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Functionalized silicon dioxide nanoparticles (nano-fSiO2) were uniformly deposited on the surface of carbon fibers (CFs) using a coating process which consisted of immersing the fibers directly in a suspension of nano-fSiO2 particles and epoxy monomers in 1-methyl-2-pyrrolidinone (NMP). The 0° flexural properties, 90° flexural properties, and Interlaminar shear strength (ILSS) mechanical properties of unidirectional epoxy composites made with nano-fSiO2+epoxy sized carbon fibers, with control fibers, and with epoxy-only sized fibers were measured and compared. An obvious increase of the fiber/matrix adherence strength was obtained with the nano-fSiO2+epoxy coating. The nano-fSiO2+epoxy sized CF/epoxy composites showed a relative increase of 15%, 50%, and 22% in comparison to control fibers, for the Interlaminar shear strength, the 90° flexural strength and the 90° flexural modulus, respectively, but little e difference was measured between the different systems for the 0° flexural properties. The observation of the fracture surfaces by scanning electron microscopy of composite fracture confirmed the improvement of the interfacially dependent mechanical properties. POLYM. COMPOS., 38:1474-1482, 2017. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, a novel method consisting of coating carbon fibers (CF) with graphite nanoplatelets (GnP) is investigated for its ability to modify the mechanical properties in the interphase region. Coating the CF was achieved by immersing CF in a solution of GnP dispersed in an epoxy-based solution for a few seconds. The influence of the processing conditions on the properties of the coating (thickness, homogeneity, quality of the GnP dispersion) is reported. Interfacial adhesion and the associated failure modes were evaluated by the single fiber fragmentation test. The maximum value of interfacial shear strength (IFSS) was achieved when a relative GnP concentration of 7.9 wt% on CFs, which led to 45 and 34% improvements in IFSS in comparison with the non-coated CF and epoxy coated CF, respectively. POLYM. COMPOS., 37:1549-1556, 2016. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, carbon fibers (CFs) were coated with graphene nanoplatelets (GnP), using a robust and continuous coating process. CFs were directly immersed in a stable GnP suspension and the coating conditions were optimized in order to obtain a high density of homogeneously and well-dispersed GnP. GnP coated CFs/epoxy composites were manufactured by a prepreg and lay-up method, and the mechanical properties and electrical conductivity of the composites were assessed. The GnP coated CFs/epoxy composites showed 52%, 7%, and 19% of increase in comparison with non-coated CFs/epoxy composites, for 90° flexural strength, 0° flexural strength and interlaminar shear strength, respectively. Meanwhile, incorporating GnP in the CF/epoxy interphase significantly improved the electrical conductivity through the thickness direction by creating a conductive path between the fibers. [ABSTRACT FROM AUTHOR]

A reactive sizingwas designed to achieve high levels of interfacialadhesion and improved mechanical properties with a carbon fiber–acrylatesystem cured by electron beam (EB). The sizing was made of a partiallycured epoxy sizing with a high density of pendant functional groups(acrylate functionality) to facilitate covalent bonding with the matrix.The interlaminar shear strength improved from 61 to 81 MPa (+33%)without postprocessing, reaching a shear strength similar to thatof the same system cured by a thermal treatment. Observation of thefracture profiles clearly highlighted a change in the fracture mechanismfrom a purely adhesive failure to a cohesive failure. To the bestof our knowledge, such improvements of the mechanical properties ofcarbon fiber composites cured by EB, without any postcure, have notbeen reported previously. This constitutes a breakthrough for theindustrial development of EB curing of composites. [ABSTRACT FROM AUTHOR]

Recent advances in large‐scale additive manufacturing (AM) with polymer‐based composites have enabled efficient production of high‐performance materials. Cellulose nanomaterials (CNMs) have emerged as bio‐based feedstocks due to their exceptional strength and sustainability. However, challenges such as hornification and poor dispersion in polymer matrices still limit large‐scale CNM–polymer composite manufacturing, requiring novel strategies. This review outlines an approach starting with atomic‐level simulations to link molecular composition to key parameters like bulk density, viscosity, and modulus. These simulations provide data for finite element analysis (FEA), which informs large‐scale experiments and reduces the need for extensive trials. The strategy explores how atomic interactions impact the morphology, adhesion, and mechanical properties of CNM‐based composites in AM processes. The review also discusses current developments in AM, along with predictions of mechanical and thermal properties for structural applications, packaging, flexible electronics, and hydrogel scaffolds. By integrating experimental findings with molecular dynamics (MD) simulations and finite element modeling (FEM), valuable insights for material design, process optimization, and performance enhancement in CNM‐based AM are provided to address ongoing challenges. [ABSTRACT FROM AUTHOR]

