This project aims at developing, optimizing and validating laminated hybrid composites that possess excellent damping and stiffness properties. The hybrid composites comprising both commercial carbon fibers and surface-grown carbon nanotubes (CNTs) offer attractive alternative to fiber reinforce composites (FRPs) and cheaper alternative to pristine CNTs composites. The hybrid composites also incorporate vanadium oxide (VO2) that exhibits a negative stiffness behavior in thermal environments induced by vibrations. We anticipate the hybrid composite to acquire high specific stiffness due to the CNTs? elevated stiffness (TPa level) while gaining enhanced damping through the negative stiffness of VO2 together with the inherent matrix viscoelastic damping properties. Finite element methods and multi-objective optimization environment will be employed to optimize the topology of the hybrid composites to yield superior stiffness and damping properties. To validate the hybrid composites? dynamics performance, laboratory controlled vibration tests will be carried out to exploit their responses to specific excitations. The analysis of data from these tests will be used for characterization and identification of the vibrating system parameters (damping, stiffness and nonlinear parameters).
Vibrations can compromise the safety and durability of structural components FRPs. Despite their attractive mechanical properties, the low through-thickness mechanical properties of FRPs have restricted their application in structures to mitigate out-of plane dynamic loads. The developed hybrid composites with enhanced damping have an impact on applications that utilize FRP such as commercial and military aircraft frames (ex. Boeing 787 Dreamliner), ship vessels, auto industries, infrastructures and sport goods. Considering the emerging applications of FRPs in civil infrastcrtures (bridges, columns, etc..) the developed materials offer an attractive and practical solution to mitigate random vibrations such as those encountered in earthquakes also they can extend the fatigue life of these structures. The educational components of the project will benefit three departments in the Virginia Tech (VT) College of Engineering. One existing graduate courses will be revised to include both theoretical and hands-on modules based on the project tasks. One graduate student will participate hands-on in the synthesis, fabrication,characterization, topological optimization, vibration testing and parametric identification of the hybrid composites toward a Ph.D. degree.
