Multi-scale Hybrid Composites Research Articles

Improvement of electrical conductivity in glass bubble-carbon nanotube/polyamide 6 hybrid scale composite through novel mechanical forming and segregated network morphology

The study suggests that GB-CNT/PA6 multiscale hybrid composite can be used to create a network structure with controllable electrical conductivity, making it a promising material for various practical applications. The paper introduces a new method for controlling electrical conductivity of composite materials by creating a segregated network morphology (SNM) using a glass bubble (GB)-carbon nanotube (CNT)/polyamide 6 (PA6) multiscale hybrid composite. Instead of relying solely on CNTs, the addition of GB allows for a more economical process by reducing the required CNT concentration to achieve the desired electrical conductivity. The paper also analyzes the effects of varying GB and CNT content on electrical conductivity based on percolation theory. The results demonstrate an 18.8 times increase in electrical conductivity with the SNM approach. The study proposes that this approach could be used to create composite materials with controllable electrical conductivity, making them suitable for various applications.

Thermal conductivity controlled by a segregated network prepared using carbon nanotube/polyamide 6 composite with glass bubbles

AbstractIn this study, a carbon nanotube‐glass bubble/polyamide 6 (CNT‐GB/PA6) multiscale hybrid composite was manufactured. Through a coagulation process including CNT and GB, a segregated network was formed to produce a composite structure with tunable thermal conductivity. Within the segregated network structure, a complex phenomenon of decrease and increase in thermal conductivity owing to the interaction by CNT and GB, and an equation to predict thermal conductivity through the contents of GB and CNT was formulated. A model to predict the thermal conductivity using the RSM analysis was presented, and the contents of GB and CNT were adjusted according to the required thermal conductivity. It was confirmed through the LFA thermal conductivity measurement that the thermal conductivity increased with GB and CNT contents. Moreover, when 30% of GB was added to the 5 wt% CNT composite, the thermal conductivity increased by about 17%. However, in the experiment to confirm the effect of GB alone, it was confirmed that the thermal conductivity decreased as the GB content increased. Thus, the size of the structural path, which was controlled by the GB content through which electrons pass, played an important role in this study. The results of this study can be used in astronautic fields that require insulation to save energy and in construction engineering where thermal insulation and heat emission are important.

Effects of the Simultaneous Strengthening of the Glass Fiber Surface and Polyamide-6 Matrix by Plasma Treatment and Nanoclay Addition on the Mechanical Properties of Multiscale Hybrid Composites

To strengthen the mechanical properties of a fiber-reinforced plastic without deteriorating its toughness caused by adding nanomaterial, multiscale hybrid composites (MHC) composed of polyamide 6 (PA6), woven glass fibers (WGFs), nanoclay, and various additives were fabricated and characterized. A surfactant was used to improve the dispersion of the nanoclay in the composite, and a compatibilizer and toughening agent were added to enhance the interfacial interactions between the nanoclay and PA6 and the toughness of the MHC, respectively. In addition, the WGFs were pretreated with atmospheric-pressure air plasma to enhance the interfacial bonding between the WGF and the mixture composed of PA6/nanoclay/compatibilizer/toughening agent, which constitutes the matrix. The optimal composition of the PA6 mixture, optimal content of the nanoclay, and optimal conditions of the plasma pretreatment of the WGF surface were experimentally determined. A suitable manufacturing process was employed using a material composition that maximizes the mechanical properties of the MHC by mitigating the toughness deterioration owing to nanoclay addition. An appropriate quantity of the nanoclay increased the tensile properties as well as the elongation at the break of the MHC because the toughening agent prevented the reduction in the degree of elongation caused by increasing the clay content to a certain extent. Moreover, the plasma treatment of the WGF enhanced the flexural properties and impact resistance of the MHC. Therefore, not only the tensile strength, modulus, and elongation at the break of the PA6 nanocomposite, which constitutes the matrix of the MHC, increased up to 39.83, 40.91, and 194.26%, respectively, but also the flexural strength and modulus, absorbed impact energy, and penetration limit of the MHC increased by 20.2, 26.8, 83.7, and 100.0%, respectively.

