Reinforcing composite materials with carbon nanotubes (CNTs) has the potential to improve mechanical and/or multifunctional properties due to their nano-size. Research has been done on using CNTs to reinforce the interlaminar strength of carbon fiber reinforced composites (CFRPs), but most of the previous work is about randomly oriented carbon nanotubes. Currently, one of the main challenges regarding CNT integration into polymers is mitigating their agglomeration and controlling their dispersion in the polymer matrix. By aligning CNTs with an external field, more tailored structure control can be achieved, and a better understanding of how CNT agglomeration and dispersion relate to external field application and CNT concentration is needed. In this work, we studied the effects of magnetic field magnitude, CNT concentration, and matrix viscosity on CNT agglomeration and morphology. We measured the fracture toughness reinforcement of epoxy-CNT nanocomposites at various CNT concentrations (0.1 vol.% and 0.5 vol.%), magnetic field magnitudes (no field, 180 G, and 300 G), and matrix viscosities (older epoxy-hardener system with higher viscosity and newer epoxy-hardener system with lower viscosity). Our results demonstrated that aligning CNTs with a magnetic field can lead to extra reinforcement when compared to using randomly oriented CNTs if the field magnitude, CNT concentration, and matrix viscosity are selected accordingly. The maximum fracture toughness reinforcement achieved with the higher viscosity epoxy-hardener system (~72%) was with 0.5 vol.% of CNTs with a 180 G field, whereas the maximum reinforcement with the lower viscosity epoxy-hardener system (~62%) was observed for the samples fabricated with 0.1 vol.% of randomly oriented CNTs. COMSOL simulations were also conducted to understand the behavior of CNT agglomeration and alignment at different field magnitudes and CNT concentrations, and were compared with the experimental results. To maximize CNT reinforcement, more work needs to be conducted to address the challenge of CNT agglomeration and dispersion control in a polymer matrix, such as a more in-depth study of how different field magnitudes affect fracture toughness improvement and new methods to improve CNT dispersion.
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Effect of Carboxymethyl Cellulose (CMC) Functionalization on Dispersion, Mechanical, and Corrosion Properties of CNT/Epoxy Nanocomposites
Carbon nanotube (CNT)/epoxy nanocomposites have a great potential of possessing many advanced properties. However, the homogenization of CNT dispersion is still a great challenge in the research field of nanocomposites. This study applied a novel dispersion agent, carboxymethyl cellulose (CMC), to functionalize CNTs and improve CNT dispersion in epoxy. The effectiveness of the CMC functionalization was compared with mechanical mixing and a commonly used surfactant, sodium dodecylbenzene sulfonate (NaDDBS), regarding dispersion, mechanical and corrosion properties of CNT/epoxy nanocomposites with three different CNT concentrations (0.1%, 0.3% and 0.5%). The experimental results of Raman spectroscopy, particle size analysis and transmission electron microscopy showed that CMC functionalized CNTs reduced CNT cluster sizes more efficiently than NaDDBS functionalized and mechanically mixed CNTs, indicating a better CNT dispersion. The peak particle size of CMC functionalized CNTs reduced as much as 54% (0.1% CNT concentration) and 16% (0.3% CNT concentration), compared to mechanical mixed and NaDDBS functionalized CNTs. Because of the better dispersion, it was found by compressive tests that CNT/epoxy nanocomposites with CMC functionalization resulted in 189% and 66% higher compressive strength, 224% and 50% higher modulus of elasticity than those with mechanical mixing and NaDDBS functionalization respectively (0.1% CNT cencentration). In addition, electrochemical corrosion tests also showed that CNT/epoxy nanocomposites with CMC functionalization achieved lowest corrosion rate (0.214 mpy), the highest corrosion resistance (201.031 Ω·cm2), and the lowest porosity density (0.011%).
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- Award ID(s):
- 1750316
- NSF-PAR ID:
- 10406477
- Date Published:
- Journal Name:
- Chinese Journal of Polymer Science
- ISSN:
- 0256-7679
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Carbon‐based nanoparticles are widely regarded as promising nanofillers in nanocomposites to pursue advanced properties. To date, there has been a lack of systematic investigation into the structural variations of nanofillers and their influences on dispersion characteristics, as well as the resulting mechanical properties of nanocomposites. In this study, nanodiamond (ND), carbon nanotube (CNT), and graphene (GNP) were selected as the representative zero‐, one‐, and two‐dimensional nanofillers, respectively. A novel functionalization technique utilizing carboxymethyl cellulose (CMC) was employed to disperse nanofillers. The various characterization techniques and experimental results revealed that CMC functionalization was effective in reducing the agglomeration and improving the distribution uniformity of all three nanofillers. Among the three nanofillers, zero‐dimensional ND exhibited the most homogeneous dispersion quality in epoxy nanocomposites. The strongest abrasion resistance was found in ND‐reinforced epoxy nanocomposites, while CNT‐reinforced epoxy nanocomposites exhibited the best tensile properties.
