Load Introduction into Aerospace Structures

Transcription

1 Load Introduction into Aerospace Structures Dr. Tamas Havar, Airbus Group Innovations Symposium 5 th anniversary of Institute of Carbon Composites POC: tamas.havar@airbus.com

2 Introduction Investigated Composite Load Introduction Structures in Aircraft CFRP Rear Link CRFP Flap Load Introduction Rib Composite 4-Bar Linkage Flap Support A340 CFRP Spoiler

3 Innovative Flap Load Introductions Aircraft Structures: Continuous development of aircraft structures Increased use of composite materials Composites currently used in frame structures Metallic Load Introductions A330 / A340 High Lift System Composite Flap: Composite skin with stringers Composite ribs and Spars Except metallic load introduction rib Aim: Innovative composite design for Load Introduction Rib (LIR) LIR Flap

4 Innovative Flap Load Introductions Composite Flap Aim of Project: Redesign of metallic LIR => innovative composite LIR Requirements: Equal design space, attachments, Load transmission from flap track into flap Resistance against temperature, humidity, chemicals, Metal - LIR Flap Structure Project Goals: Innovative composite design (No black metal!) Low manufacturing costs Low weight High robustness => low maintenance costs Project Team: Airbus Group Innovations Airbus (Lead) Airbus Helicopter Airbus Defense and Space & Premium AEROTEC IVW Kaiserslautern Composite LIR

5 Innovative Flap Load Introductions New Composite Textile Preform Design FS Attachment LIR DS Rib RS Attachment RL Attachment SL Attachment DS Bracket

6 Innovative Flap Load Introductions Design Process Modification of exist. Flap FEM New Design of LIR (CAD) New FEM Model of LIR Integration of LIR Model in Flap Model Analysis of Stresses Application of Loads Integration of Rivets Part C Part B Part A

7 Innovative Flap Load Introductions 3D Sizing with effects of defects Plies milled (Waviness => too thick) Fiber orientation taken from pre-form Results of Analysis Successful Sizing of LIR Few critical points Local small Reserve Factors (RF) dependent on load case Fiber compression S11min Matrix tension S22max No critical delaminations calculated S12, S13 und S23 No matrix crack at gusset fillers

8 Innovative Flap Load Introductions Manufacturing (Airbus Helicopters) Preforming of Parts Automated NCF Cut Out Positioning of Load Introduction Draping of Rib Layers Precompatcting Adding of Reinforcement Layers 3D Stitching of Edges 3D Cutting of Edges Automated Pre-form QS

9 Innovative Flap Load Introductions Manufacturing (Premium Aerotec) Infiltrated Parts LIR with CFRP Lugs 3D Reinforcement Drive Ribs Drive Bracket Pi Profiles FS-Attachments Aux Spar

10 Innovative Flap Load Introductions Manufacturing (Airbus) Assembly Shortening of A340 OB Flap Reinforcement of Lower Skin Assembly of LIR Assy. DS Rib and Bracket Assy. Clamping Ribs Top View Bottom View

11 Innovative Flap Load Introductions Validation (Premium Aerotec) Testing of 5 Critical Load Cases Testing of Flap with integrated LIR BVID (Barely Visible Impact Damage) VID (Visible Impact Damage) NDI after Damages Static Loads partly with EKDF Fatigue Loads with LEF 3 Actuators 80 Strain gauges BVID + NDI Fatigue Phase, LEF 1,15 Damage Tolerance Phase VID + NDI

12 Innovative Flap Load Introductions Validation (Premium Aerotec) Finished Testing Small Delamination of Gusset Filler of DS Bracket Possible Delamination in inner LIR Radius Loads were carried despite small damages Fatigue Testing without further damages

13 Innovative Flap Load Introductions Summary LIR Design and Sizing New Innovative Composite Design of Flap Load Introduction Rib Ability to analyze complex 3D Composite Parts Integration of effects of defects into sizing Verification Verification with Risk Reduction Articels Spring Back etc. Verification of Preforming Abilities of all Parts Curing of Load Introduction Ribs with VAP Process QS of finished Parts Validation Integration of LIR in existing A340 outbaord flap Fatigue and damage tolerance Testing Over 25% Weight Reduction Over 5% Cost Reduction