A refined spectral element model for wave propagation in multiscale hybrid epoxy/carbon fiber/graphene platelet composite shells

The propagation of elastic waves in heterogeneous media is of interest for impact dynamics and non-destructive detection. This work presents a refined spectral element model (RSEM) to study the wave propagation in multiscale hybrid composite (MHC) shells subjected to impulsive loadings. The doubly-curved MHC shell consists of epoxy, carbon fibers, and graphene platelets (GPLs). The GPLs are functionally distributed along the thickness of the shell. For the three-phase MHC, the Halpin-Tsai micromechanical model in conjunction with the Mori-Tanaka approach is exploited to determine the effective material properties. In the framework of four-variable shear deformation theory, the governing equations along with the natural boundary conditions are derived using Hamilton's principle. A two-node spectral shell element is developed according to the closed-from solutions. The accuracy of the RSEM is verified by comparison with published results in aspects of the natural frequency and transient responses. The wave dispersion characteristics, including the wave number, phase velocity, and group velocity are examined. In the context of high frequency and short wavelength, the proposed RSEM achieves high computational efficiency benefiting from its independence of mesh structure. The time domain responses clearly indicate the wave-boundary interactions, e.g., wave reflection, dispersion, and interference. It is revealed that the present model can well capture the fundamental wave modes of the MHC shell. Moreover, the inclusion of GPLs plays a significant role in improving transverse moduli and mitigating the discontinuities of inter-laminar shear stress.

Multi-scale hybrid composites are making their way

Multi-scale hybrid composites are making their way

The influence of carbon nanotube coated-carbon fibers on thermal residual stresses of Multi-Scale hybrid composites: Analytical approach

The effect of carbon nanotube (CNT) coated-carbon fibers on thermal residual stresses of multi-scale hybrid composites is assessed employing analytical approach. The model comprises carbon fiber, coating region and surrounding matrix, in which the coating region around core fiber encompasses CNTs and matrix. Considering three configurations of grown CNTs on the fiber surface including axially, radially and randomly oriented, the mechanical properties of various coating regions are acquired employing the Eshelby–Mori–Tanaka method in conjunction with an equivalent continuum approach. Utilizing the total energy minimization method, the closed-form solution of the thermal residual stresses of hybrid composite is obtained. The results disclose a noteworthy influence of CNT–coating on the reduction of interfacial stresses which precludes debonding at interface and attenuates the effect of thermal expansions mismatch between the carbon fiber and matrix. Furthermore, the results demonstrate that unlike radially oriented CNTs, the existence of axially and randomly oriented CNTs at the coating region has a remarkable diminishing effect on residual interfacial stresses. It is also shown that increasing the coating thickness leads to reduction of maximum interfacial stresses even at a constant CNT volume fraction. A close agreement exists between predicted outcomes by the proposed analytical approach and published data in the literature.

Comparative study of the thermoresistive behavior of carbon nanotube-based nanocomposites and multiscale hybrid composites

Advances in carbon nanotube (CNT) based composites over the past decade have demonstrated broad potential of utilizing them as multifunctional sensors because of their unique electrical properties. This article studies the thermoresistive behavior of two-component (CNT-epoxy) nanocomposites and hierarchical (CNT-fiber-epoxy) multiscale composites using in situ electrical resistance measurements during thermal cycling from 25 to 145 °C. A series of CNT-based composites with controlled nanotube morphologies were created via three-roll-milling, dip-coating and electrophoretic deposition methods. The results show that the thermoresistive behavior of CNT-based composites is influenced by the CNT concentration, thermal expansion, fiber/polymer properties, and interfacial interactions. CNT-epoxy nanocomposites with randomly dispersed CNTs show a positive temperature correlation. In comparison, multiscale composites with fibers show a double-crossover-shaped temperature dependence of their electrical resistance influenced by the changes of the CNT network that are induced by the polymer thermal motions and the residual thermal stresses. The thermal expansion behavior of the composites was characterized using a thermomechanical analyzer and a simplified finite element model was used to qualitatively examine the fiber-matrix interfacial residual stresses. While the thermoresistive behavior of nanocomposites has been investigated more broadly, this research is a first step in understanding the processing-structure-thermoresistive response relationship of multiscale CNT/fiber composites.

