in structural battery composites

Structural battery composites are multifunctional materials intended to provide energy storage capacity while maintaining their strength and load bearing capacity under significant mechanical loads. In this study, we investigate the mechanics of carbon fiber debonding, a critical failure mechanism in structural battery composites. The carbon fibers are intended to serve both as an electrochemically active material and to bear mechanical load in the composite system. We derive an analytical solution to the energy release rate for steady-state fiber debonding for different electrochemical and mechanical loading cases with the aid of the classical solution for the Eshelby inclusion problem. The analytical solutions are validated with finite element simulations. We find a higher energy release rate and thus a greater driving force for fiber debonding is caused either by a lower lithium concentration in the fiber and/or by greater transverse mechanical loads such as biaxial tension or shear applied at the far field in the matrix. We find that the model is predictive even for transversely isotropic fibers despite the assumption that the fiber is elastically isotropic in the model. This work can provide guidance for the design of mechanically robust structural batteries.

Effects of fiber type, content, orientation, and surface treatments on the mechanical properties of PAFRP composite

In present scenario, natural fibers are the preferred choice of manufactures to fabricate the sustainable polymer matrix composites. These composites may be a good substitute for synthetic materials after achieving the comparable strength with some treatments. Pineapple leaf fiber (PALF) contains high cellulose with low micro fibrillar angle which leads to decent inherent fiber strength. It is used for reinforcement in the proposed work to fabricate the epoxy matrix composite using hand layup method. During testing of composite, the effects of fiber content, type, and orientations on mechanical properties have been examined. Samples were prepared by varying the fiber type (short and long fiber), fiber orientations (at 0°, 90°, and 45°) and fiber contents by weight % (i.e., 5, 10, 15 and 25). The results of mechanical characterization reveal that the tensile and flexural strength for short fiber composite is found maximum at 25% of fiber content (20.85 MPa and 42.70 MPa, respectively). However, long fiber reinforced composite with 5% of fiber content exhibits maximum tensile and flexural strength as: 35.72 MPa and 56.19 MPa. The maximum flexural strength and impact strength of composite were found as 52.98 MPa and 25.30 J m−2, respectively when the fibers are oriented at 0°. The maximum values of water absorption in composite were found as: 1.74% for short fiber and 1.25% for long fiber reinforced composites. The Fourier transform infrared radiation (FTIR) spectroscopy confirms the removal of non-cellulose contents within the composite. Finally, the morphological analysis was carried out to find the debonding, splitting and pull-out of fibers within the composites which are the major reasons of composite failure.

Dynamic tensile behavior of fiber reinforced materials based on fiber layering modeling

Among the failure forms of fiber reinforced materials, interface failure caused by fiber debonding is the most common but complex failure mode. This research proposed a fiber layering modeling method based on the different mechanical properties of the outer and inner parts of fiber yarn, then investigated the mechanical behavior of fiber reinforced materials under dynamic loads with different loading speeds. Two pullout models were established, considering the layering feature of fiber caused by the matrix penetration. The simulated results were compared with the existing experimental data to determine reliable parameters values of the fiber-matrix interface. Based on the values, another pullout model and tensile model were built. Distribution and development of stress in the loading process were discussed. Results show that fiber modeling with inner and outer parts, as well as the cohesive property with reliable parameters, could effectively represent the interface characteristics of fiber reinforced materials under dynamic load.

The influences of international standards on structural performance and fracture behaviour of 3D printed long fiber composite structures

The material properties of the additive manufactured composite structures are usually done following international standards, that show some difference dimensionally. This study focuses on the impact-induced on the tensile properties of the 3D printed continuous carbon fiber reinforced composite part due to the standards applied for sample preparation. The specimens were fabricated by Markforged® Mark two 3D printing machine using carbon fiber as reinforcement and Onyx® as matrix material based on ASTM D638 and ASTM D3039-D3039M standards. The experimental results revealed that the specimens fabricated based on ASTM D638 showed a premature failure at the location where the straight gauge section of the specimen ends, and the curved transition regions begin due to stress concentration. The tests based on ASTM D3039-3039M standard showed better tensile strength and less stress concentration compared to ASTM D638. Fracture test with SEM reveals fiber breakage, debonding, and fiber pullout, which created cavities and voids between layers as the reasons for the tensile failure.

Effect of fiber volume fraction on hybrid effects of tensile properties of unidirectional aramid/carbon fiber hybrid composites

