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Research in Composites for Aero Engine Applications
- 1. Composite Research Relevantto Aero Engine Applications Dr. Giuliano Allegri
- 2. Key drivers inmaterial developments for Aero Engines 1. Performance: stiffness, strength & operating temperatures 2. Reliability and durability: impact damage, containment, fatigue, creep 3. Cost: material selection, manufacturing technology, maintenance 4. Fuel consumption and emissions: high specific properties for lighter rotating parts, effective damping for noise reduction
- 3. Material potential inAero Engine Applications
- 4. Materials in AeroEngine Applications: historical trends
- 5. Materials in AeroEngine Applications: historical trends
- 6. Materials in AeroEngine: polymer based composites 1 Electronic Control Unit Casing: Epoxy carbon Prepregs 2 Acoustic Lining Panels: Carbon/glass Prepregs, high temperature adhesives, aluminum honeycomb 3 Fan Blades: Epoxy carbon Prepregs or Resin Transfer Molding (RTM) construction 4 Nose Cone: Epoxy glass Prepreg, or RTM 5 Nose Cowl: Epoxy glass Prepreg or RTM construction 6 Engine Access Doors: Woven and UD carbon/glass Prepregs, honeycomb and adhesives 7 Thrust Reverser Buckets: Epoxy woven carbon Prepregs or RTM materials, and adhesives 8 Compressor Fairing: BMI/epoxy carbon Prepreg. Honeycomb and adhesives 9 Bypass Duct: Epoxy carbon Prepreg, non-metallic honeycomb and adhesives 10 Guide Vanes: Epoxy carbon RFI/RTM construction 11 Fan Containment Ring: Woven aramid fabric 12 Nacelle Cowling: Carbon/glass Prepregs and honeycomb
- 7. Materials in AeroEngine: CFRP fan blades •Manufactured by RTM; final curing in high precision press followed by milling •Leading edge, trailing edge and tips protected by Titanium cladding •Extremely thick at the root: up to 4 inches in the GE90 engine fan •Slender tips: typical thickness 0.25 inches
- 8. Materials in AeroEngine: MMC •Titanium matrix composites are the most common choice (SiC/Ti-6Al-XX) •Improved specific strength •Improved fatigue life (crack bridging) •Suitable for compressors disks and secondary turbine stages
- 9. Materials in AeroEngine: CMC •CMC (Si-Ti-C-/SiC) suitable for applications in combustion liners, high temperature turbine discs and nozzles •Polytitanocarbosilane as ceramic fibre precursor •Woven fabric architecture used for 3D reinforcement
- 10. Composite material expertise 1. FE simulation of delamination growth in composite structures comprising TTR reinforcement (Z-pinning & Tufting) 2. Simulation of polymer composite curing 3. Aniso/iso-grid composite structures 4. Stochastic mechanics of composite materials & structures 5. Meshless-Galerkin simulation of crack growth in composites 6. Design for manufacturing 7. Aeroleastic tailoring of composite structures
- 11. 1. Delamination growthmodelling (with optional TTR) FE model for delamination/debond: interface groups • Interface elements represent the adhesive layer between overlapping plies • Interface element: Two rigid elements, to prevent penetration under compressive loading (RBE2) Three linear springs before failure (CELAS2): one for peel (Z, yellow), two for shear (X-Y, blue) Three nonlinear springs after failure (CBUSH1D): Z-pins response under mixed mode loading
- 12. 1. Delamination growthmodelling (with optional TTR) Through the thickness reinforcement: constitutive equations •Explicit constitutive laws: TTR modelled as a beam embedded in an elastic foundation •Mode I: pre-debonding ; pull-out •Mode II: pre-debonding ; pull-out where and
- 13. 1. Delamination growthmodelling (with optional TTR) Through the thickness reinforcement: constitutive equations
- 14. 1. Delamination growthmodelling (with optional TTR) Through the thickness reinforcement: constitutive equations
- 15. 1. Delamination growthmodelling (with optional TTR) Delamination growth modelling in Z-pinned T-joints Initiation Failure Load
- 16. 1. Delamination growthmodelling (with optional TTR) Delamination growth modelling in Z-pinned T-joints •T-joint: FE analysis - pinned configuration - 0.28 mm diameter, 4% density 1600 Control Case Experimental 1 Experimental 2 1200 FEM t = 30 MPa Load (KN) 800 400 0 0 2 4 6 Displacement (mm)
