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In order to enhance the interfacial adhesion of carbon fiber (CF) and polymer matrix, a multiscale gradient modulus intermediate layer with rigid-flexible (GO-PA) hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy. The polarity, roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed. The IFSS, ILSS, compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement (76.8%, 46.4%, 40.7% and 37.8%) for the interfacial and mechanical properties than other previous reports. Consequently, the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new, viable and promising route to obtaining high-performance composites.

In this paper, a novel approach to evaluate the neutron shielding performance of multiphase neutron absorber reinforced aluminum matrix composites was proposed through the establishment of a direct relationship between equivalent B areal density (EBAD) of the composite and its thermal neutron shielding coefficient. It was found when the EBAD of the composite was 0.1105 g/cm 2 , the thermal neutron shielding coefficient will achieve 99%. Based on this proposed approach, (1% Gd+15% B 4 C)/6061Al composite plates were successfully fabricated using vacuum hot pressing method followed hot rolling. The results showed that when the EBAD of the composite was 0.1871 g/cm 2 , the thermal neutron shielding coefficient was above 99.9%, which was consistent with the theoretical calculation. The 5 mm-thick composite plate also had a good shielding effect on the Am-Be neutron source. Meanwhile the composite possessed a 380 MPa tensile strength as well as an elongation of 5% after hot rolling. In all, the (Gd + B 4 C)/6061Al composite designed in this paper showed better comprehensive performance compared with the literature's. The work of this paper has a great guiding significance for the design and preparation of neutron absorbing composites with high thermal neutron shielding performance as well as high strength and plasticity.

A novel and effective method was proposed for grafting carbon nanotubes (CNTs) with amino groups onto the surface of carbon fibers (CFs) by using one-pot aryl diazonium reaction in mild, eco-friendly conditions. Based on the diazonium reaction, CNTs were grafted with phenyl amino groups, and then functionalized CNTs (CNT-NH2 ) were modified onto the fiber surface to enhance fiber surface roughness and wettability , which could potentially increase interfacial strength of composites. Homogeneous multi-scale structures with different concentrations of CNTs were achieved. Interfacial properties of hybrid composites were closely dependent on the grafting density. The resulting hierarchical reinforcements improved composites interfacial strength significantly by the enhanced mechanical interlocking and the formed chemical bonding at the interface.

This study was conducted to obtain a type of aluminum matrix composites exhibiting a good strength and certain ductility at high temperature. The 25 vol% TiO2-75 vol%2024 Al systems were selected to fabricate the (Al3Ti+Al2O3)/2024 Al composites with residual ∼32 vol% Al matrix through powder metallurgy. The (Al3Ti+Al2O3)/2024 Al exhibits a good strength and certain ductility at high temperature as in the design. The microstructure of (Al3Ti+Al2O3)/2024 Al composites was investigated. It was discovered that the in-situ Al3Ti reinforcement was in coarse block-shaped particles of approximately 6.9 μm in size and the Al-Al3Ti interface was clean. The Al2O3 particles were in the nano-scale and distributed in the Al matrix in a cluster form. The high temperature compression testing of the composites was conducted at the temperatures of 573 K, 623 K, 673 K, 723 K and 773 K with the strain rate of 10−3 ∼ 0.42 s−1. The results demonstrated that the composites exhibited higher strength at the same high temperature than the other Al matrix composites with a similar volume fraction. The massive Al3Ti and Al2O3 phases played a load bearing role at high temperatures. The residual ∼32 vol% Al matrix led the composites to acquire certain ductility.

A novel boron carbide and gadolinium particles reinforced Al neutron shielding composite (1% Gd+15% B4C)/6061Al was successfully fabricated by vacuum hot pressing method, and its microstructure and tensile properties during hot rolling were studied. The results indicated that, the main Gd-containing phase during hot rolling was Al5Gd3O12, and the size decreased with the increase of the derformation amount. The results of thermodynamic calculations confirmed the possibility of the formation of Gd-containing phases in the preparation process. The main defects of the Gd-containing phases were stacking faults. During the hot rolling process, the mechanical properties of the (1% Gd+15% B4C)/6061Al composite were better than the 15% B4C/6061Al composite. The increase in strength came from the strengthening effect of the Gd-containing phases, which was consistent with the theoretical calculations. Stacking faults in the Gd-containing phases allowed dislocations to slip through, thereby improving the plasticity of the composite.

The ternary roles of polyethyleneimine (PEI) as a polymer matirx, a reducing agent and a surface modifier have been presented to fabricate graphene oxide (GO) reinforced polymer nanocomposite films. GO is modified with PEI-glycerol diglycidyl ether (GDE) cross-linking networks in aqueous solution and in situ reduced by PEI simultaneously. Synergistic reinforcement of mechanical interlocking and hydrogen bonding leads to dramatic increases in tensile strength and Young’s modulus by 98.3% and 87% respectively, at 7.5 wt% GO loading of PEI. The partial reduced GO sheets serve as moisture barriers for water-soluble PEI, and the nanocomposite films are shown to be structurally robust humidity sensors over the relative humidity (RH) range of 40–90%.

