CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS

Transcription

1 27 TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS C. Candra*, T. Y. Wong* and J. Bayandor** * Te Sir Lawrence Wackett Aerospace Centre Royal Melbourne Institute of Tecnology, Melbourne, VIC, Australia **Center for Intelligent Material Systems and Structures Virginia Tec, Blacksburg, VA, U.S.A. Bayandor@vt.edu Keywords: Advanced Aerospace Design, Craswortiness, Water Ditcing, Smooted Particle Hydrodynamics, Coupled Lagrangian-Eulerian Abstract In tis paper, a comparative study as been performed between te Mesless Lagrangian and Coupled Lagrangian-Eulerian scemes, to evaluate teir overall efficiency and effectiveness for analyzing fluid-structure interactive systems. Soft body impact events onto composite laminates representing primary and secondary aircraft structures ave been studied. Several cases wit different bird velocities ave been simulated to observe te non-linier beavior of soft body impact, along wit te sortcomings of te modeling metodologies applied. Te Mesless Lagrangian model produced a iger initial peak force, wereas te Coupled Lagrangian- Eulerian approac captured te impact window more smootly wit less obvious spikes. Tese scemes ave also been compared wit te conventional Lagrangian approac, wic proved to be less accurate due to ig mes distortion and loss of mass from erosion. Te study was furter extended to analyze birdstrike on a composite wing leading-edge. Wit validation from experimental results, te developed modeling metodology was also used to analyze oter fluid-structure interactive systems suc as structural damage caused by aircraft ditcing over water. 1 Introduction Composites are extensively used in modern aircraft structures due to teir superior material properties, fatigue caracteristics and design flexibility. However, wit igly unidirectional properties, aerospace grade composites in particular are susceptible to impact damage and relatively brittle forms of failure. Damage due to soft body impact is of major concern because of te complexities it introduces in crasworty analysis and design. Soft body impact is caracterized by tree stages wic occur in quick succession. Initially, wen te soft body comes in contact wit te target structure, tere is solid-structure interaction. At te instant of impact, a sock wave is generated, wic propagates along te lengt of te soft body, crusing te internal structures of te bird. Tis causes a pase cange witin te soft body, resulting in its transformation from solid to fluid. Finally, te impact progresses as a fluidstructure interactive system, instigating furter damage on te target structure. Current metods of studying fluid-structure interaction rely eavily on empirical data and experimentation. Suc metods are usually too resource intensive and costly. Consequently, te use of explicit numerical modeling tecniques can be considered as a practical alternative for analyzing soft body impacts. Te tree types of numerical modeling scemes tat are commonly used to study suc scenarios are te Lagrangian, Mesless Lagrangian and Coupled Lagrangian- Eulerian scemes. Te Lagrangian sceme is a more conventional numerical approac, owever in soft body scenarios can tend to produce less accurate results wen mes distortions become very large. Te Mesless 1