Carbon fiber (CF) is a versatile material renowned for its excellent mechanical, thermal, and electrical properties. Polyacrylonitrile (PAN)-based CFs dominate the market in part due to their high tensile strength, rendering them suitable for structural applications in a wide variety of applications ranging from sporting goods to aerospace. Over five decades of commercial development of PAN-based CF has resulted in a range of varieties with different tensile moduli and tensile strengths. The microstructures, nanostructures, and crystal structures of PAN-based CF all play pivotal roles in the macroscale properties of this material. In particular, the crystal structure and crystallite orientation in CF is closely related to the mechanical properties. The crystal structure of PAN-based CF generally consists of turbostratic carbon, a disordered form of graphite, the characteristics of which can be effectively characterized in a bulk format through wide-angle x-ray diffraction (WAXD). In this work, we employed a three-part approach to the analysis of WAXD patterns collected from four intermediate modulus PAN-based CFs. The approach incorporates a Scherrer analysis, a Debye analysis, and an orientational analysis to provide precise estimates of crystallite sizes, crystallite distributions, and crystallite orientations with the fiber axis. The results presented here suggest that intermediate modulus PAN-based CF mostly consists of small turbostratic crystallites (<4 nm), with larger crystallites having increased orientation with the fiber axis. The results here imply the presence of curvature and/or wrinkling of the turbostratic layers within the CF structure. [Display omitted] [ABSTRACT FROM AUTHOR]

The viscoelastic and thermomechanical properties of pitches are responsible for their melt-spinning behavior, a critical step for manufacturing high-performance pitch-based carbon fibers. Here, we systematically explore the impact of methyl group modifications on the viscoelastic and thermal properties of mesophase pitches. We employ a range of atomistic modeling approaches, including Density Functional Theory (DFT), Density Functional Tight Binding (DFTB), and Classical Molecular Mechanics (MM), to provide detailed insights into the molecular interactions and structural changes. Our results revealed the molecular mechanisms that promote layered structures leading to the anisotropic nature of the viscoelastic behavior of mesophase pitch. Furthermore, we propose a modified molecular representation of naphthalene-based mesophase pitch based on the analysis of x-ray diffraction measurements. This study provides fundamental insights into the molecular structures of mesophase pitch and the role of methyl groups controlling its viscosity, which offer valuable insights into mesophase-based carbon fiber production. [Display omitted] [ABSTRACT FROM AUTHOR]

Mild direct coal liquefaction (autogenous pressure, no catalyst, no H 2 gas) of Springfield coal in fluid catalytic cracking decant oil is shown to effectively produce coal extract precursors to spinnable mesophase pitch. This work demonstrates that the coal extract can be thermally treated to obtain mesophase pitch in a facile one-step process, bypassing the production of an intermediate isotropic pitch. Furthermore, the presence of 25 wt.% coal in the initial slurry can increase the yield to mesophase pitch nearly twofold and yield to carbon fiber by approximately 70%. The coal extract-derived mesophase pitch was melt-spun and heat treated to produce carbon fiber with graphitic texture, high modulus (>400 GPa) and tensile strength up to 943 MPa. Overall, this work demonstrates that coal can be effectively utilized to markedly amplify the mesophase pitch and carbon fiber yield from fluid catalytic cracking decant oil by relatively simple processing, while conserving utility as a precursor to high performance carbon fiber and potentially other high value graphitic products. [Display omitted] • Mild direct coal liquefaction in decant oil was used to obtain a coal extract. • The coal extract was thermally converted to a spinnable mesophase pitch. • Coal utilization improved yield to mesophase pitch nearly twofold. • Coal extract-derived carbon fiber displayed high modulus (>400 GPa). • Coal utilization resulted in a ∼70 % increase in yield to carbon fiber. [ABSTRACT FROM AUTHOR]