Octamaleamic acid-polyhedral oligomeric silsesquioxanes (OMA-POSS) were chemically modified onto the surface of carbon fibers (CFs) by a facile and high efficient two-step method. CF was grafted with hydroxyl groups via aryl diazonium reaction, and then covalently functionalized with OMA-POSS. The grafting density could be tuned through the concentration of OMA-POSS. Fiber surface structures were characterized by confirming the covalent bonding nature between OMA-POSS and CF. OMA-POSS was scattered on CF surface uniformly, and fiber polarity and roughness increased with the increased grafting density of OMA-POSS. Interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the modified CFs composites enhanced as the grafting density grew, which could be ascribed to OMA-POSS interface with providing different degrees of chemical bonding and mechanical interlocking. Moreover, the hydrothermal aging resistance of composites is highly dependent on the amounts of the introduced OMA-POSS. The storage modulus and the glass transition temperature could increase by 8 GPa and 14 °C based on dynamic mechanical analysis testing. In addition, the interfacial reinforcing mechanisms have been also analyzed, and surface modification maintained fiber tensile strength.

A novel amine-based functionalization method was developed to improve the interfacial adhesion between TiO 2 NWs and CFs in supercritical water. The microstructure, morphology and mechanical properties of CFs were investigated. It was found that introducing hexamethylenetetramine (HMTA) dendrimers and branched polyethyleneimine (PEI) on CF could increase significantly the adhesion strength between CF and TiO 2 NWs and their interfacial shear strength with epoxy resin, and the order is CF-PEI-TiO 2 NWs > CF-HMTA-TiO 2 NWs > CF-COOH-TiO 2 NWs > CF-TiO 2 NW. Meanwhile, the reinforcing mechanisms and interfacial failure modes have also been discussed. We believe that these effective methods may provide theoretical foundation for the preparation of high performance composite materials.

Controlling interfacial microstructure and interactions between carbon fiber (CF) and matrix is of crucial importance for the fabrication of advanced polymer composites. In this paper, a hierarchical reinforcement (CF-g-SiO2) was prepared through directly grafting 3-aminopropyltriethoxysilane (APS) functionalized silica nanoparticles (SiO2-APS) onto CF surface by the covalent linkage for the first time. SiO2-APS nanoparticles distributed onto the fiber surface uniformly, which could increase surface polarity and roughness obviously. CF-g-SiO2 exhibited a low contact angle and high surface free energy, and thus enhanced the wettability between CF and matrix greatly. Simultaneous increases of interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) of CF-g-SiO2 composites were achieved, increasing 53.27% in ILSS and 40.92% in IFSS compared with those of untreated composites. These enhancements can be attributed to the existent of SiO2-APS interface with providing sufficient chemical bonding and strong mechanical interlocking between the fiber and matrix. Moreover, impact resistance of CF-g-SiO2 composites was enhanced with increasing the amplitude of 34.95%. In addition, the introduction of Si-O-Si bonds at the interface by SiO2-APS grafting leads to the remarkable enhancement of the hydrothermal aging resistance.

Introducing nano-scale reinforcements into carbon fiber (CF)-matrix interface is a useful method to enhance interfacial strength of composites. In this work, we demonstrated a facile and high efficient strategy of preparing octa(aminophenyl) polyhedral oligomeric silsesquioxane (OapPOSS)/CF hierarchical reinforcements (CF-g-POSS) by directly grafting OapPOSS on CFs by covalent bonding. OapPOSS distributed on fiber surfaces uniformly, and enhanced surface polarity as well as roughness significantly. CF-g-POSS exhibited a low contact angle and high surface free energy, which helped to change the wettability between CF and the matrix. Simultaneous enhancements of interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CF-g-POSS/methylphenylsilicone resin (MPSR) composites were achieved, increasing 47.83% in IFSS and 59.04% in ILSS compared to those of untreated composites. These enhancements could be attributed to OapPOSS interface with providing sufficient covalent bonding and strong mechanical interlocking. Additionally, anti-hydrothermal aging behaviors were also increased obviously owing to the introduction of Si O Si bonds at the interface.

A novel boron carbide and gadolinium particles reinforced Al neutron shielding composite (1%Gd + 15%B4C)/Al was successfully fabricated by vacuum hot pressing method, and its microstructure and tensile properties before and after hot extrusion were studied. The results indicated that, when adding 1% Gd particles in the composite, Gd-containing phases, parts of which were identified as Al2Gd3, Al5Gd3O12, and Al11GdO18 by TEM, were produced in the composite and can be treated as reinforcement. After hot extrusion, the mechanical property of the composite was obviously improved. Under 54:1 extrusion ratio, the tensile strength of (1%Gd + 15%B4C)/Al reached about 260 MPa, which increased by 15% compared to 15%B4C/Al under the same condition. Hot extrusion was beneficial to improved interface bonding and uniform distribution of Gd-containing phases, so as to change fracture mechanism from interface debonding to near-interface fracture, which facilitated to exert the transferring load ability of Gd-containing phases and thereby increasing the strength.