2 C. CHANDRA, T. Y. WONG AND J. BAYANDOR Lagrangian and te Coupled Lagrangian- Eulerian scemes are able to overcome suc inaccuracies, wile imposing teir own constraints. A comparison of Mesless Lagrangian and Coupled Lagrangian-Eulerian scemes is terefore necessary to better identify te specific applications of eac analysis metod. Peak forces experienced and impact damage sustained by structures constitute two of te major parameters in analysis of fluidstructure interactive systems. As part of tis study, a flat panel and a leading edge, representing aircraft primary and secondary structures respectively, ave been used to analyze different soft body impact scenarios. Peak forces as well as progressive impact damage traces ave been compared between te two metods to provide a more detailed understanding of eac sceme. 2 Nomenclature C D L P P s W b c r u o u p u s v v m = Constant of normalization for kernel function = Bird diameter = Bird overall lengt = Pressure in sock region = Stagnation pressure = Smooting kernel = Specific body force vector = Convective velocity = Lengt of cylindrical portion of bird model = Smooting lengt = Bird radius = Impact velocity = Particles velocity in soft body = Sock velocity = Particle velocity = Mes velocity ρ = Bird density σ = Caucy stress tensor (y) = Auxiliary function for smooting kernel u = Particle approximation for Mesless Lagrangian particles. 3 Pysics of Impact As a soft body collides wit a target, it experiences a pase cange. Wilbeck [1] explained tis penomenon based on te ydrodynamics teory, wic included impact initiation, sock wave and subsequent release wave formations, steady flow condition and impact termination. In is ypotesis, front interacting particles of te soft body may reduce to zero velocity immediately wen come in contact wit te target surface. Given a ig enoug relative impact velocity, a sock wave is ten formed, propagating witin te soft body. Te formed sock wave brings succeeding particles of te soft body to rest and compresses te impactor s constituent material as it progresses troug te soft body. As te pressure witin te compressed region increases drastically, it exceeds te strengt of material and triggers a solid to fluid pase transition. Subsequently, te material in te pat beind te sock wave transforms to a fluidic bulk and can be treated as a non-newtonian fluid (or Newtonian in an idealized modeling platform). Considering reasonable rigidity of te target, te particle velocity in te soft body, u p, will be equivalent to te impact velocity, u o. Applying conservation of mass and momentum teories, pressure in te sock region can be expressed as: P u u 1 S o (1) After te sock initiation, te iger energy portion of te sock propagates backwards along te soft medium of te projectile. Due to te circumferential pressure difference witin te projectile, soft body particles, now in fluidic state, accelerate radially outward. Tis is instigated troug te formation of a series of release waves. Te lateral and ten longitudinal propagations of te release waves reduce te pressure in te compressed region of te soft body and tus weaken te rebound sock velocity. Tis process continues until te sock dissipates and a steady flow condition is establised. For an impact on a rigid plate, a stagnation point exists at te centre of te target. Te stagnation point as a corresponding zero velocity and a 2

3 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS stagnation pressure, P s. Assuming tat te fluid is incompressible, stagnation pressure can be expressed as: 2 1u P o s (2) 2 Once te pressure release waves reac te end of te soft body, te remainder of te projectile continues to move toward te target in a steady fasion until te impact is terminated. 4 Numerical Modeling Scemes To analyze soft impact, tere are tree establised metods of numerical modeling adapted widely by researcers: Lagrangian, Mesless Lagrangian and Coupled Lagrangian- Eulerian scemes. Different scemes use different governing teories, wic ave teir own advantages and disadvantages. 4.1 Lagrangian Sceme Te Lagrangian sceme is a mes intensive numerical approac. In tis sceme, individual nodes of te computational mes follow teir associated material movements witin a Lagrangian framework [2]. Te material domain (R X ) and spatial domain (R x ) are two key elements tat define tis framework. Te motion of te material in te material domain can be mapped into te spatial domain by a mapping function, φ, and material velocity (v). Teir matematical representations are expressed troug Eqs. (3) and (4), respectively. X, t x, t (3) x vx, t (4) t Wen te material coordinates are fixed, te material velocity can be determined using Eq.(4). Tis facilitates te tracking of te material motion. Since te material grid is te same as te spatial grid, te sceme supports time istory dependent constitutive relations. x 4.2 Mesless Lagrangian Sceme In te Mesless Lagrangian sceme, te material is represented by a set of discrete particles, were te velocity vector for eac particle is related to te rest of te particle field troug a flexibility matrix, unlike te Lagrangian sceme tat relates te displacement in eac node to te traction in oter nodes troug te stiffness matrix. A significant advantage of tis sceme is te adaptive nature (i.e., resolution of solution is automatically adapted to suite local environment) of particle approximations. Due to its specific formulation, te sceme is not affected by arbitrariness of particle distribution [3]. Since tis metod is mes-free, it is favored over traditional FEM for problems involving large structural distortions. Numerically, te soft body can be represented as a cluster of particles moving at te flow velocity. Eac of te Mesless Lagrangian particles symbolizes an interpolation point on wic all material properties are known. Te solution in its entirety is ten calculated on every particle wit a regular interpolation function, called te smooting lengt. Te equations of conservation of momentum are ten equated to fluxes or inter-particular forces to obtain te final solutions [4]. A summary of te teory beind particle metods and approximations to te smooting function is given below [3,4]. Let S be a set of particles, x i (t) be te location of particle i, and w i (t) be its weigt. Particle metods for moving particles are based on quadrature formulae. Te quadrature formula can be written for tis case as, f ( x) dx w ( t) f ( x ( t)) (5) jp Relating te idea of smooting kernels, an approximation of te function can be made. An auxiliary function Ө can be introduced to define te smooting kernel. Te most suited function for Mesless Lagrangian analysis is te cubic B- spline function, wic provides suitable regularity. Tis is given by Eq. (6), and is grapically represented in Fig. 1. i j 3

