Smart Materials for Automotive and Aircraft Design Materials, Basics and Examples
Agenda Smart Materials Materials, Basics, Applications Piezoceramics Shape-Memory-Alloys Dielectric Electroactive Polymers Rheological Fluids Advantages 2
Smart Materials An overview Smart materials are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimulation, such as stress, temperature, moisture, ph, electric or magnetic fields. Activation fields Electrical field Magnetic field Temperature Light... actuator sensor Material property geometry stiffness viscosity Electrical resistance Heat conductivity... Development of solid-state actuators Multi-functional Material is sensor an actuator in one element Actuator characterization by reachable stress and strain scaling by length and cross-section of material 3
Smart Materials An overview 4
Piezoceramics Mechanism: Deformation of dipoles in the chrystal creates a dislocation of charge carriers electrical voltage - High blocking forces (100N/mm2) - Small strains (0,2%) - Very high actuation frequency (>100kHz) Direct Effect Sensor Mode L (b) indirekter Effekt Indirect Effect V + - Fuel-Injektor Flexible Patch-Actuator 5
Piezoceramics Application Example Vibration Reduction Motivation: Improving the acoustic behaviour of lightweight automotive components Experimental analysis: Problem first bending mode of drive shaft at 210Hz Status Quo: Concept: Integration of piezoceramicactuators in automotive drive shafts Drive tests: Noise reduction of 12 db at 210 Hz System and control design Application/Integration (FRP) of Piezo-Patch-Actuators 6
Piezoceramics Application Example Injector Injector for direct fuel injection High pressure of up to 2000 bar Very quick reaction of piezo actuator Large forces (2500N), 40 µm stroke In production since 2000 Source: Bosch Source: Audi AG 7
Piezoceramics Application Example Tool Positioning Motivation: Extending limits of manufacturing processes to open new design possibilities Manufacturing of micro contours and micro structures Piezoactuators Spindle Auslegung und Konstruktion des adaptronischen Werkzeugsystems Tool Center Point Concept: High precision by means of piezo-based sub-kinematics Active control of cutting edge Deformation - oben - Adaptronic Tool System Deformation - Mitte - Target Contour 10 µm Machined Contour 8
Shape Memory Alloys Mechanism: Thermal induced Phase Transformation of NiTi changes the lattice structure (Martensite Austenit) changing of stress-strain behavior - High strains (5 %) - Very high Blocking Forces: 350 N/mm 2 - Low actuation frequency: <1Hz - Excellent spezific workload Miniaturization SM-Actuators made of different semifinished product σ T>A f Aktor gegen Feder blockierter Aktor T<M s freier Aktor ε Stress-Strain-Behavior Drive for pneumatic valves in automotive seats Source: Alfmeier specific workload [J/cm 3 ] 9
Shape Memory Alloys First Application 1970 Sourde: NASA Source: Intrinsic Inc. Quelle: Intrinsic Inc. 10
Shape Memory Alloys Application Example Petrol Cap Task: Releasing petrol cap Benefits: Lightweight design, cross section Drive characteristics: Fast switching Drive parameters: Reset by spring Force: 10 N Diameter: 0,3mm Deflection: 5 mm Length: 120mm Electric drive with gear head SMA-drive Parameter Electric Drive SMA-Drive Weight 104 g 10 g Number of parts 10 3 Cross section see figure see figure SMA-Drive completely noiseless Petrol cap release device 11
Shape Memory Alloys Application Example Pneumatic Valve First series application in cars Developed by sub-contractoralfmeier Präzision AG SMA based 3/3-way-valve applied in seats to realize massage function Produced in Mio quantities Source: Alfmeier : Alfmeier 12
Shape Memory Alloys Application Example Smartphone Camera Autofocus Currently realized by voice coil actuator Substitution by SMA actuator possible Several prototypes exist, but automated manufacturing expensive Autofocus with SMA, Source: Actuator Solutions GmbH Optical Image Stabilisation OIS New concept for compensation of low frequency vibrations excited by hand Lens moves agains movement of hand 2 SMA wire actuators realize tilting in two DoFs Series production follows OIS with SMA, Source: Cambridge Mechatronics Ltd. 13
Shape Memory Alloys Application Example Variable Geometry Jet Noozle Objective morph chevron shape to optimize engine performance Community noise reduction Shockcell noise reduction Cruise performance Fully integrated, distributed actuation Conventional components given additional capability Does NOT add weight Simple mechanisms Used in flight tests to develop 787 static fan chevrons Source: Boeing 14
Shape Memory Alloys Application Example Electrical Connector In electrical engineering connectors are commonly used for connecting and releasing electrical conductors if contact force decreases the conductor can become loose current density increases exceeding heat in the clamp area Solution: Integration of SMA-Element in the conmnector Arising heat causes geometry change of the SMA Elementes Actuation of force resets the contact and resistance decreases Thermal picture of a loosen connector Conventional connector SMA connector 15
Shape Memory Alloys Application Example Oxygen Mask Specifications of solenoid: Weight: 82 g Dimension: 21 cm³ Power input: 11 W Number of elements: 30 Specifications of SMA system: Weigth: 10g (-88%) Dimension: 4cm³ (-80%) Power input 1,8W (-84%) Number of elements: 5 (-83%) Example A380 (600 oxygen masks) possible weight reduction of 43 kg per flight Releasing device for oxygen masks: solenoid device with SMA vision: integrated SMA-actuator 16
Electroactive Polymers Mechanism: actuation caused by electrostatic forces between two electrodes squeeze the polymer compression in thickness and Expansion in width - Very high strains (10 %) - Medium blocking Forces: 0,1 N/mm 2 - High actuation frequency: >1kHz - Excellent efficiency, excellent specific workload Buckling EAP Actuator EAP Loudspeaker EAP driven airship 17
Electroactive Polymers Applications Energy Harvesting: EAP energy harvesting in shoes EAP ocean wave generator 18
Electroactive Polymers Applications Facade: Source: Decker Yeadon, New York/USA 19
Rheological Fluids Mechanism: Fluid changes its properties (e.g. viscosity) if a field (magnetic or electric) is applied, changes in fluidic properties - Very high shear strength - Low blocking Forces: N/mm 2 - high response frequency: >1000Hz - Unique fluidic properties functional integration MRF Damper MRF Clutch 20
Rheological Fluids Application Example Magnetic ride 21
Advantages Complexity of Smart Material Applications 22
Thank you very much! Kenny Pagel Fraunhofer Institute for Machine Tools and Forming Technology, Dresden kenny.pagel@iwu.fraunhofer.de 23