It is widely accepted that the interfacial properties of carbon fiber (CF) reinforced composites tend to be weak due to the poor wettability and chemically inert surface of CF, which greatly limits the reinforcement effect of CF in composites. Here, size-controllable graphene oxide sheets (GO) were grafted on CF using Poly(oxypropylene) Diamines (D 400 ) as the bridging agent to improve the interfacial properties of CF composites. It was found that the size and content of active functional groups on GO played important roles in controlling the surface morphology of GO grafted CF. Moreover, the interfacial shear strength (IFSS) of the middle sized GO sheets grafted CF/epoxy composites reached a maximum value of 82.2 MPa, with an enhancement of 75.6% compared with untreated CF. That is to say, the strong mechanical interlocking between CF and epoxy resin and the improved wettability of resin on CF surface were responsible for the enhancement of IFSS. Instead of decaying of fiber tensile strength after treatment, the tensile strength of GO grafted CF increased from 4.73 GPa to 5.02 GPa. The reason for the enhancement may be due to that GO bridged the surface defects on CF. This hierarchical reinforcement was believed to have widely potential applications in high performance polymer matrix composites.

We report on a green method of using poly(oxypropylene) diamines (D400) as coupling and curing agent to functionalize carbon fiber in water. We propose to enhance the interfacial properties of carbon fiber composites, together with the tensile strength of carbon fibers. The microstructure and mechanical properties of carbon fibers before and after modification are investigated. The results show that D400 do not change the surface morphology, but significantly increase the polarity, wettability and roughness of the carbon fiber surface. The interfacial shear strength (IFSS) of modified carbon fiber/epoxy composite and the tensile strength of carbon fibers increase by 79.1% and 8.2%, respectively. It is believed that D400 can effectively improve the interfacial adhesion of the composites by improving resin wettability, increasing chemical bonding and mechanical interlocking. This green and simple method can have applications in continuous production of high-performance carbon fiber composites.

Effects of silane and silica enrichment of carbon fibers (CFs) on interfacial properties of methylphenylsilicone resin (MPSR) composites were investigated. CFs were oxidized, grafted with 3-aminopropyltriethoxysilane (APS) and then modified with silica nanoparticles prepared by the sol-gel polymerization of tetraethoxysilane (TEOS). Chemical structures of CFs were characterized by confirming the successful grafting. Scanning electron microscopy (SEM) showed a uniform distribution of silica nanoparticles on the CFs surface. The interlaminar shear strength (ILSS) and impact toughness of silanized CF (CF-Siloxane) composites were 12.05% and 7.46% higher than those of untreated composites. However, ILSS and impact toughness of the hybrid fiber (CF/Si) composites obtained from the hydrolysis of different concentrations TEOS improved significantly, especially for grafting silica enrichment with the TEOS concentration of 0.05 mol/L (CF/Si0.05), increasing 45.64% in ILSS and 29.59% in impact properties. Moreover, the hydrothermal aging resistance was also improved greatly. Meanwhile, functionalization processes did not decrease fiber tensile strength.

A new hierarchical reinforcement was fabricated by growing ZnO nanowires (NWs) onto poly( p -phenylene benzobisoxazole) (PBO) fibers using a mild hydrothermal method, which served as a platform for the polyhedral oligomeric silsesquioxanes (POSS) grafting, using 3-aminopropyltrimethoxysilane (APTMS) as a bridging agent. Scanning electron microscopy (SEM) was employed to characterize the surface morphologies of PBO fibers and the de-bonding surface morphologies of their composites. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the chemical bonding nature between ZnO NWs and APTMS, as well as between APTMS and POSS. The reinforcement offered a 83.4% enhancement in the interfacial shear strength (IFSS) without degrading the base fiber. Moreover, the possible interfacial property enhancing reasons were explored. The hydrothermal aging resistance of PBO/epoxy composites was also greatly improved.

