MATEC Web of Conferences 29, 00003 (2015)
DOI: 10.1051/matecconf/20152900003
C Owned by the authors, published by EDP Sciences, 2015

Standardisation of ceramic matrix composites
Philippe Gomeza
DGA Aeronautical Systems, 47 rue Saint Jean, 31131 Balma Cedex, FranceAbstract. The standardisation on ceramic matrix composite (CMCs) test methods
occurred in the 1980’s as these materials began to display interesting properties foraeronautical applications. Since the French Office of standardisation B43C has participatedin establishing more than 40 standards and guides dealing with their thermal mechanicalproperties, their reinforcement and their fibre/matrix interface. As their maturity has
been demonstrated through several technological development programmes (plugs, flaps,blades . . . ), the air framers and engine manufacturers are now thinking of develop industrial
parts which require a certification from airworthiness authorities. Now the standardisationof CMCs has to turn toward documents completing the certification requirement for civil
and military applications. The news standards will allow being more confident with CMCs
in taking into account their specificity.

1. IntroductionThe development of ceramic matrix composites (CMCs) began several decades ago when therequirement for lighter materials that could sustain high temperatures became necessary.
Quickly, people involved with CMCs started to discuss and to establish standards in order to achievecommon basic material properties.
More recently CMCs demonstrated their maturity through the success of technological development
programmes (plugs, flaps, blades . . . ). Consequently air framers and engine makers included CMCs forpossible usage in their programmes.
Currently in civil aeronautics, the CMC applications are at the certification stage and industry has toobtain the airworthiness certificate.
Now the standardisation of CMCs has to turn towards documentation to complete the certification
requirement for civil and military applications. The new standards will help industry and authorities
by establishing a common basis for discussion and allow then to be more confident with CMCs when
taking into account their unique characteristics.

2. Brief history of CMCs in France
The CMCs arrived on the market in the early of the 70’s to respond to spatial propulsion requirements.
We are including carbon/carbon composites (C/C) in the family of CMCs.

a e-mail: philippe.gomez@intradef.gouv.fr

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Figure 1. C/SiC secondary flaps of the M88, engine of the French fighting aircraft Rafale.

Figure 2. CFM56 CMC plug demonstrator. Developed by Herakles and tested in flight on an Airbus A320.

Since this period, C/C composites have been used for rocket throat nozzle as well as divergent andexpendable divergent. Nevertheless, the probable most important use of C/C in volume is discs foraircraft brakes.
In the 80’s Europe launched a programme of development of a re utilizable space shuttle namedHermes. The necessity to operate a long time at high temperature under oxidant atmosphere excluded
C/C as potential candidate. This opened the way to develop C/SiC and SiC/SiC.
When the European space shuttle programme collapsed in 1992, the companies working on CMCs
took advantage of their experience to set up a second generation of CMCs which could be adapted toaeronautical challenges. The temperature of material requirements decreased but the operating duration
exploded: tens of hours for a space shuttle, thousands of hours for military engine aircraft and then tensof thousands of hours for civil engine aircraft.
The first aeronautical CMCs applications were produced in the frame of military programmes.
They aimed to demonstrate the feasibility of different engine parts such as flaps, combustion chambers,
nozzles, plugs . . . In 1996, the C/SiC secondary flaps of the M88, engine of the French fighting aircraft
Rafale, were the first parts qualified for flight.
The third generation of CMCs appeared in the early 2000’s with thermo mechanical characteristics
and life durations which suggested this kind of material was mature enough for more critical applications
and/or for civil applications. The CMCs seemed to be a good candidate to meet the lightening andperformance requirements for engine hot parts and to replace nickel based superalloys wheneverpossible.
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3. Data material requirements for design
Engine makers continuously search materials capable of sustaining ever higher temperature in order
to increase the thermodynamic efficiency of their turbo machines. Initially they were interested bymonolithic ceramics which displayed lower density and higher thermal resistance than alloys usuallyemployed in the hot parts. Unfortunately, the brittle behaviour of the monolithic ceramic made their use
impossible in the aeronautical field.
The CMCs provided a solution that avoided brittle behaviour by introducing a ceramic fibre intoa ceramic matrix. This structure allowed a crack deflection inside the fibre coating and increases thecrack propagation energy. Then the CMCs showed an elastic damageable behaviour due to the matrix
microcracks. The maximum elongation at failure increased at about 1%.
At the same time the design offices size parts with well-established methods to predict theirbehaviour and their life. These methods are suitable for homogeneous and isotropic materials but are
not adapted for CMCs which are nonhomogeneous and exhibit an orthotropic behaviour.
Models and methods to size CMC components developed require material data. New specific tests
different from the existing tests used for monolithic ceramics, metallic alloys and organic matrix
composites had to be developed.

