24TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES AN IMPROVED LONG LIFE DURATION CERAMIC MATRIX COMPOSITE MATERIAL FOR JET AIRCRAFT ENGINE APPLICATIONS L. Baroumes, E. Bouillon, F. Christin Snecma Propulsion Solide Abstract time evaluation by fatigue testing. This A new concept of Ceramic Matrix Composite characterization program provides a basic (CMC) material, mainly based on the use of a database used for the stress analysis of CMC self–sealing technology for matrix and the use composites through mechanical behavior of a multilayer woven reinforcement, has been models using Continuum Damage Mechanics. A developed by Snecma for achieving high thermomechanical analysis is presented with the performance levels targeted by future jet comparative behavior of two materials. A sub engines. The driving force for this development element testing validate the orthotropic non- has been to increase both lifetime and linear law. temperature capability of previous C/SiC and SiC/SiC composites materials using a 2 Materials for gas turbine engine monolithic SiC CVI matrix and finishing treatment against oxidation. The application of advanced materials has played a vital role in the development of gas turbine engines over the last fifty years. An estimated 50% of the increase in efficiency and 1 INTRODUCTION performance has been directly attributed to In order to meet high performance levels material development. Material developments targeted by future jet engines components [1], come in two forms: Snecma Propulsion Solid (SPS), has developed · the easiest being the study development of a a new concept of self-sealing Ceramic Matrix known material system through iterations of Composites (CMC) materials named material and processing : In this way, the temperature capability of nickel base CERASEP®A410 and SEPCARBINOXâ A500 combining improvements of fiber superalloys has increased by over 350°C since the 1940’s, reinforcement, interphase and matrix [2]. These materials, manufactured by SPS are designed · the other way is the introduction of new for thermo-mechanical applications such as long types of advanced material, tailored to the term parts for gas turbine engine. The specific requirement of gas turbine engines. development of these CMCs has been This approach is more difficult and requires milestoned by steps, which as specified in considerable continuous investment over many different papers [3]. years. The introduction a new materials takes The aim of this paper is to present typically a minimum of fifteen years. The thermomechanical characteristics and analysis necessary levels of safety and reliability dictate validated by sub-element testing of these CMCs. that all risk associated with the introduction of a After reviewing the material development story, new technology are adequately assessed and the CMC's development phases, we focus on the addressed. In gas turbine engines the measured thermomechanical properties and life components are subjected to many potentially 1 L. BAROUMES, E. BOUILLON, F. CHRISTIN, Snecma Propulsion Solide detrimental factors including high temperature C.G. from Nippon Carbon, with pyrocarbon and loads, vibrations and load cycling thermal interphase, and a SiC matrix deposited by shock, oxidation, corrosion, abrasion, erosion, chemical vapor infiltration (CVI). handling and occasional impacts. In this context CERASEPâ A373 (A300 serie) material very new materials, however promising, cannot was characterized by a high specific strength, at instantly be put into engines room temperature, of about 300MPa and a non- The silicon bases ceramics, primarily Silicon brittle behavior, with an enhanced failure strain, Nitride and silicon Carbide have been the focus of about 0.5%. This material, protected by an of much interest and development during the appropriate finishing treatment against last twenty years. These materials retain oxidation was also characterized by a relatively strength at over 1200°C where there has been no good life time capability, in flexural creep, other material available (Fig. 1). under air, at temperature between 873 to 1473K. Nevertheless, testing in more severe conditions, Fig. 1 Usable strength for high temperature materials especially for tensile/tensile fatigue tests for gas turbine engines. performed at a stress level of 120MPa, failure of Specific Ultimate Strength - Mean value the material occurred rapidly, due to a partial 40 oxidation of the interphase. This was illustrated Titanium alloys 35 Maximum temperature for steady-state use up by a life time duration of about 10 to 20 hours at to 400°C (Ti6.2.4.2.) 