1. Dr. Benjamin K. S. Woods
13/10/2014

2. Fish Bone Active Camber Morphing Airfoil
Key Features of the FishBAC:
 Highly anisotropic compliant core
 Thin central bending beam spine
 Stringers branch off to support skin
 Soft in camber direction, stiff spanwise
 Pre-tensioned elastomeric skin
 Fiber reinforced elastomeric matrix composite
 Antagonistic tendon drive system
 Non-backdriveable spooling pulley system
 “Rigid” main spar
 Carries global loads

3. FishBAC work to date
 3 generations of demonstrators
 Structural analysis and testing
 Aerodynamic simulation (low and
high-fidelity)
 Wind tunnel testing
 20-25% increase in Cl/Cd over a
traditional trailing edge flap
 Actuation system design
 Fluid-Structure Interaction
analysis
 Multi-objective optimization
 Mass, Cl/Cd,energy
 GA wrapped around FSI
FishBAC Mk 3.0
FishBAC Mk 2.0

4. FishBAC Work to Date – example results
Wind tunnel tests show a 20-25%
increase in L/D compared to flaps
for 0°≤ α ≤10°
Good agreement between low and
high fidelity aero models
Analytical model of stiffness
behaviour well validated
Fluid-Structure Interaction analysis predicts equilibrium
deformation under coupled aero and actuation loads
(not yet validated)
Analytical model of antagonistic tendon actuation
system has been validated

5. Adaptive Aspect Ratio (AdAR) Wing Concept
 “Adar” is Welsh for “bird” – the inspiration for the
smooth continuous span change we seek
 Capable of 100% increase in span of active section
 Compliant skin over mechanical core
 Four key technologies:
 Elastomeric Matrix Composite (EMC) skin
 Telescopic rectangular spar
 Sliding ribs
 Strap drive

6. Design Configuration
- The telescoping spar is rectangular and
overlaps into the non-morphing region
- The ribs slide over the spar and have
max/min distance constraints
- The EMC skin is bonded onto the ribs
- Pre-tension is applied before bonding
0.5 m1.0 m
1.0 m 1.0 m
Retracted state
Extended state
-A kevlar strap runs from the inner
spar to the outer and then to the
wing root
-Strap tension drives extension
-The strap winds onto a motor
driven drum
-Hyperelastic skin stretches over 130%
The skin is by far the most important design driver – as you will see in Ted’s talk tomorrow

7. Morphing Flap Transition
 The discrete ends of current trailing edge
flaps are a source of drag and noise
 SU’s answer:
 compliance based, passive transition
 Trailing edge deflection and angle are coupled
structurally: smooth and continuous
 Tensioned elastomeric skin surface
 High chordwise and through-thickness stiffness,
low camber and spanwise stiffness
 Applying for an EPO Patent… can’t show you
the cool bits yet!
Airbus A380: lots of flap gaps!
Rigid end
Flap end
Smooth and continuous 3D morphing
Modular design: retrofitable and replaceable

8. Negative Stiffness for Passive Energy
Balancing - Concept
 Compliant structures have intrinsic elastic stiffness
 Creates a severe design trade off:
 we want high structural stiffness to give good shape control and
aeroelastic response
 we also want low actuation requirements to minimize mass and
power penalties
What if we could passively balance the
stiffness of the compliant structure
with a negative stiffness spring?

9. Spiral Pulley Negative Stiffness Concept
 SPNS Device: a positive stiffness linear spring acting through a spiral
pulley which rapidly increases the moment arm of the force to turn
decreasing linear force into increasing torque with rotation.
Drive spring and load spring are in equilibrium over a wide range of rotations
90% reduction in
energy required
92% reduction in
max torque

10. Conclusions and Outlook
 We have created a family of solutions with shared DNA:
 Compliance based – exploiting anisotropy to focus compliance
 Simplicity of design – prescribed architectures
 Not afraid to strain! – reinforced elastomers create smooth continuous
surfaces
 Varying degrees of progress made in different areas
 FishBAC is currently the furthest along, but we’re making good progress
on the others
 Are looking to continue and expand our work
 Want to explore a wide range of applications
 Commercial airliners, UAVs, rotorcraft, wind turbines, tidal stream
turbines, etc.
 Keen to collaborate with government, academic, and industrial
partners

11. Cheers!
Dr. Benjamin K. S. Woods
b.k.s.woods@swansea.ac.uk