4 C. CHANDRA, T. Y. WONG AND J. BAYANDOR y y ( y) C (2 y) for for for y 1 1 y 2 y 2 (6) In Eq. (6), C is te constant of normalization, wic depends on te space dimensions. Te smooting kernel W is ten defined as, 1 xi xi W ( xi xi, ) (7) In Eq. (7), W( xi xi, ) wen 0, were is te Dirac function, is te smooting lengt of te kernel. Te particle approximation u is ten given by, Fig. 1. Cubic B-spline type auxiliary function u ( x ) w ( t) u( x ) W( x x, ) (8) i j j were is te virtual viscous pressure, allowing te singular peak forces, initiated by individual particles, to be smeared over te impact region. Te smooting lengt represents a mean value of distance between elements i and j. Over time, it as been sown tat tis approximation can lead to unstable results. A reasonable selection of smooting lengt can be ( x i ), wic is known as gater formulation. Tis means tat te neigbors for any given particle are included in a spere centered at x wit a radius of x ). ( i j i j i 4.3 Coupled Lagrangian-Eulerian Figure 2a sows a scematic of te Lagrangian sceme. Te Lagrangian sceme is capable of tracking free surfaces and interfaces between different materials. Te sceme also facilitates istory dependent constitutive relations. However, Lagrangian sceme treats eac particle in te mes as an individual. Particles move independent of eac oter and can diverge in space. Te divergence can lead to excessive distortion of te Lagrangian mes. Tere is also a possibility of mes overlap [5], affecting te accuracy of te result. Te Eulerian sceme is also a mes dependent approac. Individual nodes in te computational mes in Eulerian frame are fixed [1]. Particles in te frame move wit respect to te grid as sown in Fig. 2b. Eulerian sceme is capable of analyzing structures wit large distortion. Particles cannot experience any overlapping since particles move in and wit respect to te grid specified. However, te sceme is not able to trace movement of eac individual particle. Coupled Lagrangian-Eulerian is an approac to solve soft body problems using bot Lagrangian as well as Eulerian reference frames. Tis tecnique is developed to minimize te limitations associated wit using eiter sceme independently. a) b) c) Fig. 2. Representation of a) Lagrangian, b) Eulerian, and c) Coupled Lagrangian-Eulerian scemes Coupled Lagrangian-Eulerian is derived by using te combination of material time 4

5 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS derivative and grid time derivative into continuum mecanics governing equations. Tere are tree domains in Coupled Lagrangian-Eulerian sceme: material domain, R X, spatial domain, R x, and reference domain, Rχ. Te reference domain is introduced to identify grid points [1]. Te reference domain is mapped into te material and spatial domains by ψ and Φ, respectively. Particle motion is defined by φ. Equation (9) expresses te relationsip between te tree mapping function. After mapping of all te domains, motion of te system can be determined. Te relationsip between material velocity, v, and mes velocity, v m, is defined by convective velocity, c. Convective velocity is te particle velocity as seen troug te spatial domain. R X ψ Rχ φ Φ R x Fig. 3. Mapping of te tree domains 1 (9) c v (10) If te material domain is equivalent to te grid reference domain, material and mes velocity are equaled, and Lagrangian formulation is acieved. Wen te spatial domain is equivalent to te grid reference domain owever, mes velocity is zero and te convective velocity is equal to te material velocity as stated in Eq. (10), ence satisfying te Eulerian formulation. Terefore, in te Coupled Lagrangian-Eulerian sceme a proper relationsip between te domains needs to be establised so tat a feasible solution can be obtained. Dealing wit impact analysis, conservation of mass and momentum equations are applied. Tese equations can be expressed in te differential form as: t v t v m c v c v b (11) a) b) c) Fig. 4. Illustration of soft body impact on a rigid plate a) Lagrangian b) Mesless Lagrangian c) Coupled Lagrangian-Eulerian 5

