1. Composite Research Relevant to Aero
Engine Applications
Dr. Giuliano Allegri

2. Key drivers in material 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 in Aero Engine Applications

4. Materials in Aero Engine Applications: historical trends

5. Materials in Aero Engine Applications: historical trends

6. Materials in Aero Engine: 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 Aero Engine: 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 Aero Engine: 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 Aero Engine: 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 growth modelling (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 growth modelling (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 growth modelling (with optional TTR)
Through the thickness reinforcement: constitutive equations

14. 1. Delamination growth modelling (with optional TTR)
Through the thickness reinforcement: constitutive equations

15. 1. Delamination growth modelling (with optional TTR)
Delamination growth modelling in Z-pinned T-joints
Initiation Failure
Load

16. 1. Delamination growth modelling (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 growth modelling (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 composite joints 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 composite joints 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 monitoring via 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 monitoring via optical fibres
•Simulation for an high temperature curing case: finite difference time integration

22. 3. Iso/anisogrid composite structures
•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 composite structures
•An example of anisogrid cylinder (300 mm diameter x 400 mm height); wet filament
winding and oven polymerization

24. 3. Iso/anisogrid composite structures
•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 Analysis of 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 Analysis of 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 simulation of 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 simulation of 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 for manufacturing: 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 tailoring of 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 Fluidic Thrust Vectoring nozzles

32. Design of Fluidic Thrust Vectoring nozzles

33. Design of Fluidic Thrust 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