Impact and post-impact properties of multiscale carbon fiber composites interleaved with carbon nanotube sheets

The effects of the integration of continuous sheets of randomly oriented multi-walled carbon nanotubes on the low velocity impact behavior of cross-ply carbon/epoxy laminates have been investigated. Three different energy levels were used, namely 5 J, 10 J, and 20 J and significant reductions in delaminated area in the range 11%-39% compared to the baseline laminates were achieved by incorporating interleaves at each 0/90 interface. This resulted in a better flexural damage tolerance of modified laminates. The combination of ultrasonic C-scans, profilometry, and scanning electron microscopy showed that interlaminar crossing between CNT sheets and carbon fibers occurred in modified laminates and that nanotube pull-out, bridging and improved fiber/matrix adhesion are the mechanisms responsible for the enhanced impact performance.