14 Further Investigations CFRP Lug Sizing Rules

15 Force [kn] Airbus Group Innovations Tamas Havar - 5th Anniversary LCC CFRP Lug Sizing Rules Motivation Increased use of composites in current high-lift lightweight designs Mostly extensive testing needed for new structural components => Costly: most critical several load cases are to be tested There are only few guidelines / designers experience More general approach from specific part towards common design guidelines for high-lift structures are needed Comparison between FEA and Test for Composite Lugs Fiber Failure 400 Aim: General Design Rules for Lugs and Loops Inter-Fiber Failure FEA: QI FF 100 Test: QI FF 50 Test: QI IFF FEA: QI IFF Radius Ratio r a/r i

16 Failure Load [KN] Failure Load [KN] Failure Load [KN] Airbus Group Innovations Tamas Havar - 5th Anniversary LCC CFRP Lug Sizing Rules 500 Failure Load Verification of Laminates with Lug under 0 Loading Test vs. FEM and Analytical Calc Approach Analysis of composite load introductions (analytical and FEA) Validation of composite lugs and loops First Ply Failure / Residual Strength ,3 1,4 1,5 1,6 1,7 1,8 1,9 2 Ratio of Radius: ra/ri [ ] Test-Lug-Failure FEM-Lug-Failure Analyt-Lug-Failure Test-Lug-Non Linear FEM-Lug-First Failure Analyt-Lug-First Failure 0 Loading: 90 Loading: Loops better performance: Loops low performance: => Fiber in load direction => Matrix in load direction Lugs low performance: Lugs low performance: Parameter study at 90 Loading => Fiber cut in load direction => Fiber partly in load direction 700 Parameter study at 0 Loading Lug vs. Loop (with and without inner ring) 300 Lug vs. Loop (with and without inner ring) FEM-Loop-Innerring-Failure FEM-Loop-Failure FEM-Lug-Failure Test-Lug-Failure 50 FEM-Loop-Innerring-Failure FEM-Loop-Failure FEM-Lug-Failure 0 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 Ratio of Diameter: Da/Di [ ] 0 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 Ratio of Diameter: Da/Di [ ]

17 CFRP Lug Sizing Rules Progressive Failure Analysis of Lugs and Loops => AIM: Virtual Testing of Composite Lugs and Loops Damage Initiation using 3D Puck Damage evolution: failure mode dependent Gradual softening for inter-fiber fracture Stiffness degradation (not E ) depending on failure mode Instantaneous degradation for fiber fracture, representing total structural failure Coupling of Fortran subroutine (including 3D Puck and degradation scheme) within every incremental calculation of nonlinear simulation IFF, n 0 Analysis at every integration point Evaluation in layers possible FF IFF, n

18 Shear modulus G 12 [N/mm 2 ] Airbus Group Innovations Tamas Havar - 5th Anniversary LCC CFRP Lug Sizing Rules Scientific Approach (by Carolin Werchner) Verification of gradual and instantaneous stiffness degradation Comparison Strain Distribution: Test vs. FEA IFF FF IFF FF Test FEA Softening factor h Increments Increments softening factor h degraded shear modulus G 12 Comparison Fracture Mode Very good qualitative accordance But strong calibration needed (mesh dependency etc.)

19 Further Investigations Next Applications

20 Next Applications Metal Track Rear Link Kinematics Basis: Composite 4 Bar Linkage Flap Support Replacement of metal carriage Full Composite Linkage System Linkages Brackets Flap Composite 4 Bar Linkage Kinematics Wing Linkages mostly as composite loops Lugs: thick laminate load introduction Failure case reduction: No jam of carriage Linkages with bearings Maintenance reduction No ball bearings Self lubricant bearings Major weight reduction

21 Next Applications Innovative High Lift Systems for Future Aircraft

22 Questions? Thank You!