CLEAN SKY 2 - nari.arc.nasa.gov
Transcript of CLEAN SKY 2 - nari.arc.nasa.gov
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CLEAN SKY 2FRC-IADP
NextGen Civil tiltrotor crashworthiness approaches
presentersLuigi Di Palma
Francesco Di CaprioMarika Belardo
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ContributorsAerosekur, Leonardo Helicopters, Magnaghi Group, SSM, University of Campania “L Vanvitelli”
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Outline
• THE TWO PROJECTS ARE PART OF THE AIRFRAME AND SYSTEMS DEVELOPMENTS TO BE APPLIED TO THE NEXT GENERATION CIVIL TILTROTOR TECHNOLOGY DEMONSTRATOR UNDER DEVELOPMENT AT LEONARDO HELICOPTERS DIVISION
• THE ITALIAN AEROSPACE RESEARCH CENTER IS INVOLVED IN TWO COLLABORATIVE PROJECTS FUNDED BY CLEAN SKY 2 JOINT UNDERTAKING WITHIN THE HORIZON 2020 RESEARCH FRAMEWORK
• THE TWO PROJECTS ARE NAMED “T-WING” AND “DEFENDER”• THEY ARE R&D PROJECTS AIMED AT FLYING THE NGCTR-TD VEHICLE• PERMIT to FLY IS REQUESTED
NGCTR-TD
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T-WING OUTLINE
• T-WING is a collaborative project funded by Clean Sky2 in the framework of EU Horizon2020 program
• AIM: design, manufacturing and qualification up to flight (TRL6) of the WING STRUCTURE of the NGCTR-TD
• BUDGET: 26 M€• DURATION: 2018 - 2023• PARTNERS
Loads & AeroelasticityLoad monitoring design
WTM design
Structural DesignAnalysis
Crashworthiness analysis
Structural Design & stressQualification, Airworthiness
Composite manufacturing, NDI & assembly
Metallic parts manufacturingTools & Jigs
Nacelle primary structure manufacturing
Ground Vibration Test, Noise, Dissemination
Project CoordinationInnovations, Advanced Analyses, Testing, Wing instrumentation,
Dissemination
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DEFENDER OUTLINE
• DEFENDER is a collaborative project funded by Clean Sky2 in the framework of EU
Horizon2020 program
• AIM: design, manufacturing and qualification up to flight (TRL6) of the Fuel Storage
System of the NGCTR-TD
• BUDGET: 1.4 M€
• DURATION: 2018 - 2022
• PARTNERS
Design, analysis and innovations
Design manufacturing and
qualificationProject
CoordinationModeling
strategies and analyses
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CRASHWORTHINESS ACTIVITIES
• T-WING• CRASH ANALYSIS OF THE WING. Requirement is to show that any cabin occupants
are protected in a crash situation from equipment mounted externally above the cabin including the wing. The requirement stipulates that under prescribed vertical down crash load factor, the wing has to fail in a prescribed section (frangible section), this means that the cabin needs only withstand the weight of the remaining portion of the wing above the fuselage and the fire is prevented.
• BIRD STRIKE ANALYSIS OF THE WING LEADING EDGE: The aircraft must be capable of continued safe flight and landing during which likely structural damage or system failure occurs as a result of a bird strike in A/C (4 lb bird) of VTOL mode (2 lb bird)
• DEFENDER: CRASH OF THE MOST CRITICAL FUEL TANK BAY• REQUIREMENT: to show that the most critical fuel tank bay, under a survivable crash
condition, prevents any occurrence of fuel leakage and fire, to let the occupants safely escape from the cabin.
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CRASHWORTHINESS HIGHLIGHTS
• T-WING• CRASHWORTHINESS RELATED TO WING DESIGN: very peculiar requirement dictated
by VTOL capabilities of tiltrotors: the design of the wing that breaks at prescribed section under specific crash load factor requires:
• special structural features to drive suitably the phenomenon (actually under patent evaluation),
• methods to model and aid the design of the wing• experimental validation to extend the solution to a future certified product.
• BIRD STRIKE ANALYSIS OF THE WING LEADING EDGE: in a multi-cells wing box the vehicle capability to “get home” after bird strike should be easily achievable. The safety requirement satisfaction for a VTOL machine is more demanding in order to prevent undesired failure of inter-connecting drive shaft and additionally fire triggering. Special design of leading edge is required.