An effective approach to the fabrication of progressive epoxy nanocomposites by the incorporation of hydroxyl-terminated dendrimers functionalized graphene oxide (GO-TCT-Tris) is reported. The relationship between surface grafting, chemical construction, morphology, dispersion, and interfacial interaction as well as the corresponding mechanical properties of the composites were studied in detail. It was shown that hydroxyl-terminated triazine derivatives have been resoundingly bonded onto the GO surface through covalent bonding, which effectively improved the dispersion and compatibility of GO sheets in epoxy resin. The tensile and flexural tests manifested that the GO-TCT-Tris/epoxy composites exhibited greater tensile/flexural strength and modulus than either the pure epoxy or the GO/epoxy composites. For GO-TCT-Tris (0.10 wt%)/epoxy composite, the tensile strength and elastic modulus increased from 63 &plusmn, 4 to 89 &plusmn, 6 MPa (41.27%) and from 2.8 &plusmn, 0.1 to 3.6 &plusmn, 0.2 GPa (28.57%), and the flexural strength and modulus increased from 106 &plusmn, 5 to 158 &plusmn, 6 MPa (49.06%) and from 3.0 &plusmn, 0.1 to 3.5 &plusmn, 0.2 GPa (16.67%), respectively, compared to the pure epoxy matrix. Moreover, the fractographic analysis also illustrated the ameliorative interfacial interaction between GO-TCT-Tris and epoxy matrix.

Equivalent amount of B (BEq) can be used to evaluate the thermal neutron shielding property of materials. Based on the calculation of BEq, a novel boron carbide and gadolinium particles reinforced Al composite (15%B4C + 1%Gd)/Al was designed. The composite was successfully prepared by vacuum hot pressing method. The B4C particles and Gd phase were homogeneously distributed in the Al matrix. The Monte Carlo Particle transport program MCNP simulation and thermal neutron shielding tests demonstrated that the (15%B4C + 1%Gd)/Al composite definitely had an almost equivalent neutron shielding property as the 30%B4C/Al composite, which in turn proved the accuracy of the design. The macroscopic transmission cross section (Σ) of (15%B4C + 1%Gd)/Al composite was as high as 21.3 cm−1, which was better than that of 30%B4C/Al composite. Tension tests indicated that by decreasing B4C content, the elongation of the composite reached as much as 9%. The addition of Gd can replace a part of B4C content in the composite, which can increase the plasticity of the composite, and keep the neutron shielding property simultaneously. Keywords: B4C/Al, Gd, Neutron shielding property, Plasticity

Poly( p -phenylene benzobisoxazole) (PBO) fibers are ideal candidates for cables in tether application and reinforcements in advanced composites. Upon exposure to atomic oxygen (AO) in low earth orbit (LEO), PBO fibers are severely eroded. In this study, the AO erosion behaviors of PBO fibers and their composite were investigated in simulated AO environment, based on the evaluation of microstructure, surface chemistry, thermal stability and mechanical properties. Surface morphologies and crystalline structure confirmed that PBO fibers were significantly eroded after AO irradiation. X-ray photoelectron spectroscopy (XPS) showed that the relative content of C C decreases with the increase of AO irradiation time, suggesting a chain scission of PBO fibers. After 8 h AO exposure, the tensile strength of PBO fibers was decreased by 31.6%, and the onset decomposition temperature was reduced by 30.8 °C. Monofilament pull-out tests showed that the interfacial shear strength (IFSS) of PBO/epoxy composite was as low as 61.3% that of pristine composite due to the interface damage caused by AO penetration.

Metallic foams with a high fraction of porosity, low density and high-energy absorption capacity are a rapidly emerging class of novel ultralight weight materials for various engineering applications. In this study, Y-Cr and Ce-Cr-coated Ni-Cr-Fe alloy foams were prepared via the pack cementation method, and the effects of Y and Ce addition on the coating microstructure and oxidation performance were analyzed in order to improve the oxidation resistance of open-cell nickel-based alloy foams. The results show that the Ce-Cr coating is relatively more uniform and has a denser distribution on the surface of the nickel-based alloy foam. The surface grains of the Ce-Cr-coated alloy foam are finer compared to those of the Y-Cr-coated alloy foam. An obvious Ce peak appears on the interface between the coating and the alloy foam strut, which gives rise to a “site-blocking” effect for the short-circuit transport of the cation in the substrate. X-ray diffraction analysis shows that the Y-Cr-coated alloy foam mainly consists of Cr, (Fe, Ni) and (Ni, Cr) phases in the surface layer. The Ce-Cr-coated alloy foam is mainly composed of Cr and (Ni, Cr) phases. Furthermore, the addition of Y and Ce clearly lead to an improvement in the oxidation resistance of the coated alloy foams in the temperature range of 900-1000 °C. The addition of Ce is especially effective in enhancing the diffusion of chromium to the oxidation front, thus, accelerating the formation of a Cr2O3 layer.

