“Brick-and-Mortar”\nNanostructured Interphase for Glass-Fiber-Reinforced Polymer Composites

Abstract

The\nfiber–matrix interface plays a critical role in determining\ncomposite mechanical properties. While a strong interface tends to\nprovide high strength, a weak interface enables extensive debonding,\nleading to a high degree of energy absorption. Balancing these conflicting\nrequirements by engineering composite interfaces to improve strength\nand toughness simultaneously still remains a great challenge. Here,\na nanostructured fiber coating was realized to manifest the critical\ncharacteristics of natural nacre, at a reduced length scale, consistent\nwith the surface curvature of fibers. The new interphase contains\na high proportion (∼90 wt %) of well-aligned inorganic platelets\nembedded in a polymer; the window of suitable platelet dimensions\nis very narrow, with an optimized platelet width and thickness of\nabout 130 and 13 nm, respectively. An anisotropic, nanostructured\ncoating was uniformly and conformally deposited onto a large number\nof 9 μm diameter glass fibers, simultaneously, using self-limiting\nlayer-by-layer assembly (LbL); this parallel approach demonstrates\na promising strategy to exploit LbL methods at scale. The resulting\nnanocomposite interphase, primarily loaded in shear, provides new\nmechanisms for stress dissipation and plastic deformation. The energy\nreleased by fiber breakage in tension appear to spread and dissipate\nwithin the nanostructured interphase, accompanied by stable fiber\nslippage, while the interfacial strength was improved up to 30%.