SAMPE Journal - May/June 2016 - 36

White Paper

from the

Technical Excellence Committee

Next Generation High Temperature Materials
James K. Sutter/SCRA, Ali Sayir/AFOSR, Leslie J. Cohen/SGL
Michael Maher/DARPA-Defense Science Office, Charles Rowe/Consultant
Mark M. Opeka/Naval Surface Warfare Center-Carderock

The SAMPE Next Generation High Temperature Materials
initiative is a global source for creation, documentation,
presentation and dissemination of material and process
knowledge for materials, processes, manufacturing
technology and fabrication for hypersonic vehicles.
Through a combination of SAMPE High Temperature
Materials tracks at Global and Sector Conferences, Keynote
Address, Work Shops and Panel Sessions of Global experts
the knowledge will be disseminated and documented.
The high temperature materials mission is a materials
limited application. The combination of aerodynamic
environment, loads, temperature and pressure demand
performance and reliability that are at the edge of the
technology landscape. The goal of this focused journey
by SAMPE is to bring the knowledge state to the level of
understanding such that material systems, document
processes, procedures along with time standards can be
established and disseminated across the application and
market enterprises. This is a complex application and
our mission will be to make it possible for designers and
application engineers to have a source data base that
they can use to create, conceptualize and manufacture
hypersonic platforms for civil, military and industrial
applications.
Striking the right balance between strength, weight, and
thermal protection must be carefully achieved through
reproducible fashion. The need for strong, light-weight,
heat resistant, and cost effective materials has long
been considered one of the most critical in high speed
propulsion applications. A balance between weight and
strength is desirable, and this poses a unique problem. In
order to compensate for payload weight, designers prefer
lighter materials, but these may not be strong enough to
withstand the operational thrust, moments, and pressure
loads. Thermal protection adds another complication that
often require special materials, such as heat resistant
paints, to assist with thermal shielding. These additional

Figure 1. HTV-3X: Blackswift.

materials inevitably result in increased vehicle weight.
Material selection and structure configurations needed to
compensate for the aerothermal loads comprise the two
leading decisions that designers face.
Forces encountered in high speed flight include pressure,
skin friction or shearing stresses, and aerodynamic
heating. Pressure and skin friction participate in lift and
drag coefficients whereas aerodynamic heating influences
the structure and stability of the craft. Aerothermal
heating causes a rise in temperatures which in turn
affects elastic properties. One effect is to decrease Young's
modulus and ultimately reducing the materials capability
to handle aerodynamic loads. Additional concerns consist
of a decrease in allowable stress and the time-dependent
phenomenon creep. Thermal stresses then become
prevalent due to local or global expansions or contractions
that induce increased deformation, a change in buckling
loads, and flutter behavior further decreasing the stability
of the hypersonic vehicles.
The vision for science and technology expressed by the
U.S. Air Force in Technology Horizons describes "game
changing" capabilities that maintain U.S. dominance in
air, space, and cyberspace domains. In this vision, the
hypersonic vehicle is considered to have revolutionary
capability. The joint investment of NASA and Department
of Defense has created unprecedented longevity of basic
research investment in extending over a decade. Yet, the
maneuverable hypersonic vehicles remain constrained
by the structural materials, including thermal protection
system materials limitations, in particular for sharpprofile control surface and leading edge applications.
Areas of basic science research interest include, but are
not limited to the following research concentration areas.
1. Ultra High Temperature Materials. Design and
develop ultra-high temperature materials that can
withstand combined loads of hypersonic environments.
The materials based on boride and carbide systems have
been considered in 1960's and at that time it was shown that
neither oxidation resistance nor fracture toughness were
sufficient. The R&D investment of the last two decades on
boride and carbides has not demonstrated breakthroughs
in either oxidation resistance or fracture toughness and
progress is rather incremental. The clear message from
superalloy experience as well as the ceramic matrix
composite community is the importance of multiphase
microstructures and overall structural performance. The
take away lesson is to focus on composite structures and
microstructures that exhibit predictable and graceful
failure and/or strain capability at hypersonic conditions.
SAMPE Journal, Volume 52, No. 3, May/June 2016

Table of Contents for the Digital Edition of SAMPE Journal - May/June 2016