Abstract
The present study characterizes orientation changes of randomly oriented nanotubes in carbon nanotube (CNT) sheet under externally applied tensile load. The tensile loads were applied using a microtester placed inside a scanning electron microscope (SEM) that allowed in-situ observations of morphological changes in the CNT sheet as the applied load increased. It was observed that randomly entangled CNTs in a sheet align themselves along the applied loading direction. The aligned CNTs eventually form separate distinct bundles prior to catastrophic failure. The alignment of CNTs is permanent and irreversible. The overall stiffness and strength of the CNT sheet also increases with increasing alignment. Reloading a fully aligned CNT sheet in tension exhibits very stiff behavior with a higher Young’s modulus and proportional limit when compared to a virgin CNT sheet that goes through an alignment phase prior to failure. The strength of a virgin CNT sheet was evaluated to be 40 MPa, while that of a CNT sheet with pre-existing alignment was evaluated to be 95 MPa. Raman spectroscopy confirmed that the CNTs exhibited preferential alignment in the loading direction after tensile testing. The CNT sheet fails closer to the grip region where the constraints created by the grip prevent full alignment of the CNTs resulting in an overall weaker region near the grip in comparison to the rest of the CNT sheet.
Accepted Version (
Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call