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CRASHWORTHINESS HIGHLIHTS
• DEFENDER• CRASHWORTHINESS REQUIREMENT FOR THE FUEL TANK (CFR/CS §29.952). For a
“winged” VTOL vehicle having the fuel tanks inside the wing (i.e. tiltrotors), the current airworthiness requirement is followed to design the tank and the surrounding structure (i.e. wing). The prescribed drop test to be passed with no fuel leakage could be conservative for no standard helicopter machine like tiltrotor. What are the more realistic fuel tank crash conditions?
Wing span 6.0 m
Example 1 Example 2
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WING CRASHWORTHINESS APPROACH
SIMPLIFIED PROGRESSIVE FAILURE ANALYSIS
HIGH FIDELITY NONLINEAR ANALYSES MAKING USE OF EXPLICIT CODES
2018 2020 2021 2023WING CDR
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SIMPLIFIED PROGRESSIVE FAILURE OF THE WING, BASED ON LINEAR STATIC ANALYSIS
1) SELECTION OF CRITICAL WING SECTION
2) DEMONSTRATION OF PROGRESSIVE FAILURE OF FRANGIBLE SECTION
TWING CRASH ACTIVITY
1) SELECTION OF CRITICAL WING SECTION
WING + Wing to Fuselage link
FEM
APPLY 12 g VERTICAL LOADING
LINEAR STATIC
ANALYSIS
CRITICAL AREAS VS REQUESTED FRANGIBLE
SECTION
• Detailed FEM• Model is constrained at the base of the
wing links• Inertia loads applied via GRAV card on
entire model• Fuselage-wing links included
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SIMPLIFIED PROGRESSIVE FAILURE OF THE WING, BASED ON LINEAR STATIC ANALYSIS
1) SELECTION OF CRITICAL WING SECTION2) DEMONSTRATION OF PROGRESSIVE FAILURE OF FRANGIBLE SECTION
TWING CRASH ACTIVITY
2) DEMONSTRATION OF PROGRESSIVE FAILURE OF FRANGIBLE SECTION
WING + Wing to Fuselage link
FEM
APPLY PRESCRIBED VERTICAL LOADING
LINEAR STATIC
ANALYSIS
CRITICAL AREAS VS MATERIAL STRAIN
LIMITS
prescribed vertical loading is a vertical g-level between ditching and fuselage link max load
REMOVE FAILED ELEMENTS
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TWING CRASH ACTIVITY1) SELECTION OF CRITICAL WING SECTION
UPPER/LOWER PANEL (composite material only)
Peak strains zones at 12g
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TWING CRASH ACTIVITY2) DEMONSTRATION OF PROGRESSIVE FAILURE
Max strain criterion
REFERENCE ALLOWABLE STRAIN:
• OHC RTD for compressive strain
• FHT RTD for tensile strain
Black colour: elements that exceed allowables
LOWER SKIN
UPPER SKIN
compression
tension
LOOP 1 : 5 g
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TWING CRASH ACTIVITY2) DEMONSTRATION OF PROGRESSIVE FAILURE
PROGRESSIVE FAILURE
Animated Gif (please see in presentation mode)
FAILED ELEMENTS LOOP 1
FAILED ELEMENTS LOOP 2
FAILED ELEMENTS LOOP 3
FAILED ELEMENTS LOOP 4
LOWER SKINUPPER SKIN
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T-WING CRASH ACTIVITY
• The wing has been designed to withstand specific inertial load to prevent any relevant composite failure in order to protect the fuel tanks from fuel spillage (fire protection requirement)
• The wing will adopt the necessary features to induce the wing breaking at relevant sections in order to reduce the inertial loads on the fuselage during the crash (escaping requirement)
• A possible improvement to increase the maximum sustainable inertial load by wing structure will be investigated by using high-fidelity numerical methods taking into account the L/G and fuselage kinetic energy absorption capabilities during crash.
