Influence of ultrasonic dual mixing on thermal and tensile properties of MWCNTs-epoxy composite

Multiwalled carbon nanotubes (MWCNTs) reinforced epoxy based composites were fabricated by using an innovative ultrasonic dual mixing (UDM) process consists of ultrasonic mixing with simultaneous magnetic stirring. The effect of addition of varying amount of MWCNTs on thermal stability and tensile properties of the epoxy based composite has been investigated. It is found that the thermal stability, tensile strength and toughness of the epoxy base improves with the increase of MWCNTs addition up to 1.5 wt.% and UDM processing at certain capacity of the system. Tensile tests and thermal gravimetric analysis (TGA) were performed on each group of composites containing different amount of MWCNTs to determine their mechanical and thermal properties respectively. The dispersion of 1.5 wt.% MWCNTs fillers in epoxy nanocomposites was studied by transmission electron microscopy (TEM) as well as by field emission scanning electron microscopy (FESEM) applied on their tensile fracture surface.     

Mechanical performance of epoxy matrix hybrid nanocomposites containing carbon nanotubes and nanodiamonds

A novel class of epoxy matrix hybrid nanocomposites has been developed containing multiwalled carbon nanotubes (MWCNTs) and nanodiamonds (NDs) to explore the combined effect of nanoreinforcements on the mechanical performance of nanocomposites. Both the nanofillers were functionalized before incorporating into epoxy matrix to promote interfacial interactions. The concentrations of both MWCNTs and NDs in the nanocomposites were increased systematically, i.e. 0.05 wt.%, 0.1 wt.% and 0.2 wt.% while composites containing individual nanoreinforcements were also manufactured for comparison. The developed nanocomposites were characterized microstructurally by scanning electron microscopy (SEM) and mechanically by tensile, flexural, impact and hardness tests. Homogeneous dispersion of MWCNTs and NDs was observed under SEM, which resulted in the enhancement of mechanical properties of nanocomposites. The composites containing 0.2 wt.% MWCNTs and 0.2 wt.% NDs showed 50% increase in hardness while tensile strength and modulus enhanced to 70% and 84%, respectively. Flexural strength and modulus also showed a rise of 104% and 56%, respectively. Interestingly, fracture strain also increased in both the tensile and flexural testing. The impact resistance increased to 161% showing a significant improvement in the toughness of hybrid nanocomposites.     

Cryogenic mechanical behaviors of carbon nanotube reinforced composites based on modified epoxy by poly(ethersulfone)

Cryogenic mechanical properties are important parameters for epoxy resins used in cryogenic engineering areas. In this study, multi-walled carbon nanotubes (MWCNTs) were employed to reinforce diglycidyl ether of bisphenol F (DGBEF)/diethyl toluene diamine (DETD) epoxy system modified by poly(ethersulfone) (PES) for enhancing the cryogenic mechanical properties. The epoxy system was properly modified by PES in our previous work and the optimized formulation of the epoxy system was reinforced by MWCNTs in the present work. The results show that the tensile strength and Young’s modulus at 77 K were enhanced by 57.9% and 10.1%, respectively. The reported decrease in the previous work of the Young’s modulus of the modified epoxy system due to the introduction of flexible PES is offset by the increase of the modulus due to the introduction of MWCNTs. Meanwhile, the fracture toughness (K_IC) at 77 K was improved by about 13.5% compared to that of the PES modified epoxy matrix when the 0.5 wt.% MWCNT content was introduced. These interesting results imply that the simultaneous usage of PES and MWCNTs in a brittle epoxy resin is a promising approach for efficiently modifying and reinforcing epoxy resins for cryogenic engineering applications.     

Superior mechanical and electrical properties of multiwall carbon nanotube reinforced acrylonitrile butadiene styrene high performance composites

In-house synthesized multiwall carbon nanotubes (MWCNTs) have been dispersed in acrylonitrile butadiene styrene (ABS) using a micro twin-screw extruder with back flow channel. The electrical and mechanical properties of MWCNTs in ABS with different wt% have been studied. Incorporation of only 3 wt. % MWCNTs in ABS leads to significant enhancement in the tensile strength (up to 69.4 MPa) which was equivalent to 29% increase over pure ABS. The effect of MWCNTs on the structural behaviour of ABS under tensile loading showed a ductile to brittle transition with increase concentration of MWCNTs. The results of enhanced mechanical properties were well supported by micro Raman spectroscopic and scanning electron microscopic studies. In addition to the mechanical properties, electrical conductivity of these composites increased from 10⁻¹² to 10⁻⁵ Scm⁻¹ showing an improvement of ∼7 orders of magnitude. Due to significant improvement in the electrical conductivity, EMI shielding effectiveness of the composites is achieved up to −39 dB for 10 wt. % loaded MWCNTs/ABS indicating the usefulness of this material for EMI shielding in the Ku-band. The mechanism of improvement in EMI shielding effectiveness is discussed by resolving their contribution in absorption and reflection loss. This material can be used as high-strength EMI shielding material.     

