Auxetic materials and structures to be used in morphing aircraft applications

1. Morphing with auxetic materials
and structures: a design
perspective
Fabrizio Scarpa, Giuliano Allegri
f.scarpa@bristol.ac.uk,
giuliano.allegri@bristol.ac.uk
www.bris.ac.uk/composites

2. Acknowledgements
FP6-NMP-STRP-2004-01364 CHISMACOMB, FP7-NMP3-
LA-2010-246067 M-RECT, US Army ARO, UK TSB 16093
REACTICS, Royal Society/China NSF
Massimo Ruzzene, Alessandro Spadoni, Jamie Martin,
Chrystel Remillat, M. Roshdi Hassan, Davide Bornengo,
Kalyan Hazra, Katarzyna Boba, Robin Neville, Arthur Monti,
Thomas Trehard, Yijin Chen, Yangqing Hou, Kismat Virk,
Marco Marsh, Carmine Porcaro, Xabier Otegui-Van Leuuw,
Jinsong Leng
Morphing Aircraft Seminar–
Bristol, 26/03/2013

3. Content
• Introduction
• Chiral honeycomb morphing concept
• PEEK SILICOMB curved honeycombs for large
deflections
• Gradient cellular structures
• Kirigami wingbox for MAV/UAV
• Elastomeric auxetic skins
Morphing Aircraft Seminar–
Bristol, 26/03/2013

4. Introduction
• From the Greek auxetos: “that can expand”
• Indicates Negative Poisson’s ratio (NPR) materials
− 1 < ν < 0.5 Homogeneous, isotropic solid
E1ν 21 = E2ν12 Special orthotropic solid
(
3FR 2 1 − υ 2 ) Central deflection
δ= of a clamped
16 Et 3 circular plate
1 Hardness –
H∝ increase with NPR
2 23
(1 −ν ) – the material
wraps around the
indenter
Synclastic curvature – easy
manufacturing of dome-shaped
structures
Morphing Aircraft Seminar–
Bristol, 26/03/2013

5. Chiral topologies
(D. Prall and R. Lakes, Int. J. Mech.
Sci., 39, 305-314, 1996)
• Hexagonal chiral (hexachiral)
honeycomb
• Rotations of the nodes induce
bending of the ligaments
• Isotropic in-plane properties (ν = -1)
• Constant ν for large deformations
(~ 25 %)
(A. Alderson et al., 2010. Comp. Sci. Tech. 70, 1042. Special Issue on Chiral Smart Honeycombs)
(Y. J. Chen, F. Scarpa, Y. J. Liu, J. S. Leng, 2013 . Int. J. Solids Struct. 50, 996.)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

6. Chiral wingbox concept
Aeroelastic tailored
continuous camber airfoil
Actuation at high frequencies for BL control
through bumps
(Bornengo D., Scarpa F., Remillat C D L., 2005. IMechE Part G: J. Aerospace Eng. 219,185)
(Spadoni, A., Ruzzene, M., Scarpa, F., 2006. J Int. Mat. Syst. Struct. 17(11), 941.
(Martin J. et al, 2008. Physica Status Solidi B 245(3), 570)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

7. Chiral SMA antenna demonstrator
u Chiral topology offers NPR ~
-1 and isotropic dilation when
a thermal loading is applied
u The mechanism has been used
to develop an antenna
prototype for ESA with SMA
ligaments
(S Jacobs, C Coconnier, D DiMaio, F Scarpa, M Toso, J Martinez, 2012. Smart Materials and Structures 21 (7), 75013-75024)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

