Parametric optimization for drilling of multi-fiber (glass and steel) reinforced epoxy composites

Glass fiber reinforced polymer (GFRP) composites are widely used in structural applications, where drilling is essential for mechanical assembly but often causes damage that reduces joint quality. This study investigates the drilling performance of a newly developed hybrid composite reinforced with alternate layers of glass fiber and steel wire mesh and compares it with a conventional glass-epoxy composite. The effects of spindle speed, feed rate and drill diameter on thrust force, torque and exit delamination are evaluated. The hybrid composite exhibits higher thrust force and torque than the glass-epoxy composite due to the presence of steel wire mesh. However, it demonstrates significantly lower delamination, indicating improved resistance to drilling induced damage and enhanced hole quality. Feed rate is identified as the dominant factor governing overall drilling performance, followed by drill diameter, while spindle speed has the least influence. SEM analysis reveals that the steel wire mesh effectively restricts crack propagation and reduces fiber pull-out, matrix cracking, and interfacial debonding. These findings demonstrate that incorporating steel wire mesh enhances the drilling damage resistance of GFRP composites and provides practical guidance for improving the machinability and structural reliability of hybrid composite components.