AbstractAramid/carbon fiber hybrid reinforced polymer (A/CHFRP) composites were prepared via compression molding to obtain carbon‐fiber‐reinforced polymer (CFRP) composites with better toughness. Based on the existing theoretical model, the effects of the carbon fiber volume fraction on the properties of the A/CHFRP were studied using thermal gravimetric analysis (TGA), tensile tests, and scanning electron microscopy (SEM) analysis. According to the TGA results, the hybrid fiber improved the thermal stability of the CFRP. With increasing carbon fiber content, the thermal stability of the A/CHFRP composites also increased. The tensile results showed that the A/CHFRP composite with a carbon fiber volume fraction of 22.7% exhibited “pseudo‐ductility,” with the failure strain 54.09% higher than that of the CFRP composite. With increasing carbon fiber content, the ductility of the A/CHFRP composites decreased. The elastic modulus of the A/CHFRP composites conformed to the prediction model of the rule of mixtures (ROM). The strength was found to fall in the triangular area surrounded by the ROM and the bilinear ROM and exhibited a positive hybrid effect. The SEM results showed that the tensile failure modes of the A/CHFRP composites were mainly fiber and resin matrix debonding and fiber fracture. Brittle fracture of the carbon fibers was observed in the A/CHFRP composites, while aramid fibers appeared to peel off and silk crimp for ductile failure. Thus, this study provides a theoretical basis for toughening CFRPs.Highlights The volume ratio of the two fibers affects the hybrid effect of A/CHFRP. The thermal stability of A/CHFRP increases with increasing carbon fiber content. The carbon fiber volume ratio of 22.7% in A/CHFRP exhibited pseudo‐ductility. A/CHFRP exhibiting a failure strain 54.09% higher than that of the CFRP. The strength prediction of A/CHFRP depends on the failure mode.

Effect of fiber treatment on physical and mechanical properties of natural fiber-reinforced composites: A review

Abstract Due to environmental and financial concerns, there is a growing demand for composite materials in a wide range of industries, including construction and automotive industries. In 2020, the market for wood plastic composites was estimated to be worth $5.4 billion. By 2030, it is expected to have grown to $12.6 billion, with a compound annual growth rate of 8.9% between 2021 and 2030. The fundamental disadvantage of reinforced composites by natural fibers is the different nature of the hydrophilic lignocellulosic and the hydrophobic thermoplastic polymers, although natural fibers would lower total costs. These composites typically fail mechanically as a result of fiber debonding, breaking, and pull-out. In a fiber-reinforced composite, the matrix’s function could be described as distributing the force to the added fibers using interfacial shear stresses. A strong connection between the polymeric matrix and the fibers is necessary for this procedure. Weak adhesion at the interface prevents the composite from being used to its maximum potential and leaves it open to attacks from the environment that could damage it and shorten its lifespan. Poor mechanical performance is caused by insufficient adhesion between hydrophobic polymers and hydrophilic fibers in natural fiber-reinforced polymer composites. Consequently, during the past 20 years, a variety of chemical, thermal, and physical methods have been employed to address these issues. These methods largely concentrated on the grafting of chemical groups that could enhance the interfacial contacts between the matrix and natural fibers. This review article aimed to give information on several types of fiber treatments and natural fiber-treated composites with a specific focus on their physical and mechanical properties.

Surface damage characteristics and identification based on acoustic emission in diamond point grinding carbon/carbon ceramic matrix composites

This study mainly investigated the effect of machining parameters on acoustic emission (AE) characteristics in grinding three-dimensional carbon/carbon ceramic matrix composites with superabrasive diamond grinding points. Signal processing techniques including fast Fourier transform (FFT) and short-time Fourier transform (SWFT) were applied to evaluate frequency features of AE signals. The RMS values were used as an indicator to detect grinding energy releasing characteristics. Results indicated that grinding speed and grinding depth were the main influencing factors on RMS values, while feed speed presented limited effects. The maximum undeformed chip thickness hmax and active grits number were two key factors affecting RMS variation of the AE signals, which corresponded to the intensity of single AE source and the number of total AE ones, respectively. The material removal mechanisms were studied via detailed SEM micrographs of machined surfaces, revealing that fiber fracture and debonding were the main material removal modes in point grinding carbon/carbon composites. The material removal mode can be possibly identified from the frequency of AE signal, as the band of 12–35 kHz mainly corresponded to fiber fracture, 35–70 kHz referred to debonding between the fiber and matrix, 70–90 kHz indicated the frictions, and the fourth band (90–120 kHz) was related to the matrix cracks.

Analyzing the effect of fiber path curvature on the fracture behavior of braided composite cylinders; experimental study

AbstractDifferent failure modes occur in textile‐reinforced composite under applied loads. Fracture mechanism of braided composites are closely related to the geometry of braids. In the present study, fracture mechanism of glass/epoxy braided composite cylinders is investigated under tensile loads. For this purpose, glass/epoxy braided composites were fabricated using braids with braiding angles of 30°, 45°, and 57° to find the role of fiber path on the fracture mechanism. To determine the fiber path, helixes on the cylinders with aforementioned angles was considered and analyzed. New fixtures (jaws) were designed and manufactured for tensile testing of cylindrical composites. Tensile tests were carried out on the prepared samples to evaluate the failure modes of composites. The SEM micrographs of samples are provided after tensile test. Various failure modes were observed regarding the angle of the braid. Fiber breakage, matrix fracture, and debonding are the dominant modes that occur in braided composites proportional to the angle of braids. Fiber breakage is the dominant mode in the 30° angle braid reinforced composite, while the dominant failure mode in the 57° angle braid reinforced composite is matrix fracture. In composites with a braid angle of 45°, a combination of fracture modes occurred. In addition, energy absorption as well as specific energy absorption (SEA) of braided composite cylinders were also investigated and obtained from load–displacement curves. The results showed that the reinforced composite with a braid angle of 30° absorbs the lowest amount of energy (21.5 J) and also the lowest amount of specific energy (5375 J/kg). The maximum absorbed energy (67.7 J) and the maximum SEA (9675 J/kg) were observed in the reinforced composite with a braid angle of 45°.Highlights Fiber breakage is the dominant mode at the 30° angle braid reinforced composite. The dominant failure mode at the 57° angle braid reinforced composite is matrix fracture. In composites with the braid angle of 45°, a combination of fracture modes occurred. The composite reinforced with a braid angle of 30° absorbs the lowest amount of energy (21.5 J) and also the lowest amount of specific energy (5375 J/kg). The maximum absorbed energy (67.7 J) and the maximum SEA (9675 J/kg) were observed in the reinforced composite with a braid angle of 45°.