The effect of multiscale hybridization on the mechanical properties of natural fiber‐reinforced composites

AbstractThe main objective of this work was to investigate the effect of reinforcements at different scales on the mechanical properties of natural fiber‐reinforced composites. Pure jute and interlaminar hybrid jute/glass fiber‐reinforced polymer composites were fabricated. Different types of fillers in two weight fractions (1 and 3 wt. %) were used as second reinforcements in the hybrid jute/glass composites. Tensile, flexural, and impact tests were performed. It was found that the macroscale inter‐play hybridization significantly improved the mechanical properties of the pure jute fiber based composites. When the fillers are used as second hybridization, the modified composites presented higher mechanical properties when compared to pure jute composites. However, the effect of fillers on the mechanical properties of the hybrid composites presented various trends due to the interaction between several factors (i.e., particle scale, content, and nature), which cannot always be separated. Increasing the synthetic filler content improved the tensile properties of the filled hybrid composites, while increasing the natural filler content worsen the tensile properties. The flexural strength of the multiscale hybrid composites was improved, while the impact properties were negatively affected.

Thermal postbuckling of shear deformable multiscale hybrid composite beams

This research is deal with thermal buckling and post-buckling of carbon nanotube/fiber/polymer composite beams. The beam is considered to be under uniform temperature rise. Firstly, the effective material properties of a two phase nanocomposite consisting of CNT and polymer are extracted. Then, the modified Chamis rule is utilized to obtain the equivalent thermo-mechanical properties of multiscale hybrid composite (MHC). Based on the first order shear deformation theory, Von-Karman type of geometrically nonlinear strain-deformation equations and also the virtual work rule, the equilibrium equations of a three phace composite beam are derived. Bifurcation buckling and also the thermal post-buckling is analysed using the generalized differential quadrature technique. In the thermal buckling phenomena, a linear eigenvalue problem is solved; however, due to the nonlinearity, the thermal postbuckling study is performed using an iterative displacement control strategy. After validation study, several novel results demonstrate the influences of length-to-thickness ratio, agglomeration of applied CNTs and fibers in the composite media and number and orientation of layers on the critical temperature and displacement loading path.

The rheological behaviour and thermal ageing characteristics of PP/MWCNT/glass fibre multiscale composites

Multiscale hybrid composites were prepared using varying weight percentages (0 to 5) of multiwalled carbon nanotubes (MWCNTs) as nanofiller and a fixed weight percentage (20) of short glass fibres as micro filler (in polypropylene (PP) matrix. The shear and extensional viscosity of the composites was measured using a capillary rheometer. It was observed that even at higher shear rates the synergism of micro and nanofillers in the matrix significantly enhanced the melt viscosity. The complex nanotube network entanglement with micro fillers and PP chains imparted restrictions to the polymer chain movements. The prepared samples were subjected to thermal ageing at 100°C for 4 days in hot air oven. After ageing, multiscale composite with 3 wt% MWCNTs exhibited 28.57% enhancement in strain at break, whereas the tensile strength and modulus reduced by 6.8% and 8% respectively. The fracture toughness properties like strain energy release rate and critical stress intensity factor were not affected for multiscale composite at the optimum content of 3 wt% MWCNT, even after thermal ageing.

Experimental investigation, modeling and optimization study on the mechanical properties of B4Cp/MWCNT/epoxy multi-scale hybrid composite

In this study, process parameters and mechanical properties of the multi-scale composite were investigated experimentally and predictably. Multi-scale material includes boron carbide particles and multi walled carbon nanotubes (MWCNTs) in the epoxy-based matrix. Both reinforcements were reinforced into the matrix with various rates simultaneously. Average three tensile strength and hardness values were determined. The tensile strength and hardness were enhanced thanks to high rate of B4C usage up to 54.09% and 2.54%, respectively. The microstructure of the hybrid composite was investigated by Scanning Electron Microscopy. Also, Fourier Transform Infrared Spectroscopy was used to interpret spectral bands. The experimental data were analyzed using optimization method. Optimal process parameters for tensile strength and interfacial properties were determined. The Analysis of Variance (ANOVA) was used to obtain most significant factor and optimum levels of parameters. Finally, it was observed that B4C ratio is the most dominant factor affecting the mechanical and thermal properties.