Large-scale atomistic models for complex polycyclic aromatic hydrocarbon systems help understand the chemical properties and behaviors of complex feedstocks such as coal or petroleum. However, the development and utilization of large-scale models remain limited due to the difficulty in achieving the varied structural characteristics necessary to capture stochastic nature of these feedstocks. We demonstrate a systematic workflow to construct stochastic molecular systems from a broad analytical suite: high-resolution transmission electron microscopy (HRTEM), carbon-13 nuclear magnetic resonance spectroscopy (13C NMR), laser desorption ionization mass spectroscopy (LDI-MS), and elemental analysis. We present a model construction and analysis utility of a new Python-based module. We selected one subbituminous and three high-volatile bituminous coals to construct large-scale models (∼40,000 atoms). The constructed models were utilized to examine the affinity for solvent extraction (naphthalene or tetralin) and the effect of structural properties (e.g., aromatic cluster size, functional groups, and cross-linking) in reactive molecular dynamics simulations. Complex chemical reactions were monitored with bond order transitions, intermediates formation, and mass distributions. Reactive molecular dynamics simulations suggest a plausible chemical extraction process and products for the complex fossil feedstocks. The results indicated that radical formations with bond breaking of bridging oxygens and carbons were required at high temperatures to facilitate hydrogeneration and extraction of gas molecules from radical-free molecules. We observed that aliphatic chains of tetralin were easily decomposed and combined with radicals to form small size of molecules with aryl bonding, mainly increasing molecules in the 500–1000 Da, while naphthalene had little impact on chemical extraction process. [Display omitted] • Groundbreaking advance for the unbiased, autonomous construction of atomistic models for coals and pitches of arbitrary size. • Generated models well align with a diverse set of experimental data allowing chemical studies of coal and pitch materials. • Utilization of constructed models with MD simulations to understand conversion process of coals with solvent extraction step. [ABSTRACT FROM AUTHOR]

[Display omitted] • Understanding molecular alignment in mesophase using experiments and simulations. • Methyl groups stabilize the layered structure of conventional pitch precursors. • Reduction of the face-edge (π-CH) interaction by replacing CH with CH 3. • Coal tar-based mesophase pitch formed even with a low number of methyl groups. • π-π interaction organizes the layered structure with a low number of methyl groups. The role of methyl groups on the liquid–crystal structure of mesophase pitches was investigated by combining experimental characterizations and atomic-scale computational modeling, using three pitches synthesized from different precursors. Of the three pitches, C-9 alkyl benzene and naphthalene-based pitches have 13 and 7 methyl groups per average polyaromatic hydrocarbon, respectively. By contrast, mesophase produced from a coal-tar pitch has about one methyl group. The coal tar–based mesophase pitch is hydrogen deficient or more aromatic compared with C-9 alkyl benzene- and naphthalene-based pitches. Additionally, X-ray diffraction data showed that average coherent domain sizes of C-9 alkyl benzene (3.7 nm) and naphthalene-based (3.6 nm) pitches with more methyl groups are larger than that of coal tar–based mesophase (2.4 nm). Based on the identified features, the influence of the methyl group on the layering structures was investigated via molecular dynamics simulations. The results revealed that methyl groups are critical in mesophase layering in C-9 alkyl benzene- and naphthalene-based pitches, by reducing CH-π interaction. However, similar alignment could be achieved without the same degree of methyl substitutions for the coal tar-based pitch because of stronger π-π interaction than the other precursors. The insights from this study contribute to our understanding of the formation of conventional mesophase pitch and have implications for the processing of coal-derived materials. This knowledge is vital to produce valuable products like carbon fiber and graphite from pitches. [ABSTRACT FROM AUTHOR]

Carbon fibers are unique reinforcing agents for lightweight composite materials due to their outstanding mechanical properties and low density. Current technologies are capable of producing carbon fibers with 90–95% of the modulus of perfect graphite (∼1025 GPa). However, these same carbon fibers possess less than 10% of the theoretical carbon fiber strength, estimated to be about 100 GPa. Traditionally, attempts to increase carbon fiber rigidity above a certain level results in lower breaking strength. Therefore, to develop advanced carbon fibers with both very high strength and modulus demands a new manufacturing methodology. Here, we report a method of manufacturing moderate strength, very high modulus carbon fibers from a very high molecular weight (VHMW) polyacrylonitrile (PAN) precursor without the use of nanomaterial additives such as nucleating or structure-templating agents, as have been used by others. [ABSTRACT FROM AUTHOR]

Carbon black has been a key ingredient in high-performance composites, such as tire rubber, for over a hundred years. This reinforcing filler increases rubber rigidity and reduces tire wear, among many other useful effects. New nanomaterials, such as graphene and carbon nanotubes, may bring new performance improvements. However, their usefulness cannot be evaluated unless worker safety is assured by demonstrating that the nanoparticles are not released at harmful concentrations during manufacture and testing. Here, we present a flexible, general method for the quantitative evaluation of nanoparticle release from rubber nanocomposites. We evaluate manufacturing steps such as powder handling, uncured rubber milling, and curing. We also evaluate particle emission during cured rubber abrasion as an aggressive example of the testing rubber goods are subjected to. We quantify released nanoparticle concentrations for clay nanoparticles, graphene-like materials, and carbon nanotubes. We also describe a mechanistic framework based on the balance of adhesive and kinetic energies, which helps understand when nanoparticles are or are not released. This method contributes to the assessment of workers' exposure to nanoparticles during the various stages of the industrial process, which is an essential step in managing the risk associated with the use of nanomaterials in manufacturing. [ABSTRACT FROM AUTHOR]