Highlights Nanodiamond with a spherical structure had better dispersion characteristics.
Cylindrical carbon nanotube and planar graphene tended to agglomerate.
Nanodiamond reinforced nanocomposites had better abrasion resistance.
Carbon nanotube reinforced nanocomposites had better tensile properties.
Carboxymethyl cellulose functionalization was valid for all three nanofillers.
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Carbon fiber reinforced polymer (CFRP) composites have been increasingly used to replace metal parts in many industries such as aerospace, marine, automotive, and sporting goods. The CFRP parts compared with their metallic counter parts have the advantages of lightweight, significantly higher tensile strength, stiffer, and corrosion resistant. On the other hand, compared with many metal parts, the CFRP parts have many well-known disadvantages including the lower toughness, lower through-thickness tensile and shear strengths, lower thermal conductivity, lower electrical conductivity, and lower operating temperature. These disadvantages have made the conversion from metal parts into CFRP parts challenging and costly to design, manufacture, and maintain. The use of nanoparticles in polymer has been studied in the recent two decades. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been dispersed in various thermoset and thermoplastic polymers and improved the mechanical, electrical, and thermal properties; however, the properties were not comparable to CFRP. Later, researchers tried to infuse CNTs or CNFs into either carbon fiber preforms [1] or glass fiber preforms [2] for improving the mechanical properties. But the results were marginal and with great uncertainty due to the challenges of nanoparticle dispersion, filtering, and alignment while being infused through the fiber preform. The glass fiber preform experiments ended with relatively more consistent improvement than the carbon fiber preform experiments since that the glass fiber preform has significantly larger pores than the carbon fiber preform' s. The small pore size presented a great challenge for infusing millions of unaligned long CNTs or CNFs through the carbon fiber preform without being filtered. To infuse long CNFs or CNTs through the carbon fiber preform and achieve reliable improvements, especially for 55% or higher carbon fiber volume fraction with increasingly tighter pores, an innovative plan for the processing and nano-reinforcing strategy is necessary. The z-threading strategy [3, 4, 5] has been reported to have consistent experimental successes in achieving the statistically meaningful improvement in multifunctional properties. The manufacturing steps of the CNF z-threaded CFRP (ZT-CFRP) are: (1) disperse the CNFs in a resin, (2) use a strong electrical field to align the CNFs in either the B-stage epoxy film or a CNF/resin impregnated sponge layer, whereas the CNFs are aligned in the through-thickness direction of the film or sponge layer. (3) place the resin film or sponge layer on a preheated dry carbon fiber fabric and press the resin film into the hot carbon fabric and allow the resin flow to carry the well-aligned CNFs to thread through the pores in the carbon fabric. (4) cool down the resin saturated and CNF z-threaded carbon fiber fabric to obtain the ZT-CFRP prepreg. (5) use the ZT-CFRP prepreg to make the ZT-CFRP laminate. Compared with the traditional CFRP, the ZT-CFRP laminates were reported of having improvement in the Mode-I delamination toughness, interlaminar shear strength, longitudinal compressive strength, through-thickness electrical conductivity, through-thickness thermal conductivity, and can reach the carbon fiber volume fraction of 55-80%. It is an effective approach to achieve a multifunctional CFRP for potentially expanding CFRP's applications.more » « less
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In order to achieve effective monitoring of concrete structures for sound structural health, the addition of carbon nanotubes (CNTs) into cementitious materials offers a promising solution for fabricating CNT-modified smart concrete with self-sensing ability. This study investigated the influences of CNT dispersion method, water/cement (W/C) ratio, and concrete constituents on the piezoelectric properties of CNT-modified cementitious materials. Three CNT dispersion methods (direct mixing, sodium dodecyl benzenesulfonate (NaDDBS) and carboxymethyl cellulose (CMC) surface treatment), three W/C ratios (0.4, 0.5, and 0.6), and three concrete constituent compositions (pure cement, cement/sand, and cement/sand/coarse aggregate) were considered. The experimental results showed that CNT-modified cementitious materials with CMC surface treatment had valid and consistent piezoelectric responses to external loading. The piezoelectric sensitivity improved significantly with increased W/C ratio and reduced progressively with the addition of sand and coarse aggregates.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s10118-023-2928-0