The interface between carbon fibers (CFs) and matrix resin makes a critical contribution to bulk performance of composites. In order to enhance interfacial properties and anti-hydrothermal aging behaviors of methyl phenyl silicone resin (MPSR) composites, octamaleamic acid-polyhedral oligomeric silsesquioxanes (POSS-acid) were directly grafted onto CFs surface by chemical bonding for the first time. Surface chemical groups and morphologies of CFs before and after POSS-acid grafting were systematically characterized. Scanning electron microscopy and atomic force microscopy images showed a uniform distribution of POSS-acid on the fiber surface and the improved surface roughness. POSS-acid cages grafting could improve obviously the fiber polarity, wettability, and free energy by dynamic contact angle analysis testing. The interlaminar shear strength (ILSS) of MPSR composites reinforced with the POSS-acid-modified CFs (CF-POSS) was 45.01 ± 1.69 MPa, which increased by 52.73 % compared to that of MPSR composites reinforced with untreated CFs (29.47 ± 0.94 MPa). And, impact strength of CF-POSS composites (77.69 ± 2.83 kJ m−2) was increased by 32.89 % compared to that of untreated CF composites (58.46 ± 1.91 kJ m−2). Moreover, ILSS of CF-POSS composites after hydrothermal aging treatment was 40.89 ± 1.51 MPa with a decrease of just 9.15 % compared to that of untreated CF composites (20.52 ± 0.65 MPa) with an obvious decrease of 30.37 %. Meanwhile, POSS-acid functionalization did not decrease fiber tensile strength. Based on our design starting from simple chemistry and inexpensive materials, such hierarchical reinforcements with improved interfacial strength and anti-hydrothermal aging behaviors have great potential in advance polymer matrix composites.

Octaglycidyl polyhedral oligomeric silsesquioxane (gly-POSS) was successfully grafted on carbon fibers (CFs) surface to enhance interfacial properties and impact toughness of CFs reinforced methylphenylsilicone resin (MPSR) composites. After gly-POSS modification, POSS grafted CF (CF-POSS) with many epoxy functional groups was modified with tetraethylenepentamine (TEPA) to further enhance the interfacial strength. Atomic force microscopy (AFM) images showed that POSS and TEPA were grafted onto CFs surface uniformly and the surface roughness enhanced obviously. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the chemical bonding nature between CFs and POSS, as well as between POSS and TEPA. POSS and TEPA modification could increase the fiber polarity, wettability and surface energy significantly. The interlaminar shear strength (ILSS) and impact toughness of composites showed a dramatic improvement, especially for grafting with POSS and further with TEPA (CF-POSS-TEPA). Additionally, the reinforcing and toughening mechanisms were also analyzed. Meanwhile, single fiber tensile strength (TS) had no decrease after modification.

The surface topographies of carbon fibers treated by sizing agents with different graphene oxide (GO) content were investigated by scanning electron microscopy. The surface elements compositions of carbon fibers were determined by X-ray photoelectron spectrometer. The interfacial properties of composites were studied by interfacial shear strength. The thermo-mechanical properties of two typical specimens (CF-G0 and CF-G1 composites) were investigated by dynamic mechanical thermal analysis. The results showed the introduction of GO sheets on carbon fibers surfaces effectively improved the mechanical properties of carbon fibers/epoxy composites. POLYM. COMPOS., 38:2425–2432, 2017. © 2016 Society of Plastics Engineers

The grafting of trisilanolphenyl-polyhedral oligomeric silsesquioxanes (trisilanolphenyl-POSS) onto carbon fibers (CFs) was achieved using toluene-2,4-diisocyanate (TDI) as the bridging agent. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful modification of trisilanolphenyl-POSS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed that trisilanolphenyl-POSS nanoparticles were grafted uniformly onto the surface of CFs and the surface roughness increased significantly. The results of dynamic contact angle (DCA) measurements demonstrated an improvement in the surface energy and wettability that related to the increased polarity of the obtained hybrid fibers (CF-g-POSS). The effects of trisilanolphenyl-POSS grafting on the interfacial, impact, and heat-resistant properties of methylphenylsilicone resin (MPSR) composites were also studied. The interlaminar shear strength (ILSS) and impact resistance of methylphenylsilicone resin (MPSR) composites after POSS modification were improved significantly with increasing amplitudes of 41.91% and 28.65%, respectively. Moreover, the interfacial reinforcing and toughening mechanisms of composites have also been discussed. In addition, the thermal oxygen aging experiments indicated a remarkable improvement in the heat oxidation resistance by the introduction of trisilanolphenyl-POSS in the interphase. Meanwhile, the grafting processes do not decrease fiber tensile strength (TS).

We proposed an easy and effective method to prepare multiwall carbon nanotubes (CNTs) modified sizing agent suited for carbon fibers (CFs) reinforced methylphenylsilicone resin (MPSR) composites. In order to improve the dispersion of CNTs in sizing agent and interfacial adhesion between CNTs and MPSR, CNTs were covalently functionalized with 3-aminopropyltriethoxysilane (APS) and the silanized carbon nanotube (CNT-APS) was introduced into the interface by sizing process as well. The CFs with and without sizing treatment reinforced MPSR composites were prepared by a compression molding method. Scanning electron microscopy (SEM) showed a uniform distribution of CNTs on the fiber surface and the enhancement of the surface roughness. Compared with untreated CFs composites, the interlaminar shear strength (ILSS) and impact toughness of CFs after sizing treatment containing 0.1 wt.% CNTs composites increased slightly owing to the serious agglomeration of excessive CNTs. However, the sized fibers modified with 0.5 wt.% CNT-APS composites revealed a significant increase 46.52% in ILSS and 31.12% in impact properties. Moreover, the reinforcing and toughening mechanisms were also discussed. In addition, the tensile strength (TS) of sized CFs showed a slightly increase in comparison with that of untreated CFs. Keywords: Carbon fiber, Sizing agent, Carbon nanotube, Composite material, Interfacial property, Impact performance