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WING LEADING EDGE BIRD STRIKE APPROACH
Metallic leading edgeABAQUS model of the entire wingABAQUS sub-model
Bird strike analysis for a set of impact angles and LE thicknessIdentification of the thickness compliant with the reqmts
Inclusion of the hydraulic and electrical lines in the model Assessment of lines strengthMost critical impact condition
Complete scenario of bird strike analyses by including the linesWeight optimization
2018 2020 2021 2022WING CDR
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TWING LEADING EDGE BIRD STRIKE APPROACH
• Demonstration of A/C “get home condition” in case of bird strike
• Prevention of double failure of hydraulic and electrical lines in case of bird strike
• Weight reduction of LE
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TWING LEADING EDGE BIRD STRIKE APPROACH
• Bird material model calibration
• Bird impact analysis on entire wing of
the Next Generation Tilt Rotorcraft
(NTGRT)
• Comparison Full-Model vs. Reduced
Model
• Sensitivity Analysis respect to leading
edge thickness
Upper skin
Leading Edge
Tip Rib
Root Rib
Adopted strategy - Workflow
• Damage status Evaluation on
internal sub-systems
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TWING LEADING EDGE BIRD STRIKE APPROACH
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Proj
ectio
n Di
amet
er [m
]
Time [ms]
Projection Diameter
Experimental
Numerical
0
20
40
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0.0 0.5 1.0 1.5 2.0 2.5 3.0
Velo
city
[m/s
]
Time [ms]
Velocity
Experimental
Numerical
T = 0 ms T = 0.66 ms T = 1.32 ms T = 1.98 ms
Num
eric
alEx
perim
enta
l
• The numeric model was calibrated w.r.t experimental literature data: Bird's substitute tests results and evaluation of available numerical methods. M.A.Lavoie, A. Gakwaya, M. Nejad Ensan, D.G.Zimcik, D.Nandlallc. Int. Journal of Impact Engineering, Vol 36, Issues 10–11, 2009
Bird numerical model calibration
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TWING LEADING EDGE BIRD STRIKE APPROACH
• Bird Mass = 4 lb (1.8 kg)
• Impact velocity: Vmax in Airplane Mode = 243.6 knots; (127 m/s)
• No. of impact Station: 4
• Impact angles: 0° with respect to the angle of incidence of the wing (which is 3°) @ the L.E. apex
point
• The projectile is 226mm long and 113 mm wide (diameter)
• Impact Energy: 14.5 kJ
S1 S2 S3 S4
D D/2D/2
D/2
Impact Conditions
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TWING LEADING EDGE BIRD STRIKE APPROACH
• The main structural part is, the wing box that is joined to the fuselage by means of 4 metallic fittings which are bolted on the spars and on the root tip.
• The wing box consisting in: front spar, the middle spar, the rear spar, the upper and lower stringer, four inner ribs, the tip rib and the root rib, two upper stringers and one lower stringer.
Inner Trailing edge
Flaperon
Manoeuvrable Surface
Wing Box
Leading EdgeFusulage-wing fitting
Tip Rib
Spars of Central Wing Box
Upper skin
Leading Edge
Upper Stringers
Lower Stringer
RibsCentral Wing Box
Tip Rib
Root Rib
Access Panels
FittingLower skin
• The entire structure is made in composite material with the exception of the leading edge, the spars in the central wing box, the tip and root ribs and the fittings (and other smaller parts like lags and splices).
• The model consisting in more than 60 parts which are connected each other by means of tied constraints.
Full model vs. Reduced Model
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TWING LEADING EDGE BIRD STRIKE APPROACH
• In order to reduce the computation cost a reduced model has been used.• The Sub-Model consists in: Leading edge, nose ribs, partial rid, partial tip and root ribs, partial upper skin, partial lower
skin, front spar.• The entire structure is made in composite material with the exception of the leading edge, the spars in the central wing
box, the tip and root ribs and the fittings (and other smaller parts like lags and splices).• The model consisting in about 30 parts which are connected each other by means of tied constraints.
