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Bird Strike Simulation
for Composite Aircraft
Structure
Mostafa Rassaian, Ph.D., P.E.
Technical Fellow
Structural Technology – BR&T
April 23, 2009
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Bird Strike Simulation of Composite Aircraft Structure
AMTAS New Project Proposal
•
There is an increasing trend of birds colliding with aircraft. Aircraft are most
susceptible to bird impacts during takeoff and landing. Typical impacts occur on
components such as wing leading edges, radomes, turbofan engines, and cockpit
windshields. These components should be capable of withstanding the impact
load without experiencing catastrophic failures or penetration that might
compromise continued safe flight. The use of full scale testing to assess all
possible components is time consuming and cost prohibitive.
•
Significant savings can be achieved by using state of art modeling tools capable
of predicting the structural damage due to impact. However, there is a large
variability in modeling approaches and complexity of simulation processes to
design the forward facing components of the aircraft. Available closed form
solutions are over-simplistic. FEA is the tool of choice to capture the details
required to accurately assess these events. LS-DYNA is one such tool and is being
selected because it is widely used in the industry and has the ability to model the
bird using different formulations: Lagrangian, Eulerian (ALE), SPH (meshless).
•
The objective of this research is to standardize the numerical methods and
develop a simplified analytical approach to evaluate compliance of aircraft
structures to bird impacts during the design phase. The project is to leverage both
the numerical and experimental efforts available in this field. The deliverables of
the project are a standardized and simplified analysis tool with numerical
guidelines to enable generating design curves and parametric studies to size
structure to variables such as impact velocity, angle, bird size, structure
geometry, and material at any point in the aircraft.
Abstract
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Outline
•
Related Accidents
•
Motivation
•
Objectives
•
Existing Analysis Methods
•
Technical Approach
•
Validation Test
•
Collaborators
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Bird Strike Related Accidents
Air Transport Article: 18/03/09
•
Number of strikes reported annually increased 336%, from 1,759 in 1990 to
7,666 in 2007
•
Numbers climbed due to an increase in both the number of aircraft
operations and number of ��hazardous wildlife species��
Aviation Week & Space Technology (Feb. 23, 2009)
•
Estimated damage worldwide
$1.2B
•
Fatalities worldwide (since 1988)
219
•
Strikes in U.S.
7,600
•
Bird strike vulnerability altitude
below 3,000 ft
•
Strikes unreported, U.S. airports with airline service 80%
•
In North America, the Canada geese population grew to more than 3.5
million in 2007 from 1 million in 1990
•
More than 1,400 strikes by Canada geese were reported in the U.S. in 1990-
2007 and more than 40% involved multiple birds
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Bird Strike Related Accidents
•
US Airways Flight 1549 ditched in the Hudson River after striking one or
more Canada geese on departure from LaGuardia Airport. No one was
killed in the accident.
•
UTube – Ditching of a US Airways A320 on Hudson River
http://www.youtube.com/watch?v=HKkCzXxu7ks
US Airways Flight 1549 Ditching in Hudson River
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Motivation
• There is limited information in the public domain on the
simulation of bird impact events correlated with
experimental data
• Analytical bird models are considered proprietary by
their developers
• There is no rigorous closed form analysis formulation
• The bulk of historical experience is with traditional
metallic structure
• There is limited field experience with bird strike on
composite primary structure
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Objectives
•
Develop design guidelines for composite
damage resistance to bird strike
•
Provide numerical guidelines for bird
strike analysis using available commercial
FE codes
•
Develop analytical PD methods for rapid
sizing/optimizing bird-strike-designed
structure
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Structural Technology
Existing Analytical Methods
Bell Helicopter,
LS-DYNA
DLR PAM-
Shock, SPH
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Technical Background
• Primary bird threat velocity is in the range of 100 to 250 knots
• Various bird models have been proposed in the literature but limited
information is actually available
– Lagrangian Bird, Arbitrary-Lagrangian-Eulerian formulation ALE, Smooth
Particle Hydrodynamics SPH
• Various FEA codes are available that can handle composite material
failure and bird impactor behavior
– LS-DYNA has been the tool of choice for these applications
• Composite prepreg materials are available that have already been
characterized for other research efforts
– BMS8-212 material characterization exist for rotor burst analysis tool
– Toray AGATE Plain Weave material being used for CMH-17 Crashworthiness
round robin
• Key variables need to be defined:
– impactor (bird size, angle, velocity)
– targets (shape, size, composite material system, etc.)
• Potential collaboration may exist with on-going NASA and FAA high-strain
rate impact research programs
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Technical Approach
•
Perform literature review (analytical methods, FEMs, failure models,
existing test data) and Regulatotry Requirements (FARs)
•
Identify any public domain bird models validated by industry
•
Validate Lagrangian, ALE and SPH Bird model with existing
literature data
•
Identify numerical parameters for the impactor:
– Fixed size 4 lbs bird
–
Sensitivity studies (e.g., strain rate effects, bird shape, speed, angle)
•
Identify numerical parameters for the target:
– Panel geometry (flat and curved))
–
Sensitivity studies (e.g., strain rate effects, composite layup, material
system)
•
Depending on success and availability of budget, extend the
capability for stiffened panels representative of aircraft structure
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Technical Approach (cont��d)
•
Perform selected validation testing
–
Impact rigid surface with simulated bird to validate bird model
–
Impact composite flat and curved panels with hard impactor to calibrate
composite material
–
Impact composite flat and curved panels with the simulated bird
•
Validate the FEA models with test data and expand the design space
using FEA
•
Develop FEA guidelines for bird and composite material models (link
to CMH-17 and other FAA safety and certification initiatives)
•
Adapt or develop closed-form solution analysis methods for rapid
sizing, correlated with experimental and FEA results
•
Develop design curves for composite bird impact damage resistance,
for different levels of structural complexity from flat unstiffened
panels up through curved stiffened panels (level of complexity will
depend on project initial success and funds available)
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Overall Approach
Leveraging Rotor Burst Analysis Tool Development
Measured vs. Computed Velocities; Al target t=1/16"
-200.0
0.0
200.0
400.0
600.0
800.0
1000.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
impact velocity (ft/sec)
residual velocity (ft/sec)
45 deg ref line
test
msh1; course
msh2; medium
msh0; very course
Approach:
•
Start with a flat panel target and
generic bird model
•
Validate impactor and target
models
•
Add curved test panels
•
Develop validated general
modeling strategy
Goals:
•
Rapid modeling solution
•
Calibrated bird model
•
Validate material failure model
•
Boeing-UW to negotiate
composite lay-up details
•
leverage and complement FAA-
NASA high-strain rate research
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Collaborators
PI��s
Mostafa Rassaian – Boeing
Paolo Feraboli – UW
FAA
Chip Queitzsch (Chief Scientist for Engine System Dynamics and
Project Technical Advisor)
Larry Ilcewicz (Chief Scientist for Composites)
Curt Davies (JAMS Program Manager)
Test partners (tentative)
Kevin Housen – Boeing
Mike Pereira – NASA Glenn