Metal nanoparticles are commonly used for surface modification in fiber reinforced polymer composites because of their large specific surface area and electronic, magnetic and other related properties. In this study, morphology-controllable silver nanoparticles (Ag NPs) were deposited on a carbon fiber surface via a facile and green electro-chemical deposition method in the presence of poly(vinylpyrrolidone) (PVP). It was found that the presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the Ag NPs. Interestingly, electro-chemical deposition of Ag NPs improved both the tensile strength of the carbon single fiber and the interfacial property of the carbon fiber/epoxy composite by as much as 57.2% and 27.2%, respectively. Moreover, the Ag NPs-loaded carbon fibers exhibited superior electrical conductivity, which was a 2-fold enhancement as compared with that of the virgin carbon fibers. It meant that the Ag NPs-loaded carbon fibers could be used as ideal reinforcement materials for advanced aerospace systems.

The one-step generation of nano-silica (SiO2) on graphene oxide (GO) surface via using diethylenetriamine (DETA) and ammonium hydroxide (NH4OH) base catalysts was respectively designed to improve the dispersion and interfacial interaction between GO and epoxy resin. The structures and morphologies of GO, GO-SiO2(i) and GO-SiO2(ii) sheets were tested by FT-IR, XRD, XPS, TG, SEM and TEM. Epoxy composites containing GO, SiO2, GO-SiO2(i) and GO-SiO2(ii) with 0.1 wt% loadings were prepared and systemically investigated. It was indicated that the GO-SiO2/epoxy composites displayed higher tensile, flexural and impact strength and modulus than that of GO composites. For epoxy composites containing 0.1 wt% GO-SiO2(i) and GO-SiO2(ii), the flexural strength increased by 34.35% and 25.08% compared to that of GO composites, respectively. Furthermore, the reinforcing mechanisms have been also illuminated. This work is expected to offer a potential scale application of high-performance nanocomposites.

The gradient modulus intermediate layer between CF and epoxy by designing double “rigid-flexible” structure using CNTs and polyamide (PA) on the CF surface was firstly established, and the effects of modulus intermediate layer on interfacial and mechanical properties of CF composites were investigated. The constructing of double “rigid-flexible” structure on the CF surface can greatly increase the polar functional groups, roughness and wettability of the CF surface as well as the thickness of intermediate layer, which could balance the modulus of fiber and resin to achieve the best matching. The interfacial shear strength (IFSS), interlaminar shear strength (ILSS), flexural strength, and impact strength of CF composites increased by 75.6%, 44.1%, 41.3%, and 34.6%, respectively. In addition, the interfacial failure behaviors and strengthening mechanisms of composites have been studied. This novel design and method built a multistage gradient modulus intermediate layer of composite with strong physicochemical interaction and good wettability, which has greatly potential for high-performance composite.

A novel and effective strategy was first proposed for the codeposition of a mussel-inspired nanohybrid coating with excellent wettability onto the surface of carbon fibers (CFs) by simultaneous polymerization of bioinspired dopamine (DA) and hydrolysis of commercial tetraethoxysilane (TEOS) in an eco-friendly one-pot process. Mussel-inspired nanohybrids could be adhered onto the surface of CFs firmly. The novel modification could afford sufficient polar groups and significantly improve fiber surface roughness and energy without decreasing fiber intrinsic strength, which were advantageous to promote interfacial compatibility and wettability between CFs and matrix resin. As a result, the interfacial shear strength of composites increased to 48.21 ± 1.45 MPa compared to that of untreated composites 29.47 ± 0.88 MPa. Meanwhile, the nanohybrid coating increased significantly composites’ hydrothermal aging resistance. The efficient strategy shows a promising and green platform of surface functionalization of CFs for preparing advanced polymer composites arising from broadly mechanical-demanding and energy-saving usages.

