Post on 24-Mar-2018
Improved aircraft wing designs using composite aeroelastic
tailoring
Jonathan Cooper
RAEng Airbus Sir George White Professor of Aerospace Engineering
www.bris.ac.uk/composites
2/14Outline• Overview of current work on use of composites to improve
wing designs
• Carl Scarth– ACCIS DTC (yr2)– Embraer
• Olivia Stodieck– CASE award student (yr2)– Airbus
• Guillaume Francois– ACCIS DTC (yr1)– Part funded by EOARD
Composite Aeroelastic Tailoring
3/14EU Initiatives for Aerospace Industry• 2020 Vision
• 50% reduction by 2020 of:– aircraft fuel use, – emissions – noise
– Flightpath 2050– 75% reduction in CO2,
90% NOx, 65% noise– Emission free taxiing
• Environmental friendly aircraft
• Fast design and certification methods
Composite Aeroelastic Tailoring
4/14Range Equation and Composite Design
R= 𝑉𝑉𝑓𝑓𝑓𝑓
𝐶𝐶𝐿𝐿𝐶𝐶𝐷𝐷𝑙𝑙𝑙𝑙 𝑊𝑊1
𝑊𝑊2
Achieve desired shape throughout
flight envelope Reduce weight through loads
alleviation
Reduce weight by increasing flutter speed
Determination of sensitivity to variations in structure, manufacturing and aerodynamics
L/D
Weight
Improvement through better
Aerodynamics
WeightEngines
Composite Aeroelastic Tailoring
5/14Structural Design
•Structure must be strong enough to withstand loads encountered in lifetime and also aeroelastic effects
Trade-off between strength and weightUse anisotropic composite properties to influence loads and aeroelastics - composites are NOT just a “black metal”
Composite Aeroelastic Tailoring
6/14Aeroelastic Tailoring
• Aeroelastic Tailoring – Structural and Aerodynamic behaviours are optimised by
varying composite fibre angles and layup sequence
>> Wing bending and torsion stiffness >> Passive elastic coupling between wing bending and torsion deformations
Optimisation Objectives:• Weight • Lift to Drag ratio• Static strength • Flutter & Divergence
airspeeds• Control effectiveness• Gust load alleviation
Grumman X-29
Fibre angle
Composite Aeroelastic Tailoring
7/14Tow-Steered / VAT Composites• Fibres follow curvilinear paths within the plane of the ply • First investigated in the early 1990s
Effect of Fiber Waviness, Kuo et al. (1988) Buckling Resistance, Hyer and Lee (1991) Variable Stiffness Concept, Gurdal and Olmedo (1993)
• Improved, more flexible manufacturing methods are being developed (AFP, CTS)
• Application here to aeroelaticity
Continuous Tow Steering (CTS)
Composite Aeroelastic Tailoring
8/14
TipRoot
Maximum Instability Airspeed
Optimum VAT laminate
0 50 1000
100
200
300
Freq
uenc
y (H
z)
Mode 1Mode 2Mode 3Mode 4Mode 5
0 50 100-100
0
100
Airspeed (m/s)
Dam
ping
Rat
io (%
)
InstabilityAirflowRoot Tip
0
1
-1
Composite Aeroelastic Tailoring
9/14Internal Wing Structural Design
Spars
Ribs
• Novel aircraft configurations
CFRP Composite Wing Structure
• Conventional wing
• Better to use curved spars and ribs?
Composite Aeroelastic Tailoring
10/14Optimisation Results - Shapes
DecisionVariable Set
Full ShapeOptimisation
Spar ShapeOptimisation
Cost = 0.9219Vdivergence = 180.2 m/s
Mass = 47.48kg
Cost = 0.8362Vdivergence = 166.6 m/s
Mass = 34.84kg
Both Ribs and Spars shape control offer advantagesBoth should be considered in wing design
Composite Aeroelastic Tailoring
11/14Uncertainty in Composite Designs• Increasing use in aircraft
structures– Use bend-twist coupling to offset
aeroelastic instability
• Manufacturing processes prone to variability e.g.– Layup tolerance– Thickness and geometrical tolerance– Fibre waviness
Boeing 787
PD
FCritical Air Speed
Design Instability Speed
Deterministic Design
Robust Design
Material uncertainty
UncertaintyQuantification
Minimise failure probability
Composite Aeroelastic Tailoring
12/14Uncertain Flutter Prediction
Feasible Region
• Approach using lamination parameters, PCE and Bayesian emulators enables fast prediction of probability bounds
Composite Aeroelastic Tailoring
13/14Response Mechanisms: [452-452 02 902]S
• Plot of aeroelasticresponse in ξ11–ξ12space
• Assume deterministic values for ξ9 and ξ10
• Discontinuities caused by switch in response mechanism
• ξ11–ξ12 PDF crosses discontinuity
• PDF peaks attributed to divergence & flutter
Divergence
Flutter 1Flutter 2
Flutter Peak
Divergence Peak
Composite Aeroelastic Tailoring
14/14Conclusions and Future Work• Design techniques show promising results for
improvement of composite wings• Tow-steering
– Application to high aspect ratio and forward swept wings
• Novel internal composite structures– Application to high aspect ratio and forward swept wings– Experimental testing
• Uncertainty quantification– Application to full aircraft test case– Robust design
• Plenty of room for further ACCIS PhD work for those interested
Composite Aeroelastic Tailoring