Nanofiller Inclusion Methods in Thermoplastic Composites: History
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Contributor:
Kailashbalan Periasamy
,
Everson Kandare
,
Raj Das
,
Maryam Darouie
,
Akbar A. Khatibi

Although the absence of cross-linked polymer chains and chemical bonds on solidification enables the thermoplastics to be remelted, it creates weak interfacial adhesion between fibre reinforcements and the thermoplastic matrix. The weak fibre-matrix interface bonding reduces the efficiency with which the applied load can be transferred between these composite constituents, causing the composite to fail prematurely. Their need for high-temperature processing, poor compatibility with other polymer matrices, and relatively high viscosity render thermoplastics challenging when used to manufacture composite laminates. Therefore, various methods, including nanoparticles, changing the polarity of the fibre surface by plasma etching, chemical treatment with ozone, or an oxidative attack at the fibre surface, have been applied to improve the fibre/matrix bonding in thermoplastic composites.

  • interfacial bonding
  • thermoplastic composites
  • nanoparticle inclusion

1. Introduction

The nanoparticles coated over the fibre affect its surface roughness and improve wettability and resin impregnation through mechanical interlocking between fibre and matrix [1]. The commonly used nanoparticles include single- and multi-walled carbon nanotubes, graphene oxide, thermally reduced graphene oxide, and silver nanowires. Titanium dioxide, tungsten disulfide, silica, and rubber nanoparticles have also been extensively used. Adding these nano fillers to the fibre surface reduces the crack propagation in the fibre-matrix interfacial region via toughening mechanisms like crack front pinning, fibre crack bridging, particle bridging, particle/fibre joint fracture, nanoparticle pull out, crack deflection, crack meandering, and micro crack toughening [2]. Available techniques for surface coating of continuous fibres using various nanoparticles include electrophoretic deposition (EPD), chemical vapor deposition (CVD), direct immersion, spraying, nanoparticle grafting, and flame synthesis. These techniques, together with their advantages and limitations, are discussed in the following sections.

2. Electrophoretic Deposition

In the electrophoretic deposition (EPD) method, charged micro/nanoparticles (mixed in the electrolyte suspension) move towards the carbon fibre with an opposite charge under the application of electric current. The charged nanoparticles are then physically deposited on the fibre surface in a random orientation [3].
Liu et al. [1] increased the interfacial bonding between carbon fibre (CF) reinforcement material and polycarbonate (PC) thermoplastic matrix by depositing Multiwalled carbon nanotubes (MWCNTs) over the carbon fibre surface using the ultrasonic-assisted EPD method. The carbon fibres were desized by heating at 600 °C in a nitrogen gas atmosphere. The desized carbon fibres were then passed through the pulse ultrasonic-assisted electrophoretic depositor. It had a mixture of ultrasonically diluted acid oxidized CNTs, isopropanol and ammonium bicarbonate (NH4HCO3). The ultrasonicator was used to create a uniform dispersion of CNTs in the electrolyte unit, precluding CNT agglomeration during its deposition on the fibre surface. The CNT-coated carbon fibres were then immersed into a waterborne emulsion, a mixture of 50% bisphenol A diglycidyl ether epoxy resin and 50% polycarbonate. The final CNT/carbon hybrid fibres were oven-dried and then irradiated by Q-switched neodymium-doped yttrium aluminium garnet (QS Nd: YAG) laser to heat the binder polymer on the carbon fibres. The laser irradiation effectively removed the extra polymer binder from CNT/CF hybrid fibres. The CNT length increased the resin infusion and the mechanical interlocking between fibre and matrix. Among the different CNT lengths tested, CNTs ranging from 1–5 µm were found to overlap and entangle to form a uniform network for resin infiltration with a CNT suspension concentration of (0.5–1) wt.%. Using the process mentioned above, the interfacial shear strength (IFSS) of the MWCNT-modified sample increased by 68% more than the bare CF-reinforced sample. The integration of MWCNTs at the interface region dissipated the energy of the propagating crack by pinning the crack and deflecting the crack tip.
In another similar research project, short carbon fibres coated with MWCNTs using EPD were used as reinforcements in a PPS matrix composite [4]. With optimized EPD parameters (30 V and 5-min deposition time), the coated fibres were prepared, and then hybrid fibres were melt-blended with PPS in a twin-screw extruder. They were pelletized, compression molded at 320 °C and cut into the required dimensions for property testing. The results showed improved IFSS and electrical conductivity by 42% and 78%, respectively.
To reduce the peeling of CNTs from the CF surface after the EPD process, CNT-deposited CFs were immersed in a pre-impregnation solution made of PC/dichloromethane (CH2Cl2) [5]. These treated CFs were hot-pressed with PC films to prepare CF-PC laminates. This EPD process, combined with pre-impregnation treatment, improved the contact area and wettability of the CF surface, which in turn improved the interface connection between the CF and PC matrix. This technique increased the tensile strength, tensile modulus, impact strength, storage modulus, and electrical conductivity by approximately 47%, 58%, 269%, 78%, and 54%, respectively.
In another work, EPD and poly (phthalazinone ether ketone) (PPEK) sizing was combined to deposit and attach the CNTs on CFs more firmly [6]. This CF-CNT was used to reinforce the PPEK matrix and tested for IFSS. EPD, followed by thermoplastic sizing on CF, increased its surface wettability, thereby increasing the IFSS by 36%.
Wu et al. [7] fabricated MWCNT/polyimide (PI) composite films through electrophoretic deposition of carboxylated-MWCNTs and poly (pyromellitic dianhydride-co-4,40-oxydianiline) (PMDA-ODA). These negatively charged MWCNTs, and PMDA-ODA were deposited on a positive anode electrode under an electric field and formed MWCNT/PI composite film. The presence of MWCNTs in the PI matrix decreased the surface resistivity by approximately 100% and increased the tensile strength and modulus by 14% and 50%, respectively.
Limitations:
  • When acid-oxidized graphene nanoplatelets (GNPs) were deposited on CFs, this led to an increase in the interfacial strength between CF and epoxy. The improvement in the interfacial strength was attributed to the creation of a multiple crack propagation zone [8]. It should be noted that the deflection of cracks into various paths is more prevalent in thermosets than in cases of thermoplastic matrices due to the relatively higher intrinsic toughness of thermoplastic matrices. The stiffness and brittle nature of the thermoset matrix support the nanoparticles to deflect the propagating crack in multiple pathways, which is rare in the case of relatively ductile thermoplastics.
  • The EPD is an automated process suitable for large-scale industrial applications, and it has the potential to damage fibres.
  • The EPD technique may not achieve a uniform deposition of the nanoparticles leading to agglomeration.
  • The EPD method is suitable for fibre reinforcements with relatively high electrical conductivity, such as carbon fibres. This technique is unsuitable for electrically insulative fibres such as glass and aramid [3].