Upper skin
Leading Edge
RibsCentral Wing Box
Tip Rib
Root Rib
Lower skin
Front Spar
• The sub-model was constrained (fixed support) on the cut section, which lead to consider rigid the no-modelled wing parts
Full model vs. Reduced Model
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TWING LEADING EDGE BIRD STRIKE APPROACH
Global Displacements - USUM
Time 0.42 ms Time 0.9 ms Time 6 ms
Full
Mod
elSu
b-M
odel
Full model vs. Reduced Model
• The comparison has been performed considering fixed the impact angle (0° with respect to the angle of incidence of the wing )
• Impact station S2 and impact angle equal to 0° with respect to the angle of incidence of the wing (which is 3°) @ the L.E. apex point
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TWING LEADING EDGE BIRD STRIKE APPROACH
S1 S2 S4
Max displacement @ LE Apex (x-Dir) [mm] 87.01 88.01 87.97
Tip-Wing Displacement (USUM) [mm] 1.04 8.20 11.84Without RIB With RIB
2.37 6.42
Internal Energy of the Remaining Wing [kJ] 0.09 0.34 4.52 0.48 0.54
Internal Energy - Remaining Wing respect to Impacted bay [%]
1.30% 5.51% 190.43% 7.48% 8.68%
Summary Results
80.05
6.87
S3
6.176.236.57Internal Energy of Impacted bay (only LE) [kJ]
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
0 5 10 15 20 25 30
Dis
plac
emen
t [m
m]
Time [ms]
Displacement Time-History - ALL Impact Points
S1 - USUM - Tip
S2 - USUM - Tip
S3 - USUM - Tip
S4 - USUM - Tip
S4
Ductile damage initiation criterion @ 30 ms
S1 S2
S3 0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20 25 30
Ener
gy [k
J]
Time [ms]
Internal Energy Time-History - ALL Impact Points
S1 - ALLIE Wing
S2 - ALLIE Wing
S3 - ALLIE Wing
S4 - ALLIE Wing
• Considering different impact conditions theamount of energy absorbed by the entire wing(without leading edge) is a very small respect tothe total energy absorbed only by the leadingedge.
Full model
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S4 – Bay5
S1 - Bay 1 S2 – Bay 3
S3 – Bay3/Bay4
Global Displacement – Section viewFull Model Results
TWING LEADING EDGE BIRD STRIKE APPROACH
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Deleted elements
TWING LEADING EDGE BIRD STRIKE APPROACH
Sensitivity analysis w.r.t. leading edge thickness• Bird Mass = 4 lb (1.8 kg) • Impact velocity: Vmax in Airplane Mode = 243.6 knots; (127
m/s)• No. of impact Station: 4• No. of impact angles/points: 4 angles; 4 impact locations• Total number of impact scenarios: 16• Leading edge thickness: T1, T2, T3, T4, T5
The final thickness configuration and hence thepotential weight saving opportunity of the leadingedge will be defined w.r.t the acceptable damagestate on the front spar.
In order to evaluate the most conservative solution in each bay a large zone of leading edge and frontal spar were removed and the most critical loading conditions were investigated. The wing is still able to sustain the applied loads.
Undamaged model Model with removed elements
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TWING LEADING EDGE BIRD STRIKE APPROACHTh
= T
1Th
= T
2Th
= T
3Th
= T
4
Step Time 1 Step Time 2 Step Time 3
Th =
T5
Lead
ing
Edge
Thi
ckne
ss
Sensitivity analysis w.r.t. leading edge thickness
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TWING LEADING EDGE BIRD STRIKE APPROACHTh
= T
1Th
= T
2Th
= T
3Th
= T
4Th
= T
5
Lead
ing
Edge
Thi
ckne
ss
Sensitivity analysis w.r.t. leading edge thicknessStep Time 1 Step Time 2 Step Time 3
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TWING LEADING EDGE BIRD STRIKE APPROACH
Damage Evaluation on the internal systems • New solution with intermediate shield
Hydraulic (x2)Electric (x2)
Leading Edge
FEM Details
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TWING LEADING EDGE BIRD STRIKE APPROACH
Damage Evaluation on the internal systems • The most critical configuration is reported (minimum leading edge thickness)
Skin Damages Status
Displacement (UX) Shield Damage status
Skin Damage Status
Without Shield With Shield
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TWING LEADING EDGE BIRD STRIKE APPROACH
Damage Evaluation on the internal systems • The most critical configuration is reported (minimum leading edge thickness)
Hydraulic and Electric Damage status
Displacement Displacement
Hydraulic Damage status
Without Shield With Shield
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TWING LEADING EDGE BIRD STRIKE APPROACH
Damage Evaluation on the internal systems • The most critical configuration is reported (minimum leading edge thickness)
