High Quality, High Productivity Composite and Multilayer Drilling

Modern military and commercial airframes are comprised of aluminum, titanium and fiber reinforced composites mated together with rivets inserted in tens of thousands of pre-drilled holes. Drilling in assembly operations is performed on components made from stack-ups of composites, aluminum and titanium. Problems associated with hole quality, tool life and interlayer burrs are pervasive and result in costly destack and debur operations. Trial-and-error methodologies for improving drilling processes can be expensive, time consuming and have little guarantee of success. Development of new innovations has been hampered by empirical methodologies. It is therefore desirable to develop new physics-based modeling technologies for composite/metal stack-up drilling. Physics-based modeling will eliminate trial-and-error testing and enable the identification of process parameters and tooling to alleviate rework and scrap. Our Phase II program will further develop and demonstrate physics-based modeling for improved drilling processes of composite/metal stack-ups. Our Phase I results demonstrated model correlation to improved tool life and productivity. In Phase II, we enhance the constitutive model for composite workpieces and demonstrate improvements in conjunction with industry partners. Physics-based models will allow detailed analysis of new drill designs and process parameters, predict forces, temperature and hole quality, and ultimately reduce costs and cycle time.