testing of composite materials for use in pressure vessels in a
TRANSCRIPT
Testing of Composite Materials for Use in Pressure Vessels in a Cryogenic Environment
H y P e r C o m p
E n g in e e r in g , In c .
Dan Swenson
Utah State University
4130 Old Main Hill
Logan, Utah 84322
Dr. Thomas Fronk
Utah State University
4130 Old Main Hill
Logan, UT 84322
Jared NordaHypercomp Engineering1080 N. Main Suite 2P.O. Box 505Brigham City, Utah [email protected]
SummaryFuture NASA missions will rely on the use of composite overwrapped pressure vessels (COPVs) to store fuels,
oxidizers, and other cryogenic fluids for launch and space
missions. The COPV must be able to operate at the cryogenic conditions imposed by typical propellants, liquid
oxygen (90K) and liquid methane (110K), in addition to withstanding the effects of low energy impact from space
debris.
In order to develop reliable composite structures for use as cryogenic fuel storage, human habitation, or other
mission critical applications, a solid understanding of constituent material environmental capabilities is required.
The database of properties is growing to include the effects
of load, strain, and temperature on resins, fibers, interfaces, and the incorporation of impact resistance and metal-to-
composite bonding capabilities are also needed.Utah State University and Hypercomp Engineering have
begun to evaluate aerospace-grade composite materials for
use in composite overwrap pressure vessels (COPVs) in a cryogenic-impact environment. This study incorporated two
high performance fibers (both separately and in combination) and two epoxy resins (one widely used and one
experimental).
USU and Hypercomp Engineering have also evaluated the impact resistance of several different neat (pure resin
without fiber) resin systems at ambient and cryogenic temperatures. These resin systems include “typical” wet and
prepreg resin systems as well as a variety of experimental
systems.
Neat ResinsAmbient and Cryogenic Izod Impact of Resins
Average Breaking Energy Minus 3σ
0
5
10
15
20
25
30
Epon 828 Epon
862/W
UF3325* CTD 7.1 MX 130
10%
MX 130
20%
MX 130
30%
Urethane HEI 535 TD 72204 TD
111103
Resin System
*Minus 3 Deviations of UF3325 is less than zero for Cryo
Bre
akin
g E
nerg
y (
in-l
bs)
(-3σ
)
Ambient
Cryo
Tensile Tests Results
0
100
200
300
400
500
600
700
800
Epon 828 HEI 535 Epon 828 HEI 535 Epon 828 HEI 535
IM7 Zylon IM7/Zylon
Fiber/Resin System
De
liv
ere
d F
ibe
r S
tren
gth
(k
si)
Ambient
Cryo No Damage
Cryo Low Impact
Cryo High Impact
Tube Specimen Coupon SpecimenCoupon specimen made of IM7, Zylon, and an IM7/Zylon mix were
made using Epon 828 and HEI 535
resins. They were then tensile tested to failure at both ambient
and cryogenic temperatures. Before some of the specimen were
tensile tested at cryogenic
temperatures they were subjected to different levels of impact loading.
Several resins were subjected to
Izod impact testing at ambient and
cryogenic temperatures. The energy required to fracture the
specimen provides a quantitative measure of the impact strength.
From the results of the of the impact tests, two resins were
chosen for the composite
cryogenic impact testing. These two were Epon 828 a
common commercial resin and HEI 535 an experimental
resin.
It was discovered that the biggest
challenge when testing the tubes was obtaining a good bond
between the steel inserts and the composite tubes. Aggressive
surface preparation with a tap on
the inner surface of the tubes produced the best results.
The tensile tests were designed to
produce a fiber failure. However, this type of failure was never achieved.
When a satisfactory bond between the insert and tube was achieved the
inner layers of fibers pulled away
from the outer layers of fibers. When different lay-ups were used, shear
failure occurred.
From the results of the of the impact tests, two resins were chosen for the
composite cryogenic impact testing. These two were Epon 828 a common commercial resin and HEI 535 an experimental resin.