Evaluation of bending after impact and piezoresistive behavior of seawater aged glass fiber reinforced polymer composites containing hybrid carbon nanofillers

The effect of low-velocity impact loading and seawater aging on the residual bending properties of glass fiber reinforced polymers (GFRPs) was evaluated. The self-sensing capability of the composite laminates provided by a hybrid combination of multiwall carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) was also examined. The composite laminates were fabricated by RTM with the incorporation of different contents of MWCNTs and GNPs onto the glass fiber surface using the spray coating technique. Impact tests were performed on specimens with and without seawater (SW) aging and then bending specimens were taken to evaluate the after-impact bending behavior. An important reduction in mechanical properties of composite laminates produced by SW aging, caused by plasticization and swelling effects of the polymer matrix, was confirmed. Despite this physical degradation in the mechanical behavior of GFRP composites, a positive synergistic effect of the carbon nanostructures (CNSs) in the composite laminates was observed. Carbon nanofillers cause the maximum force during the impact test increase in comparison with neat specimens; this effect was exhibited by both samples, with and without seawater aging. Previous impact damage reduced flexural strength and flexural modulus of dry (14% and 43%, respectively) and wet samples (15% and 26%, respectively); however, the reduction in flexural strength is slightly smaller in a certain hybrid combination of CNSs. Another important finding was that the self-sensing capability of GFRPs with CNSs was preserved, even after the impact loading and even after the seawater aging, making this technique suitable for structural health monitoring of marine components.