3. Chemical Vapor Deposition (CVD)

In the chemical vapor deposition (CVD) technique, the fibre is placed inside a quartz tube with a volatile catalyst precursor and heated using a hydrocarbon source like ethane or methane gas [9]. The reaction burns the precursor and allows it to settle after vaporization on fibre material, thereby depositing CNT onto fibre surfaces. Sometimes, carrier gases like hydrogen and argon are introduced along with hydrocarbon sources to improve the reaction rate in the quartz tube.
Jianguo et al. [9] deposited CNTs on discontinuous and randomly distributed CFs using the chemical vapor deposition process before mixing them into a polyimide matrix to form composite laminates. The CFs were nitric acid-treated to create surface functional groups before carrying out the CVD process. Benzene was used as the hydrocarbon source, and the CVD process was conducted at 700 °C for 45 min. The tensile strength and impact strength in the modified composites improved by 30% and 29%, respectively, for the CNT weight concentration of 3 wt.%. However, the tensile and impact properties decreased with an increase in nanofiller inclusion beyond 3 wt.%. The SEM images of fracture morphology showed that the carbon fibres pulled out from the matrix in the baseline laminate, leading to annular cracks in the matrix, which led to delamination. However, when the CNTs were added to the CF/PI composite, a brittle fracture with a flatter fracture surface was observed. The pull-out length of CF from the matrix was decreased by the mechanical interlocking between fibre and matrix formed by CNTs. It produced fewer annular matrix cracks with shorter CF pull-out from the matrix.
In another CVD method, CNTs were deposited on CFs using Fe (C2H5)2 (ferrocene) as a catalyst and ethanol as a carbon source [10]. The process was conducted at 750 °C for 900 s. The CVD process created a continuous and dense deposition of CNTs on CF. Catalytic deposition in the CVD process created defects in CFs, reducing the CNT grafted fibre strength by 12%. PP (polypropylene) matrix penetrated the CNTs, which increased the IFSS by 35% for modified CF/PP samples. The fibre/CNT joint fracture was observed to be the dominant failure mode for the grafted fibres.
Tanaka et al. coated nickel catalyst particles on CF through the electrolytic nickel-plating method. These catalyst-coated CFs were used with ethanol as a carbon source and argon as the carrier gas in the CVD process to deposit CNTs on the CF surface. The CNT grafting on unsized CF increased the mechanical properties of CF/PA6, such as IFSS [11] and Charpy impact value [12], by 50% and 10%, respectively. It was also noted that the presence of CNTs in the interfacial region reduced the IFSS degradation of CF/PA6 samples when they were subjected to water absorption [13] and high-temperature tests [13][14]. The above results proved the significant role of CNTs in increasing the mechanical interlocking between CF and PA6 matrix.
Limitations:
  • The CVD method is very effective in forming an even deposition throughout the fibre surface, but it can result in thermal-induced fibre damage, ultimately degrading the composite mechanical properties [15].
  • While thermosetting polymers can form covalent chemical bonds with the treated nanoparticles or with the surface functional groups on the carbon fibre surface, thermoplastic polymers can form only non-covalent chemical bonding [16]. The absence of strong chemical bond formation could be the primary reason behind the relatively low research effort to enhance interfacial bonding in thermoplastic composites using CVD and other chemical-based techniques like chemical coating or nano grafting.
  • While the CVD method provides a homogeneous deposition at the nanoscale level, the requirement for hydrocarbon gases and quartz tube testing apparatus makes it an expensive approach.
  • Catalyst contamination during processing can also be a drawback in the CVD process [17].

4. Direct Immersion Sizing (DIZ) of Nanoparticles

Direct immersion sizing is the most applied method to increase the adhesive strength between fibre and thermoplastic matrix in composite laminates. It involves directly dipping fibre material into the sizing unit containing nanoparticles mixed with a polymer solution [18] or other supporting chemical agents [19]. A thorough literature survey shows that the nanoparticles most used with DIZ are graphene oxide (GO), multiwalled carbon nanotubes (MWCNT), and nano-silica particles.

4.1. GO Nanoparticles

Chen et al. [19] enhanced the interfacial bonding between CF and PEEK using a mixture of polyetherimide (PEI) and graphene oxide sizing on CFs in different mixing ratios. The bare carbon fibres were pulled through the sizing agent, a mixture of PEI granules dissolved in N-methyl-pyrrolidone (NMP) and GO. The carbon fibres coated with PEI and GO were then IR heated at about 300 °C. After drying, the sized CFs were pulled through a suspension mixture of PEEK, Triton X-100, and deionized water. After PEEK suspension, carbon fibres were placed in an oven and consolidated to produce CF/PEEK prepregs. The CF/PEEK prepregs coated with PEI and GO were stacked in unidirectional orientation and hot-pressed to produce composite laminates.
The presence of PEI on the CF surface slightly reduced debonding between fibre and matrix. However, adding GO nanoparticulate to the PEI sizing further improved the fibre wettability and fibre/matrix adhesive quality. The interfacial shear strength (IFSS) increased by 14% for CF/PEEK composite laminate containing CFs coated with PEI only. However, when GO sheets were added together with PEI sizing on CFs, the IFSS of the composite laminate increased by 44%. The optimal amount of GO loading for the IFSS was found to be 10 wt.% of the PEI sizing agent. Extensive fibre pull-out and interfacial debonding were the predominant failure mechanisms for control samples. These failure mechanisms were less prominent after incorporating GO at the CF/polymer matrix interface. In another set of research, the interfacial properties of carbon fibre/polypropylene (CF/PP) composites were improved by coating graphene oxide and branched-polyethyleneimine on the CF surface via a layer-by-layer assembly process [16]. The nanomaterial deposition and thermoplastic sizing on CF increased the IFSS, tensile strength, storage modulus, and elongation at the break of CF/PP composite by approximately 102%, 48%, 20%, and 101%, respectively.
Treating nanoparticles in acid can create physical and chemical modifications on the nanofiller surface, enhancing its interaction with fibre and matrix. However, the functionalization of nanoparticles cannot form a chemical bonding with a thermoplastic matrix unless they have been functionalized using a compatible polymer or a chemical agent. In work done by Liu et al. [20], a novel sizing compound containing polyether sulfone (PES), functionalized GO, and dimethylacetamide (DMAC) was integrated to increase the interfacial strength of CF/PES composites. The GO nanoparticles were covalently functionalized by 4,4’-diamino diphenyl sulfone (DDS) and 4,4’-diamino diphenyl ether (DDE), which have similar chemical structures to the PES matrix. The PES/GO-DDS sizing increased the IFSS by 74% and ILSS by 40% compared to the baseline specimens.
A biodegradable polymer called shellac flakes was dissolved in iso propanol, and plasma-treated CFs were immersed in that shellac solution. These modified CFs were then annealed at 700 °C in a tube furnace under vacuum conditions to form shellac-derived reduced graphene oxide (SRGO) on the CF surface. These SRGO-grafted CFs were then coated with a sizing agent made of PA and SRGO. The physical and chemical bonding mechanism that occurred at the interphase due to the interaction between the sizing agent and SRGO increased the ILSS, flexural strength, and modulus of CF/PA6 composite by 71%, 73%, and 84%, respectively [21].
Similarly, sulfonated poly (ether sulfone) (s-PSF) was mixed with GO and used as a sizing agent to increase the interfacial bonding between CF and PEEK. Carboxyl groups on GO formed hydrogen bonds with oxygen-containing functional groups of s-PSF, creating a well-dispersed sizing solution. This sizing agent also withstood the high-temperature processing of CF/PEEK laminate fabrication. The results showed that the ILSS, flexural strength, and modulus improved by 128%, 102%, and 83%, respectively [22].
Desized CF was cut into 3–5 mm and added to the GO aqueous suspension to prepare GO-coated short carbon fibres (GO-SCF). GO-modified PP was obtained by extrusion and melt mixing of GO and PP. Then, the GO-SCF-reinforced GO-PP composite was prepared using the extrusion and injection molding process. The chemical reaction and mechanical interlocking between GO on the SCF surface and GO in the PP matrix increased the flexural, impact, and tensile strength by approximately 33%, 31%, and 94%, respectively [23].
SCFs desized using acetone were treated using thermoplastic polyimide (TPI), graphene oxide (GO), and GO-TPI hybrid sizing to obtain the TPI-sized SCF, GO-sized SCFCF, and GO-TPI-sized SCF, respectively. These three types of sized SCFs were mixed individually with PEI using extrusion and injection molding to prepare SCF-reinforced PEI composite. Among the TPI, GO, and TPI-GO hybrid sizing on SCF, the TPI-GO hybrid-sized SCF/PEI sample exhibited a better tensile strength of about 13% increment to the control sample SCF/PEI [24]. It is due to the crack-blocking effect of GO and the miscibility of TPI with PEI.
Large-size reduced graphene oxide (LRGO) was mixed with ammonium polyphosphate (APP) to produce LRGO-sized APP (LRAPP). These LRAPPs were blended with thermoplastic polyurethane (TPU) using a roll mixing mill and hot-pressed to form thin sheets. Compared to APP-modified TPU, the addition of LRAPP in TPU increased the tensile strength of the polymer up to 190% [25]. LRGO acted as a linking agent in the interfacial region between APP and TPU.
In another study, GO modified with ferrites (GO-Fe3O4) was mixed with acrylic-styrene (AS) sizing emulsion and coated on CFs [26]. The sized carbon fibres were introduced to the magnetic field to orientate and modify the morphology of GO-Fe3O4 sizing. These sized- and magnetic-field-treated CFs were then used to reinforce the PP matrix using a hot compression molding process. The presence of oriented GO-Fe3O4 in the AS sizing agent increased the ILSS of CF/PP composites by 32% [26].

