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LARGE COMPOSITE SPACE STRUCTURES: FAILURE ANALYSIS AND EXPERIMENT
• One primary stowed, other placed atop adapter• Requires Latching Lightband (LLB) low shock separation
d l d b l S C i
Vibration Suppression – Precision Motion Control
systems, developed by Planetary Systems Corporation• Bonded only joint between LLB/CASPAR
6
CASP• Test designed to drive failure in the transitional radius between the conic
section and the aft flange
PAR T
ESTD
section and the aft flange
• Shear, moment, and axial load combination balanced to maximize aft compression while preventing failure in other critical regions
M i t FWD H d t < 3X li it
DESIG
N
• Max compression at FWD Hg adapter < 3X limit
• Max tension at lightband < 4X limit
• Maximize aft CASPAR flange compression
opposite access doors (270o)
Critical Aft Flange (Failure Region) Line LoadCritical Separation System Line LoadCritical Forward Adapter Line LoadLine Load (lbs/in) Line Load (lbs/in) Line Load (lbs/in)
Max Compression at Limit -252 Max Tension at Limit 114 Max Compression at Limit -252Max Applied Compression -755 Max Applied Tension 440 Max Applied Compression -1421
Predicted Failure -1000
Percent above Limit 564%
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M.S. at Max Applied Load 0.00 M.S. at Max Applied Load 0.03 Percent above Predicted Failure 142%
7
CASPA
R
A t t L d (lb )*
• Two axial actuators apply pure compression (no bending)
• Lateral actuator applies moment
Test Stack
Applied Loads R TEST
Lateral AXI090 AXI27035760 -20250 -20250
Actuator Loads (lbs)*
*A positive load indicates a tensile actuator load
and shear
• Axial actuators biased to offload the weight of the load head and Hg adapter
• 100% represents flight line load used to
100 kip Axial Actuators
100% represents flight line load used to design the structure
• Failure test includes:• 50% and 100% checkout run
% f fl d
900
44 kip
Lateral Actuator
Load Head
• 250% Aft flange strain demonstration
• 884% failure run
Failure Test Profile
400
500
600
700
800
900
Lim
it Lo
ad
Primary LoadsCounter Balance
Actuator
Peak t i
Forward Hg Adapter
0
100
200
300
400
0 200 400 600 800 1000 1200 1400
% o
f L stress in aft flange 180° from the door
Failure Test Setup
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Load Step Failure Test Setup
8
ATLA
SV
What is This Beast?• Atlas V CCB Conical ISA
Test Design• Test designed to drive failure in the top
corner of the door • Failure mode suggested by ULA analysts
• First load case applied to as‐built ISA
• Failure load represents 200% of the A ANDTES
g gtooling development program
• Graphite/epoxy and honeycomb mandrel
• Typical composite tooling made from Invar• Long lead times and expensive
pgreatest FWD Flange Peq in ULA test plan
• Limited by the actuator capacities
• Second door installed since original door section did not fail ST
DESIG
N
Long lead times and expensive
• Heavy and difficult to work with
• Currently manufactured in Spain• Creates schedule and cost issues for ULA
C t d i d it b l t
section did not fail• 180o opposite original door, eliminating
pad up around door
• Door section cutout using original ATK tooling , process, and technician• Component redesign render unit obsolete
at the end of a 5 year, $6 million effort
g , p ,
• Second load case same as the first, applied max compression over new door
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9
ISA T
• Test stack modified from Qualification Configuration
• Forward stiffness simulator removedR d
Qualification Test SetupTEST• Aft LOx tank simulator removed
• Center actuator biased to offload the weight of the load head
• Failure test includes:
Removed
• Failure test includes:
• 40% and 100% checkout run
• 200% failure run
• As‐built structure successfully withstood 200%
Removedy
load condition
• Second door installed
• Second case conducted by reversing the direction of the applied loads
Failure Test Setup
180%
200%
direction of the applied loads
Load Profile
20%
40%
60%
80%
100%
120%
140%
160%
% of Failure Load Primary Loads
Counter Balance
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0%
0 100 200 300 400 500 600 700 800
Load Step
10
FAILU
• Produce a composite failure in the test article
• Record critical strain and displacement data at each load step RETEST
O
• Record critical strain and displacement data at each load step
• Acquire adequate load, strain, and displacement data such that quantitative assessment of the load bearing capacity of O
BJECTIVES,
the structures can be made and to allow comparison to pre‐test analytical models
• Identify resulting initial and final failure mechanism , AKA
SUCC
• Identify resulting initial and final failure mechanism
• Assemble test results, conclusions, and disseminate to community CESS
CRITEERIA
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11
ANALY
Real World Failure Exercise• Provide blind failure predictions of large composite structures YSIS
OBJEC
• Provide blind failure predictions of large composite structures
• Predict initial failure, progression, and final failure
• Transfer new technology to the commercial analysis community CTIVES
• Model entire structure with a single detailed model
• Reasonable time frame (weeks)
• Why Firehole: Under the direction of AFRL, Firehole Technologies has been developing an advanced composites analysis technology for several years. The Structural Failure Test program was an great y p g gopportunity to validate the software, or learn where improvement was needed.
