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Manufacturing Technology Portfolio
  Leave-In
Mandrels
Rotomolding
Rotational molding, or rotomolding, is an innovative
process used in manufacturing composite solid rocket motors (SRMs)
and other tank-like vessels. A rotomolding technique developed
by CRG eliminates mandrel removal from the manufacturing process
of SRMs. The process involves using unique leave-in mandrels rigid
enough for filament winding and also suitable to remain in place
and be used as insulation material in the SRM itself. Originally
funded by the Missile Defense Agency (MDA), this SRM manufacturing
is compatible with a variety of materials, resulting in low-cost,
insulating, leave-in mandrels.
Leave-in
Mandrels
Leave-in mandrels can be inserted into the traditional
filament winding process used to manufacture SRMs. Conventional
methods involve fabricating SRMs on multi-piece metal mandrels,
a process that is both expensive and labor-intensive. In the conventional
scenario, the mandrel is assembled, the insulation is applied,
and the part is filament wound. The composite is then cured, and
the metal mandrel is disassembled and removed.
CRG’s
rotomolding
technique
uses
the
mandrel
as
the
insulation.
Since
there
is
no
need
to
remove
the
mandrel
after
fabrication,
this
novel
process
eliminates
more
than
50%
of
the
manufacturing
labor,
with
the
added
benefit
of
customizing
insulation
designs
tailored
to
specific
applications.
Benefits
Future
tactical
SRMs
may
have
to
operate
at
pressures
nearly
twice
those
of
current
designs
for
improved
performance
requirements.
They
will
require
greater
maneuverability
and
longer
burn
times
and
will
need
the
ability
to
withstand
higher
G-forces
and
carry
additional
propellant
loading.
CRG’s
rotomolding
process
provides
these
properties
with
the
capability
of
high
specific
strength
composite
parts
made
from
high-temperature
materials
and
high-performance
insulation.
This
technology
supports
missile
systems
with
enhanced
multi-layer
composite
cases,
providing
improved
performance
with
significantly
reduced
unit
cost.
Leave-in mandrels improve upon conventional rotational
molding processes by using a new approach to mold design, dynamic
loading, and heat transfer to accommodate a wider variety of component
configurations, materials, and cure processes. CRG’s rotomolding
is designed to allow for several processing variables including
spin rate, angle of spin, and heating capability, resulting in
leave-in mandrels with properties tailored to fit customers’
needs.
Additional
details
on
leave-in
mandrels
can
be
found
in
the
published
article:
Stahl,
J.,
Pora,
E.,
and
Freeman,
P.
“Innovative
Manufacturing
for
Solid
Rocket
Motors,”
SAMPE
Journal,
Vol.
42.
No.
6.
November/December
2006.
pp.
21-27.
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