SHAPE MORPHING OF FLEXIBLE SURFACES AND ACTUATOR …

Technische Universität München

Lehrstuhl für Leichtbau (LLB)Institute of Lightweight Structures

SHAPE MORPHING OF FLEXIBLE SURFACES AND ACTUATOR INTERACTION

Horst Baier, Leri Datashvili

Institute of Lightweight Structures (LLB)Technische Universität München, Germany



Membrane and reflector structures

Advanced fiber composites / hybridmat. & structures

Smart Structures Multidisc. design optimization and procedures

Research areas at LLB / TU München



„Classical“ adaptive structures: dyn. load alleviation



Low speed

High speed

Human eye

Morphing biological systems

Flight systems Optical (RF) Systems



high loads and stiffness… and morphing

high shape precision… and morphing

Morphing Aerospace StructuresMassive change in geometry



Morphing wing: rereference mission



Morph. param. influence on diff. criteria



Spoke concept

Skin integrated actuators Pneumatic concept

Wing morphing machanisms



Institute for Lightweight Structures LLB

Morphing wing

Morphing actuators Morphing surfaces

?

Friswell, Swansea



Massively morphing sat reflectors …

... to achieve non-isotropic RF beam radiationin (space) antennas

requires actuators and a morphing surface with• low in-plane and shear stiffness

• moderate bending stiffness

• very low CTE

• good thermal and electr. conductivity



Micro-mech. FE model(stiffness, CTE, …)

Simul and test results

Triax C-fibre shell-membrane material (soft silicone matrix): CFRS

Structural and reflector material

• excellent thermo-mechanical properties• good RF properties• moderate - good morphing behavior



Triax CFR-matrices with different Young‘s moduli

Mat. properties and level of anistropy depend on specimen size



Possible actuator types

Stroke: 20mmForce: 15N

Low mass actuators with high strokes; space compatibility = ?

EAP „bubble“ actuator



Actuator – structure interface



Lab demonstration model

“Proper” concept also requires ..

…proper actuator length + alignment + smooth load introduction into morphing surface

Refl. membrane

Manually driven actuators in lab model

Actuator i/f toreflect. surface



Determination of actuator strokes

… typically 50 – 100 actuators per m2 of reflecting surface

Discretized goal shape generated shape

(step-wise sol. incase of nonlin. behav.)

with uij

displacement at dof

i from unit stroke at actuator j

xj

actual strokes to be determined from optim. problem

i= 1, .. N, N: number of dofs

of FEM

J= 1, .. m , m: number of actuators



Some typical results

•Surface rms deviation of actual shape vs. goal (required) shaperms < 0.15 mm (for 1 m diam. reflector)

•Surface rms deviation between simalation vs. test resultsrms < 0.1 mm

shape morphing amplitudes of 10-15 mmwith high spatial frequency possible

concurrent mechanical and RF simulation and optimization preferable / feasible? simultaneous determination of design (+mat.!) parameters preferable / feasible ? other / better mech. design options e.g. by higher integration level ?

Further open points:



Morphing in biol. cells flexible cell walls with morphable reinf.

Morphing in biology

lense

Actuating muscles

Human eye



Integrated Integrated displdispl. . fieldfield identification identification

Measurement of strain at

many positions

Reconstr. model using.

• modal data

• Krylov vectors

• other FEM data

• exp. data

[C]

0100200300400500600700800900

0

500-10

-8

-6

-4

-2

0

2

x 10-3

y [mm]

x [mm]

disp

lace

men

t[mm

]

real displacement fieldestimated displacement field

Displacement field

Real and reconstructed displ. field

FOS in CFRS



• high forces (many tons)

• high strokes

• moderate resolution

• low spatial frequency

• high reliability

• low mass / volume

• self locking

• moderate temp. range

•low frequency

• small forces

• small or high strokes

• high resolution (µm range)

• high spatial frequency

• good reliability

• low mass / volume

• self locking

• extreme temperature range

• quasi-static

Morphing requirements

Aero-elasticity RF-elasticity

Coupling Aeodyn. Coupling RF. structureModelling:

Struct.

Documents

SHAPE MORPHING OF FLEXIBLE SURFACES AND ACTUATOR …