6 C. CHANDRA, T. Y. WONG AND J. BAYANDOR 5 Bird and Target Modeling Tree types of artificial bird sapes are often used for bird strike analysis: straigt ended cylinder, emisperical ended cylinder, and ellipsoid [6]. Due to its advantages, in tis paper emisperical ended cylinder is adopted for calibration and analysis purposes [7]. Bird mass, density, ρ, and diameter, D can be correlated using equations developed by Budgey [6]: 0.063log 10 mass (12) log 10 D 0.335log 10 mass 0.9 (13) Setting te diameter of te bird model as 100 mm, te bird mass was determined as 1922 g for a density of g/cm 3. Te dimensions of te bird were fixed by te set indicated in Eqs. (14). Once all te bird properties were determined, tey were used Mesless Lagrangian and Coupled Lagrangian- Eulerian analytical scemes. Volume mass/ Volume Volume cylinder emispere r 2 4r 3 / 6 (14) A flat primary aerospace panel and a leading edge were selected as targets representing an aircraft structure. Tey were constructed from composite laminates wit a ply lay-up of [0,45,90,-45] 2. According to impact teory [1], target surface must be several times te diameter of te soft body. To ensure te target surface was sufficiently large, an 800 mm x 800 mm panel was used trougout te analysis. A representative leading edge model was also constructed using NACA 0012 aerofoil profile. Te bot structures were clamped at four edges. Te panel ad a finer mes density at te impact centre. Te outer region of te panel ad 4 2 u 0 = 116 m/s Fig. 5. Non- dimensionalized pressure wit respect to time [1] 6 Fig. 6. Pressure wit respect to time for Lagrangian, Mesless Lagrangian and Coupled Lagrangian- Eulerian sceme

7 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS a relatively coarser mes. Te fine and coarse mes regions were bridged via a transition mes zone [8]. Te leading edge owever modeled wit a uniform mes density. 6 Calibration of Numerical Bird Model Te numerical bird models in bot analytical scemes were ten calibrated against a rigid plate test data [1]. Te numerical bird was set to impact onto te rigid plate at 116 m/s wit te direction of impact set to normal. Figure 5 sows te experimental pressure-time istory by Wilbeck [1], versus Fig. 6 tat depicts te simulated pressure-time using bot Mesless Lagrangian and Coupled Lagrangian-Eulerian scemes. Comparison of te trends of bot scemes wit tat of Wilbeck s underlies similar beavior. In agreement wit te experimental results, te numerical birds in bot approaces identified a peak pressure region at te moment of impact. Mesless Lagrangian sceme sowed a iger peak pressure tan te Coupled Lagrangian-Eulerian metod. Past te peak pressure region, te impact pressure for bot scemes dropped gradually until reacing zero at te end of te impact window. Bot Mesless Lagrangian and Coupled Lagrangian-Eulerian scemes predicted te impact window witin a reasonable margin of error. However, te Mesless Lagrangian sceme sowed a more volatile variation in pressure after reacing te peak pressure tan te competing sceme. 7 Results and Discussion Te impact scenario was analyzed for different bird velocities ranging from 75 to 100 m/s. Eac sceme of modeling was ten compared qualitatively for impact damage of target area, followed by a qualitative assessment of te impact force. Te analysis was ten extended to numerically model bird-strike on a wing leading edge. 7.1 Impact Damage Area Significant damage to te target was observed at velocities closer to 100 m/s. Te impact damage area is sown for eac sceme in Fig. 7. a) b) c) Fig. 7. Impact damage at u 0 = 100 m/s and t = s a) Lagrangian. b) Mesless Lagrangian. c) Coupled Lagrangian-Eulerian 7

8 C. CHANDRA, T. Y. WONG AND J. BAYANDOR Fig. 8. Force-time istory for all scemes at u 0 = 100 m/s Te impact damage trace detected on composite panels was rater different for eac of te modeling scemes used. Te damage areas identified by te Mesless Lagrangian metod were te smallest for all cases considered, wit te largest ones being tose of te Coupled Lagrangian-Eulerian. Damage from te Lagrangian bird model was intermediate, despite te fact tat te model suffered from unacceptable values of mass loss due to erosion and ig mes distortions after impact. It was observed tat te difference in damage areas in te tree metods was mostly due to large variations in teir predicted peak forces. Te ig peak forces for Mesless Lagrangian model caused immediate failure of te contact surface, leaving no leverage for te panel to yield. 7.2 Impact Force Figure 8 sows te force-time istory of eac modeling sceme for impact on a flat plate at 100 m/s. Te grap clearly identifies te peak forces at impact for eac sceme. Forces at te moment of impact for te Lagrangian and Mesless Lagrangian bird models were respectively 48% and 110% larger tan tat of te Coupled Lagrangian-Eulerian model. Tis can well be a reflection of te nature by wic eac type of numerical bird model can interact wit te target. For instance, te Mesless Lagrangian sceme is particle based, were as te Coupled Lagrangian-Eulerian approac treats te material as evenly distributed. Tis distinction in modeling approac can be a possible cause for large differences in peak t = 0 t = s a) b) c) Fig. 9. Bird model impact on wing leading edge at u 0 = 75 m/s a) Lagrangian b) Mesless Lagrangian. c) Coupled Lagrangian-Eulerian 8