8. Zero-ν SILICOMB structures
Ø Cellular structures with ν = 0 proposed for 1D
morphing of wings and blades
Ø Used also as scaffolds for tissue engineering of
cardiac anisotropy
Ø SILICOMB topology is alternative to accordion
honeycomb, with higher degree of tailoring for
the in-plane and out-of-plane properties
(R. Olympio, F. Gandhi, 2009. J. Int. Mat. Syst.
Struct. DOI: 10.1177/1045389X09355664 )
(Attard, D. and Grima, J. N. 2010. Phys. Stat. Solidi B 248(1), 52)
Grima, J. N. et al, 2012. Proc. Royal Soc. A. DOI: doi: 10.1098/rspa.2011.0667(C. Lira,
F. Scarpa, M. Olszewska, M. Celuch, 2009. Physica Status Soldi B, 246(9), 2055)
(C. Lira, F. Scarpa, Y. H. Tai, J. R. Yates, 2011. Comp. Sci. Tech. 71, 1236)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

9. SILICOMB – Curved honeycombs
• SILICOMB curved cellular panels
manufactured from PEEK films using Kirigami
techniques (Origami + cuts)
• Samples subjected to 3-point tests on
special DTC rig with SS conditions
• Linearity of the deformation until ~ 25 %
• Samples flattened completely
• Return to original shape with < 1 % residual
vertical strain
(FP7 NMP4-LA-2010-246067 M-RECT project, Report D5.20, University of Bristol, 2012)
(Y. J. Chen, F. Scarpa, C. Remillat, I. R. Farrow, Y. J. Liu, J. S. Leng, 2013. J. Intell. Mat. Syst. Struct. Submitted)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

10. Gradient cellular configurations
Gradient cellular Polymorphism of gradient cellular
structure for fan structures under applied loads
blades cores
• Gradient cores provides variable stiffness and curvature distributions within the panel
• Provide also tailoring of the dynamic stiffness properties
(C. Lira, F. Scarpa and R. Rajasekaran, 2011. J. Int. Mat. Syst. Struct. 22, 907)
(Y. Hou, Y. P. Tai, F. Scarpa, J. R. Yates, B. Gu, 2013. Comp. A. http://dx.doi.org/10.1016/j.compositesa.2013.02.007 )
Morphing Aircraft Seminar–
Bristol, 26/03/2013

11. Kirigami process for MAV/UAVs
u Complex geometries can be
manufactured using modular
moulds and thermosets/
thermoplastics prepregs
u Possibility of embedding sensors/
actuators for morphing during the
production process
(K. Saito, F. Agnese and F. Scarpa, 2011. J. Int. Mat. Syst. Struct. 22, 935)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

12. Kirigami wingbox concept for MAVs
u Different cellular configurations
lead to variations of torsional,
bending stiffness and mass
distributions
u Higher divergence speeds with
auxetic configurations
u Modular structure with distributed
actuators/sensors for MAVs
(C. Porcaro, 2012. MEng Report, University of Bristol)
(X. Otegui Van Leuuw, 2013. MSc IASD Report, University of Bristol )
Morphing Aircraft Seminar–
Bristol, 26/03/2013

13. Elastomeric auxetic skins
• Silicone/carbon elastomeric composites
developed for morphing aircraft
applications
• Very high auxetic effect with variable
stiffness (νxy up to -34)
• Failure at 3.5 % strain
• High loss factor (~ 0.52) in vibration
transmissibility
(YJ Chen, F Scarpa, IR Farrow, YJ Liu, JS Leng, 2013. Smart Materials and Structures 22 (4), 045005)
Morphing Aircraft Seminar–
Bristol, 26/03/2013

14. Conclusions
• Auxetic configurations can be used in shape
morphing. Their deformation mechanism is static
(linearly scalable)
• Chiral lattices can be used to design wingboxes with BL
control properties and continuous camber variation
• Zero-ν curved and gradient cellular structures offer
potential for large recoverable deformations and
polymorphism
• Elastomeric auxetic polymeric/carbon skins offer
large strain deformation, stiffness tailoring and
vibration transmissibility performance
Morphing Aircraft Seminar–
Bristol, 26/03/2013

15. Thank you for your
attention
Morphing Aircraft Seminar–
Bristol, 26/03/2013