Investigation of mechanical properties of TiO2 filled glass and carbon fiber reinforced composites and their milling with cryogenic cutting tools

In this study, the mechanical properties of unfilled and nano titanium dioxide (TiO2) filled carbon and glass fiber reinforced composites were investigated and the effect of cryogenic cutting tool and TiO2 filler on milling results was investigated. TiO2 was added as 1% by weight in filled composites and all composites were produced by hand lay-up method. After conducting tensile, flexural, and compressive mechanical tests on the composites, scanning electron microscope (SEM) images of the fracture surfaces were examined after the tensile tests. Furthermore, the composites were milled using cryogenic and non-cryogenic cutting tools under different cutting parameters to investigate cutting forces, surface roughness, and chip morphology. For both fiber types, the addition of TiO2 filler particles was found to improve the tensile, compressive, and flexural strengths of the composites. The TiO2 filler provided an 8% to 12% increase in the tensile strength of the composites. 1% nano TiO2 filler increased the flexural strength of glass fiber reinforced composites (GFRC) to 429 MPa and carbon fiber reinforced composites (CFRC) to 632 MPa. The TiO2 filler contributed 5% to the compressive strength of CFRCs and approximately 7% to GFRCs. On the fracture surface of the TiO2-filled composite examined by SEM, it was observed that the fibers were concentrated in a certain region and broke as bulk fiber bundles. While the increase in feed rate in milling of GFRC and CFRC caused the cutting forces and surface roughness values to increase, the increase in cutting speed caused the cutting forces and surface roughness values to decrease. Furthermore, TiO2 filler reduced the cutting forces and surface roughness values in the milling of composites. The cryogenic treatment applied to the cutting tools had a reducing effect on the cutting forces and surface roughness values in both GFRC and CFRC. When the SEM images of the chips after milling of TiO2 filled GFRC and CFRC were examined, it was determined that the fiber particles were shorter in length and had a more homogeneous structure. When the chip morphology of GFRC and CFRC milled with cryogenic cutting tool was examined, a chip structure with small fiber particles and clustered fiber bundles was observed.