The post manufacturing by machining of composites parts is becoming much more usual. The aim of this study is to define the performance of existing cutting tools for composites, in order to suggest the best choices and the optimal cutting conditions for the trimming process of carbon fibres reinforced plastics (CFRP). The evaluation is based on the cutting forces and the surface quality produced through the trimming process. A systemic approach, using weighting factors, is proposed to help the end user for the performance evaluation of the cutters based on its production environment. This work also describes a design of experiments to determine the geometrical parameters which influence the performance of the cut with the objective to design more efficient cutting tools.
For both aspects, the research method used includes the development of a classic design of experiments with multiple factors. The factors discussed are the cutting parameters, the thickness of quasi-isotropic laminated carbon / epoxy material and the different types of cutting tool materials. The data acquisition is done using a dynamometric table for the force evaluation, a profilometer for the surface roughness evaluation as well as optical microscopes for the surface integrity estimation. It is found that the cutting forces in the direction of feed is proportional to the feed rate, while cutting forces in the axial direction and normal to the machined surface are proportional to the cutting speed and feed rate. Of the four tool types analyzed, the tool C4 with inserts of PCD is the best performing tool evaluated by the method of weighting factors in the equation of the performance index. As part of this work, a comprehensive analysis of the roughness was made and the main results obtained show that the roughness is dependent on cutting parameters and fiber orientation. Composites with fibers oriented at 0 degree have the best surface roughness and those fiber with a -45 degrees orientation have the worst surface roughness for the same cutting parameters and the same tool. The cutting tools should have positive rake angle for their cutting edges with a value ranging between 8 to 10 degrees and have a coating able to withstand the abrasiveness of carbon fibers.
Two recommendations are made in the context of this work for the continuity of this research. The first recommendation is to evaluate the tool wearing due to the trimming process with the best cutting tools proposed in order to determine the cost per length of machining for each of these. This performance index has to be evaluated since it is directly related to the final choice of a best cutting tool. The second recommendation is to manufacture new cutting tools based on the optimal geometric parameters proposed in this study and evaluate their performance as compared to the other tools tested in this work.
Bérubé, S. (Author),
Songmene (Supervisor) &
Chatelain (Co-supervisor),
5 Jul 2012Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering