JEC COMPOSITES MAGAZINE - Issue #89 - May 2014 - 29

CMC

Ceramic matrix composite
jet engine exhaust

By
Yann Richard
Program Manager
Herakles
Groupe Safran

S

The Safran group reviewed the different
parts and assemblies that would require
disruptive innovations, and put Herakles
in charge of designing, developing and
producing CMC afterbodies for the
engines of the future.

Materials developed at Herakles
The material solution contributed by
Herakles led to successive developments
that were guided mainly by the service
life in oxidizing conditions. We will refer
to the following materials:

Ceramic matrix composites

The Sepcarbinox family:
- carbon fibres
- pyrocarbon interphase
- SiC (silicon carbide) matrix
infiltrated using the chemical
vapour infiltration (CVI)
process. This type of material is used
in series for the secondary flaps on the
Rafale M88 engine. It has a service life
limited to 5,000 hours, so cannot be used
for parts with very long service lives.

Main properties
CMCs are in the family of thermostructural composites, which are materials
that maintain their structural properties
at high temperature. These composites
are made of carbon or ceramic fibres in
the form of preforms, with the porosities
filled in by a matrix (i.e. densified).
Unlike monolithic ceramics or graphites,
CMCs have non-brittle behaviour, and
are also much lighter than the metal
alloys that might otherwise be competitive at high temperatures.

Density

CMC:

Carbon-carbon
~1.7
SiC-SiC
~2.2
Alumina-alumina ~2.9

Metal alloys:
Titanium
Inconel

~4.5
~8.3

The SiC-matrix Cerasep family:
- SiC fibres
- pyrocarbon interphase
- SiC matrix
The self-healing-matrix Cerasep family:
- carbon fibres
- pyrocarbon interphase
- Si-B-C matrix
The oxide/oxide Cerasep family :
- alumina or aluminosilicate fibers

No89 May 2014 /

Feature Aeronautics

afran's work in the field of ceramic
matrix composites (CMC) for a
civilian aircraft engine afterbody
started with the DTP (Développement
Technique Probatoire, or Experimental Technical Development) project
on nozzles for civilian use, and continues with the Arcoce programme. For
Herakles, Safran's centre of excellence for
thermostructural composite materials,
the challenge over the next few years is to
become a major supplier of CMC parts
for civilian aviation.
The Advisory Council for Aeronautics
Research in Europe (Acare) defined the
technical goals for future aircraft, including a 50% reduction in CO2 emissions
and perceived noise. These goals are
upheld by the French civil aviation research committee Corac (Conseil pour la
recherche aéronautique civile française).
For products and technologies, implementation will include the introduction
of composite materials that are lighter
than the metal materials currently used
and the incorporation of noise control
systems.

The Arcoce plug is emblematic of Safran's commitment to introduce
ceramic matrix composites (CMC) into civilian aviation. CMCs have
a number of advantages over metal alloys, like up to 50% weight
savings and high-temperature resistance. The Arcoce prototype was
tested on the ground in 2011 and in flight on the Airbus A320 test
aircraft in early 2012, a world first. Certified in 2014, it will be flight
tested on Air France aircraft from 2014 to 2016.

jec composites magazine 29
JEC COMPOSITES MAGAZINE - Issue #89 - May 2014

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