Enhanced glass fiber-reinforced phenolphthalein poly(ether ketone) composites by blending poly(phenylene sulfide)

The mechanical properties of glass fiber-reinforced phenolphthalein poly(ether ketone)/ poly(phenylene sulfide) (PEK-C/PPS) composites have been studied. The morphologies of fracture surfaces were observed by scanning electron microscope. Blending a semicrystalline component, PPS, can improve markedly the mechanical properties of glass fiberreinforced PEK-C composites. These results can be attributed to the improvement of fiber/matrix interfacial adhesion and higher fiber aspect ratio. © 1996 John Wiley & Sons, Inc.     

Enhanced mechanical properties in Cf/LAS composite with yolk-shell structure interface

A new approach to improve the interfacial matching of carbon fiber-reinforced lithium-aluminum-silicon(C_f/LAS) composites is proposed, which is achieved by Ni nanoparticles catalyzing the formation of a tunable graphite layer on the surface of C_f. The interfacial structure between the composites can be effectively improved by tuning parameters such as Ni²⁺ content and sintering holding time, and ultimately, the mechanical properties of the composites can be improved. Interestingly, due to the introduction of Ni²⁺, a yolk-shell type graphite layer is formed between the C_f and LAS, and the bridging effect of the graphite layer improves interfacial bonding. The highest flexural strength (515 ± 30 MPa) and fracture toughness (14.7 ± 1.6 MPa·m^1/2) were obtained. Taking C_f/LAS as an example, the relationship between interfacial matching and mechanical properties of composites is systematically investigated and may provide a new idea for the improvement of mechanical properties of fiber-reinforced composites.     

Preparation and characterization of 3,3′‐bis (maleimidophenyl)phenylphosphine oxide (BMI)/polysulfone modified epoxy intercrosslinked matrices

An intercrosslinked network of polysulfone (PSF)—bismaleimide (BMI) modified epoxy matrix system was made by using diglycidyl ether of bisphenol A (DGEBA) epoxy resin, hydroxyl terminated polysulfone and bismaleimide (3,3′‐bis(maleimidophenyl) phenylphosphine oxide) with diaminodiphenylmethane (DDM) as curing agent. BMI–PSF–epoxy matrices were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and heat deflection temperature (HDT) analysis. The matrices, in the form of castings, were characterized for their mechanical properties such as tensile strength, flexural strength, and unnotched Izod impact test as per ASTM methods. Mechanical studies indicated that the introduction of polysulfone into epoxy resin improves the toughness to an appreciable extent with insignificant increase in stress–strain properties. DSC studies indicated that the introduction of polysulfone decreases the glass transition temperature, whereas the incorporation of bismaleimide into epoxy resin influences the mechanical and thermal properties according to its percentage content. DSC thermograms of polysulfone as well as BMI modified epoxy resin show a unimodal reaction exotherm. The thermal stability and flame retardant properties of cured epoxy resins were improved with the introduction of bismaleimide and polysulfone. Water absorption characteristics were studied as per ASTM method and the morphology of the BMI modified epoxy and PSF‐epoxy systems were studied by scanning electron microscope. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Influence of carbon nanotubes on the thermal, electrical and mechanical properties of poly(ether ether ketone)/glass fiber laminates

Novel poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT)/glass fiber laminates incorporating polysulfone as a compatibilizing agent were fabricated by melt-blending and hot-press processing. Their morphology, mechanical, thermal and electrical properties were investigated and compared with the behavior of similar non-compatibilized composites. Scanning electron micrographs demonstrated better SWCNT dispersion for samples with polysulfone. Thermogravimetric analysis indicated a remarkable improvement in the thermal stability of PEEK/glass fiber by the incorporation of SWCNTs wrapped in the compatibilizer, ascribed to a significant thermal conductivity enhancement. Differential scanning calorimetry showed a decrease in the crystallization temperature and crystallinity of the polymer with the addition of both wrapped and non-wrapped SWCNTs. The laminates exhibit anisotropic electrical behavior; their conductivity out-of-plane is lower than that in-plane. Dynamic mechanical studies revealed an increase in the storage modulus and glass transition temperature in the presence of polysulfone. Mechanical tests demonstrated significant enhancements in stiffness, strength and toughness by the incorporation of wrapped nanofillers, whilst the mechanical properties of non-compatibilized composites only improved marginally. Samples with laser-grown SWCNTs exhibit enhanced overall performance. This investigation confirms that SWCNT-reinforced PEEK/glass fiber compatibilized composites possess excellent potential to be used as multifunctional engineering materials in industrial applications.     

