Machining parameters for an intelligent machining system for composite laminates

Composite laminates exhibit very high in-plane strengths but are plagued by delamination damage when subjected to machining. This is due to their poor transverse strengths and low delamination fracture toughness. In drilling, delamination is initiated when the thrust force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. To minimize damage, therefore, it is important to monitor process variables such as the machining forces and the position of the tool relative to the workpiece. The availability of a suitable model coupled with an intelligent control scheme would be a large advancement in the machining of composite laminates. This paper explores the development of such models for machining of composites and for coupling the models to intelligent control strategies. Using a machining center, a series of drilling experiments were conducted on carbon fiber-reinforced composite laminates to determine key process parameters for various cutting conditions. An intelligent machining scheme is proposed as the basis for the design of a new machine tool. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.