4.2. MWCNT Nanoparticles

A methyl methacrylate (MMA)-based liquid thermoplastic resin was used by Shanmugam et al. [27] to fabricate ultra-high-molecular-weight polyethylene (UHMWPE)-reinforced Elium composite laminate. Benzoyl peroxide (2 wt.%) was used as a polymerization initiator for Elium 188 resin. A mixture of deionized (DI) water, polydopamine (PDA), hydrochloric acid, and 0.03 wt.% of MWCNTs were used as a sizing solution. Transverse fibre bundle test and mode I fracture toughness test were conducted to determine the effect of sizing on fibre-matrix interfacial bonding [28]. The fracture toughness improved by 42.5% after sizing due to stick-slip behavior and crack-blunting. The toughness enhancement can be attributed to the strong fibre-matrix adhesion enhanced by MWCNTs. In another study, glass fibres (GFs) were sized using a mixture of surfactant Triton X100, DI water, carboxylic functionalized MWCNTs, and polyphenylene sulfide (PPS) [29]. The one wt.% of MWCNTs used for sizing increased the thermoplastic composite’s fracture toughness and interlaminar shear strength by 25% and 23%, respectively.
The carbon nanotube sizing on fibre material was used as a healing sensor along with improving the fibre-matrix bonding [30]. MWCNTs were coated on GFs using the immersion sizing method, and the sized GFs were then used to reinforce the ethylene-vinyl acetate (EVA) thermoplastic matrix. The MWCNTs in the interfacial region increased the IFSS by 49% and acted as a sensor to monitor and heal the cracks developed in the interfacial region. The interfacial damage was healed by heating the MWCNTs using electric power [30].
Wu et al. [31] used the sizing process to introduce silanized CNTs on the CF surface and increase its bonding with methyl phenyl silicone resin (MPSR). Silane functionalization on CNTs increased its dispersion in the sizing agent and improved the interfacial adhesion of CNTs with CF and MPSR. The test results of modified samples showed an increase of 47% in ILSS and 31% in impact toughness.
A sizing agent made of PI and loosely packed CNT arrays was used to modify the CF surface to increase the wettability and polarity of the CF surface [32]. The CF/PEEK laminate prepared from the sized fibre exhibited a significant increase of 71% in ILSS, 63% in flexural strength, and 70% in flexural modulus. The loosely packed CNT arrays were proved to be better than the dense CNT networks in improving the flexural properties due to the more effortless flow of viscous PEEK melt into the loosely-packed CNT arrays.
Silanized GFs were immersed in a sizing unit containing oxidized MWCNTs dispersed in it, and then these sized GFs were used to reinforce the PPS matrix. The chemical bonding was formed between amine groups on the GF surface, and carboxyl groups linked with MWCNTs created strong MWCNT anchor points on the GF surface, increasing the load transfer between fibre and matrix. The results showed that the tensile and flexural strength increased by 126% and 155%, respectively [33].
GFs were added to the PEI-CNT dispersion before being used to reinforce the PA6 matrix. The GF/PA6 composite was prepared by a twin-screw extruder and injection molding process [34]. The network structure and high surface reactivity provided by PEI-CNT sizing on the GF surface increased the GF-PA6 interfacial performance, thereby enhancing both the tensile strength and flexural strength of modified composites by 7%.

4.3. Nano Silica Particles

Chen et al. [18] prepared a complex PEEK suspension made of fine PEEK powders, nano-silica materials, emulsifier Triton-100, and deionized water. The mixture was stirred and ultrasonically vibrated. The CFs were immersed in this complex PEEK suspension and consolidated using an oven to form CF/PEEK prepregs. These prepregs were stacked and hot-compressed to form a composite laminate. The nano-silica added to the CF/PEEK composite laminate acted as a strong obstacle to crack initiation and propagation. The load transfer in the interlaminar region was also enhanced during loading. Nanomodification increased the interlaminar shear strength, flexural strength, and flexural modulus by approximately 16%, 14%, and 9%, respectively. Similarly, silica nanoparticles improved the fibre/matrix interfacial bonding five times in GF/PP thermoplastic composites after nanoparticle sizing [35].
Nano-silica sizing was also found to promote hydrophobic fibre surface properties. When the nano-silica-sized GFs were used in GF/polymerized poly (cyclic butylene terephthalate) composites, it was found that after hydrothermal aging, the water absorption and effect of heat and moisture on the properties of the composite laminates were diminished [36]. Thus, the silica nanoparticles decreased the strength degradation of the composite laminate due to the hydrothermal effects [37].