30 Ceramic Matric Ceramic Matric 873K and less than 1 hour at 1123K. In Composite A 410 Composite A 500 25 conclusion, for these series of SiC/SiC 20 composites life time duration in air, at moderate 15 Nickel base alloys Max temperature for and high temperature was considerably reduced Specific ultimate strength (Ksi) steady-state use 10 between 600°C (Inco718) and beyond the elastic yield point (about 80MPa). A 900°C (Rene77) 5 Cobalt base alloys Maximum temperature for steady- state use up to 950°C (Mar-M 509) first evaluation of the SiC/SiC material series 0 100 350 600 850 1100 1350 1600 1850 2100 A300 behavior was established in real temperature (F) However monolithic ceramic technology was conditions by the design, manufacturing and considered unsuitable for structural components bench testing of Rafale engine M88-2 inner : in an environment when catastrophic failure is nozzles flaps in 1992. This highlighted early to be avoided at all cost. The very low defect cracking of some components which resulted tolerance and low failure strain of this material from local stresses. These stresses were was considered to impact too high of a risk and generated by the combination of non-uniform consequently has not been specified in thermal gradient and higher temperatures than production engines. Composite material anticipated by thermal analysis. It was found combining the advantages of ceramics with a that these stress levels were twice than that of material capable of offering an improved the SiC/SiC series A300 design allowable (80 tolerance to strain have captured all the recent MPa) and induced micro-cracking of the efforts to use ceramics in larger aero-engines. material leading to an oxidation rate The incorporation of continuous ceramic fibers incompatible with long life span. In the same period, Snecma developed a offer the ultimate in the ability to control the â properties of the material. C/SiC (SEPCARBINOX , Carbon fiber/Silicon carbide matrix) material for engine nozzles 3 BACKGROUND operating at intermediate temperature and life span objective over one thousand hours. A SiC/SiC (Silicon Carbide fiber/ silicon typical example of application is the M88-2 carbide matrix) composite material series A300 engine outer flaps. â developed by SPS (originally SEP) before 1992 SEPCARBINOX A262 is made of a were made of a 2D reinforcement (2D : 2 multilayer reinforcement with carbon fiber, a directions of reinforcement), using NicalonTM pyrocarbon interphase, a SiC CVI matrix and an 2 AN IMPROVED LONG LIFE DURATION Ceramic Matrix Composite MATERIAL FOR JET AIRCRAFT ENGINE APPLICATIONS enhanced finishing treatment to improve its know-how achieved on C/SiC A262, the behavior in oxidative atmosphere. combination of a carbon reinforcement with a SEPCARBINOXâ A262 is characterized by a self-sealing matrix has been studied. This non-brittle behavior with failure strength of approach provides better economical outlook about 250 MPa at room temperature, and life considering the gap between the cost of carbon time duration, for temperatures below 973 K, and carbide fibers. matching the application requirements. Qualification of the SEPCARBINOXâ A262 4.2 A410 and A500 description technology was pronounced in 1996 for the M88-2 engine outer flaps, after completion of Plane multi-layer reinforcement named endurance testing based on accelerated mission GUIPEXâ has been developed, in order to cycles. The lifetime objective of the component prevent the natural delamination sensitivity of has now been demonstrated on the M88-2 2D materials. GUIPEXâ preforms are made of engine and serial production is underway. layers, linked together and the technology is Moreover, destructive evaluation, after applicable to carbon and ceramic fibers. representative engine life duration (1000 hours Number of layers is adjustable, in order to engine test, resulting from 375 hours ground test obtain composite thickness range between 2 and and 625 hours flight test), performed by tensile 7 mm, or variable thickness composite. These properties measurements, at room temperature, reinforcements have been optimized to obtain has confirmed the excellent capabilities of such orthotropics composites, with in-plane material : characteristics close to a 2D material. - s/sinitial > 0.90, A hardening step is necessary to obtain - e/einitial > 0.90, the desired shape, with the desired fiber volume fraction, before the matrix infiltration. Specific - E/ E initial > 0.90 CVI route, combining both interphase and 4 NOVEL SELF-SEALING MATERIALS hardening process has been selected. A self-sealing route has been selected for 4.1 General approach the matrix in order to eliminate finishing SPS decided in 1992 to engage the treatment. The principles of the self-sealing development of a new CMC material concept, approach are to consume part of the incoming matching long life span at high temperature with oxygen and