Electrophoretic deposition: Novel in situ film growth mechanism of carbon nanocomposite films within non-conductive fabrics for multi-scale hybrid composites

A novel electrophoretic deposition (EPD) technique is developed to create uniform coatings of functionalized carbon nanotubes (CNTs) on non-conductive fabrics. EPD enables the creation of porous CNT composite films not just on the outer surface of the fabrics but onto individual fibers within fiber bundles or woven fabrics. This process can be conducted at room temperature without using any hazardous chemicals, making it inherently scalable, and can be applied to a wide range of fibers and textile structures to fabricate mechanically reinforced or multifunctional composites. A key advantage of EPD is the ability to control the CNT film thickness and microstructure because of the unique in situ film formation mechanism and by varying the process parameters. Unlike the mechanism for conductive carbon fibers, results for glass fibers suggest that positively charged nanotubes are destabilized by a local pH gradient and precipitate onto the negative electrode, which is followed by CNT film growth onto the fibers in direct contact with the electrode. Intimate contact is critical for both film extension from the electrode to fiber and throughout the filaments in a fabric. The electrically conductive CNT film acts as an extension of the electrode, promoting deposition throughout the fabric. Our model system studies aqueous dispersions of multi-walled CNTs functionalized with polyethyleneimine (PEI) deposited onto glass fibers. Key experiments are designed at different length scales, from single filaments to macroscopic composite rods, to visualize the film formation.

Synergistic Mechanical Reinforcement of Woven Carbon Fiber/Polypropylene Composites Using Plasma Treatment and Nanoclay

Polypropylene (PP) nanocomposite films reinforced with surface-modified nanoclay, maleic anhydride-grafted PP (PP-g-MA), and surfactants, such as cetyl-trimethyl-ammonium bromide (CTAB) and octadecyl-trimethyl-ammonium bromide (ODAB), were fabricated by extrusion, and the effect of surfactant type used for the nanoclay and the take-up speed of extrusion on the mechanical properties and crystallinity of the nanocomposite films were investigated. Multi-scale hybrid composites (MHCs) consisting of plasma-treated plain woven carbon fiber (WCF) and nanocomposite films were manufactured by hot pressing. Flexural and impact tests were performed to measure the mechanical properties at various plasma treatment times. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) were used to observe the surface morphology and detect polar functional groups, respectively. Results of XPS analysis showed a considerable increase in the oxygen atomic percentage after plasma treatment. The mechanical properties of the MHCs were greatly affected by the presence of nanoclay in the composite and the plasma treatment. The flexural modulus and strength, impact force, and absorbed impact energy of the MHC specimens treated with plasma (15 s) and reinforced with nanoclay/ODAB(5:1, 1.5 wt%) and PP-g-MA(3 wt%), increased by 69, 87, 49 and 54%, respectively, compared to the neat non-plasma-treated WCF/PP composites.

Electro spun nanomats strengthened glass fiber hybrid composites: Improved mechanical properties using continuous nanofibers

Hybrid multiscale fiber reinforced epoxy composite laminates were developed and characterized from woven glass fiber mats reinforced with nonwoven PAN nanofibers (diameters of 200 nm) produced via electrospinning. An electrospinning setup was designed and developed to produce continuous E‐spun nonwoven nanofiber (NWNF) mats, which were then used as interlaminar reinforcements for producing multiscale hybrid composites. A detailed study for producing E‐spun nanomats considering both solution and operation parameters was undertaken discussed and optimum spinning parameters were obtained. These parameters were used to produce the E‐spun NWNF mats, which were inserted into the interlaminar region of glass fiber reinforced epoxy laminates. The impact absorption energy, tensile strength, and flexural strength of the hybrid multiscale composites were found to increase with an increase in E‐spun NWNF mat weight fraction. These properties were compared to those of a conventional glass fiber composite laminates prepared from the neat epoxy resin with 32% glass fiber volume fraction. The effectiveness of the strengthening/toughening strategy formulated in this study indicates that the feasibility of using the E‐spun NWNF mat reinforcements for improving the mechanical properties of structured high‐performance composites. In addition, the present study provides motivation for the long‐term development of high‐strength high toughness bulk structural nanocomposites for broader engineering applications.

