Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite while the effect on the axial properties is shown to be insignificant.

The influence of monomer functionality on the mechanical properties of epoxies is studied using molecular dynamics (MD) with the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. Comparison between the network structures of distinct epoxies is further advanced by the monomeric degree index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli. Therefore, ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 255–264

Structural components of modern aircraft, such as the fuselage and control surfaces, are commonly constructed using carbon‐filled polymer composites. The addition of graphene nanoplatelets (GNP) to traditional fiber‐reinforced composites often increases the tensile modulus. In this work, composites were fabricated with epoxy (EPON 862 with EPIKURE Curing Agent W) and 1–4 wt% (0.6–2.44 vol%) GNP. The GNP used in this study was Asbury Carbon's TC307. To the authors' knowledge, mechanical data for composites with TC307 have not been published before. Composite specimens were tested for macroscopic tensile modulus and modulus as determined by nanoindentation. The macroscopic tensile modulus increased from 2.72 GPa for neat epoxy to 2.93 GPa for 4 wt% (2.44 vol%) TC307 in epoxy. The modulus as determined by nanoindentation showed a similar trend. For all these composites, the tensile strength ranged from 76 to 81 MPa. A multiscale modeling approach, using molecular dynamics data and micromechanical modeling, was used to verify the experimental data, and both experiments and modeling demonstrated that a three‐dimensional random dispersion of GNP (∼3 to 4 layers) in epoxy was achieved. The constant level of strength with GNP loading is important in applications where GNP is added to the epoxy matrix to increase thermal and electrical conductivity. POLYM. COMPOS., 39:1845–1851, 2018. © 2016 Society of Plastics Engineers

Cycloaliphatic epoxies (CEs) are commonly used for structural applications requiring improved resistance to elevated temperatures, UV radiation, and moisture relative to other epoxy materials. Accurate and efficient computational models can greatly facilitate the development of CE‐based composite materials for applications such as Aluminum Conductor Composite Core high‐voltage power lines. In this study, a new multiscale modeling method is developed for CE resins and composite materials to efficiently predict thermal properties (glass‐transition temperature, thermal expansion coefficient, and thermal conductivity). The predictions are compared to experimental data, and the results indicate that the multiscale modeling method can accurately predict thermal properties for CE‐based materials. For 85% crosslink densities, the predicted glass‐transition temperature, thermal expansion coefficient, and thermal conductivity are 279 °C, 109 ppm °C−1, 0.24 W m−1 K−1, respectively. Thus, this multiscale modeling method can be used for the future development of improved CE composite materials for thermal applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46371.

Cycloaliphatic epoxy (CE) resin systems are of primary interest in applications that require improved resistance to harsh conditions relative to other epoxy systems.Because other epoxy systems have demonstrated improved resistance to hydrothermal aging with the addition of carbon-based nanoparticle reinforcement, it is expected that the hydrothermal resistance of CE resins will likewise be improved with incorporation of nanoparticles. Therefore, the objective of this study is to determine the influence of graphene nanoparticles (GNP) on the hydrothermal aging resistance of CE resins. CE specimens are fabricated with varying levels of GNP and exposed to elevated temperatures and moisture levels for varying amounts of time up to 400 hours. The results from flexure and dynamical-mechanical testing indicate that the addition of GNP provides modest improvements in the stiffness and glass transition temperature for all aging levels, while the strength is improved for aging times below 400 hours.