Effect of matrix glass transition on reinforcement efficiency of epoxy-matrix composites with single walled carbon nanotubes,multi-walled carbon nanotubes,carbon nanofibers and graphite

This study compares the mechanical and thermal properties of glassy and rubbery epoxy–matrix composites reinforced with 1 and 4 wt.% single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphite, and carbon nanofibers (CNFs). The tensile modulus of most glassy composites was higher than that of the epoxy and increased with higher filler concentration and 4% graphite/epoxy and 4% SWCNT/epoxy exhibited approximately the same highest tensile modulus. The elongation of glassy composites was significantly lower than that of the epoxy and decreased with increasing filler loading. Most rubbery composites showed a higher tensile modulus and elongation than the epoxy and the modulus increased with rising filler content and 4% SWCNT/epoxy showed the highest tensile modulus and tensile strength. In the rubbery regime, glassy and rubbery composites displayed a higher storage modulus than the corresponding epoxy and 4 wt.% SWCNT/epoxy composites showed a 300% improvement in storage modulus compared to the epoxy.     

Crystalline morphology and properties of multi-walled carbon nanotube filled isotactic polypropylene nanocomposites: Influence of filler size and loading

Isotactic polypropylene (PP) nanocomposites with multi-walled carbon nanotubes (MWCNTs) of various diameters (10–50 nm) were fabricated by extrusion and compression-molding techniques and characterized by X-ray diffraction measurements, differential scanning calorimetry, scanning electron microscopy, mechanical test and differential thermal analyses. The pure PP exhibits both the a- and b-axes oriented α-crystal, whereas the MWCNTs induce the b-axis orientation of the α-crystal along with the formation of minor γ-phase crystal in nanocomposites. Crystallinity, long period of lamellae, tensile strength, tensile modulus (TM) and microhardness (H) of PP considerably change by different loading and sizes of MWCNTs. The estimated values H/TM = 0.09–0.10 for all samples approach the predicted value of 0.10 for polymers. The increase in crystallinity has been demonstrated by both XRD and DSC studies. Mathematical models have been invoked to explain the changes in mechanical properties. An increase in thermal stability of polymer matrix occurs with increasing MWCNTs size and loading.     

CF/EP composite laminates with carbon black and copper chloride for improved electrical conductivity and interlaminar fracture toughness

An experimental study was conducted to improve the electrical conductivity of continuous carbon fibre/epoxy (CF/EP) composite laminate, with simultaneous improvement in mechanical performance, by incorporating nano-scale carbon black (CB) particles and copper chloride (CC) electrolyte into the epoxy matrix. CF/EP laminates of 65 vol.% of carbon fibres were manufactured using a vacuum-assisted resin infusion (VARI) technique. The effects of CB and the synergy of CB/CC on electrical resistivity, tensile strength and elastic modulus and fracture toughness (K_IC) of the epoxy matrix were experimentally characterised, as well as the transverse tensile modulus and strength, Mode I and Mode II interlaminar fracture toughness of the CF/EP laminates. The results showed that the addition of up to 3.0 wt.% CB in the epoxy matrix, with the assistance of CC, noticeably improved the electrical conductivity of the epoxy and the CF/EP laminates, with mechanical performance also enhanced to a certain extent.     