Improvement of polyimide/polysulfone composites filled with conductive carbon black as positive temperature coefficient materials

In this study, polyimide (PI)/polysulfone (PSF) blends filled with carbon black (CB) were developed for the use as positive temperature coefficient (PTC) materials in order to achieve the volume resistivity as lower than 10⁴ Ω.cm at room temperature. The weight ratios of PI/PSF were various from 100/0 to 10/90 with CB varied from 0 to 20 wt%. The use of conductive filler was reduced when PSF was blended with PI; the blends clearly possessed a percolation threshold decreased by 90%. The electrical conductivity of the CB-filled blends was higher than those of CB-filled pure PI. The transition temperature for PTC material was reported in the range of 180 to 210 °C. The preferential location of CB filler in PI domains could be observed using the optical microscope. In addition, the composites met the standards for the obtained mechanical and thermal properties, exhibiting the potential use as PTC materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48482.     

Mechanical and microwave dielectric properties of SiCf/SiC composites with BN interphase prepared by dip-coating process

The BN interphase of SiC fiber-reinforced SiC matrix (SiCf/SiC) composites was fabricated by dip-coating process with boric acid and urea as precursor. The results show that the tensile strength of SiC fiber decreases about 30% after BN coating treatment, but the BN coating has little influence on the electrical resistivity of SiC fiber. Compared with the as-received SiCf/SiC composites, the SiCf/SiC composites with BN interphase exhibit a toughened fracture behavior, and the flexural strength is about 2 times that of the as-received SiCf/SiC composites. From the microstructural analysis, it can be confirmed that the BN interphase plays a key part in weakening interfacial bonding, which can improve the mechanical properties of SiCf/SiC composites remarkably. Owing to the close dielectric properties between SiC and BN, the complex permittivity of SiCf/SiC composites with and without the BN interphase is similar.     

Characterization of thermotropic liquid crystalline polyester/polysulfone blends

The morphology, rheology, and mechanical properties of blends of polysulfone (PSF) with up to 65% of a wholly aromatic liquid crystalline polymer (LCP) were investigated. In injection molded specimens a skin-core morphology was observed with the LCP minor phase oriented in the skin and globular in the core. Scanning electron microscopy of fractured surfaces showed sharp phase boundaries, suggesting low interfacial adhesion. The neat PSF and blends with low amounts of LCP exhibited a low shear Newtonian plateau not observed in the blends with high LCP levels. The addition of LCP to PSF resulted in an increase in stiffness, a small increase in tensile strength, and a significant improvement in processability.     

Biochar as a filler in mixed matrix materials: Synthesis,characterization, and applications

The use of mixed-matrix materials (MMM) has become a major topic of research in recent years, due to unique properties achieved in these composites. In this work, biochar from sunflower seed hull pyrolysis and biochar/polysulfone (PSF) MMMs were produced and characterized. The optimal pyrolysis temperature for biochar production was determined to be 500 °C. The resulting biochar properties were an iodine number of 203 mg/g and a pore volume of 0.595 mL/g. In MMM fabrication, the use 4% ethanol as nonsolvent in the wet phase inversion process increased the glass transition temperature by 8 °C, indicating improved biochar/PSF interaction. The presence of biochar was shown to create pores in otherwise dense surfaces. The critical surface energy was also increased by the addition of biochar from 28.6 mN/m in pristine PSF to 35.7 mN/m in biochar/PSF MMMs. We identified and discussed several potential applications based on the determined properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48027.     

环氧胶粘剂的韧性与增韧机理

本文通过测定三种典型环氧结构胶粘剂：环氧-聚矾，环氧-丁腈40环氧-CTBN的动态力学性能，剥离强度和断裂韧性，观察其断面的电镜照片，分析了三者不同的韧性特点和增韧机理。并发现了PSF改性胶固化后奇特的两相结构。     

Effects of heat treatment on mechanical and dielectric properties of 3D Si3N4f/BN/Si3N4 composites by CVI

In this study, three-dimensional silicon nitride fiber-reinforced silicon nitride matrix (3D Si₃N_4f/BN/Si₃N₄) composites with a boron nitride (BN) interphase were fabricated through chemical vapor infiltration. Through comparing the changes of microstructure, thermal residual stress, interface bonding state, and interface microstructure evolution of composites before and after heat treatment, the evolution of mechanical and dielectric properties of Si₃N_4f/BN/Si₃N₄ composites was analyzed. Flexural strength and fracture toughness of composites acquired the maximum values of 96 ± 5 MPa and 3.8 ± 0.1 MPa·m^1/2, respectively, after heat treatment at 800 °C; however, these values were maintained at 83 ± 6 MPa and 3.1 ± 0.2 MPa·m^1/2 after heat treatment at 1200 °C, respectively. The relatively low mechanical properties are mainly attributed to the strong interface bonding caused by interfacial diffusion of oxygen and subsequent interfacial reaction and generation of turbostratic BN interphase with relatively high fracture energy. Moreover, the Si₃N_4f/BN/Si₃N₄ composites also displayed moderate dielectric constant and dielectric loss fluctuating irregularly around 5.0 and 0.04 before and after heat treatment, respectively. They were mainly determined based on the intrinsic properties of materials system and complex microstructure of composites.     

Three-dimensional carbon fiber-reinforced silicon carbide matrix composites by vapor silicon infiltration

Three-dimensional carbon fiber-reinforced SiC matrix composites (C_f/SiC) were fabricated by vapor silicon infiltration (VSI) successfully. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and wavelength dispersive spectrometer (WDS) analysis revealed that the microstructure and composition of constituent phases are strongly dependent on temperature. At 1973 K, the obtained C_f/SiC composite mainly consists of SiC, carbon fiber and residual Si, and shows a densified microstructure. The flexural tests show non-catastrophic fracture behavior for composites fabricated by VSI process, and the ultimate flexural stress is comparable to those of composites fabricated by other processing techniques, demonstrating VSI is an effective way to fabricate the dense C_f/SiC composites with good mechanical properties.     

Pultruded fiber-reinforced poly(methyl methacrylate) composites. I. Effect of processing parameters on mechanical properties

A feasibility study of pultrusion of fiber-reinforced thermoplastic PMMA composite has been conducted using a proprietary method. Effect of processing parameters, preparation of methyl methacrylate (MMA) prepolymer on the mechanical properties (tensile, flexural strength and modulus, impact strength, etc.) of fiber-reinforced PMMA composites by pultrusion has been studied. Processing parameters investigated included pulling rate, die temperature, postcure time and temperature, and filler content. From the study of Brookfield viscometer and FTIR spectrum the processing conditions can be defined. It was found from SEM photographs that the wetting out of fibers by PMMA resin was complete, and the fiber bundles were distributed evenly in the PMMA matrix. From the study of ¹H-NMR, GPC, and Brookfield viscometer, the conversion, molecular weight, and viscosity of MMA prepolymer data were obtained. From the DSC diagram, molecular weight measurement, and the rule of polymerization rate, the optimum die temperature was determined. It was found that the mechanical properties increase with increasing filler content and postcure temperature, and with decreasing die temperature and pulling rate.     

Mechanical behavior of two-dimensional carbon/carbon composites with interfacial carbon layers

Effect of interfacial carbon layers on the mechanical properties and fracture behavior of two-dimensional carbon fiber fabrics reinforced carbon matrix composites were investigated. Phenolic resin reinforced with two-dimensional plain woven carbon fiber fabrics was used as starting materials for carbon/carbon composites and was prepared using vacuum bag hot pressing technique. In order to study the effect of interfacial bonding, a carbon layer was applied to the carbon fabrics in advance. The carbon layers were prepared using petroleum pitch with different concentrations as precursors. The experimental results indicate that the carbon/carbon composites with interfacial carbon layers possess higher fracture energy than that without carbon layers after carbonization at 1000°C. For a pitch concentration of 0.15 g/ml, the carbon/carbon composites have both higher flexural strength and fracture energy than composites without carbon layers. Both flexural strength and fracture energy increased for composites with and without carbon layers after graphitization. The amount of increase in fracture energy was more significant for composites with interfacial carbon layers. Results indicate that a suitable pitch concentration should be used in order to tailor the mechanical behavior of carbon/carbon composites with interfacial carbon layers.     

Effect of multi-walled carbon nanotubes on microstructure and fracture properties of carbon fiber-reinforced ZrB2-based ceramic composite

Multi-walled carbon nanotubes (MWCNTs) were used to optimize the microstructure and improve the fracture properties of hot-pressed carbon fiber-reinforced ZrB₂-based ultra-high temperature ceramic composites. Microstructure analysis indicated that the introduction of MWCNTs effectively reduced the carbon fiber degradation and prevented fiber-matrix interfacial reaction during processing. Due to the presence of MWCNTs, the matrix contained fine ZrB₂ grains and in-situ formed nano-sized SiC/ZrC grains. The fracture properties were evaluated using the single edge-notched beam (SENB) test. The fracture toughness and work of fracture of the C_f/ZrB₂-based composite with MWCNTs were 7.0±0.4 MPa m^1/2 and 379±34 J/m², respectively, representing increases of 59% and 87% compared to those without MWCNTs. The excellent fracture properties are attributed to the moderate interfacial bonding between the fibers and matrix, which favour the toughening mechanisms, such as fiber bridging, fiber pull-out and crack deflection at interfaces.     

Three-Dimensional Carbon/Silicon Carbide Composites Prepared by Chemical Vapor Infiltration

Continuous-carbon-fiber-reinforced silicon carbide composites (C/SiC) were prepared by chemical vapor infiltration in which the preforms were fabricated with the three-dimensional braid method. The mechanical properties and microstructures were investigated. For the composites with no interfacial layer, flexural strength and fracture toughness increased with density of the composites, and the maximum values were 520 MPa and 16.5 MPa·m^1/2, respectively. The fracture behavior was dependent on the interfacial bonding between fiber/matrix and fiber bundle/bundle which was determined by the density of the composites. Heat treatment had a significant influence on the mechanical properties and fracture behavior. The composites with pyrolysis interfacial layers exhibited characteristic fracture and relatively low strength (300 MPa).     

Interfacial adhesion between ionic copolymers and high-modulus surface-treated carbon fibers

High-modulus carbon-fiber-reinforced thermoplastic composites typically fail at the interface due to poor adhesion between fiber and matrix. To increase interfacial strength, the research described herein focuses on modifying the fiber surface (via high-temperature acid treatment or zinc electrolysis) to facilitate chemical functional groups on the fiber that might increase fiber-matrix inter-actions. The thermoplastic matrix materials used in this study were random copolymers of ethylene and methacrylic acid in which the carboxyl groups in the methacrylic acid segments were neutralized with either sodium or zinc counterions. Mechanical tests were performed to determine the macroscopic effects of fiber pretreatment on the ultimate mechanical properties of the composites. Fabrication was designed such that fiber-matrix separation provides the dominant contribution to mechanical gracture. Composites containing fibers treated with nitric acid, or a mixture of nitric and sulfuric acids exhibit a 20 to 25 percent increase in transverse (tensile) fracture stress relative to composites fabricated with as-received fibers. Scanning electron microscopy of the fiber-matrix interface at fracture allows one to “zoom-in” and obtain qualitative details related to adhesion. Fracture surface micrographs of the above-mentioned acid-treated fiber-reinforced composites reveal an increase in the amount of matrix material that adhered to the fiber surface relative to the appearance of the fracture surface of composites fabricated with as-received fibers. The presence of acid functionality in the matrix, rather than the divalent nature of the zinc counterions, produces the largest relative enhancement of transverse (tensile) fracture stress in the above-mentioned composites containing surface-treated carbon fibers.     