9 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS forces, particularly if te smooting lengt or te virtual viscous pressure (dealing wit te inerent singularity problem of te metod) ave not been correctly identified. Notwitstanding te fact tat te Mesless Lagrangian sceme suffers from singularity induced errors and cannot identify contact areas, it is a robust sceme tat can substitute and improve on te fast aerospace design tools, wic are mostly created based on te more conventional Lagrangian and Coupled Lagrangian-Eulerian approaces. Te mesless metod can furter completely avoid discrepancies due to plasticity and material distortions. Te Lagrangian model sowed irregularity trougout te impact regime. Erratic spikes of peak forces can be attributed to ig mes distortion after te initial impact pase. Tis sporadic beavior can furter be exacerbated by material erosion and timescaling, wic was initially introduced to promote contact stability. 7.3 Wing Leading Edge Figures 9 and 10 sow te impact of bird model for all tree modeling scemes. Te previous arguments on using te tree metods in modeling impact scenarios onto te primary aircraft panels remain valid. Furter, wen dealing wit curved targets, it as to be noted tat mes distortion in pure Lagrangian models is overly large, rendering te results of soft impact analyses using tis metod unacceptable. t = s Damage to wing leading edge a) b) c) Fig. 10. Impact damage to wing leading edge at u 0 = 100 m/s a) Lagrangian. b) Mesless Lagrangian. c) Coupled Lagrangian-Eulerian 9

10 C. CHANDRA, T. Y. WONG AND J. BAYANDOR 8 Aircraft Ditcing In te aviation istory, tere as been a very few open reports on known cases of large commercial passenger jets surviving emergency water landing. Tis is except for te landing of te Airbus A-320 under te banner of US Airways Fligt number 1549 and te command of Captain Cesley Sullenberger over Hudson River in January 15, 2009, success of wic would ave to be mostly attributed to te remarkable pilot s skills and is calm, yet calculated conduct. Tis incident and oter reported or unreported accidents alike, call for furter researc in te area of soft collision during te Tecnology Readiness and Aircraft Design pases. Tis necessity is furter justified as passenger safety, particularly for large airliners, is of paramount. Given te resource intensiveness and ig costs associated wit field trials, it is almost impractical to obtain pre- detailed design experimental data using full scale, fully functional prototypes or even scaled models to assess te craswortiness of concept aircraft designs in possible soft cras scenarios. Developing an accurate modeling metodology tat can numerically examine aircraft ditcing incidents over water can assist manufacturers tremendously in designing improved and safer aerospace structures. Te ditcing scenario can be categorized as soft cras, an event typical of fluid-structure interaction. As part of tis study, a preliminary analysis was conducted on aircraft ditcing using te Mesless Lagrangian sceme. Figure 11 sows te model of a generic large passenger jet constructed wit sell elements, aving an approximate weigt of 52 tons. Tis model was assigned an initial pitc of -10º wit a resultant velocity of 118 m/s. Figure 11 also depicts te body of water containing 360,000 equally distributed Mesless Lagrangian elements. Fig. 11. Numerical model for aircraft ditcing analysis Fig. 12. Aircraft ditcing force-time istory 10

11 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS 1) t = s 2) t = s 3) t = s 4) t = s Fig. 13. Resultant velocity contours for an aircraft ditcing scenario 11