4.4. Mixing of Nanoparticles

Sharma et al. [38] studied the synergistic bridging effects of mixing GO and CNT with polycarbonate (PC) matrix resin. The nanofiller-modified resin was applied over aramid fibres (Kevlar 49) and compression molded. The resulting specimens showed improved static and dynamic mechanical properties. Similarly, a polyimide (PI) suspension containing Fe3O4 nanoparticles and reduced graphene oxide (RGO) was prepared [39] and used as a sizing agent for the CFs. The sized CF reinforcements were combined with PI to form the CF/PI composite laminate. Fe3O4 nanoparticles prevented the agglomeration of graphene and increased the ILSS by 159%.

4.5. Innovative Non-Conventional Sizing Approaches

Some unique and unconventional interfacial engineering approaches have also been introduced under the Direct Immersion Sizing (DIZ) category, including:
  • Immersing carbon fibres in hydroxylated PEEK grafted multiwalled carbon nanotubes (HPEEK-g-MWCNT) solution to improve the bonding strength with the PEEK matrix [40]. Flexural strength and ILSS were increased by 94% and 55%, respectively, for the modified samples. The formation of chemical bonding between the PEEK matrix and HPEEK-g-MWCNT, along with the mechanical interlocking between fibre and matrix provided by MWCNT, contributed to the improvement in interfacial bonding between CF and PEEK.
  • Creating a sizing agent made of polyetherimide (PEI) and in situ-grown nanocrystals made of zeolitic imidazolate framework-67 (ZIF-67) to enhance the strength of CF/PEEK composite laminates [41]. Miscibility of PEI with PEEK and rough structure of ZIF-67 helped to increase the IFSS between CF and PEEK up to 41%.
  • Using the pie-shaped PEI nanoparticles to size the CF surface and heating the PEI-coated fibres to melt a few nanoparticles to increase the surface energy of CF when used to fabricate thermoplastic composites [42]. PEI surface modification increased the IFSS for CF/PVC, CF/PC, CF/PA6, CF/PP, CF/PA66, and CF/PEI by 21%, 38%, 53%, 50%, 43%, and 58%, respectively. The compatibility of thermoplastic resins and PEI coating increased the IFSS between CF and thermoplastic resins. The effect is even better if the surface of PEI coating is in nanoparticle morphology.
  • Modifying the short flax fibre surfaces using cellulose nanocrystals, xyloglucan CNC/XG, and maleic anhydride-grafted polypropylene (MAPP) coupling agent. This CNC/XG biomass by-product adsorption on the flax fibres and the covalent bond provided by the MAPP coupling agent with the fibres enhanced the bonding strength between flax fibre and polypropylene (PP) in flax fibre/PP bio composite [43]. The work of rupture of the flax fibre/PP samples measured by micromechanical tensile tests was improved by 13% and 22% for CNC and CNC/XG treatments, respectively.
Limitations:
One prominent shortcoming of the Direct Immersion Sizing method is the variability of the coated thickness. If the dispersion of nanoparticles in the sizing unit is not adequately regulated, agglomeration and uneven distribution of nanomaterials over fibre surfaces can occur.

5. Spray Gun Technology

The spray gun technique is used to spray nano-fillers mixed with volatile solvents like ethanol on a fibre surface at a specific spraying speed to size the fibre surface with nanoparticles [44]. Although this method has not been used frequently in the research, it proves to be effective in creating strong physical adsorption between fibre and matrix with no chemical bonding between them.
Cortes et al. [45] enhanced the electrical conductivity of carbon fibre-reinforced polyether ketone ketone (PEKK) by adding silver nanowires using two fabrication methods: film stacking and powder impregnation through spray coating. The powder impregnation method produced a more homogenous material with good dispersion of nanowires. This method gave conductivity up to 250 S/m for a 2.5% volume of Ag nanowires. In the case of film stacking, PEKK impregnation was poor since the silver nanowire film only stayed on the fibre surface. Furthermore, due to the high viscosity of PEKK, poor penetration into carbon fibre tows created a heterogeneous distribution. Meanwhile, the powder impregnation using the spray gun resulted in improved impregnation with no voids. The inclusion of silver nanowires created a percolation mechanism in CF/PEEK laminates which further enhanced the electrical conductivity.
Likewise, CNTs were sprayed on CF/PEEK prepregs to enhance their electrical and thermal conductivity [44]. A 0.5 wt.% of CNTs proved to be the optimal mixing concentration in CF/PEEK laminates. The CNTs generated an effective conductive pathway between fibre and matrix. Flexural strength, flexural modulus, and ILSS were increased by approximately 25%, 24%, and 36%, respectively, after CNT spray deposition. Crack bridging through fibres and nanoparticles was observed as the predominant toughening mechanism.
He et al. [46] sprayed a mixture of nano-silica and poly (ɛ caprolactone) PCL onto basalt fibres to enhance the mode I interlaminar fracture toughness (ILFT) of basalt fibre reinforced poly lactic acid (PLA) composite laminates. The hybrid coating having PCL and nano-silica mixed in a ratio of 1:5 gave the best performance. The crack deflection was the primary toughening mechanism observed. The SiO2 and PCL were constructed as rigid and flexible phases in the interfacial region. The nanofiller modification improved the tensile strength and mode I ILFT by 29% and 110%, respectively.
Limitations:
Controlling the thickness of the coating and creating uniformly distributed nanoparticles is challenging while using spray gun technology.