The improvement of mechanical properties of SiC/SiC composites by in situ introducing vertically aligned carbon nanotubes on the PyC interface

In order to improve the mechanical properties, vertically aligned carbon nanotubes (VACNTs) were in situ introduced on the pyrocarbon (PyC) interfaces of the multilayer preform via chemical vapor deposition (CVD) process under tailored parameters. Chemical vapor infiltration (CVI) process was then employed to densify the multilayer preform to acquire SiC/SiC composites. The results show that the growth of VACNTs on PyC interface is highly dependent to the deposition temperature, time and constituent of gas during CVD process. The preferred orientation and high graphitization of VACNTs were obtained when temperature is 800?℃ and C₂H₄/H₂ ratio is 1:3. The bending strength and fracture toughness of SiC/SiC composites with PyC and PyC-VACNTs interfaces were compared. Compared to the SiC/SiC composite with PyC interface, the bending strength and fracture toughness increase 1.298 and 1.359 times, respectively after the introduction of PyC-VACNTs interface to the SiC/SiC composites. It is also demonstrated that the modification of PyC interface with VACNTs enhances the mechanical properties of SiC/SiC composites due to the occurrence of more fiber pull-outs, interfacial debonding, crack branching and deflection     

Effects of the single layer CVD SiC interphases on the mechanical properties of the SiCf/SiC composites fabricated by PIP process

Owing to the degradation of the mechanical properties of the SiC fiber reinforced SiC matrix (SiCf/SiC) composites with the pyrocarbon (PyC) and BN interphases under oxidation environment and neutron irradiation, single layer SiC interphases prepared by chemical vapor deposition (CVD) process were employed to substitute for them. Effects of the CVD SiC interphases on the mechanical properties and interfacial characteristics of the SiCf/SiC composites fabricated by precursor infiltration and pyrolysis (PIP) process were investigated. Compared with the as-received SiCf/SiC composites, the SiCf/SiC composites with the single layer CVD SiC interphases exhibit an obvious toughened fracture behavior, the flexural strength of which is about 4 times that of the as-received SiCf/SiC composites. From the microstructural analysis, it can be confirmed that the SiC interphases play a key part in protecting the fibers from damage during composite preparation and weakening interfacial bonding, which can provide high in situ fiber strength and appropriate interfacial bonding strength for the SiCf/SiC composites.     

Processing and mechanical properties of hydroxyapatite–polysulfone laminated composites

Designing biocomposites that mimic bone with specific mechanical properties of toughness and elastic modulus is a long-standing challenge in the biomaterials field. Traditional biocomposites comprise polymer matrices reinforced with ceramic particles. Laminated composites are structures also found in nature that can offer improved mechanical properties such as strength, elastic modulus and toughness. Hydroxyapatite/polysulfone laminated composites were fabricated to develop biologically compatible, toughened composites that would match the elastic modulus of bone. Multilayered composites were successfully designed with improved toughness measured by the work of fracture. Toughness measurements were more than an order of magnitude greater than monolithic hydroxyapatite. The toughness and modulus values of hydroxyapatite/polysulfone were within the range of cortical bone.     

Enhancing hygrothermal resistance of aeronautical carbon fabric/epoxy composites via air plasma processing

Air plasma processing is introduced as a surface modification technique for carbon fibers to enhance the hygrothermal resistance of carbon fabric/epoxy composites. On carbon fiber surface subjected to 4-min plasma processing, there are 37.6% of carbon species present as –C–O–C groups and 9.3% of carbon species as –COOH groups. The moisture adsorption behavior of composites can be described by Fick’s law. Increase in temperature accelerates the initial moisture adsorption rate and results in a higher diffusion coefficient. The decreasing interlaminar shear strength (ILSS) of composites is mainly ascribed to the loss of adhesion at the fiber/matrix interface. A lower equilibrium moisture content of composites is caused by air plasma processing, which leads to the improved interfacial bonding strength and the higher retention rate of ILSS of carbon fabric/epoxy composites. The interface sensitivity and temperature dependence of moisture adsorption for carbon fabric/epoxy composites are discussed. The results presented herein demonstrate an effective strategy for enhancing hygrothermal resistance of carbon fiber-reinforced composites.