In-situ constructing ultra-high-aspect-ratio core–shell nanostructures to achieve high-performance epoxy thermosets and their carbon fiber reinforced epoxy composites

Using block copolymers to improve the mechanical properties of materials was a promising method, and the effect was positively correlated with the aspect ratio of the nanostructures. However, except for worm-like and branched worm-like nanostructures, nanostructures with higher aspect ratios have not been reported so far and its forming methods was unknown. In this paper, a feasible approach was provided to in-situ construct ultra-high-aspect-ratio core–shell nanostructures in epoxy, and the morphology evolution during the epoxy preparation process was clarified. It was shown that the tensile strength, elongation at break, fracture toughness and tensile modulus of the nanostructured epoxy were simultaneously improved when the content of block copolymer was as low as 1.75 wt%, achieving 93.6 MPa (31.3% improved), 7.9% (79.5% improved), 133.5 N/mm3/2 (184%) and 2693 MPa (5.6% improved), respectively. The interlaminar shear strength (ILSS) of the corresponding carbon fiber reinforced polymer (CFRP) composites was 32.5% higher than that of the control CFRP composites. Meanwhile, it was worth pointing out that the glass transformation temperatures (Tg) of the modified epoxy matrices and their corresponding CFRPs were similar to those of the unmodified materials. The improvement mechanisms on tensile strength, toughness and ILSS were also systemically investigated. It was expected that this work could provide a feasible routine for in-situ constructing complex morphological nanostructures in epoxy resins and some new ideas for the design of next-generation advanced composites.