Mechanical characterization of electrospun boron nitride nanotube-reinforced polymer nanocomposite microfibers

Boron nitride nanotubes (BNNTs) are promising fillers for reinforcing polymers toward lightweight and high-strength nanocomposite materials. Understanding the interfacial load transfer mechanism is of importance to take advantage of the extraordinary structural and mechanical properties of BNNTs. Here, we investigate the mechanical properties of electrospun BNNT-reinforced polymethyl methacrylate (PMMA) nanocomposite microfibers. The local load transfer on the BNNT–PMMA interface inside the nanocomposite microfiber is characterized based on in situ Raman micromechanical measurements. The effective interfacial shear strengths of 0.1%, 0.5%, and 0.65% BNNT-PMMA microfibers are found to be about 78.4 MPa, 60.9 MPa, and 50.7 MPa, respectively, which correspond to the increases of Young’s modulus (tensile strength) of about 67% (25%), 108% (60%), and 133% (69%) from pure PMMA microfibers. The study reveals the constitutive role of the nanotube–polymer interfacial strength in the composite’s mechanical property enhancement. The findings contribute to a better understanding of the process–structure–property relationship and the reinforcing mechanism of nanotube-based nanocomposites. Graphical abstract