Experimental Building Block Approach to Support the Crashworthiness Evaluation of Composite Aircraft Structures

Transcription

1 Experimental Building Block Approach to Support the Crashworthiness Evaluation of Composite Aircraft Structures 2011 FAA/EASA/Industry Composite Transport Fatigue, Damage Tolerance, Maintenance & Crashworthiness Workshop Gerardo Olivares Ph.D. May 19 th 2011 Atlanta, GA

2 Aerospace Structural Crashworthiness Crashworthiness performance of composite structures to be equivalent or better than traditional metallic structures Crashworthiness design requirements: Maintain survivable volume Maintain deceleration loads to occupants Retention items of mass Maintain egress paths Currently there are two approaches that can be applied to analyze this special condition: Method I: Large Scale Test Article Approach Experimental: Large Scale Test Articles (Barrel Sections) Component Level Testing of Energy Absorbing Devices Simulation follows testing Numerical models are tuned to match large test article/ea subassemblies results. Computational models are only predictable for the specific configurations that were tested during the experimental phase. For example if there are changes to the loading conditions (i.e. impact location, velocity,..etc.) and/or to the geometry, the model may or may not predict the crashworthiness behavior of the structure. Method II: Building Block Approach Experimental and Simulation Coupon Level to Full Scale Predictable modeling 2

3 Composite Structures Crashworthiness Methodology 3

4 Composite Structures Crashworthiness Methodology cont. 4

5 Passenger Seat Models Certification by Analysis Methodology per AC for Aircraft Seats/Installations FAA JAMS funded project Phase I: HII and HIII FAA Numerical ATD Validation [July July 2010]: Test variability HII and HIII FAA ATD with 2,3, and 4-point restraints. Numerical ATD V&V Procedure. Comparison HII and HIII FAA dynamic performance. SAE ARP 5765 ATD reference data. Phase II: Seat Structural Modeling Techniques Strain rate: 0.45 Strain rate:2.18 Strain rate: 5.3 [September September 2010]: Seat Structure: Material models, joint definitions, and modeling techniques using FE and MB approaches. Strain rate: 0.25 Strain rate: 1.4 Coupon and Component Level Testing Protocols: Seat Cushion, Seatbelt Webbing, and structural components. Modeling Techniques: Pitch and Roll Modeling Procedures.. Numerical model application, documentation and validation per AC

6 N A T I O N A L I N S T I T U T E F O R A V I A T I O N R E S E A R C H Experimental Building Block Approach CRASHWORTHINESS EVALUATION - specific to structural configuration - interactions between mechanisms Full Aircraft BENCHMARKING -Constitutive models Failure theories LOCALIZED IMPACT PROBLEMS - Bird, hail, projectile impact - Damage Resistance CRASHWORTHINESS - Crush behavior Structural integrity Section Test Sub-assembly Component Level Energy Absorbing Devices Failure Modes Strain Gradients Connections Coupon Level Material Characterization Constitutive Laws Strain Rate Effects Failure Criteria 6

7 Coupon Level Experimental and Computational Program Overview Quantify the high strain rate coupon level mechanical properties test variability for: Composites: Toray - T800S/3900-2B Unitape Newport - E-Glass Fabric NB321/7781 Toray - T700G-12K-PW/ (fabric) Orientations: [0 ] N, [0 /90 ] 3S, [15 /-15 ] NS, [30 /-30 ] NS, [45 /-45 ] NS Metallic: Aluminum 7075-T6 Orientation: L Identify variables and coupon level tests required to define material cards (MAT 54 and MAT 58 in LSdyna). Evaluation of LSdyna MAT 54 and MAT 58 coupon level models with quasi-static and high strain rate data: Tension, Shear and Compression Mesh Sensitivity Studies Develop detailed FE models of the experimental test equipment. Coupon Level geometric scaling effects studies, Identify current limitations of the coupon level experimental test procedures and numerical material models. 7

8 N A T I O N A L I N S T I T U T E FOR A V I A T I O N R E S E A R C H High Stroke Rate Servo-Hydraulic Slack Inducer Mechanism NIAR/WSU HS Load frame Specifications: Current High Stroke Rate Testing Capabilities: Rated for 5,000 lbf at rates as high as 500 in/s In-plane tension Rated for 9,000 lbf at quasi-static rates In-plane shear In-plane compression 8

9 Rate Sensitivity Composite Metallic Material Systems: Toray - T800S/3900-2B Unitape Newport - E-Glass Fabric NB321/7781 Toray - T700G-12K-PW/ (fabric) Aluminum 7075-T6 Test Setup: In-plane Tension per ASTM D 3039 NIAR HS Servo Hydraulic Stroke Rates: Quasi-static, 1 in/s, and 10 in/s Rate Sensitivity: Dependent on material Dependent on loading condition ( tension, compression, shear) Toray T800S/3900-2B Unitape - [0] 2 Aluminum 7075-T6 9

