Aerospace & Defense Technology - September 2022 - 4

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INSIDE STORY
The Spirit AeroSystems, Inc. facility located in Biddeford, Maine, has been a supplier of hightemperature
composite materials for over 50 years. Mark Lippold is a senior application engineer
in Biddeford, the company's center of excellence for high-temperature composite materials
where significant emphasis is directed toward hypersonic flight material solutions.
A&DT: We hear a lot about hypersonic flight, what are the
challenges suppliers like Spirit are facing in meeting the
customer application requirements?
Lippold: Spirit AeroSystems has been
making high-temperature composite
materials for aerospace and defense
applications, including re-entry vehicle
leading edges that reach hypersonic
speeds. However, next generation hypersonic
solutions require longer operational
duration and more challenging
flight profiles. As a result, the hightemperature
material community is assessing
more capable solutions than
those currently in use. While ablative materials have a long
history of success in high-temperature hypersonic flight, new
hypersonic applications often require non-ablating/non-eroding
materials and components that will maintain shape during flight
at temperatures exceeding 4,000°F. Spirit's development efforts
are focused on ceramic matrix composites (CMC) to address
the demand for enhanced hypersonic performance.
A&DT: Why are aerospace and defense hypersonic vehicle
manufacturers so interested in CMCs?
Lippold: Spirit's carbon/carbon (C/C) material has been a workhorse
for DOD high-temperature re-entry vehicles and solid
propellant motors for decades. CMCs, unlike the traditional ablative
C/C material solutions, resist erosion and oxidation at
extremely high-temperatures. Retaining shape by eliminating
ablation can extend flight durations and accuracy. Flight dynamics
are more predictable with non-ablating solutions allowing
optimized flight profiles. Relative to high-temperature metallics,
CMC components can be less than 50% of the mass and perform
at high-temperatures. In addition, Spirit's CMC can be engineered
or tailored for specific application requirements. This
tailoring makes the CMC adaptable to differing flight requirements
or applications. Spirit's CMC solutions are enabling for
hypersonic flight objectives.
A&DT: What are the elements of Spirit CMCs that can be
engineered for specific applications?
Lippold: In my applications engineering role, it is critical to
understand the customer's component requirements, and then
determine how to optimize the material for the design. The
material engineering, or tailoring, includes assessing fiber type,
preform-fabric architecture, matrix constituents, density/porosity,
and thermal-environment barrier coatings. With application
specific materials, the performance, aerothermal environment,
integration, and unit cost can be optimized while addressing
mission requirements.
A&DT: What do you see as the most enabling aspect of your
engineered materials?
Lippold: Spirit utilizes a building block approach for developing
material solutions. This allows the customer to employ an array
of options to achieve design requirements. The various material
tailoring options, coupled with the commonality of fabrication
methods, results in predictable transition from development
and first article to low-rate initial production and then on to full
production. Two building-block elements are typically key: the
fiber woven preform-architecture style and the matrix constituents.
Each of these elements have a considerable number of
options and therefore much flexibility for the component/system
designer.
A&DT: Can you provide an example of perform-architecture
style?
Lippold: Spirit focuses on multi-directional fiber reinforcement
for both small intricate and large acreage near-net shape components.
Utilizing our specialized preforms eliminates interlaminar
issues and failures experienced with more traditional
two-directional layup composites. Spirit's three directional (3D)
woven materials incorporate through thickness reinforcement
that is optimized for the application requirement. The fiber architecture
is determined early in the design process with the
customer. In many cases, multiple preform architectures are
employed within a system, as different components have different
requirements. Because our CMC fabrication processes are
common, there is no loss in production efficiency.
A&DT: Last, what CMC attributes are you currently working
on and find the most compelling to enhance customer specific
applications?
Lippold: Spirit's development team is working in two areas that
will be extremely enabling for next generation hypersonic systems.
First, advanced 3D net-shape placed-fiber preforms. This
novel robotic technology will allow rapid prototyping of complex
shapes and seamless transition to production. Second, enhanced
environment and thermal barrier coatings that will extend
flight duration and increase maximum operational temperature.
Both developments are being efficiently integrated
with Spirit's existing high-temperature CMCs process capability.
These development efforts are the direct result of our customers'
input for addressing future mission challenges.
Visit Spirit AeroSystems for more info. at www.spiritaero.com
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