Both silane and multiwall carbon nanotubes (CNTs) were grafted successfully onto carbon fibers (CFs) to enhance the interfacial strength of CFs reinforced methylphenylsilicone resin (MPSR) composites. The microstructure, interfacial properties, impact toughness and heat resistance of CFs before and after modification were investigated. Experimental results revealed that CNTs were grafted uniformly onto CFs using 3-aminopropyltriethoxysilane (APS) as the bridging agent. The wettability and surface energy of the obtained hybrid fiber (CF-APS-CNT) were increased obviously in comparison with those of the untreated-CF. The CF-APS-CNT composites showed simultaneously remarkable enhancement in interlaminar shear strength (ILSS) and impact toughness. Moreover, the interfacial reinforcing and toughening mechanisms were also discussed. In addition, Thermogravimetric analysis and thermal oxygen aging experiments indicated a remarkable improvement in the thermal stability and heat oxidation resistance of composites by the introduction of APS and CNTs. We believe the facile and effective method may provide a novel interface design strategy for developing multifunctional fibers.

The multi-scale reinforcement and interfacial strengthening on carbon fiber (CF)-reinforced methylphenylsilicone resin (MPSR) composites by adding silica-coated multi-walled carbon nanotubes (SiO2-CNTs) were investigated. SiO2-CNT has been successfully prepared via the hydrolysis of tetraethoxysilane in the presence of acid-oxidized multi-walled carbon nanotubes. Transmission electron microscopy, X-ray diffraction, and Fourier Transform infrared spectroscopy were carried out to examine the functional groups and structures of CNTs. Then, SiO2-CNT was incorporated into MPSR matrix to prepare CF/MPSR-based composites by the compression molding method. The effects of the introduced SiO2-CNT on the interfacial, impact, and heat-resistant properties of CF/MPSR composites were evaluated by short-beam bend method, impact test, and thermal oxygen aging experiments, respectively. Experimental results revealed that the CF/MPSR composites reinforced with 0.5 wt% SiO2-CNT showed a significant increase 34.53% i...

A novel supercritical method for deposition of polyethyleneimine (PEI) onto carbon fibers (CFs) surface was reported. The surface functional groups, morphology, wettability and interphase properties of CFs grafted with PEI (CF-g-PEI) were studied, and compared to physically-adsorbed and chemically-adsorbed ones (CF-c-PEI and CF-ad-PEI). The CF-g-PEI exhibited the highest deposition amount and interfacial adhesion strength. Interface enhancement mechanism and failure mode have also been explored in details. However, impact resistance and single fiber tensile strength of CF-g-PEI were not optimal. Hence, based on different applications, a property balance of the resulting composite should be considered.

Silica–graphene oxide (SiO 2 –GO) hybrid nanoparticles have been prepared by the hydrolysis of tetraethoxysilane (TEOS) in the presence of GO sheets. The results indicated that silica nanoparticles were densely and uniformly grafted onto the GO surface by covalent linkage. The thermal stability of SiO 2 –GO has been improved greatly according to thermogravimetric analysis (TGA). Methylphenylsilicone resins (MPSR) with various proportions of SiO 2 –GO were synthesized by solution blending method. The incorporation of SiO 2 –GO was beneficial to improve the thermal stability and oxidation resistance of composites. The 5% weight loss temperature of the composites at 1 wt% SiO 2 –GO loading was detected 34.8 °C higher than that of pure MPSR. And the T g of composites was increased by 10.4 °C. Additionally, the short-term and long-term stability of composites were improved greatly by adding SiO 2 –GO. These enhancements can be attributed to better dispersion of SiO 2 –GO in MPSR and improved interfacial adhesion between MPSR and SiO 2 –GO.

Since being discovered, graphene shows promise as reinforcements in high-performance nanocomposites. In the present study, we describe a novel strategy to design and prepare poly(p-phenylene benzobisoxazole) (PBO)/graphene composite. Graphene oxide (GO) was first modified by 4, 6-diaminoresorcinol (DAR) to improve the reactivity, solubility, and dispersivity of GO in polymer matrix. Without separation and purification, GO-DAR was further incorporated with PBO through in situ polymerization, and PBO/GO composite films were obtained by thermoforming process. The structure and morphology of GO-DAR and PBO/GO films were characterized and the mechanical and thermal properties were investigated. The incorporation of GO improved the thermal stability of PBO. Mechanical property measurements revealed that the PBO/GO films exhibited a tensile strength (148 MPa) and Young's modulus (6.2 GPa) at a GO loading of 1.5 wt%, corresponding to 39.6% and 72.2% increase compared to the PBO film, respectively. The one-pot in situ procedure wraps GO with PBO chains, improves the dispersion and alignment of GO in PBO matrix, enhances PBO chain packing order, which are considered to be the main reasons for the performance improvement of PBO.

A liquid sizing agent containing multiwall carbon nanotubes (MWCNTs) was prepared for carbon fiber (CF) reinforced methylphenylsilicone resin (MPSR) composite applications. In order to improve the dispersion of MWCNTs in the sizing agent and interfacial adhesion between CF and MPSR, MWCNTs and CF were functioned by the chemical modification with tetraethylenepentamine (TEPA) used as a MPSR curing agents. The CF before and after the sizing treatment-reinforced MPSR composites were prepared by a compression molding method. The microstructures, interfacial properties, and impact toughness of CF were systematically investigated. Experimental results revealed that a thin layer of MPSR coating containing functionalized MWCNTs (MWCNT-TEPA) was uniformly grafted onto the surface of CF. The sized CF-reinforced MPSR composite showed simultaneously remarkable enhancement in the interlaminar shear strength and impact toughness. Meanwhile, the tensile strength of CF had no obvious decrease after sizing treatment. In a...