12 C. CHANDRA, T. Y. WONG AND J. BAYANDOR Figure 12 sows te force-time istory for a time period of 0.5 s. Te aircraft experiences an initial impact force of nearly 15 MN, wic peaks to a maximum of around 32 MN at 0.075s. Te maximum force is observed wen te center portion of te fuselage impacts te water. Tis is due to te obviously muc larger impact area (now including te center of te fuselage and te area of te wings) and peraps an added force from pitcing rotation induced by te initial impact and te aircraft buoyancy. Figure 13 sows te resultant velocity contours pertaining to te four timelines marked in Fig Conclusion Tis paper presents a comparative study between te Mesless Lagrangian and Coupled Lagrangian-Eulerian scemes in an explicit finite element platform, to evaluate teir overall efficiency in analyzing fluid structure interactive systems. In particular, te focus was initially given to bird-strike events as an apparent candidate for less computationally intensive soft-body impact. Te two metods were furter compared wit te typical Lagrangian approac to bencmark teir advantages and sortcomings against a well establised tecnique. Following a parametric study and calibration of te numerical bird model, a series of simulations was carried out for various impact velocities ranging from 75 to 100 m/s, using aerospace composite primary laminate panels as te target. At iger velocities, te impact damage traces detected by Lagrangian and Mesless Lagrangian scemes were not as widespread as for te Coupled Lagrangian-Eulerian model. Tis was attributed to te iger peak forces predicted by bot Lagrangian based models, due to wic te target elements failed immediately leaving no time for te panel to yield. Te Lagrangian model suffered from ig mes distortion and erosive mass loss, rendering it an unfavorable candidate for soft impact modeling. In te Coupled Lagrangian-Eulerian sceme, te material was distributed evenly trougout te impactor, unlike te Mesless Lagrangian approac, were te model was discrete and particle based. Tis allowed te Coupled Lagrangian-Eulerian sceme to capture te impact window more smootly. Tis was not te case for Mesless Lagrangian were instabilities were recorded all troug te impact regime. Tese spikes can be reduced by introducing a stronger pressure distribution function tat can smear te nodal pressures more efficiently trougout te model. Continuing studies will aim to furter experimentally validate te selected numerical sceme. Te subsequently improved soft impact modeling metodology will ten be used to extend te scope of te current work and investigate oter fluid-structure interactive systems of interest. Soft cras scenarios, encompassing aircraft water ditcing, are in tis category, wit an example of initial undertaking in tis area presented in section Acknowledgments Te autors would like to tank and acknowledge te valuable input from Dr. Bayandor s Dynamic Damage Modeling researc team. In particular, te autors wis to acknowledge te great assistance provided by A. Zammit, M. Kim, M. Cisti, and S. Sa trougout te life of tis project. References [1] Wilbeck JS. Impact beavior of low strengt projectiles, AFML TR , [2] Donea J, Huerta A, Pontot JP. and Fodríguez- Ferran A. Capter 14 Arbitrary lagrangian-eulerian metods, Encyclopedia of Computational Mecanics, URL: ttp:// _14.pdf, [3] Lacome JL. Smoot particle ydrodynamics (SPH): a new feature in ls-dyna, Immeuble AEROPOLE - Bat 1, Blagnac, [4] Liu GR and Liu MB. Smooted particle ydrodynamics a mesfree particle metod, World Scientific, [5] Carlton A. A summary study on arbitrary lagrangianeulerian: metodology, implementation, and application, summer researc experience for undergraduates, Oregon State University, URL: ttp://wave.oregonstate.edu/education/reu/2004_r EU/Carlton.pdf,

13 CRASHWORTHINESS ASSESSMENT IN AIRCRAFT DITCHING INCIDENTS [6] Budgey R. Te development of a substitute artificial bird by te international birdstrike researc group for use in aircraft component testing, International Bird Strike Committee, IBSC25/WP-IE3, Amsterdam, [7] Bayandor J, Jonson A, Tomson RS, Joosten M. Impact damage modelling of composite aerospace structures subject to bird-strike, Te 25 t Congress of te International Council of te Aeronautical Sciences, ICAS 2006, Hamburg, Sept [8] Joosten M., Bayandor J. Coupled SPH composite coesive damage modeling metodology for analysis of solid-fluid interaction, Te 46 t AIAA Aerospace Sciences Meeting and Exibit, Reno, Jan Copyrigt Statement Te autors confirm tat tey, and/or teir company or organization, old copyrigt on all of te original material included in tis paper. Te autors also confirm tat tey ave obtained permission, from te copyrigt older of any tird party material included in tis paper, to publis it as part of teir paper. Te autors confirm tat tey give permission, or ave obtained permission from te copyrigt older of tis paper, for te publication and distribution of tis paper as part of te ICAS2010 proceedings or as individual off-prints from te proceedings. 13