Study of the energy absorption capabilities of laminated glass using carbon nanotubes

Laminated glass (LG) typically consists of two or more glass plies bonded together with a transparent thermoplastic elastomeric interlayer, often composed of polyvinyl butyral (PVB). This interlayer primarily serves as a means of preventing splintering and of absorbing energy upon blast/impact. This research attempted to enhance the impact resistance of LG by increasing PVB interlayer energy absorption by embedding carbon nanotubes (CNTs). Interlayers were formed by electrospinning aligned PVB fibers mat embedded with various concentrations of CNTs. Subsequently, the fiber mat was hot-pressed between two glass plies forming a composite film. The composite fibers were characterized using optical, SEM, and TEM microscopy. The mechanical and thermo-mechanical properties of fibers were determined by dynamic mechanical analysis (DMA), and the energy absorption capacities of the modified LGs were measured by applying the Charpy impact test of un-notched samples. A∼30% increase in composite fiber (CNT 1.5wt.%) strength was observed, along with a∼70% increase in elastic modulus, measured at a strain rate of 0.1min ^-1, in comparison to CNT-free fibers. Increased CNT loading restricted the segmental motion of polymer macromolecules and provided the geometrical confinement effect to neighboring macromolecules in the nanoscale fiber. The energy absorption of a double-layered LG embedded with carbon nanotubes increased by nearly 341%, where experimental results demonstrated the role of the CNTs pull-out toughening mechanism. In parallel, transmission of visible light decreased by 60%.