Evaluation of thrust force and delamination in drilling of CFRP by using active spring restoring backup force

Carbon fiber reinforced epoxy composites are typically difficult to machine due to their anisotropic properties which cause delamination and other damages. Introducing a backup plate beneath the workpiece during drilling has proven to be an efficient and cost-effective strategy to circumvent this problem. With a view to reduce the serious fiber pull-out and delamination problems that occur during conventional drilling of CFRP composites, a novel method of active spring restoring backup force is introduced at the bottom side of the workpiece. The thrust force and delamination are determined experimentally during the drilling of holes at various drilling parameters, with and without back-up force. This spring restoring active backup force technique aids in the continuous hole making process and is found to be a simple, inexpensive and versatile technique to adopt for reducing drilling damages. The applied active backup force contributes in the reduction of delamination even at higher thrust force. The optimal backup force is found to be 321.6 N which results in reduced delamination in drilling of composite laminate.