静电植绒法处理多壁碳纳米管改性玻纤织物/环氧树脂复合材料的制备及力学性能

为提高玻纤增强环氧树脂复合材料的力学性能,采用静电植绒法将多壁碳纳米管(MWCNTs)附着在玻纤织物表面,得到改性的玻纤织物。利用一种低黏度的环氧树脂和所制得的改性织物,采用真空辅助成型工艺(VARI)制备了MWCNTs改性格玻纤织物/环氧树脂复合材料层合板,表征了层合板的力学性能。对进行力学实验后的MWCNTs改性玻纤织物/环氧树脂复合材料试样断口进行了SEM和OPM观察。结果显示:与未添加MWCNTs的玻纤织物/环氧树脂复合材料层合板相比,添加了MWCNTs的层合板的拉伸强度降低了10.24%,弯曲强度降低了13.90%,压缩强度降低了17.33%,拉伸模量和弯曲模量分别提高了19.38%和16.04%,压缩模量提高了13%;MWCNTs与玻纤织物之间的结合较弱,在拉伸作用下,存在明显的脱粘和分层;将改性玻纤织物在200℃下热压处理2h后,制备的MWCNTs改性玻纤织物/环氧树脂复合材料层合板的力学性能均有所提高,热压处理后树脂与玻纤织物之间的界面结合得到改善。     

功能化MWCNTs网格/环氧树脂复合材料的制备及性能

采用正压过滤法制备了多壁碳纳米管（MWCNTs）网格（巴基纸）,并采用真空辅助RTM工艺制备了MWCNTs网格/环氧树脂复合材料。通过SEM、FTIR、拉伸测试等对MWCNTs网格的微观形貌和性能进行了表征,并研究了MWCNTs网格/环氧复合材料的拉伸性。结果表明,所制备的功能化MWCNTs网格比较均匀,拉伸强度在22~32 MPa之间,拉伸模量约为1 GPa,相比未功能化处理的MWCNTs网格,强度最大提高了约167%。功能化MWCNTs网格/环氧树脂复合材料的拉伸强度和拉伸模量可达到152 MPa和6.48 GPa,相比空白环氧树脂提高了约1倍以上,拉伸试样断面SEM表明,环氧树脂对功能化MWCNTs网格的浸润效果良好,界面结合紧密,有效地提高了复合材料的力学性能。     

Incorporation of liquid-like multiwalled carbon nanotubes into an epoxy matrix by solvent-free processing

Covalent attachment of 2,2'-(ethylenedioxy)-diethylamine to multiwalled carbon nanotubes (MWCNTs) produced amino-functionalized MWCNTs which behaved like liquids at ambient temperature. These liquid-like MWCNTs (l-MWCNTs) could be homogeneously dispersed and chemically embedded in an epoxy matrix by solvent-free processing. In contrast, solid MWCNTs (s-MWCNTs) functionalized by 1,8-diaminooctane were poorly dispersed in epoxy although they possess chemical structures and functionalization comparable to l-MWCNTs. An epoxy composite filled with pristine MWCNTs (p-MWCNTs) was also fabricated in the absence of a solvent at the same loading for comparison. The molecular level coupling of l-MWCNTs and epoxy provided significant improvements in overall mechanical properties relative to those composites containing p-MWCNTs and s-MWCNTs. The Young's modulus, storage modulus, tensile strength, failure strain and toughness of neat epoxy were increased by 28.4, 23.8, 22.9, 24.1 and 66.1%, respectively, by adding 0.5?wt% of l-MWCNTs. Thus, functionalized carbon nanotubes in liquid form contributed to better dispersion and superior interfacial bonding with the epoxy matrix, thereby facilitating greater mechanical reinforcement efficiency.     

Reinforcing brittle and ductile epoxy matrices using carbon nanotubes masterbatch

In this study, the mechanical and thermal properties of epoxy composites using two different forms of carbon nanotubes (powder and masterbatch) were investigated. Composites were prepared by loading the surface-modified CNT powder and/or CNT masterbatch into either ductile or brittle epoxy matrices. The results show that 3 wt.% CNT masterbatch enhances Young’s modulus by 20%, tensile strength by 30%, flexural strength by 15%, and 21.1 °C increment in the glass transition temperature (by 34%) of ductile epoxy matrix. From scanning electron microscopy images, it was observed that the CNT masterbatch was uniformly distributed indicating the pre-dispersed CNTs in the masterbatch allow an easier path for preparation of CNT-epoxy composites with reduced agglomeration of CNTs. These results demonstrate a good CNT dispersion and ductility of epoxy matrix play a key role to achieve high performance CNT-epoxy composites.     

