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Evaluation of Ceramic Matrix Composite Edge and Surface Damage
Abstract
CMCs have been developed in the 80th for the shuttle programs and commercialized as brake discs from 2000 till today. Since 2017 CMCs are used also in components of flight gas turbines. This application requires highest levels of process and material development and performance. Therefore the knowledge of any process on material damage is of highest importance.The presented work will show a method how to evaluate the quality of edges and surfaces of CMCs created by a special diamond machining operation. The objective is to develop a machining process for CMCs in gas turbine applications and a method for quality assessment for future production.
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Producers of turbomachines for the aviation and energy sectors have to meet the future challenges regarding environment protection, resource conservation and profitability. As part of the 2014 market and trend analysis on the subject of Life Cycle Engineering for turbomachinery, the market potential of the concept of Life Cycle Engineering for turbomachines as well as future trends and R&D issues have been identified. It has shown that the mechanical, chemical and thermodynamic characteristics of high-performance ceramics motivate new developments of Life Cycle Engineering in turbomachinery. However, particular material properties like high hardness and strength represent a challenge for the machining process of complex components made from high-performance ceramics. Since process and machining technologies are key components of the LCE concept, this paper will focus on the importance of a holistic hard machining of ceramic matrix composites with regard to technical and economic criteria
Machining is for many products the ultimate operation in a complex manufacturing process with the goal to give the final shape to a part and to reach the required tolerances. If this process damages the part a big economic loss is the consequence. However during those operations mechanical damage can occur which only lead to a degradation of the material. In the case of ceramic matrix composites, which already play an important role in components like turbine vanes, combustion chambers and brake disks, the damage often cannot be identified. In this paper special machining operations for different CMC materials are compared with respect to influence on part quality. A new method for quantifying the damage using an optical focus variation and image processing is presented.
Covering an important material class for modern applications in the aerospace, automotive, energy production and creation sectors, this handbook and reference contains comprehensive data tables and field reports on successfully developed prototypes. The editor and authors are internationally renowned experts from NASA, EADS, DLR, Porsche, MT Aerospace, as well as universities and institutions in the USA, Europe and Japan, and they provide here a comprehensive overview of current R & D with an application-oriented emphasis.
In this contribution a new method of drilling Ceramic Matrix Composites (CMC) with geometrically defined cutting edges is introduced. For this, tools with massive PCD (Poly Crystalline Diamond) drilling bits are applied. To evaluate the drill hole quality the damage behavior is analyzed by an optical method and a new quality index is introduced. The fundamental investigations on the basic drilling parameters of a C/C-SiC material are presented.
This progress in CMC development is still running and, therefore, the following key note will only give an impression of state-of-the-art from the viewpoint of a CMC manufacturer. This overview will be mainly concentrated on carbon/carbon (C/C) and carbon/carbon silicon carbide (C/C-SiC) composites.
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