6. Grafting of Nanoparticles

The grafting of nanoparticles takes place by coating the fibre surface with an adhesive coupling agent and bonding the nanoparticles over the adhesive chemical compound. The presence of the nanoparticles, along with the coupling agent at the fibre surface, promotes the formation of chemical bonds between the reinforcements and the polymer matrix [47][48]. In some cases, the fibre reinforcements are chemically or mechanically treated to increase fibre wettability. Improved fibre wettability enhances the adhesion of fibre with the polymer matrix and the surface-deposited nanoparticles via mechanical interlocking and chemical bonding [49].
Kim et al. [47] grafted zinc oxide nanorods (ZnO NR) on woven carbon fibres (WCFs) and applied a CNT-modified PEI silane coating onto the fibre surface. The grafting of nanorods and silane coating enhanced the mechanical strength of WCF/polyamide 6 (PA6) composite laminates. The fibre surface was initially plasma treated to desize, add functional groups, and increase nano-pits. After accomplishing the ZnO NR growth and silane coating process on the fibre surface, ultra-fast thermoplastic resin transfer molding (RTM) was used to fabricate WCF/PA6 composite laminates. The RTM was done using the caprolactam (CPL) monomer of PA6. Since the melt viscosity of CPL is about 100 times lower than that of thermoset resin, an excellent impregnation between hexagonal wurtzite structured ZnO nanorods was achieved. The ZnO NRs and CNTs maximized the mechanical interlocking effect of the fibre with the PA6 matrix, whereas the amine groups in the PEI silane coating formed a covalent chemical bond with the PA6 matrix. The integration of ZnO NR, CNTs, and silane at the fibre/matrix interface of the multiscale hybrid composite enhanced the fibre/matrix in-plane shear strength, tensile strength, and tensile modulus by approximately 107%, 41%, and 32%, respectively.
In a recent study, graphene oxide (GO) was grafted onto the CF surface by two synthetic routes with hexamethylene diisocyanate (HDI) tri-polymer as the coupling agent [48]. The first method utilized HDI tri-polymer to modify GO. The modified GO was then grafted onto the oxidized CF. The other route utilized an HDI tri-polymer to alter the oxidized CF surface and graft GO onto that modified CF surface. The first route proved more effective in improving the interfacial shear strength between CF and PA6 matrix. The interfacial shear strength increased by approximately 40%. The HDI tri-polymer acted as a coupling agent between CF and GO by connecting the two composite constituents via covalent bonding. The GO contributed to the combined effects of wettability and mechanical locking force. In another work, silica nanoparticles were grafted on the CF surface and used to fabricate CF/PA6 composite material [49]. The oxidized CFs were modified with 3-aminopropyltriethoxysilane and then grafted with silica nanoparticles dispersed in the KH560 coupling agent. The inclusion of SiO2 nanoparticles of size 30 nm at the fibre/matrix interface increased the interfacial strength by over 200%, from approximately 13 to 39 MPa.
Due to the high viscosity of the thermoplastic matrix, nanofillers are not readily applicable in these composites, and special treatment is required. In a study to anchor MWCNTs on CF, Cheon et al. [50] used the nitric acid treatment on MWCNTs and flame treatment on CF that improved surface functionalities. Flame treatment was preferred for desizing and adding oxygen-based functional groups on CF surfaces. The research was performed via two approaches: mixing MWCNTs with PA6 matrix using cryogenic pulverization and anchoring MWCNTs on flame-treated CFs with silane coating. The latter approach exhibited improved performance under impact and short beam bending conditions. Using 3 wt.% of MWCNTs increased the impact resistance by 91%; meanwhile, the integration of 1 wt.% of MWCNTs improved the ILSS by approximately 34%.
Limitations:
The main concerns for grafting nanoparticles on the surface of continuous fibres are its excessive usage of toxic chemicals and difficulty in processing a large area of fibres. In addition, achieving a well-controlled grafting density, molecular weight, and molecular weight distribution is challenging in this method.

7. Flame Synthesis of CNTs

In more recent studies, CNTs were grown on fibre materials using flame treatment of the fibres wetted with catalyst solutions. Although CVD is the most utilized process for growing CNTs on continuous fibre surfaces, carbon nanotubes have a poor affinity for polymer matrices due to their inert chemical properties. On the other hand, flame synthesis forms oxygen-rich functional groups over CNT during the growth process. Experimental observations show that the flame synthesis method gives better interlaminar fracture toughness than other methods like the spraying of CNTs, CVD, introducing CNF powder, and CNF paste but not better than through-thickness stitches and Z pinning [51].
Zhao et al. [52] grew CNTs on glass fibres wetted with nickel chloride solution using ethanol flame at 560 °C for 3 min. The same authors investigated the effect of flame synthesized CNTs on the welding of thermoplastic composites [53]. In their work, CFs were wetted with nickel nitrate solution and then heated between 740 °C and 970 °C for 1 min using an ethanol flame. The CNT-grafted carbon fibres and PEI films were hot-pressed to form the CF/PEI composite laminate used as an interlayer during the resistance welding of GF/PEI laminates. The mechanical property of the welded joint was evaluated via tensile testing of the single-lap shear strength (LSS). The LSS value increased by 24% in welded joints incorporating flame synthesized CNTs when compared to the baseline composite. The interfacial shear strength between CF and PEI increased by approximately 47% from 4.8 to 7.0 MPa upon the integration of flame synthesized CNTs. The CNTs increased the wettability of the CF surface by PEI with the help of capillary action.
CNTs were grown on the surface of short glass fibres (SGF) using nickel chloride mixed in ethanol (0.4 mol/L) as catalyst precursor and mixed with the nano grown SGFs with poly lactic acid (PLA) pellets. The mixture was fed into the extruder three times to reduce the filler agglomeration in the PLA matrix. The extruded filament was used to print 3D composite samples through fused deposition modelling (FDM) [54]. Compared to the 3D-printed PLA samples, the tensile strength and Young’s modulus of CNT-modified SGF/PLA 3D-printed samples were increased by 33% and 43%, respectively. The results proved that the flame-synthesized CNTs significantly improved the interfacial adhesion between SGF and PLA matrix in the 3D-printed composite.
Limitations:
The flame synthesis of CNTs is a relatively new method that still requires improved understanding and optimization of the process parameters. The distribution, local concentration, and thickness of the deposited CNTs depend on the catalyst, the distance of the substrate from the burner, and the exposure temperature and time, among other variables.

8. Miscellaneous Methods

In addition to the techniques discussed above, some unconventional methods have been used to engineer the fibre surface using nanoparticles. For example, in a study, 0.1 wt.% of different nanomaterials (i.e., MWCNT, RGO, Graphene, nano clay, and exfoliated graphite nanoplatelet (xGNP)) were individually tested with the plasma-treated CF/PA6 specimen. The nanomaterial was dispersed in ɛ-caprolactam, a monomer of anionic polymerized polyamide 6 (A-PA6). This modified monomer with a catalyst and an activator was passed through CFs using ultra-high-speed resin transfer molding [55]. The results showed that GO surpassed other nanomaterials in increasing the elastic modulus by approximately 29% and xGNP outperformed the remaining nanofillers in increasing the tensile strength, in-plane shear strength, and flexural strength by approximately 18%, 18%, and 29%, respectively
In another study, Rasana et al. [56] melt blended short GFs of length 3 mm and MWCNTs with PP to fabricate PP composites. The melt processing was carried out in two steps. MWCNTs were mixed with molten PP to prepare a masterbatch. The CNT masterbatch, PP, and GF were mixed in a rotating twin-screw extruder in the second step. The extruded strands were pelletized and injection molded into test specimens. The filler modification in PP composites enhanced its tensile strength, Young’s modulus, and elongation at the break by approximately 76%, 127%, and 5.5%. In a similar approach, a twin-screw extruder and injection mold were used to integrate micro fillers (i.e., molybdenum disulfide [MoS2], silicon carbide [SiC], alumina) and alumina nanoparticles into short glass fibres (SGF)-, short carbon fibre (SCF)-, and polyamide 66 (PA66)-polytetrafluoroethylene (PTFE) hybrid composite [57]. Adding nano and micro fillers decreased the tensile and flexural strength by approximately 33% and 19%, respectively, due to the increased stress concentration created by the excessive micro and nanofiller inclusion. However, the enlarged surface area of contact between micro and nano fillers increased the impact strength by approximately 18% [58].
Recently, Arao et al. [59] mixed the following nanofillers – silica, CNT, alumina, and nano clay – individually with CF/PP composites via extrusion and injection molding process. It was found that except for nano clay, the remaining nanofillers (i.e., silica, CNT, and alumina) strengthened the interface and thereby improved the tensile properties. Among the nanofillers, 1 wt.% of CNT increased the tensile strength, elastic modulus, and IFSS by approximately 7%, 9% and 186%, respectively. Hwang et al. [60] created a composite powder from PA6 and a nanofiller mixture. The nanofillers were pristine graphene nanoplatelets (P-GNPs) and acid-oxidized GNPs. The PA6/GNP mixture was melt-spun into thin fibres and tested for thermomechanical properties. The results showed that in terms of the tensile properties, PA6 fibres containing acid-oxidized GNPs performed better than those with pristine GNPs. The acid treatment on GNPs increased the surface roughness and surface functionalization of PA6 fibres, which improved the tensile strength and modulus of the composite by 76% and 70%, respectively.
Silica aerogel and rubber-based nanoparticles were also investigated to enhance the mechanical properties of thermoplastic composites. Silica aerogel nanoparticles were mixed with poly (butylene terephthalate) PBT matrix through melt extrusion and injection [61]. It exhibited poor dispersion in the PBT matrix, which decreased the mechanical performance of the PBT matrix. The agglomerated clusters of silica aerogel nanoparticles acted as stress concentration sites and decreased the tensile strength and break elongation by 25% and 58%, respectively [61]. In another study, PEI was used as a non-covalent modifier to modify the surfaces of boron nitride nanoparticles [62]. This non-covalent modified boron nitride (n-CMBN) nanoparticle coated with PEI was mixed with PEEK powder and melt-blended to form a PEEK/n-CMBN polymer nanocomposite. The nanofiller/matrix bonding improved thermal conductivity by four times that of PEEK plastic. The reduction in friction coefficient by 30% after adding n-CMBN to PEEK reflects the better dispersion of nanoparticles in PEEK due to PEI coating on boron nitride nanoparticles [62].

This entry is adapted from the peer-reviewed paper 10.3390/polym15020415

References

  1. Liu, Y.-T.; Song, H.-Y.; Yao, T.-T.; Zhang, W.-S.; Zhu, H.; Wu, G.-P. Effects of carbon nanotube length on interfacial properties of carbon fiber reinforced thermoplastic composites. J. Mater. Sci. 2020, 55, 15467–15480.
  2. Qin, Q.H. Introduction to the composite and its toughening mechanisms. In Toughening Mechanisms in Composite Materials; Qin, Q., Ye, J., Eds.; Woodhead Publishing: Sawston, UK, 2015; pp. 1–32.
  3. An, Q.; Rider, A.; Thostenson, E. Electrophoretic deposition of carbon nanotubes onto carbon-fiber fabric for production of carbon/epoxy composites with improved mechanical properties. Carbon 2012, 50, 4130–4143.
  4. Park, M.; Park, J.H.; Yang, B.J.; Cho, J.; Kim, S.Y.; Jung, I. Enhanced interfacial, electrical, and flexural properties of polyphenylene sulfide composites filled with carbon fibers modified by electrophoretic surface deposition of multi-walled carbon nanotubes. Compos. Part A: Appl. Sci. Manuf. 2018, 109, 124–130.
  5. Wu, Y.; Dhamodharan, D.; Wang, Z.; Wang, R.; Wu, L. Effect of electrophoretic deposition followed by solution pre-impregnated surface modified carbon fiber-carbon nanotubes on the mechanical properties of carbon fiber reinforced polycarbonate composites. Compos. Part B Eng. 2020, 195, 1–11.
  6. Zhang, S.; Liu, W.B.; Hao, L.F.; Jiao, W.C.; Yang, F.; Wang, R.G. Preparation of carbon nanotube/carbon fiber hybrid fiber by combining electrophoretic deposition and sizing process for enhancing interfacial strength in carbon fiber composites. Compos. Sci. Technol. 2013, 88, 120–125.
  7. Wu, D.C.; Shen, L.; Low, J.E.; Wong, S.Y.; Li, X.; Tjiu, W.C.; Liu, Y.; He, C.B. Multi-walled carbon nanotube/polyimide composite film fabricated through electrophoretic deposition. Polymer 2010, 51, 2155–2160.
  8. Nandi, A.; Das, S.; Halder, S.; Chakraborty, A.; Imam, M.A. Ultrasonically assisted electrophoretic deposition of oxidized graphite nanoparticle onto carbon fiber, amending interfacial property of CFRP. J. Compos. Mater. 2019, 54, 1615–1625.
  9. Jianguo, Z.; Gang, D. Mechanical properties of polyimide composite reinforced with carbon nanotubes and carbon fibers. J. Thermoplast. Compos. Mater. 2014, 28, 1250–1259.
  10. Yumitori, S.; Arao, Y.; Tanaka, T.; Naito, K.; Tanaka, K.; Katayama, T. Increasing the interfacial strength in carbon fiber/polypropylene composites by growing CNTs on the fibers. Comput. Methods Exp. Meas. XVI 2013, 55, 275.
  11. Tanaka, K.; Hosoo, N.; Katayama, T. Influence of Unsizing and Carbon Nanotube Grafting of Carbon Fibre on Fibre Matrix Interfacial Shear Strength of Carbon Fibre and Polyamide 6. Key Eng. Mater. 2019, 827, 178–183.
  12. Tanaka, K.; Okuda, S.; Hinoue, Y.; Katayama, T. Effect of CNT Grafting on Carbon Fibers on Impact Properties of CFRTP Laminate. Key Eng. Mater. 2018, 774, 410–415.
  13. Tanaka, K.; Uzumasa, K.; Katayama, T. Effects of Water Absorption on the Fiber–Matrix Interfacial Shear Strength of Carbon Nanotube-Grafted Carbon Fiber Reinforced Polyamide Resin. J. Compos. Sci. 2019, 3, 4.
  14. Tanaka, K.; Yamada, K.; Hinoue, Y.; Katayama, T. Effects of Temperature on the Fiber Matrix Interfacial Properties of Carbon Fiber Reinforced Highly Heat Resistant Polyamide Resin. J. Soc. Mater. Sci. Jpn. 2017, 66, 746–751.
  15. Zakaria, M.R.; Md Akil, H.; Abdul Kudus, M.H.; Ullah, F.; Javed, F.; Nosbi, N. Hybrid carbon fiber-carbon nanotubes reinforced polymer composites: A review. Compos. Part B Eng. 2019, 176, 1–20.
  16. Luo, W.; Zhang, B.; Zou, H.; Liang, M.; Chen, Y. Enhanced interfacial adhesion between polypropylene and carbon fiber by graphene oxide/polyethyleneimine coating. J. Ind. Eng. Chem. 2017, 51, 129–139.
  17. Anthony, D.B.; Qian, H.; Clancy, A.J.; Greenhalgh, E.S.; Bismarck, A.; Shaffer, M.S.P. Applying a potential difference to minimise damage to carbon fibres during carbon nanotube grafting by chemical vapour deposition. Nanotechnology 2017, 28, 1–12.
  18. Chen, J.; Zhang, T.; Wang, K.; Zhao, Y. Multiscale enhancement behavior of nano-silica modified CF/PEEK composites prepared by wet powder impregnation. Polym. Compos. 2019, 40, 1187–1197.
  19. Chen, J.; Wang, K.; Zhao, Y. Enhanced interfacial interactions of carbon fiber reinforced PEEK composites by regulating PEI and graphene oxide complex sizing at the interface. Compos. Sci. Technol. 2018, 154, 175–186.
  20. Liu, L.; Yan, F.; Li, M.; Zhang, M.; Xiao, L.; Shang, L.; Ao, Y. A novel thermoplastic sizing containing graphene oxide functionalized with structural analogs of matrix for improving interfacial adhesion of CF/PES composites. Compos. Part A: Appl. Sci. Manuf. 2018, 114, 418–428.
  21. Cho, B.-G.; Ram Joshi, S.; Hun Han, J.; Kim, G.-H.; Park, Y.-B. Interphase strengthening of carbon fiber/polyamide 6 composites through mixture of sizing agent and reduced graphene oxide coating. Compos. Part A: Appl. Sci. Manuf. 2021, 149, 1–16.