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12
COMP
Firehole Technologies
• Firehole was founded in 2000 PANYOVER
• Our mission is to deliver tools and services that enable wide‐spread application of composite materials leading to lighter, stronger, safer and more fuel efficient structures RVIEW• Two distinct business areas:
Software DevelopmentStructural Analysis
• Firehole is a profitable, employee owned company focused on delivering more accurate results and a higher degree of confidence in
Software DevelopmentStructural Analysis
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delivering more accurate results and a higher degree of confidence in composite simulations
13
FIREH
Current Products Upcoming ProductsHOLESOFTW
• Online, searchable database of composite material datasheets for material selection and comparison
• Cyclic loading simulation• Currently in Alpha• Development partnerships with a large W
ARE
SOL
material selection and comparison Development partnerships with a large Helicopter OEM and a major Naval contractor
Helius:MCT™ is an enhancement to commercial finite element packages specifically for efficiently improving the accuracy of composite structures analysesanalyses.
• Uses fiber and matrix stresses to predict failure
• Extremely efficient
d d l• Standard material inputs
• Easy to adopt
• Always converges
• Proven results
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15
CASPA
• First attempt at the CASPAR analysisAR: BLIN
DP
Model Details• Continuum shell elements PRED
ICTION
• 60 + plies through thickness (1 element)
• 15,000 elements• Handbook material N
SHandbook material characterization
• Fixed constraints at boundary• Continuous run time: overnight
• Difficult to determine where ultimate failure occurs
24
ISA A
• ISA AnalysisANALYSIS
Model details• 3D model of entire structure• 3D layered solid elements M lti l l t th h thi k• Multiple elements through thickness
• Coupon material characterization• Model generation ~ 2 weeks • 192,000 elements
Load Head‐1440 solid, linear, reduced‐integration elements (Abaqus:C3D8R)
Forward Adapter/Splice‐2902 C3D8R elements
,• Continuous run time ~1 ½ days
• 8 node desktop p.c.
Composite Conic‐186,152 solid, linear, reduced‐integration, composite elements (Abaqus:C3D8RC3)‐These elements have one integration point per ply
Aft Adapter/Splice‐1518 C3D8R elements
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ISA A
ISA As Built Helius:MCT Failure PredictionsASBUILT
HELIU
S:MCFailure of Structure
340% FL
Limit of Load Frame200% FL
T FAILU
RE
340% FL
PRED
ICTIOONS
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ISA A
ISA As Built Test ResultsASBUILT
TE
The ISA was successfully tested to 200% FL on October 3, 2008.
•The structure responded nearly linearly to the loading.k bl
ESTRESU
LT
•Testing was remarkably quiet.
