Influence of Microwave-Treated Waste Aramid Fibers on the Mechanical Behavior of 3D-Printed Composite Materials

Abstract Industrial surface modification techniques are commonly employed to enhance the adhesion between polymer matrices and aramid fibers (AFs) in composite materials. However, these techniques are often associated with high costs, operational complexity, and environmental drawbacks. This study presents the development of a cost-effective, eco-friendly, and efficient microwave-assisted surface treatment for aramid fibers. The technique utilizes microwave irradiation to increase surface roughness, disrupt crystalline bonding, and introduce oxygen-containing functional groups, thereby enhancing surface energy and fiber reactivity. Moreover, the microwave-induced electromagnetic fields promote microstructural changes within the aramid fabric, strengthening intermolecular interactions and improving interfibrillar bond integrity. The process was optimized using the Taguchi design of experiments (DOE) methodology, ensuring that the mechanical properties of the fibers remained intact while achieving precise adhesion control with thermoplastic matrices. The study also incorporates advanced additive manufacturing techniques—fused deposition modeling (FDM) and direct ink writing (DIW)—to fabricate aramid fiber-reinforced sandwich composites. These techniques were selected to enhance the composite's mechanical strength, interfacial adhesion, and resistance to environmental degradation. Experimental results demonstrate a significant enhancement in surface wettability, with the water contact angle reduced from 120 deg to 11.2 deg. Additionally, interlaminar shear strength increased substantially from 35 MPa to 96 MPa. Tensile tests revealed a modulus of 516 MPa, and Izod impact tests showed an impact resistance of 599 J/m, validating the effectiveness of the microwave-assisted surface treatment in significantly improving the performance metrics of aramid fiber-reinforced composites.