Drilling of hybrid materials made of carbon/epoxy and aluminum alloy

The stacked combination of materials such as aluminum and epoxy matrix/carbon fiber composite poses numerous problems in terms of drilling, due to the difference in their machinability. In fact, it is not possible to simply juxtapose the studies carried out on each constituent material to achieve an acceptable compromise. The aim here is to briefly review the results obtained on the two constituent families, the main features of which are anisotropy and heterogeneity for one, and isotropy and homogeneity for the other.

This article begins with a synopsis of the state of the art in conventional drilling of composite materials, aluminum and multi-materials. This is followed by the results of a dry drilling test campaign on a CFRP/Al multi-material, enabling machining with discontinuous chips while guaranteeing an acceptable surface finish. We began by investigating the machinability of a CFRP/Al multi-material using commercially available tools and the advice of tool suppliers. The objectives were to evaluate :

– the influence of cutting parameters (rotation speed and tool feed rate) on the cutting forces generated and on machining quality;

– the influence of the number of holes drilled on the evolution of thrust forces and roughness in composite and aluminum ;

– the benefits of using commercially available tools and coatings when drilling CFRP/Al multi-materials;

– the addition of a new nano-composite coating.

Secondly, a new cutting tool geometry was developed, with the aim of ensuring CFRP/Al composite drilling with discontinuous metal chips, while guaranteeing low average roughness in composite ( $Ra\le 3\text{μm}$ ) and aluminum ( $Ra\le 1\text{μm}$ ).