JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014 - 53

CMC

Cost-effective SiC fibre enabling
new CMC applications
The lack of availability of cost-effective, high-temperature ceramic fibre suitable for CMCs has limited applications to ultra-high performance areas where cost is
no concern. ACM is introducing the SI-TUFF™ 7-Series
SiC fibre, manufactured using a novel, low-cost synthesis process. This fibre enables the development of a new
class of high-performance, low-cost CMCs.

eramic matrix composites
(CMCs) are advanced materials
consisting of ceramic fibres
embedded in a ceramic matrix.
They offer a unique combination of
strength, durability, high temperature
stability, chemical resistance, and low
density that make them an attractive
candidate for a variety of commercial applications ranging from jet
engine components to high-temperature filtration systems to industrial
tooling and equipment. Despite their

DaviD MaMMarella
Director of Business DevelopMent
aDvanceD coMposite Materials, llc

incredible potential and 20 years of
development of CMC technology,
raw material and fabrication costs
have limited commercial successes to
a handful of applications.

ACM's manufacturing process is fast,
inexpensive, highly automated, and
designed from the ground up to deliver high volumes at low cost.

Advanced Composite Materials, LLC
(ACM) hopes to shift the cost/performance equation with the introduction of a cost-effective SiC fibre
called SI-TUFF™ 7-Series. Costing
an order of magnitude less than
other SiC fibres in the marketplace,
SI-TUFF™ will enable the development of a new market for CMCs that
requires better toughness and temperature stability than conventional
ceramics but has been limited by the
high cost of current CMC solutions.

Ceramic materials have a number of
properties that make them attractive
in a wide range of applications: they
are harder, stronger, and can operate
in higher temperature environments
than most metal alloys. The main disadvantage of conventional ceramics is
brittleness. They fracture easily when
exposed to mechanical or thermal
stress because of cracks initiated by
small defects or scratches. Resistance
to crack propagation is dramatically
increased by incorporating ceramic
fibres into the ceramic matrix.

Silicon carbide:
the fibre of choice

Fig. 1: Fracture surface of a long-fibre CMC
illustrating the fibre pull-out mechanism
Source: MT-Aerospace AG

Silicon carbide (SiC) is an ideal reinforcing fibre because of its high temperature stability, chemical resistance,
strength and stiffness. The SiC fibres
available in the marketplace today
are produced by slow and expensive
vapour deposition processes which
do not scale well with high volumes.

How CMCs work: fibre pull-out

Cracks do not propagate through
the fibres, and considerable force is
required to extract the fibres from the
matrix. The fibres effectively form
strong "bridges" over the cracks,
allowing for elongation before failure.
This is known as the fibre pull-out
mechanism and it is critical to the
design of CMCs.

No90 June - July 2014

/ jec composites magazine 53

JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #90 - June/July 2014