We report on a new application of branched polyethyleneimine as a coupling agent to functionalize carbon fibers in conventional and supercritical methods. The microstructure and mechanical properties of carbon fibers before and after modification were investigated. Polyethyleneimine could increase the polarity, wettability and roughness of the carbon fiber surface, and supercritical methanol was also able to improve the reaction efficiency. The interfacial shear strength and impact toughness improved significantly when using the two methods, especially in supercritical methanol. Reinforcing and toughening mechanisms have also been discussed. Functionalization does not decrease fiber tensile strength.

In the paper, by using radio frequency (rf) magnetron sputtering method, a zirconium carbonitride coating was produced on AISI 316L austenitic stainless steel. The influence of substrate temperature (Ts) on microstructure, mechanical properties, corrosion resistance and hemocompatibility were then investigated. XRD and TEM results revealed that the zirconium carbonitride coatings were almost amorphous when Ts was below 400°C, while nanostructured Zr2CN was formed at Ts of 400 °C. The nanocrystalline formation resulted in a significant increase in the nanohardness of zirconium carbonitride coatings from 17 GPa to over 32 GPa. Electrochemical testing showed that the stable zirconium carbonitride coating had improved the corrosion resistance of AISI 316L stainless steel substrate material. The characterization of platelet adhesion indicated that the zirconium carbonitride coatings presented better hemocompatibility when Ts varied from 25 °C to more than 200 °C, which may be due to the lower surface roughness, interfacial tension and the rate γ s d / γ s p , where γ s d and γ s p are the disperse component and polar component of the surface, respectively.

As the initiative thermal protection materials applied in the field of aerospace industry, the high temperature performance evolution of the dissipation thermal protection materials is essential for keeping the carrying capacity of structure and the integrity of aerodynamic configuration in the aerodynamic environment. In this paper, flexural properties and compression properties of Mg–Zn/Graphite dissipation thermal protection materials are studied by three point bending tests and compression tests from room temperature to 1000°C, and fracture morphologies are observed and analysed by scanning electron microscope. The results showed that the flexural strength and compressive strength of composites were higher than that of matrix by 115 and 84% at the room temperature. With the increasing temperature, the strength of composite showed a downward trend. The fracture scanning showed that the internal defects of composite increased owing to oxidation of metal during the heating process. However, the t...

Atomic oxygen (AO) is a dominant component of the low earth orbit and can erode most spacecraft materials. In this work, both silane and graphene oxide (GO) were introduced onto poly(p-phenylene benzobisoxazole) (PBO) fibers to prevent AO from penetrating into the interface of PBO fiber/epoxy composites. The microstructure, mechanical properties and AO erosion resistance of PBO fibers before and after modification were investigated. Experimental results revealed that the GO was successfully grafted onto PBO fibers using 3-aminopropyltrimethoxysilane (APTMS) as the bridging agent. The surface roughness (Ra) and wettability of the obtained hybrid fibers (PBO–APTMS–GO) were obviously increased in comparison with those of an untreated one. In addition, PBO–APTMS–GO showed simultaneously remarkable enhancement in interfacial shear strength (IFSS) and AO erosion resistance. Meanwhile, single filament tensile strength (TS) had no obvious decrease after the grafting processes. We believe the facile and effective method may provide a novel interface design strategy for developing multifunctional fibers.

Besides chemical bonding, surface wettability and roughness of carbon fibers (CFs) also play key roles in improving interfacial adhesion of CFs composites. In this study, the roles of surface wettability and roughness of CFs in interfacial enhancement of methylphenylsilicone resin composites were systematically studied. p-Phenylene trimethoxyaminosilane (PTMAS) was chemically grafted onto CFs to increase surface polarity and wettability. Furthermore, by bridging PTMAS, the bigger surface roughness of fibers was obtained after following epoxycyclohexyllsobutyl-polyhedral oligomeric silsesquioxanes (POSS) grafting. PTMAS grafting (CF–PTMAS) had higher wettability and surface energy than that of the grafting with PTMAS and further with POSS (CF–PTMAS–POSS). However, surface roughness of CF–PTMAS was lower than that of CF–PTMAS–POSS. Interfacial shear strength and interlaminar shear strength showed great enhancements, especially for CF–PTMAS–POSS composites, indicating that surface roughness played more important role than the wettability for interface improvement. Additionally, antihydrothermal aging behaviors were also improved obviously. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO2 particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO2 particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO2 particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO2, respectively, when the nano-SiO2 content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO2 containing sizing showed higher absorpt...