  22. Ren, T.; Zhu, G.; Hou, X.; Li, B.; Hao, Y. Improvement of interfacial interactions in CF / PEEK composites by an s-PSF /graphene oxide compound sizing agent. J. Appl. Polym. Sci. 2021, 138, 1–13.
  23. Wang, C.-C.; Zhao, Y.-Y.; Ge, H.-Y.; Qian, R.-S. Enhanced mechanical and thermal properties of short carbon fiber reinforced polypropylene composites by graphene oxide. Polym. Compos. 2018, 39, 405–413.
  24. Sun, Z.; Guo, F.-L.; Wu, X.-P.; Li, Y.-Q.; Zeng, W.; Chen, Q.; Huang, T.; Huang, P.; Fu, Y.-Q.; Ma, X.-Y.; et al. Experimental and simulation investigations of the effect of hybrid GO-thermoplastic polyimide sizing on the temperature-dependent tensile behavior of short carbon fiber/polyetherimide composites. Compos. Sci. Technol. 2022, 218, 1–11.
  25. Zhang, Y.; Wang, B.; Yuan, B.; Yuan, Y.; Liew, K.M.; Song, L.; Hu, Y. Preparation of Large-Size Reduced Graphene Oxide-Wrapped Ammonium Polyphosphate and Its Enhancement of the Mechanical and Flame Retardant Properties of Thermoplastic Polyurethane. Ind. Eng. Chem. Res. 2017, 56, 7468–7477.
  26. Bowman, S.; Hu, X.; Jiang, Q.; Qiu, Y.; Liu, W.; Wei, Y. Effects of Graphene-Oxide-Modified Coating on the Properties of Carbon-Fiber-Reinforced Polypropylene Composites. Coatings 2018, 8, 149.
  27. Shanmugam, L.; Feng, X.; Yang, J. Enhanced interphase between thermoplastic matrix and UHMWPE fiber sized with CNT-modified polydopamine coating. Compos. Sci. Technol. 2019, 174, 212–220.
  28. Shanmugam, L.; Kazemi, M.E.; Rao, Z.; Lu, D.; Wang, X.; Wang, B.; Yang, L.; Yang, J. Enhanced Mode I fracture toughness of UHMWPE fabric/thermoplastic laminates with combined surface treatments of polydopamine and functionalized carbon nanotubes. Compos. Part B Eng. 2019, 178, 1–9.
  29. Zhang, T.; Chen, J.; Wang, K.; Zhao, Y. Improved interlaminar crack resistance of glass fiber/poly (phenylene sulfide) thermoplastic composites modified with multiwalled carbon nanotubes. Polym. Compos. 2019, 40, 4186–4195.
  30. Yang, B.; Xuan, F.-Z.; Wang, Z.; Chen, L.; Lei, H.; Liang, W.; Xiang, Y.; Yang, K. Multi-functional interface sensor with targeted IFSS enhancing, interface monitoring and self-healing of GF/EVA thermoplastic composites. Compos. Sci. Technol. 2018, 167, 86–95.
  31. Wu, G.; Ma, L.; Liu, L.; Wang, Y.; Xie, F.; Zhong, Z.; Zhao, M.; Jiang, B.; Huang, Y. Interface enhancement of carbon fiber reinforced methylphenylsilicone resin composites modified with silanized carbon nanotubes. Mater. Des. 2016, 89, 1343–1349.
  32. Hassan, E.A.M.; Ge, D.; Zhu, S.; Yang, L.; Zhou, J.; Yu, M. Enhancing CF/PEEK composites by CF decoration with polyimide and loosely-packed CNT arrays. Compos. Part A: Appl. Sci. Manuf. 2019, 127, 1–7.
  33. Li, J.; Qiao, Y.; Li, D.; Zhang, S.; Liu, P. Improving interfacial and mechanical properties of glass fabric/polyphenylene sulfide composites via grafting multi-walled carbon nanotubes. RSC Adv. 2019, 9, 32634–32643.
  34. Fang, J.; Zhang, L.; Li, C. Polyamide 6 composite with highly improved mechanical properties by PEI-CNT grafted glass fibers through interface wetting, infiltration and crystallization. Polymer 2019, 172, 253–264.
  35. Pedrazzoli, D.; Pegoretti, A. Silica nanoparticles as coupling agents for polypropylene/glass composites. Compos. Sci. Technol. 2013, 76, 77–83.
  36. Yang, B.; Zhang, J.; Zhou, L.; Lu, M.; Liang, W.; Wang, Z. Effect of fiber surface modification on water absorption and hydrothermal aging behaviors of GF/pCBT composites. Compos. Part B Eng. 2015, 82, 84–91.
  37. Yang, B.; Zhang, J.; Zhou, L.; Wang, Z.; Liang, W. Effect of fiber surface modification on the lifetime of glass fiber reinforced polymerized cyclic butylene terephthalate composites in hygrothermal conditions. Mater. Des. 2015, 85, 14–23.
  38. Sharma, S.; Rawal, J.; Dhakate, S.R.; Singh, B.P. Synergistic bridging effects of graphene oxide and carbon nanotube on mechanical properties of aramid fiber reinforced polycarbonate composite tape. Compos. Sci. Technol. 2020, 199, 1–12.
  39. Hao, R.; Jiao, X.; Zhang, X.; Tian, Y. Fe3O4/graphene modified waterborne polyimide sizing agent for high modulus carbon fiber. Appl. Surf. Sci. 2019, 485, 304–313.
  40. Lyu, H.; Jiang, N.; Li, Y.; Lee, H.; Zhang, D. Enhanced interfacial and mechanical properties of carbon fiber/PEEK composites by hydroxylated PEEK and carbon nanotubes. Compos. Part A: Appl. Sci. Manuf. 2021, 145, 1–10.
  41. Liu, H.; Zhao, Y.; Li, N.; Zhao, X.; Han, X.; Li, S.; Lu, W.; Wang, K.; Du, S. Enhanced interfacial strength of carbon fiber/PEEK composites using a facile approach via PEI&ZIF-67 synergistic modification. J. Mater. Res. Technol. 2019, 8, 6289–6300.
  42. Zhu, P.; Shi, J.; Bao, L. Effect of polyetherimide nanoparticle coating on the interfacial shear strength between carbon fiber and thermoplastic resins. Appl. Surf. Sci. 2020, 509, 1–8.
