Mechanics and dynamics of machining advanced composite materials

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Composites offer an outstanding strength to weight ratio and fatigue and corrosion resistance, therefore their application has grown tremendously in a broad spectrum of productsfrom consumer to aerospace. To accommodate the surge in the application of composites, the industry demands high productivity manufacturing methods to convert the material into the final product. Machining operations such as drilling, milling and trimming are usually a critical step in manufacturing composites. These operations are commonly used in finishing and assembly stages and thus poor machining conditions may lead to scraping of the finished product. The ultimate goal of this program is to develop High Performance Machining (HPM) systems to enhance the productivity and robustness of composite machining processes by a) simulation-based optimization of the process, b) appropriate process control and monitoring and c) developing intelligent robotic machining systems. Achieving these objectives will have a transformative effect on current methods of machining composites. For example, in manufacturing the composite structure of a commercial aircraft, more than 70% of the drilling operations are performed manually; such operations can be carried out using automated robotic systems to optimize the speed and robustness of production, also to avoid workplace health and safety hazards such as white finger syndrome due to drill vibrations. The proposed research will contribute to developing HPM systems by characterizing the chip generation process in composite machining and modeling the resulting cutting forces and vibrations. These models will be used in the long term for the optimization, control and automation of the process. Mathematical modeling of the process will be studied by pursuing the following objectives in the next five years: i) characterizing the material failure modes (shear, fracture, etc.) that lead to chip generation in Fiber Reinforced Polymers (FRP), ii) developing the mathematical models of cutting forces in terms of the feed, speed, tool geometry and material's constitutive model, and iii) incorporating the structural flexibility of the tool and workpiece in cutting force models to simulate the vibrations during machining operations. Although the focus of the study in the next five years will be on FRPs, because of their broader industrial applications, modeling will be extended to other types of composites in the long term. Scientific and technological contributions of the program will be complemented by training several Highly Qualified Personnel (HQP), who will receive training on fundamental and applied fields of engineering such as fracture mechanics, dynamics, vibrations, Finite Element Modeling, hands-on experimentation, signal processing and experimental structural dynamics. This training will prepare them to take on leadership roles in academia and industry.