TS
1500
-1000
-500
00 50 100 150 200
DOOR233EMIN
800
1000
1200
14000 50 100 150 200
DOOR233EMAX
-3500
-3000
-2500
-2000
-1500
µStr
ain
% Flight Load
0
200
400
600
800
µStr
ain
% Flight Load
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Experimental Data Firehole Technologies' Predicitons Experimental Data Firehole Technologies' Predicitons
27
MODI
ModificationsIFICA
TIONS
A second access door was cut into the ISA
l d
S
•180° opposite original door•No pad up around new door•Original ATK tooling was used•Honeycomb edge potted as original
•Loads were reversed
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HELIU
Helius:MCT Predictions of Modified ISAUS:M
CT PRRED
ICTIONS
Initial fiber failure180% FL
SOFM
ODUltimate Failure
Initial matrix failure110% FL
IFIEDISA
187% FL
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HELIU
Helius:MCT Predictions of Modified ISAUS:M
CT PRRED
ICTIONSSOFM
OD
186.72 % Flight Load 187.52 % Flight Load
IFIEDISA
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187.68 % Flight Load
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VIDEO
• VideoO
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FAILU
Failure Test
The modified ISA was successfully tested to failure on October 24 2008 RETEST
The modified ISA was successfully tested to failure on October 24, 2008.
• 183% Flight Load
• Linear response
• Instantaneous event
• Door corners
Failure initiated at door corners
Rapidly propagated around circumference
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ISA F
ISA FailureAILU
RE
Close up of upper door corner
Failure occurred on interior face sheets
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33
RESU
LResults: Interior Strain Gauge
2000
ess
LTS: INTERI
1500
train
Tsai
-Wu
Max
Str e
IORSTRA
IN
1000
Prin
cipa
l St
nt CT
Hash
in
NGAUGE
500Max
P
Expe
rimen
Heliu
s:M
C
00 50 100 150 200 250 300 350 400
E
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% Load
34
CONC
• Structural Failure Test Program Successful
• Two large space structures were tested to failure
CLUSIO
NS
• Two large space structures were tested to failure.
• Analytical results within 15% of ultimate failure on CASPAR
• Analytical blind predictions with 2.5% of ultimate failure on ISA
• Traditional composites analysis technologies over predict failure by a minimum of 1.5.
“I had anticipated that most large aerospace composite structures were considerably over‐designed, and this program proved that on all structures tested With innovative analysis technologies such as Helius:MCT fromtested. With innovative analysis technologies such as Helius:MCT from Firehole Technologies, I am convinced that these composite structures could remove as much as 40% mass, which translates into tremendous savings for many space applications.” g y p pp
Dr. Jeffry Welsh
Program Director
Chief Tier 3 Division ORS Office
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Chief, Tier‐3 Division, ORS Office
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Yellowstone Park’s Firehole River
BACKUP
COMP
Composites Failure TechnologiesPO
SITESFA
Conventional technologies treat composites like “black aluminum”
• Mask interactions
l l
ILURE
TECH
• Failure single event
• Unusable degradation models
• Exotic material parameters HNOLO
GIES
• Computationally unfeasible
Action in composites occurs in the Fibers OR the Matrix SAction in composites occurs in the Fibers OR the Matrix
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37
TRA
DI
T i Hill
• Tsai‐Wu • Extension of Tsai‐Hill or
H ff t l t
ITIONALC
O
• Tsai‐Hill• Extension of von Mises to
orthotropic materials.
Hoffman to a general stress state.
• Invariant under coordinate rotation O
MPO
SITE
• Hoffman• Extension of Tsai‐Hill for
differing tensile and
• Use of tensors make mathematical operations easy
• Biaxial data required to determine failure parameters F
AILU
REC
compressive properties
• Simple to use in design
determine failure parameters.
• Hashin• Differentiates between fiber
d t i f il
CRITERIA
and matrix failure
• Distinguishes between tensile and compressive modes
All of these criteria are applied to a homogeneous composite and neglect the interaction between the fiber and matrix
38
MULT
Multicontinuum Theory (MCT)TICO
NTIN
UU
MCT decomposes composite stress into fiber and matrix stress• Based on Hill (1963)• Development @ Univ of Wyoming since 1988 U