Farzin Javanshour

Aramid fibers are high-strength and high-modulus technical fibers used in protective clothing, such as bulletproof vests and helmets, as well as in industrial applications, such as tires and brake pads. However, their full potential is not currently utilized due to adhesion problems to matrix materials. In this paper, we study how the introduction of mechanical adhesion between aramid fibers and matrix material the affects adhesion properties of the fiber in both thermoplastic and thermoset matrix. A microwave-induced surface modification method is used to create nanostructures to the fiber surface and a high throughput microbond method is used to determine changes in interfacial shear strength with an epoxy (EP) and a polypropylene (PP) matrix. Additionally, Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy were used to evaluate the surface morphology of the fibers and differences in failure mechanism at the fiber-matrix interface. We were able to increase interfacial shear strength (IFSS) by 82 and 358%, in EP and PP matrix, respectively, due to increased surface roughness and mechanical adhesion. Also, aging studies were conducted to confirm that no changes in the adhesion properties would occur over time.

Despite substantial progress being made relating to 2D-nanofiller-based composite nanolaminates, the fabrication of composite nanolaminates with enhanced ductility and toughness is still challenging. In this study, layered structure graphene oxide (GO)/gelatin powder (GP) composites nanolaminates with enhanced ductility and toughness have been achieved by a simple vacuum filtration of aqueous dispersion of GO/GP composite solution containing 5 wt% of GO. The composite film containing 5 wt% GO shows outstanding improvement of 200% in the stress at break value, with simultaneous enhancement of 52% of the strain at break value compared to GP film. A significant improvement in toughness from 2.2 MJ m⁻³ to 9.5 MJ m⁻³ is observed in the composite film containing 5 wt% GO. These significant enhancements of the mechanical properties of the composite film are obtained via the formation of an intercalated nanolaminate structure, H-bonding interactions, and the tailoring of the crystal structure of GP in the composite film, as proved via field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and wide-angle X-ray diffraction studies. The growing of fibroblast cells on the composite films signifies that they are not cytotoxic. These GO/GP composites with significant mechanical properties and biocompatibility are very promising for various biomedical applications.