Hierarchical Electrospun Veils as Potential Toughening Materials for Structural Composite Laminates

Abstract

The use of fiber reinforced polymers (FRPs) as a replacement of traditional homogeneous materials is still hindered by their brittle behavior and poor interlaminar resistance. Interleaving veils in polymer matrix, especially with fibers at the nanoscale dimension, is considered as one of the most promising toughening methods. By considering the hierarchical nature of the resulting laminated composites, their properties are intrinsically dependent on the interaction between the nanofibrous veils and the thermosetting resin and, in an attempt to tailor the interfacial adhesion between the electrospun fibers and matrix, surface modification of the fibers with the integration of inorganic nanostructures could be a solution. This work is an investigation on the use of commercially available electrospun nylon nanofibers decorated with ZnO nanorods obtained by three-step chemical synthesis. The modified veils were interleaved in carbon/epoxy prepreg composites and their mechanical properties were evaluated under Low Velocity Impact (LVI) tests at different energy levels (5 J and 7.5 J). Although the presence of ZnO nanorods did not limit the extension of the delaminated area in case of high energy level test (7.5 J), nanomaterials contributed positively to reduce the extent of the damaged area when a low energy impact was adopted (5 J). A beneficial effect of ZnO-functionalized commercial electrospun veils was observed in the flexural strength of laminated composites. After LVI tests at 5 J and 7.5 J, the flexural strength resulted higher compared to that observed in the same tests on specimens with non-decorated veils (NY4M), thus suggesting a positive role played by ZnO nanorods in hindering delamination propagation.