CAI strength of filament wound glass fiber composites toughened with carbon nanofillers

This investigation explores the damage tolerance of continuous S2-glass filament wound epoxy composites modified by the addition of carbon nanotube or nanofibers in interlayer regions. Mode I and mode II interlaminar fracture toughness tests performed on double cantilever beam and end-notched flexure specimens showed that nanofilled epoxy interlayers increase the mode II fracture toughness by 30-55% compared to the baseline material without an interlayer. The mode I fracture toughness was not significantly affected. Multidirectionally reinforced filament wound composite tubes were quasi-statically indented and subjected to compression-afterindentation (CAI) tests as an additional measure of damage tolerance. Relative to the baseline material, the initial compressive strength of the tubes was improved by 16% by adding carbon nanofibers and 19% by adding carbon nanotubes. However, following indentation, the compressive strength of the composite tubes with nanofibers was less than the baseline while that of the tubes with nanotubes was similar to the baseline. These results indicate different effects of nanofilled interlayers on interlaminar fracture toughness and CAI strength in filament wound S2- glass epoxy composites.