4. Standardization and its evolution
During the 80’s in France, industries (Aérospatiale, SEP, Dassault, . . . ) and test centres (CEAT, IMC,. . . ) worked on test methods to achieve thermo mechanical properties from CMC coupons. At the sametime, academics (LCTS, LMT, INSA Lyon, . . . ) and institutional laboratories (ONERA, . . . ) developed
constitutive equations and fatigue life models.
In 1987, most of them created the technical committee of the AFNOR B43C standard commission
which dealt with technical ceramic topics. The purpose was to harmonize test methods for CMCs
thermal and mechanical characterisation.
In 1988, the members of the AFNOR approached the European Standard Commission CEN TC184
and the subcommittee SC1 dealing with CMCs was born. During a period of 15 years the subcommittee
SC1 discussed, wrote and published approximatively 40 standards and guides (see the table below).
Finally the French standard commission joined in 2008 the ISO TC206 Technical Committee as
participant member of the Working Group 4 dealing with ceramic matrix composites. This was totransfer the European corpus of standards about CMC to the ISO level. Additionally new standards
could be developed to cover other requirements, such as in support of the airworthiness certification
process.
The standards established cover topics of elementary mechanical (tensile, compression, . . . ) andthermal (expansion, diffusivity, . . . ) properties of the composite at room temperature and at hightemperature. Furthermore we can find standards about life of the material under creep or fatigue
conditions under inert or oxidative atmospheres.
There are also standards to determine reinforcement properties and characteristics. To complete there
are standards to evaluate fibre/matrix properties interface properties, terms and symbols definition. The
Table 1 below shows the number of standards by domain. The Table 2 gives the references of the French
standards for mechanical tests and their ISO, American and Japanese, equivalents.

5. Emerging applications and new requirements: The example ofaeronautic
Since the 2000’s, CMCs have shown properties in terms of strength and life over a wide temperature
range which taken with their lower density characteristics makes their use very interesting.
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MATEC Web of Conferences
Table 1. Number of European Standards by topics.
TopicsMechanical properties of CMC
Thermal properties of CMC
Fiber/matrix interface properties
Methods of test for reinforcements
OthersNumber194210
4

Table 2. Mechanical properties of CMCs- French, ISO, American and Japanese standard references.

Figure 3. Pyramid of tests.

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The aeronautic and nuclear fields consider CMCs in industrial application projects where criticality
is higher. The problem is now not only how to size components in terms of strength and life duration but
also how to be sure that components have the probability of failure which respect the level of security
required by the authorities.
For engine makers, the process to obtain the airworthiness certificate needs justifications that current
standards cannot meet and specific requirements for nuclear applications are not covered by existing
standards.
The aeronautics current standards cover the base of the pyramid of tests (see Fig. 3) composed oftest methods to achieve elementary properties of CMCs. To meet the requirement of certification, thestandardization should deal with details such as hole, assembly or corner, to provide minimum values
for singularities. Furthermore the standardization could examine specific loadings in the case of entire
components representative of the application’s real life.

6. Conclusion and perspectives
Standards for the determination of elementary thermomechanical properties of CMCs have beenobtained. The transfer of European standards to the ISO level has been undertaken in the frameworkof the ISOTC206 WG4 technical committee “Technical ceramics- ceramic matrix composites”. This
will be completed in a few years.
However CMC applications are approaching the industrialization phase, especially in aeronautics.
This requires new standards to support and to complete the justification process for airworthinessqualification/certification.
These more product oriented standard will require cooperation at international level to share work(round robin campaign, task sharing, material coupons). This will be necessary to share costs, to reacha general agreement and above all to make the CMCs use reliable.

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