This work studied the structural, morphological, mechanical, and thermal properties of newly designed polymeric materials using high-performance hybrid fibers to reinforce the polybenzoxazine resins. To achieve this goal, hybrid fibers consisting of chopped Kevlar and carbon fibers were subjected to a silane surface treatment, incorporated into the resin matrix in various combinations, and then isothermally cured using the compression molding technique. The mechanical performances of the prepared composites were scrutinized in terms of bending and tensile tests. By way of illustration, the composites holding 20 wt % Kevlar fibers and 20 wt % carbon fibers accomplished a bending strength and modulus of 237.35 MPa and 7.80 GPa, respectively. Additionally, the same composites recorded a tensile stress and toughness of 77 MPa and 0.27 MPa, respectively, indicating an increase of about 234% and 32.8% when compared to the pristine resin’s properties. The thermogravimetric analysis denoted an excellent thermal resistance of the reinforced hybrid composites. Fourier transform infrared spectroscopy proved that the functional groups of the as-used coupling agent were effectively grafted on the external surfaces of the reinforcing systems, and further confirmed that the chemical reaction took place between the treated fibers and the polybenzoxazine matrix, although the scanning electron microscope showed a uniform dispersion and interfacial adhesion of the fibers within the resin matrix. In fact, the incorporation of treated fibers along with their good dispersion/adhesion could explain the progressive enhancement in terms of thermal and mechanical properties that were observed in the hybrid composites.

This present study details an experimental investigation on understanding the effects of surface-modified waste hemp fibers on the overall properties of thermosetting resin blends composed of dicyanate ester of bisphenol-A and bisphenol-A-based benzoxazine resins. At first, the hemp fibers were subjected to sodium bicarbonate treatment, and then various experimental tests in terms of the Fourier-transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis tests were, respectively, carried out to understand the influence of the as-used treatment on the structural, morphological, and thermal properties of the hemp fibers. The obtained results from the surface characterization evidently demonstrated the positive sodium bicarbonate impacts on the properties of the hemp fibers. After that, various amounts of the treated fibers were incorporated within the dicyanate ester of bisphenol-A/bisphenol-A-based benzoxazine resin blends and the obtained composite materials were characterized for their structural, mechanical behavior and thermal properties. The obtained results clearly revealed that the prepared blend composites were identified to possess good bending and impact strength properties; however, a slight decline was observed in the thermal properties. The scanning electron microscopy and Fourier-transform infrared spectroscopy investigations demonstrated a good dispersion of the fibers within the blend matrix, and also an enhanced fiber–blend matrix interfacial adhesion, which were plausibly behind the improved mechanical properties of the prepared blend composites.