  43. Doineau, E.; Coqueugniot, G.; Pucci, M.F.; Caro, A.S.; Cathala, B.; Benezet, J.C.; Bras, J.; Le Moigne, N. Hierarchical thermoplastic biocomposites reinforced with flax fibres modified by xyloglucan and cellulose nanocrystals. Carbohydr. Polym. 2021, 254, 1–10.
  44. Su, Y.; Zhang, S.; Zhang, X.; Zhao, Z.; Jing, D. Preparation and properties of carbon nanotubes/carbon fiber/poly (ether ether ketone) multiscale composites. Compos. Part A: Appl. Sci. Manuf. 2018, 108, 89–98.
  45. Cortes, L.Q.; Racagel, S.; Lonjon, A.; Dantras, E.; Lacabanne, C. Electrically conductive carbon fiber / PEKK / silver nanowires multifunctional composites. Compos. Sci. Technol. 2016, 137, 159–166.
  46. He, H.; Yang, P.; Duan, Z.; Wang, Z.; Liu, Y. Reinforcing effect of hybrid nano-coating on mechanical properties of basalt fiber/poly(lactic acid) environmental composites. Compos. Sci. Technol. 2020, 199, 1–10.
  47. Kim, B.-J.; Cha, S.-H.; Kong, K.; Ji, W.; Park, H.W.; Park, Y.-B. Synergistic interfacial reinforcement of carbon fiber/polyamide 6 composites using carbon-nanotube-modified silane coating on ZnO-nanorod-grown carbon fiber. Compos. Sci. Technol. 2018, 165, 362–372.
  48. Ma, Y.; Yan, C.; Xu, H.; Liu, D.; Shi, P.; Zhu, Y.; Liu, J. Enhanced interfacial properties of carbon fiber reinforced polyamide 6 composites by grafting graphene oxide onto fiber surface. Appl. Surf. Sci. 2018, 452, 286–298.
  49. Zhang, T.; Xu, Y.; Li, H.; Zhang, B. Interfacial adhesion between carbon fibers and nylon 6: Effect of fiber surface chemistry and grafting of nano-SiO2. Compos. Part A: Appl. Sci. Manuf. 2019, 121, 157–168.
  50. Cheon, J.; Kim, M. Impact resistance and interlaminar shear strength enhancement of carbon fiber reinforced thermoplastic composites by introducing MWCNT-anchored carbon fiber. Compos. Part B Eng. 2021, 217, 1–13.
  51. Du, X.; Liu, H.-Y.; Xu, F.; Zeng, Y.; Mai, Y.-W. Flame synthesis of carbon nanotubes onto carbon fiber woven fabric and improvement of interlaminar toughness of composite laminates. Compos. Sci. Technol. 2014, 101, 159–166.
  52. Zhao, G.; Liu, H.-Y.; Du, X.; Zhou, H.; Pan, Z.; Mai, Y.-W.; Jia, Y.-Y.; Yan, W. Flame synthesis of carbon nanotubes on glass fibre fabrics and their enhancement in electrical and thermal properties of glass fibre/epoxy composites. Compos. Part B Eng. 2020, 198, 1–11.
  53. Zhao, P.; Xiong, X.; Liu, S.; Ren, R.; Zhang, Z.; Cui, X.; Ji, S.; Qi, W. Resistance welded thermoplastic composites joint strengthened via carbon nanotubes from flame: Interface strength, mechanical properties and microstructure. Mater. Res. Express 2019, 6, 1–7.
  54. Zhao, G.; Liu, H.-Y.; Cui, X.; Du, X.; Zhou, H.; Mai, Y.-W.; Jia, Y.-Y.; Yan, W. Tensile properties of 3D-printed CNT-SGF reinforced PLA composites. Compos. Sci. Technol. 2022, 230, 1–11.
  55. Kim, B.-J.; Cha, S.-H.; Park, Y.-B. Ultra-high-speed processing of nanomaterial-reinforced woven carbon fiber/polyamide 6 composites using reactive thermoplastic resin transfer molding. Compos. Part B Eng. 2018, 143, 36–46.
  56. Rasana, N.; Jayanarayanan, K.; Pavithra, R.; Nandhini, G.R.; Ramya, P.; Veeraraagavan, A.V. Mechanical and Thermal Properties Modeling, Sorption Characteristics of Multiscale (Multiwalled Carbon Nanotubes/Glass Fiber) Filler Reinforced Polypropylene Composites. J. Vinyl Addit. Technol. 2019, 25, E94–E107.
  57. Rudresh, B.M.; Ravi Kumar, B.N.; Madhu, D. Combined effect of micro- and nano-fillers on mechanical, thermal, and morphological behavior of glass–carbon PA66/PTFE hybrid nano-composites. Adv. Compos. Hybrid Mater. 2019, 2, 176–188.
  58. Sun, Z.; Zhao, Z.-K.; Zhang, Y.-Y.; Li, Y.-Q.; Fu, Y.-Q.; Sun, B.-G.; Shi, H.-Q.; Huang, P.; Hu, N.; Fu, S.-Y. Mechanical, tribological and thermal properties of injection molded short carbon fiber/expanded graphite/polyetherimide composites. Compos. Sci. Technol. 2021, 201, 1–10.
  59. Arao, Y.; Yumitori, S.; Suzuki, H.; Tanaka, T.; Tanaka, K.; Katayama, T. Mechanical properties of injection-molded carbon fiber/polypropylene composites hybridized with nanofillers. Compos. Part A: Appl. Sci. Manuf. 2013, 55, 19–26.
  60. Hwang, S.-H.; Kim, B.-J.; Baek, J.-B.; Shin, H.S.; Bae, I.-J.; Lee, S.-Y.; Park, Y.-B. Effects of process parameters and surface treatments of graphene nanoplatelets on the crystallinity and thermomechanical properties of polyamide 6 composite fibers. Compos. Part B Eng. 2016, 100, 220–227.
  61. Qi, Z.; Liu, H.; Wang, J.; Yan, F. The enhanced transfer behavior and tribological properties in deep sea environment of poly(butylene terephthalate) composites reinforced by silica nanoaerogels. Tribol. Int. 2021, 160, 1–11.
  62. Liu, X.; Gao, Y.; Shang, Y.; Zhu, X.; Jiang, Z.; Zhou, C.; Han, J.; Zhang, H. Non-covalent modification of boron nitride nanoparticle-reinforced PEEK composite: Thermally conductive, interfacial, and mechanical properties. Polymer 2020, 203, 1–8.
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