10 Test Variability Tension Toray Unitape Tensile Failure Strength - Carbon Unitape Nominal Strain-Rate [s-1] % 8.3% 5.6% Failure Modes Tension Carbon Unitape [45/-45] 2S Quasi-Static 0.5 s -1 5 s -1 Stress [psi] % 5.4% 3.8% % 3.1% 4.6% 4.9% 11% 8.5% 0 [0 ] [15 /-15 ] [30 /-30 ] [45 /-45 ] Lay-up Orientation Modulus of Elasticity - Tension - Carbon Unitape 2.7% 4.7% Nominal Strain-Rate [s-1] * AGATE Methodology [4] 10 1 Strain Rate - Tension - Carbon Unitape Nominal Strain-Rate [s-1] % 1.3% 4.8% 1.5% 16.1% Modulus of Elasticity [Msi] % 0.8% 2.8% 2% 3.1% 4.9% 4.2% 14.4% 10.5% 6.2% Strain Rate [s-1] % 1.1% 1.4% 5.2% 1.5% 4.9% 20.3% 0 [0 ] [15 /-15 ] [30 /-30 ] [45 /-45 ] Lay-up Orientation [0 ] [15 /-15 ] [30 /-30 ] [45 /-45 ] Lay-up Orientation 10

11 Component Level Experimental Material Systems: NB321/7781 fiberglass Toray T700G-12K-50C/ Plain Weave Carbon Fabric [0]n and [±45]n, where n=4,8 and 12 Sensitivity to loading rate: Peak load Crush load Failure modes in/s 100 in/s 4000 Load (lb) Displacement (in) 11

12 Round Robin Coupon Level Primary Objective Characterize strain rate sensitivity of Toray T700/2510 Plain weave carbon/epoxy (F6273C-07M) material at strain rates ranging between 0.01 to 250 s -1. [CMH-17 Material] Secondary Objective Evaluate the test methods/apparatus, specifically load measurement methods, employed by the participating laboratories. Use extended tab 2024-T3 aluminum specimens (see figure bellow) 1.25 R0.375 grip region inches y x 12

13 Participating Labs/Agencies (POCs) Co-ordination, Reporting Specimen fabrication, fixturing, instrumentation (strain gage) Material Testing FAA/NIAR/WSU (A. Abramowitz, G. Olivares, K.S. Raju) Boeing MESA (M. Rassaian) Ohio State University (A. Gilat) DLR (Alastair Johnson) Oakridge National Labs (M. Starbuck) Toray America (S. Tiam) 13

14 Test Specimen Geometries and Instrumentation Aluminum specimens 1.25 R0.375 grip region grip region y x 0.6 main strain gage tab strain gage Dimensions in INCHES y, x,0 Composite specimens axial strain gage transverse strain gage NOTE : Strain gages are not drawn to scale Dimensions in INCHES Dimensions in INCHES fiberglass tabs Will be provided to participating labs by WSU/NIAR 14

15 Tension Test Apparatus Participating labs use their own load sensors CROSSHEAD LOAD CELL WEDGE CLAMPING BOLTS SLACK ROD GRIP BLOCK SPECIMEN GRIPS PIN BEARING ARREST BLOCK POLYURETHANE (60 DUROMETER) SLACK ROD CONNECTOR SLACK SLACK MECHANISM SLACKTUBE ACTUATOR Will be provided to participating labs by WSU/NIAR 15

16 Round Robin Exercise Status Document (draft) describing the round-robin activity mailed to participants Ohio State requested a different specimen geometry and adapters for use with SHPB apparatus Specimen machining completed Machining of adapters ongoing Aluminum Specimens Machining & Instrumentation has been completed Composite Specimens Machining has been completed Instrumentation ongoing Machining of test fixtures completed Specimens & test fixtures to be shipped end of May,

17 Conclusions and Future Work Current coupon level testing practices do not provide all the data required for some crashworthiness simulation configurations: Strain measurements (Failure Strain): limited by strain gage measurement capabilities and SG bonding procedures/techniques [photogrammetry may be able to solve these issues]. Ultimate strength measurements: limited by ringing observed in piezo-electric and piezo-resistive load cells. This issue is more noticeable at higher loading rates. A High Strain rate testing protocol needs to be defined in the near future. In the meantime it is necessary to generate a baseline public domain high strain material properties database for researches & industry to validate their experimental methods ( Coupon Level Round Robin Exercise Data) Disseminate the findings of the research through the CMH-17 WG and journal publications Continue the building block approach work: Component Level Testing EA Type Structural Members Strain and Strain Rate Gradients Testing Open Hole A draft report summarizing the experimental and numerical coupon level work will be submitted to the technical monitor for review in July

18 Aerospace Crashworthiness Forum Crashworthiness Forum October 2012 (Organizers G. Olivares(NIAR), and M. Rassaian (Boeing) Location NIAR and NCAT Facilities, Wichita, KS): Define steering committee by June 2011 (FAA, EASA, Industry) Experimental and Computational Methods Technical Presentations: Day 1: Crashworthiness Certification by Analysis Aircraft Interiors Day 2: Crashworthiness Evaluation of Aircraft Structures Day 3 and 4 - Workshops: Modeling Techniques: ATDs, Seats, Airframe, Material Models Airframe Modeling Techniques Coupon, Component Level Testing Sled Testing

19 Acknowledgements FAA Funded Project Joint Advanced Materials and Structures (JAMS) FAA Personnel Involved Allan Abramowitz RDP Manager Crashworthiness Joseph Pelletiere Chief Scientific and Technical Advisor for Crash Dynamics Principal Investigators & Researchers G.Olivares Ph.D. (PI) Technical Director Crash Dynamics and Computational Mechanics Laboratories, NIAR S. Keshavanarayana Ph.D. (PI) Professor, Aerospace Engineering Department, WSU J. Acosta Research Engineer, NIAR 19