Sectional Analysis of Hybrid CNT/Graphene Reinforced Composite Beams

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) can offer remarkable enhancements in the mechanical properties in the form of nanoreinforcements. CNTs have a tube-like shape while GNPs have a sheet-like shape and a therefore a combination of both may yield a better performance while avoiding the manufacturing problems such as clustering. The major load-bearing aerospace structures such as satellite booms, rotor blades, and aircraft wings are generally modeled as beam-like structures. The application of CNTs and GNPs to such structures can lead to significantly improved elastic properties which have not yet been realized. Due to the inclusion of nanoreinforcements, the accurate estimation of effective material properties and subsequently the cross-sectional constants is important for the correct global deformations and stresses. To this end, this work deals with the development and application of an efficient and accurate multiscale prediction methodology for the mechanical properties and stresses at the beam cross-sectional level. A multiscale cross-sectional formulation is developed by extending the previously developed multifield beam cross-sectional analysis along with the analytical micromechanical approach. A two-step hoomogenization is followed to compute the effective elastic constants of the hybrid nanoreinforced composite consisting of CNT/GNP/epoxy/carbon fiber. A modified Halpin-Tsai model is used to estimate the homogenized properties of nanocomposite (CNT/GNP/epoxy) as well as the hybrid macrocomposite unidirectional lamina. The multified beam formulation (which assumes both 3D cross-sectional deformations and stresses as unknowns) is used to compute the cross-sectional properties and stress distributions. The impact of CNT and GNP inclusions is investigated on the sectional properties (stiffness and mass constants) and stress distributions of several cross-sectional geometries with varying mass fractions. Both uncoupled and coupled layups are considered where positive or negative impact is seen on the stiffness constants depending on the layup. Overall, high stiffness/mass is achieved with the introduction of CNTs and GNPs. The stress distributions over the beam cross-section, especially at the layer interfaces are also examined.