Enhancing the Viscoelastic Performance of Carbon Fiber Composites by Incorporating CNTs and ZnO Nanofillers

Carbon fiber reinforced plastic composites (CFRPs) possess superior elastic mechanical properties. However, CFRPs lack sufficient viscoelastic performance, such as damping and creep resistance. In an effort to improve these properties, in this study, hybrid multiscale composites with various combinations of zinc oxide nanorods (ZnO) and carbon nanotubes (CNTs) were deposited at the interface of carbon fiber laminae. The viscoelastic properties of the corresponding composites were characterized via dynamic mechanical analysis (DMA) during both temperature and frequency sweeps. The creep activation energy for each composite configuration was also calculated. The DMA temperature sweep analysis reported that the composite incorporating both ZnO and CNTs exhibited the highest improvements in all viscoelastic properties. This composite also attained better creep resistance, evident by the highest activation energy. The DMA frequency sweep analysis revealed that composites incorporating a single nanofiller improves the viscoelastic properties more than the combined nanofiller composite. Despite these improvements in the viscoelastic properties, the non-uniform dispersion and agglomerations of the nanofillers affected some of the elastic properties negatively, such as the storage modulus.

Hybrid multi-scale thermoplastic composites reinforced with interleaved nanofiber mats using in-situ polymerization of cyclic butylene terephthalate

Abstract Mechanically flexible electrospun carbon and glass nanofiber mats (i.e., ECNF-mats and EGNF-mats) were prepared by electrospinning followed by thermal treatments; subsequently, a technique was applied to fabricate two types of multi-scale thermoplastic composites, involving infiltration of molten cyclic butylene terephthalate (CBT) followed by in-situ polymerization under compression. For the first composite type, eight conventional carbon fabrics were interleaved with seven ECNF-mats. For the second composite type, eight conventional glass fabrics were interleaved with seven EGNF-mats. Compared to the values acquired from the corresponding control samples without nanofiber mats, the interlaminar shear strength, flexural strength, flexural modulus, and work of fracture acquired from the hybrid multi-scale composite containing ECNF-mats were increased by 32%, 25%, 19%, and 33%, respectively; while the values acquired from the hybrid multi-scale composite containing EGNF-mats were increased by 66%, 43%, 17%, and 64%, respectively. Furthermore, the enhancements of out-of-plane properties were not at the expense of in-plane tensile strength or modulus. The study indicated that the employed fabrication technique could be adopted as an efficient approach to produce polybutylene terephthalate (PBT) thermoplastic composites through in-situ polymerization of CBT oligomer; and the ECNF-mats and EGNF-mats could be utilized as innovative reinforcement fillers for enhancing the performance of structural thermoplastic composites.

The effects of plasma surface treatment on the mechanical properties of polycarbonate/carbon nanotube/carbon fiber composites

The effects of plasma surface treatment on the mechanical properties of multiscale hybrid composites consisting of polycarbonate (PC), carbon nanotube (CNT) and carbon fiber (CF) were investigated. Dynamic mechanical properties and impact energy absorption of multiscale hybrid composites fabricated under various processing conditions were measured and correlated with surface roughness and surface functionality. The highest room-temperature storage modulus (E’) of 39 GPa and absorbed impact energy of 5.3 J were obtained from the plasma-treated PC/CNT/CF composite, which are increases by 387% and 194%, respectively, as compared to the neat PC/CF composite. Although the plasma treatment was more efficient for the PC/CF composites rather than the PC/CNT/CF composites, hybridization of CNT showed synergistic effects on the enhancement of mechanical properties due to the combination of increased surface roughness and functionality as well as the bridged modulus gap between PC and CF.

