An SiO2-Filled Matrix to Improve the Thermal Behavior and Surface Integrity of Fiber-Reinforced Polymers Under Dry Milling

This study discusses the thermal behavior of glass fiber-reinforced SiO₂-filled polymers in dry milling. Focus is put on the effects of the addition of SiO₂ particles on cutting-generated heat and the fresh-surface integrity of the composite. Cutting trials were developed using a Spinner U-620 5-axis CNC machine. Real-time temperature histories owing to the dry milling of both Glass/Epoxy and Glass/Polyester composites were recorded using thermocouples preinstalled within the composite specimen. SEM inspections were conducted to elucidate the prevailing failure mechanisms during the material removal process. The results showed that fiber orientation significantly dominated thermal responses. Cutting perpendicular to the fiber orientation results in a critical temperature, while the addition of SiO₂ particles effectively reduces the temperature overlaps and peak values, causing the temperature to drop. The addition of SiO₂ serves to keep the temperature sufficiently lower than the glass transition point of the matrix. However, increasing the feed rate from 50 mm/min to 150 mm/min reduced the overall temperature during cutting. Under similar cutting conditions, Glass/Polyester composites exhibited lower peak temperatures and heat quantities than Glass/Epoxy regardless of the feed rate and fiber orientation. Observations revealed that fiber orientation and matrix type strongly influence the intensity of the thermal and mechanical damages induced. These findings suggest that the addition of silicon dioxide can adjust the thermal balance in dry cutting and may improve the composite's structural integrity significantly. Such a composite design promotes the heat control of sensitive parts in advanced engineering applications.