Effect of seawater ageing on interlaminar fracture toughness of carbon fiber/epoxy composites containing carbon nanofillers

This work reports the influence of seawater ageing on the mode I and mode II interlaminar fracture toughness ( G I C and G I I C ) of prepreg-based unidirectional carbon fiber/epoxy laminates containing carbon nanofillers. Double cantilever beam and end notched flexure specimens were fabricated from composite laminates containing multiwalled carbon nanotubes and/or reduced graphene oxide at their middle plane interface. Experimental results showed that the addition of carbon nanofillers moderately increased the G I C and G I I C propagation of composite laminates before and after their immersion in seawater with respect to the reference laminate under dry condition. For double cantilever beam and end notched flexure specimens aged in seawater, it was observed that G I C and G I I C increased by 57% and 13% for specimens with multiwalled carbon nanotube/reduced graphene oxide hybrid combination, 39% and 4% for specimens with multiwalled carbon nanotubes and 53% and 8% for specimens with reduced graphene oxide respectively, as a consequence of the plasticization effect of seawater immersion on the matrix. Fracture surface examination by scanning electron microscopy revealed interlaminar failure associated to mode I and mode II delamination and toughening mechanisms produced by the multiwalled carbon nanotubes and reduced graphene oxide at delaminated regions of composite laminates