t =
1.5
ms
t = 3
ms
Without Shield With Shield
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TWING LEADING EDGE BIRD STRIKE APPROACH
Damage Evaluation on the internal systems • The most critical configuration is reported (minimum leading edge thickness)
t =
1.5
ms
t = 3
ms
Without Shield With Shield
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FUEL TANKS CRASH APPROACH
Tank mat coupon testsTank mat numerical calibration
Cube drop simulationHigh fidelity analysis of most critical fuel tank bay
Cube drop testCube num-expcorrelation
Full scale drop test of most critical fuel tank bayExperimental validation of the model
2018 2020 2021 2022FSS CDR
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FUEL TANKS CRASH APPROACH
D. Cristillo, F. Di Caprio, C. Pezzella, C. Paciello, Comparison of Numerical Models for the Prediction of Bladder Tank Crashworthiness, MEDYNA 2020
• numerical investigation on the crashworthiness of CUBE bladder tank (MIL-DTL-27422)
• Material model calibration based on coupon tests
• Comparison between two commercial codes (Ls-Dyna and Abaqus)
• Experimental test from literature
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FUEL TANKS CRASH APPROACH
D. Cristillo, F. Di Caprio, C. Pezzella, C. Paciello, Comparison of Numerical Models for the Prediction of Bladder Tank Crashworthiness, MEDYNA 2020
numerical-experimental calibration of thebladder flexible materialCoupon tests:• Tensile test on Nylon fabric layer• Tensile test on NBR layer• Tensile test on complete Fuel Tank structure
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FUEL TANKS CRASH APPROACH
D. Cristillo, F. Di Caprio, C. Pezzella, C. Paciello, Comparison of Numerical Models for the Prediction of Bladder Tank Crashworthiness, MEDYNA 2020
• Comparison between two commercial codes (Ls-Dyna and Abaqus)
• Experimental test from literature• Material model calibrated with exp tests
Ls-Dyna vs Abaqus
time histories of the impact force exerted on the soft fuel tank
• Abaqus smaller difference with respect to the experimental data
• Ls-Dyna seems more rigid than Abaqus
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FUEL TANKS CRASH APPROACH
C. Paciello, C. Pezzella, S. Magistro, G. Lamanna, F. Di Caprio, M.Belardo, L. Di Palma, Crashworthiness of a Tiltrotor Fuel tank bay,Int. Workshop on Engineering for Rotorcraft Safety, 7-9 April 2021
Preliminary high fidelity model of the most critical fuel tank bay• Model including: surrounding structure; fuel lines; fuel
systems inside the tank, 80% fuel filling (SPH approach)• Material model calibrated by tests (nylon fabric + nitrile
rubber• Drop is simulated through a dynamic analysis performed
with Ls-dyna, by imposing the pulse acceleration derivedfrom experimental data from Leader past experience
• Surrounding wing structure: rigid vs deformable
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FUEL TANKS CRASH APPROACH
C. Paciello, C. Pezzella, S. Magistro, G. Lamanna, F. Di Caprio, M.Belardo, L. Di Palma, Crashworthiness of a Tiltrotor Fuel tank bay,Int. Workshop on Engineering for Rotorcraft Safety, 7-9 April 2021
Surrounding wing structure: rigid
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FUEL TANKS CRASH APPROACH
• Surrounding wing structure: deformable• Drop test simulated by imposing free
vertical drop from 50 ft on rigid surface• PRELIMINARY RESULTS
Evolution of damage in thesurrounding structure (CFRP): LS-DYNA material models MAT58 basedon Matzenmiller’s damage mechanicsmodel with four Hashin’s failuremodes criteria
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FUEL TANKS CRASH APPROACH
NEXT STEPS
• CUBE DROP EXPERIMENTAL TEST
• NUMERICAL CUBE DROP CORRELATION
• FULL SCALE EXP. DROP TEST OF THE MOST CRITICAL FUEL TANK BAY
• FULL SCALE MODEL VALIDATED
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DEFENDER Project
Prof. Erasmo Carrera CoordinatorMatteo Filippi [email protected]@polito.it
Marika Belardo, PhD, DEFENDER Project [email protected]
Francesco Di Caprio, PhD, Project [email protected]
This project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovationprogramme under Grant Agreement number: 738078 — DEsign, development, manufacture, testing and Flight qualification of nExtgeNeration fuel storage system with aDvanced intEgRated gauging and self-sealing capabilities (DEFENDER)
THANK YOU!T-WING Project
Eng. Luigi Di Palma [email protected]
Marika Belardo, PhD, Project [email protected]