Dynamic tensile properties of carbon fiber composite based on thermoplastic epoxy resin loaded in matrix-dominant directions

The dynamic tensile properties of carbon fiber (CF) composite loaded in the matrix-dominant direction are experimentally determined. In this study, thermoplastic epoxy resin is used as a matrix of the CF composite. A dynamic tensile test is performed using a tension-type split Hopkinson bar technique. The experimental results show that there are not linear relationships between tensile strength and strain rate in case of the 10°, 30° and 45° specimens, although the tensile strength of CF composite, whose matrix is typical thermosetting epoxy resin, linearly increases with the strain rate for all fiber orientation angles. From the fracture surface observation, it is found that the ductile fracture of the matrix can be observed only when 10° off-axis specimen is tested under dynamic loading condition. It is inferred that the softening of the thermoplastic epoxy resin in the vicinity of interface area takes place with increasing strain rate.     

Microstructure and mechanical property of multi-walled carbon nanotubes reinforced aluminum matrix composites fabricated by friction stir processing

Aluminum matrix composites reinforced by different contents of multi-walled carbon nanotubes (MWCNTs) were fabricated by friction stir processing (FSP). The microstructure of nano-composites and the interface between aluminum matrix and MWCNTs were examined using optical microscopy (OM) and transmission electron microscopy (TEM). It was indicated that MWCNTs were well dispersed in the aluminum matrix throughout the FSP. Tensile tests and microhardness measurement showed that, with the increase of MWCNT content, the tensile strength and microhardness of MWCNTs/Al composites gradually increased, but on the contrary, the elongation decreased. The maximum ultimate tensile strength reached up to 190.2 MPa when 6 vol.% MWCNTs were added, and this value was two times more of that of aluminum matrix. Appearances and fracture surface micrographs of failed composite samples indicated that the composites become more and more brittle with the increase of the MWCNT content.     

Preparation and characterization of carbon nanotube/polyetherimide nanocomposite films

Multi-walled carbon nanotube (MWCNT)/polyetherimide (PEI) nanocomposite films have been prepared by casting and imidization. A homogeneous dispersion of MWCNTs throughout the PEI matrix is observed by scanning electron microscopy of fracture surfaces, which shows not only a fine dispersion of MWCNTs but also strong interfacial adhesion with the matrix, as evidenced by the presence of many broken but strongly embedded carbon nanotubes (CNTs) in the matrix and by the absence of debonding of CNTs from the matrix. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperature of PEI increases by about 10 °C by the addition of 1 wt% MWCNTs. Mechanical testing shows that for the addition of 1 wt% MWCNTs, the elastic moduli of the nanocomposites are significantly improved by about 250% while the tensile strength is comparable to that of the matrix. This improvement is due to the strong interfacial interaction between the MWCNTs and the PEI matrix which favors stress transfer from the polymer to the CNTs.     

碳纳米管含量对铝基复合材料力学性能的影响

采用搅拌摩擦加工技术制备了多壁碳纳米管增强铝基(MWCNTs/Al)复合材料,研究了碳纳米管含量对复合材料力学性能的影响规律。结果表明,MWCNTs的添加对铝基复合材料的力学性能影响显著,随着MWCNTs含量的增加,MWCNTs/Al复合材料的硬度、弹性模量、强度都逐渐提高;当碳纳米管含量为6.6%(体积分数)时,复合材料强度达218 MPa,为基体材料的2.24倍;随MWCNTs含量的增加,MWCNTs/Al复合材料的塑性逐渐变差,拉伸延伸率逐渐降低,断口韧窝逐渐变小、变浅。     

Modification of surface functionality of multi-walled carbon nanotubes on fracture toughness of basalt fiber-reinforced composites

In this work, we studied the influence of surface functionality of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of basalt fiber-reinforced composites. Acid and base values of the MWCNTs were determined by Boehm's titration technique. The surface properties of the MWCNTs were determined FT-IR, and XPS. The mechanical properties of the composites were assessed by measuring the interlaminar shear stress, fracture toughness, fracture energy, and impact strength. The chemical treatments led to a change of the surface characteristics of the MWCNTs and of the mechanical interfacial properties of MWCNTs/basalt fibers/epoxy composites. Especially the acid-treated MWCNTs/basalt fibers/epoxy composites had improved mechanical properties compared to the base-treated and non-treated MWCNTs/basalt fibers/epoxy composites. These results can probably be attributed to the improved interfacial bonding strength resulting from the improved dispersion and interfacial adhesion between the epoxy resin and the MWCNTs.     