- 17. 1. Delamination growthmodelling (with optional TTR) Engine nacelle composite joints with TTR •Cross-Joint configuration: 2 (x) : 1 (y) displacement ratio Top View Bottom View
- 18. Engine nacelle compositejoints with TTR Cross-Joint: X radiography vs. FE at failure – Unpinned – 17 KN X Rays FE: survived bonded regions are white shaded
- 19. Engine nacelle compositejoints with TTR Cross-Joint: FE Analysis – Effects of Z-fibre insertion 25 Unpinned Load X (kN) Unpinned Load Y (kN) 0.28 mm 4%Load X (kN) + 20 0.28 mm 4%Load X (kN) o 0.51mm 4%Load X (kN) 0.51mm 4%Load Y (kN) X 15 10 5 0 0 0.1 0.2 0.3 0.4 0.5 0.6 D is pla c e m e nt X ( m m ) Experimental Load vs displacement @ failure: “x” un-reinforced; “o” 0.28 4%; “+” 0.51 4%
- 20. 2. Cure monitoringvia optical fibres •Non linear thermo-elasto-kinetic model for a representative material unit cell •Strain compatibility imposed starting from the resin gelation point •Representative experimental results
- 21. 2. Cure monitoringvia optical fibres •Simulation for an high temperature curing case: finite difference time integration
- 22. 3. Iso/anisogrid compositestructures •A structural concept widely employed in the former USSR •It provides the highest specific stiffness within prescribed mass and volumetric constraints
- 23. 3. Iso/anisogrid compositestructures •An example of anisogrid cylinder (300 mm diameter x 400 mm height); wet filament winding and oven polymerization
- 24. 3. Iso/anisogrid compositestructures •Preliminary design: analytical methods + geometric programming •Detail design and topological optimization: FE + genetic algorithms •Testing for verifying the buckling strength after manufacturing
- 25. 4. Stochastic Analysisof Composite Structures •Stochastic FE allows modelling the effect of uncertainties on the mechanical response of composite materials and structures •Material/geometrical uncertainties can play a very significant role in the dynamic behaviour of fast rotating machinery •Example: multi-layered composite beam s µ = 2πρ ∑ Ri ti i =1 s χ = π ∑ C zz (α i )Ri3ti i =1 µ = µ + ∆µ, χ = χ + ∆χ s s µ = 2πρ ∑ Ri ti , ∆µ = 2πρ ∑ Ri tiξ i i =1 i =1 s s ∂C χ = π ∑ C zz (α i ) Ri t i , ∆ χ = π ∑ zz 3 3 3 α i Ri t i η i + C zz Ri t i ξ i i =1 ∂ α i i =1 αi
- 26. 4. Stochastic Analysisof Composite Structures •Weighted Integral stochastic finite element method: the random field properties are projected on the shape functions •Example random vibration of an uncertain composite truss
- 27. 5. Meshless-Galerkin simulationof crack growth in composites •An efficient technique for simulating crack growth along arbitrary patterns and in mixed mode conditions without the need of re-meshing b/a J1 (J/m2) J2(J/m2) 0.4 1.101 x 10-6 0.247 x 10-8 0.3 1.098 x 10-6 0.118 x 10-8 0.01 1.102 x 10-6 0.304 x 10-8 3 ,5 3 2 ,5 Normalised SIF 2 1 ,5 KI 1 KII 0 ,5 Bow ie & Freez e 0 0 15 30 45 60 75 90 -0 ,5 Ply Angle ± θ
- 28. 5. Meshless-Galerkin simulationof crack growth in composites •Single edge notched specimen under pure shear 10,0 9,0 8,0 7,0 KI Normalised SIF 6,0 KII 5,0 KI Chu & Hong 4,0 KII Chu & Hong 3,0 2,0 1,0 0,0 0 15 30 45 60 75 90 Ply Angles ±θ
- 29. 6. Design formanufacturing: composite structures •Adapting the structural concept to the manufacturing process in order to deliver the target performance while reducing the costs •Alternative solution compared via extensive FE analysis
- 30. 7. Aeroelastic tailoringof composite structures •Optimization of laminate layout for prescribed flutter/divergence constraints •MSC/NASTRAN as simulation engine •Interface for external aerodynamic codes (“in house” 3D panel method) •Approach suitable for applications to fan/compressor/turbine blades and cascades 5.00 2.00 4.00 1.00 Frequency (Hz) 3.00 Damping 0.00 2.00 -1.00 1.00 0.00 -2.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 EAS (m/s) Frequency Damping
- 31. Design of FluidicThrust Vectoring nozzles
- 32. Design of FluidicThrust Vectoring nozzles
- 33. Design of FluidicThrust Vectoring nozzles •Rectangular nozzle 25.00 20.00 Thrust Deflection Angle (deg) 15.00 2 FTV Angle = -0.0261MFR + 1.4135MFR - 0.3392 2 R = 0.9625 10.00 5.00 0.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 Mass flow ratio (%) RPM = 40000 RPM = 78000 RPM = 88000 RPM = 98000 RPM = 110000