Synergistic interfacial reinforcement of carbon fiber/polyamide 6 composites using carbon-nanotube-modified silane coating on ZnO-nanorod-grown carbon fiber

We report an experimental study on improvement of mechanical properties of a multiscale hybrid composite consisting of in-situ polymerized polyamide-6 and zinc oxide nanorod(ZnO NR)-grown woven carbon fiber (WCF) coated with carbon nanotube(CNT)-modified silane. The ZnO growth process and silane coating process were performed on the fiber surface, and then the composite was fabricated by ultra-fast (<30 s from infusion to polymerization) thermoplastic resin transfer molding technique with extremely low viscosity of resin. The ZnO NRs formed mechanical interlocking with polymer matrix, and at the same time, the CNTs-modified silane layer on WCFs and ZnO NRs formed covalent bond with the matrix; therefore, they induced strong interaction between matrix and fibers, thereby resulting in remarkable improvements in the mechanical properties of the composite. The morphology, coating thickness and composition of the CNTs-modified silane/ZnO/WCF surface according to amount of the silane coupling agent were analyzed and their effects on mechanical properties of the composite were investigated. As compared to neat composites, multiscale hybrid composites showed up to 32 and 41% increases in tensile modulus and strength, respectively, and 107, 179 and 159% increases in in-plane shear strength, absorbed impact energy and penetration limit, respectively.

Synergistic effects of hybrid MWCNT/nanosilica on the tensile and tribological properties of woven carbon fabric epoxy composites

An epoxy matrix incorporated with hybrid multi-walled carbon nanotube (MWCNT) and nanosilica was used to fabricate woven carbon fabric epoxy composites using vacuum-assisted resin infusion molding (VARIM). Three types of multi-scale hybrid composites containing 0.2 wt.% MWCNT + 0.7 wt.% nanosilica, 0.7 wt.% MWCNT + 0.2 wt.% nanosilica, and 0.45 wt.% MWCNT + 0.45 wt.% nanosilica were prepared to investigate both tensile and tribological properties, simultaneously. The results of tensile and tribological experiments showed that specimens containing 0.45 wt.% MWCNT + 0.45 wt.% nanosilica were better than the corresponding single-type nanoparticles with the same total weight percentages. Especially, the tensile strength and tensile modulus of composite specimens containing 0.45 wt.% MWCNT + 0.45 wt.% nanosilica increased by 25.2% and 31% in comparison with the neat composites, while their friction coefficient and wear rate decreased by 88% and 98% in comparison with the neat composites, respectively. The SEM images of fracture surfaces showed that the incorporation of nanoparticles enhanced the fiber–matrix interfacial strength, toughened the surrounding matrix, and improved resin adhesion to the fiber, which increased tensile properties of incorporated composites with hybrid nano-fillers. Moreover, by adding the hybrid nanoparticles to the unfilled carbon fabric composites, the friction coefficient variation of these specimens totally changed, which led to an improvement in the friction-reducing ability and wear rate resistance. In conclusion, a method is suggested in this paper to incorporate hybrid nanoparticles for benefitting from the properties of both nanoparticles at higher weight percentages.

Unidirectional spread‐tow carbon fiber/polypropylene composites reinforced with mechanically aligned multi‐walled carbon nanotubes and exfoliated graphite nanoplatelets

We investigated efficient methods to maximize the mechanical properties of carbon fiber/polypropylene (PP) composites by combining unidirectional spread‐tow carbon fibers (USCFs) and mechanically stretched PP films reinforced with aligned carbon nanomaterials (CNMs), such as multi‐walled carbon nanotubes (MWCNTs) and exfoliated graphite nanoplatelets (xGnPs). CNM/PP composite films were fabricated using film extrusion process, which resulted in tension‐induced orientation of CNMs. The influences of CNMs and their orientations in the films, the speed of the drawing rollers (take‐up speed), and the degree of crystallinity on the mechanical properties of nanocomposites were investigated. Multiscale hybrid composites (MHCs) consisting of USCFs and PP films reinforced with MWCNTs and xGnPs were manufactured by hot pressing. As compared with neat USCF/PP composites, USCF/PP composites containing 1 wt% aligned CNMs showed up to 18.3 and 77.3% increases in tensile modulus and strength, respectively, and 68.4 and 36.1% increases in flexural modulus and strength, respectively. In parallel, modeling and simulation of CNM/PP composite films and CNM/USCF/PP composites were performed to predict the tensile properties, taking into account the effects of CNM orientation. The mechanical properties of both nanocomposite films and MHCs were most dominantly affected by the degree of polymer crystallinity and CNM orientation. POLYM. COMPOS., 39:E1251–E1261, 2018. © 2018 Society of Plastics Engineers