Drilling damage in carbon/epoxy plates

Abstract

Industrial production of structural parts in composite materials, like carbon/epoxy, has been knowing a growing importance due to their peculiar characteristics, such as high stiffness combined with low weight. Although the issues related with high cost of these materials have been lowered, the need for finishing operations, like drilling due to assembly needs, increase the final cost of the parts. It is known that drilling of these materials is a challenging process and quality rejections can easily rise final costs. This known challenges are a result of composites inhomogeneity and their consequence is the possibility of several types of damage like delamination, fibres pull-out or thermal damages. In this work, the effect of three variables on the drilling
process of carbon reinforced epoxy plates is studied: tool diameter, tool geometry and feed rate. Parameters considered in the study include the thrust force monitoring during drilling, the assessment of the delamination extension from enhanced digital radiographies that are segmented automatically and, finally, mechanical testing of drilled coupons, using bearing test ASTM D5961M–08, for the evaluation on the loss of mechanical properties. The work here presented shows that a proper combination of the factors involved in drilling, like tool diameter, drill geometry and cutting parameters, can lead to the reduction of delamination damage with the consequent enhancement of the mechanical properties of laminated parts