Simultaneously enhanced cryogenic tensile strength and fracture toughness of epoxy resins by carboxylic nitrile-butadiene nano-rubber

Epoxy resins are important matrices for composites. Carboxylic nitrile-butadiene nano-rubber (NR) particles are employed to improve the tensile strength and fracture toughness at 77 K of diglycidyl ether of bisphenol-F epoxy using diethyl toluene diamine as curing agent. It is shown that the cryogenic tensile strength and fracture toughness are simultaneously enhanced by the addition of NR. Also, the fracture toughness at room temperature (RT) is enhanced by the addition of NR. On the other hand, the tensile strength at RT first increases and then decreases with further increasing the NR content up to 5 phr. 5 phr NR is the proper content, which corresponds to the simultaneous enhancements in the tensile strength and fracture toughness at RT. Moreover, the comparison of mechanical properties between 77 K and room temperature indicates that the tensile strength, Young’s modulus and fracture toughness at 77 K are higher than those at RT but the failure strain shows the opposite results. The results are properly explained by the SEM observation.     

Effect of acid and TETA modification on mechanical properties of MWCNTs/epoxy composites

Acid treatment and triethylene-tetramine (TETA) modification of multi-walled carbon nanotubes (MWCNTs) purposing to attain better dispersibility and stronger interfacial bonding between MWCNTs and epoxy matrix have been carried out in this paper. The epoxy and MWCNTs/epoxy composites were produced by cast molding method. Stress–strain curves show that TETA-MWCNTs/epoxy hold the greatest toughness of all samples with 0.5 wt.% nanoparticles. The Young’s modulus of TETA-MWCNTs/epoxy has a significant increase about 38% compared to the neat epoxy, while the Young’s modulus of unmodified MWCNTs/epoxy or acid-modified MWCNTs/epoxy has a bit of decrease. Tensile and impact strength tests reflect that TETA-MWCNTs reinforced epoxy composites have an obvious improvement of tensile strength about 30% and an enhancement of impact strength over 34% compared to the pure epoxy composites with only 0.5 wt.% loading of TETA-MWCNTs. Scanning electron microscopy images of fractured surface of MWCNTs/epoxy indicate homogeneous dispersibility of TETA-MWCNTs and strong interfacial adhesion between the TETA-MWCNTs and the epoxy in the MWCNTs/epoxy composite.     

Role of matrix modification on interlaminar shear strength of glass fibre/epoxy composites

Interlaminar shear properties of fibre reinforced polymer composites are important in many structural applications. Matrix modification is an effective way to improve the composite interlaminar shear properties. In this paper, diglycidyl ether of bisphenol-F/diethyl toluene diamine system is used as the starting epoxy matrix. Multi-walled carbon nanotubes (MWCNTs) and reactive aliphatic diluent named n-butyl glycidyl ether (BGE) are employed to modify the epoxy matrix. Unmodified and modified epoxy resins are used for fabricating glass fibre reinforced composites by a hot-press process. The interlaminar shear strength (ILSS) of the glass fibre reinforced composites is investigated and the results indicate that introduction of MWCNT and BGE obviously enhances the ILSS. In particular, the simultaneous addition of 0.5 wt.% MWCNTs and 10 phr BGE leads to the 25.4% increase in the ILSS for the glass fibre reinforced composite. The fracture surfaces of the fibre reinforced composites are examined by scanning electron microscopy and the micrographs are employed to explain the ILSS results.     

Preparation,characterization and properties of polycaprolactone diol-functionalized multi-walled carbon nanotube/thermoplastic polyurethane composite

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized to prepare thermoplastic polyurethane (PU) composites with enhanced properties. In order to achieve a high compatibility of functionalized MWCNTs with the PU matrix, polycaprolactone diol (PCL), as one of PU’s monomers, was selectively grafted on the surface of MWCNTs (MWCNT–PCL), while carboxylic acid groups functionalized MWCNTs (MWCNT–COOH) and raw MWCNTs served as control. Both MWCNT–COOH and MWCNT–PCL improved the dispersion of MWCNTs in the PU matrix and interfacial bonding between them at 1 wt% loading fraction. The MWCNT–PCL/PU composite showed the greatest extent of improvement, where the tensile strength and modulus were 51.2% and 33.5% higher than those of pure PU respectively, without sacrificing the elongation at break. The considerable improvement in both mechanical properties and thermal stability of MWCNT–PCL/PU composite should result from the homogeneous dispersion of MWCNT–PCL in the PU matrix and strong interfacial bonding between them.