Interface failure identification of argon/nitrogen double plasma modified hybrid laminated para‐aramid composites

AbstractThis work reveals the synergistic effect of argon/nitrogen double plasma alteration on the mechanical properties of para‐aramid fiber/epoxy resin composites with various laminating sequences. Acoustic emission monitored interface failure during tensile, bending and fracture testing. A comparative analysis was conducted on the bending performance of the composites modified by argon/nitrogen double plasma and single plasma. The results showed that the synergistic effect of nitrogen and high‐energy molecule argon optimized the modifying effect of argon/nitrogen double plasma. The optimal modification parameters obtained through fiber extraction testing analysis are power 200 W, time 120 s, and Ar/N2 double gas flow rate of 12 sccm. After plasma treatment, twill weave modifies better than plain weave. The AE signal amplitude of PX1 is minimized during stretching. Due to the difference in internal bending stiffness of PX2, interface delamination failure is more likely to occur. The PX5 had greater fiber and matrix debonding failure between mode‐II fracture tests due to the weak modification effect of plain weave and its difficulty in deformation. In ballistic testing, PX1 blocks impact force through fiber bundle stretching deformation, while PX4 is more brittle.Highlights Prepare para‐aramid/epoxy resin composites with various laminating sequences. Study on the interfacial properties of composites treated with double plasma. The composites with different gas sources treatment were analyzed. Acoustic emission analysis was used to identify interface failure modes. The bonding strength between plain and plain interfaces is the lowest.

Effect of interfacial coatings on mechanical properties of 2.5D Nextel™ 720 fiber toughened zirconia-mullite matrix composites

In this study, 2.5D bent shallow cross-linked structure Nextel™ 720 (N720) fiber-reinforced yttria-stabilized zirconia-mullite composites with pyrolytic carbon (PyC) and fugitive pyrolytic carbon (FC) interfacial coatings were prepared by using a precursor infiltration and pyrolysis approach (called as N720f/PyC/YSZ-Mu and N720f/FC/YSZ-Mu, respectively). The effects of PyC and FC coatings on the failure mechanisms and mechanical properties of the composites were investigated. The N720f/PyC/YSZ-Mu composite shows ductile fracture behavior while the N720f/FC/YSZ-Mu composite shows brittle fracture behavior. The fracture toughness and flexural strength of the N720f/PyC/YSZ-Mu composite reach ∼7.00 MPa·m1/2 and ∼ 120.79 MPa, respectively. In contrast, the corresponding properties of the N720f/FC/YSZ-Mu composite are ∼3.66 MPa·m1/2 and ∼ 59.02 MPa, respectively. Microstructure analysis indicates that the weak PyC interfacial layer contributes to toughening by promoting fiber pull-out and debonding, thus enhancing the mechanical properties of the N720f/PyC/YSZ-Mu composite. The retrogression of the mechanical properties of the N720f/FC/YSZ-Mu composite originates from the damage to N720 fibers during the preparation procedure. This paper provides a new idea for the development of high-performance oxide CMCs with a 2.5D structure.

Cutting performance and wear behavior of diamond, coated cemented carbide and PCBN tools during milling of Cf/SiC composites

As an advanced material, Cf/SiC composites are wildly used in many aerospace industries due to their excellent properties. However, machining the material often encounters many problems, such as poor machining quality, severe tool wear, and low processing efficiency. Tool materials have a significant influence on the cutting performance of tools and the surface quality of the workpiece being machined. In this study, milling experiments have been performed on Cf/SiC composites with different tools. The tool wear pattern, progression, mechanisms, and milling temperature were investigated. The machined surface quality and removal mechanisms of Cf/SiC composites were studied. The results indicated that polycrystalline diamond (PCD) tools have better cutting performance in milling Cf/SiC composites than other tools. Surface defects, milling temperature, and machined surface roughness (Sa = 2.9 μm) obtained by machining Cf/SiC composites using the PCD tool would be lower. The material removal mode is brittle fracture, and the surface damage (including fiber debonding, fiber pullout, and pits, etc.) is related to the direction of the fibers. Fibers in the X and Y directions can lead to more machined surface defects. Since hard particles formed in the machining process and protruding fibers constantly scratched the flank face, diamond grains were spalled off from PCD tools, resulting in abrasive wear.