The objectives for this dissertation are to push forward the current state of knowledge in the area of machining fiber-reinforced plastic (FRP). The most common machining operation performed on these materials is drilling owing to the need for component assembly in mechanical pieces and structures. Among the defects caused by drilling, delamination appears as to be of the most critical and may occur at both the entrance and exit plane. A number of theoretical and experimental studies have been made to create an analytical model of delamination in composite laminates. In this dissertation, the critical thrust force (force which initiates the delamination) is predicted using linear elastic fracture mechanics - assuming Mode I. Delamination is investigated by studying the evolution of feed force and torque applied by the tool on the workpiece. A four components piezoelectric dynamometer KISTLER 9272 with special PC-software is used for measuring and evaluating of torque and cutting forces, when drilling two different composite materials: carbon/epoxy laminate fabricated by hand lay-up technique and glass/polyester composite made by pultrusion. Wear mechanisms and location of the wear on the tool are also investigated (with respect to cutting material). The tool wear is measured with help of a common workshop microscope and recorded with scanning electron microscope PHILIPS XL30. Drilling experiments are performed to give complex technical information (i.e. cutting conditions, tool geometry, tool wear and so on) which enables efficient machining of composite materials. Delamination-free drilling is given special emphasis in the experiments. Methods of statistical analysis (DOE) are used to determine which factors have the most influence on delamination.

Les composites utilisés dans l'industrie aéronautique sont hétérogènes. Ils sont composés d'une matrice polymère souple et ductile et d'un renfort dur et fragile. Les différentes phases ainsi que l'anisotropie du matériau peuvent rendre l'usinage de ces matières, difficile. Deux problèmes majeurs peuvent être rencontrés lors de l'usinage : garder l'intégrité de la matière usinée et réduire l'usure de l'outil de coupe. Les niveaux de qualité demandés dans le secteur aéronautique imposent une coupe sans défaut, ces derniers pouvant entrainer une altération ultérieure de la pièce. Les principaux défauts rencontrés sont : le délaminage des plis, la surchauffe de la résine, les plis non coupés francs ou l'écaillage. / Aeronautic composites are inhomogeneous and most often consist in two distinctly phases. The reinforcement fibres are relatively hard and brittle whereas the matrix is soft and ductile. The anisotropy causes some severe challenges when machining composites. People in the field often experience a trade-off between two main problems ; on one hand, keeping the composite parts integrity and quality, and on the other hand, reducing the wear of the cutting tools. The quality level required in aeronautic applications imposes a high quality cut of machined parts. Common defects that may occur during machining of these materials are delamination, overheat of the resin, uncut fibres, and fibre pull-out.