Leichtbaukonstruktionen - ETH Z€¦ · Courtesy of Dr. Markus Zogg, Inspire ICS PAOLO ERMANNI...

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Paolo Ermanni23. September 2015

Vorlesung 151-3207-00L Leichtbau, HS 2015

Leichtbaukonstruktionen

23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 1

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§ Allgemeines über den Entwicklungsprozess

§ Leichtbaustrategien

§ Auslegungskriterien

Leitfaden


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Leichtbaukonstruktionen

Optimale GestaltEine möglichst gleichmässigeBeanspruchung in möglichst allenBereichen der Bauteile

Sicherheit gegen VersagenEine unter allen Betriebs-bedingungen ausreichende Sicherheit gegen Versagen infolge Bruch, Fliessen, Knicken, Beulen, zu grosse Deformation, Ermüdung etc.

WirtschaftlichkeitGeeignetes Material für das Bauteilmöglichst kostengünstige Fertigung

Die Bauteilgestalt ist so zu wählen, dass optimale

Gesamtlösungen resultieren


|| 9/23/15Gerald Kress 4

“Function and form are intimately related to one another.

The function describes what the purpose of a technical object is;; the form or structure describes how this product will do it.”

Ulman, D.G., The Mechanical Design Process, vol. 2, McGraw-Hill, New York (1997)

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Werkstoffwahl: Stahl, Aluminium, Titanium, FV-Kunststoffe…..

Topologie Gestaltung Abmessungen

Strukturmerkmale


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Automated structural analysis process

Quelle: Ch. Ledermann, Parametric Associative CAE Methods In Preliminary Aircraft Design, Diss. ETH Nr. 16778, 2006 23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 6

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Flügel General Arrangement

Quelle: M.C. Niu, Airframe Structural Design, Conmilit Press, 199123.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 7

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Vergleichsspannungen (von Mises)

Quelle: Ch. Ledermann, Parametric Associative CAE Methods In Preliminary Aircraft Design, Diss. ETH Nr. 16778, 2006


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Spannungsverteilung in der Haut nach der Optimierung



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Optimierte Dickeverteilung



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Optimization results

Best individual of initial generation Best individual after 60 generations

Fitness plot Design objective: mass



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Generische Produktentwicklung

Ledermann, Christoph, Parametric associative CAE methods in preliminary aircraft design, Diss. ETH Zurich Nr. 16778, Zürich, 2006

Conceptualdesign

Embodimentdesign Detail design


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§ Material-Substitution

§ Formleichtbau

§ Konzeptleichtbau (Bauweisen)


Leitfaden


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Show case: Sample dimensions

aluminum plate (reference):• length: l = 200 mm• width: w = 50 mm• thickness: talu = 4 mm• mass: malu = ρalu ⋅ l ⋅ w ⋅ talu = 108.0 g

plates made of alternative materials:• length: l = 200 mm• width: w = 50 mm• thickness: talt = varied to reach requested

performance• mass: malt = ρalt ⋅ l ⋅ w ⋅ talt

Courtesy of Dr. Markus Zogg, Inspire ICS


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Show case: loads

§ Weight comparison of monolithic plates made of different materials all with same length and width

§ Thickness designed for same…§ tensile stiffness§ tensile strength§ compression stiffness§ compression strength§ bending stiffness§ bending strength



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Lightweight material parameters

§ Reference (Aluminum alloy)

§ Key lightweight material parameters→→ E0 = 73 GPa;; σσmax-0 = 400 MPa;; ρρ0 = 2.7 ⋅⋅ 10³ kg/m³

2 x specific stiffness2 x specific stiffness > same specific strength and density→→ Estiff = 2 ⋅⋅ E0;; σσmax-stiff = σσmax-0;; ρρstiff = ρρ0

2 x specific strength2 x specific strength > same specific stiffness and density →→ Estrength = E0;; σσmax-strength = 2 ⋅⋅ σσmax-0;; ρρstrength = ρρ0

0.5 x density0.5 x density > same specific stiffness and specific strength →→ Edensity = 0.5 ⋅⋅ E0;; σσmax-density = 0.5 ⋅⋅ σσmax-0;; ρρdensity = 0.5 ⋅⋅ ρρ0



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reference

2 x specific stiffness

2 x specific strength

0.5 x density

Courtesy of Dr. Markus Zogg, Inspire ICS23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 17

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Courtesy of Dr. Markus Zogg, Inspire ICS 23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 18

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Material comparison

6401917.9steel - V2A

aluminum alloy (reference)

E-GF / Epoxy

CF-HT / Epoxy

CF-HM / Epoxy

CF-UHM / Epoxy

titanium (TiAl6 V4 F89)

densityρ

[103 kg/m³] quasi-isotropic

strengthσmax [106 N/m²]

quasi-isotropic

modulusE [109 N/m²]

400732.7

8901204.5

34118.91.88

40843.61.53

33566.61.55

22385.61.55source: Markus Zogg;; Neue Wege zum Recycling von faserverstärkten Kunststoffen;; Diss 11'946, ETH Zürich, 1997

properties

materials

laminates calculated with 50 %vol fiber contentCourtesy of Dr. Markus Zogg, Inspire ICS


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Material weight saving potential

GF/EP-qi

CF-UHM/EP-qi

CF-HM/EP-qi

CF-HT/EP-qisteelaluminum

titanium



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GF/EP-qi

CF-UHM/EP-qi

CF-HM/EP-qi


titaniumlimits

of metalslimits

of metals



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Materials to be compared: Material orientation

6401917.9steel - V2A

aluminum alloy (reference)

E-GF / Epoxy

CF-HT / Epoxy

CF-HM / Epoxy

CF-UHM / Epoxy

titanium (TiAl6 V4 F89)

densityρ

[103 kg/m³] uni-directional

quasi-isotropic

strengthσmax [106 N/m²]

uni-directional

quasi-isotropic

modulusE [109 N/m²]

400732.7

8901204.5

34118.91.88

40843.61.53

33566.61.55

22385.61.55source: Markus Zogg;; Neue Wege zum Recycling von faserverstärkten Kunststoffen;; Diss 11'946, ETH Zürich, 1997

properties

materials

laminates calculated with 50 %vol fiber content

-

-

-

38.0

113.0

183.8

242.2

-

-

-

1'015

1'219

927

632



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GF/EP-qi

CF-UHM/EP-qi

CF-HM/EP-qi


titanium

GF/EP-UD

CF-HT/EP-UD

CF-HM/EP-UD

CF-UHM/EP-UD



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quasi-isotropicunidirectional



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§ Formleichtbau



Leitfaden


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Direct loadintroduction

Maximization of themoment of inertia

Ribbing of structures

Application of curvedstructures and panelsheets

Adoption, wherereasonable, ofintegral constructions

Selective localreinforcement in themain load directions

Some design rules for lightweight structures (according to B. Kleint)


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Direct load-introduction

Directly introduce loads in the main structure

Avoid load deviation

Distribute loads over large surfaces

Locally support load-introduction

Source: B. Klein, Leichtbaukonstruktion, Berechnungsgrundlage und Gestaltung, 8. Auflage Vieweg und Teubner, 2009

Unfavourable Better Comments


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Maximization of the moment of inertia

Utilization of thin-walled profiles with

light supporting cores




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Ribbing of structures

Lattice panel sheet Studded panel sheet


Utilization of thin-walled profiles



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Application of curved structures and panel sheets


Curved shapes show an increase of the critical buckling loads compared to

flat ones

In curved plates and panels the

resistance against deflection and snap-through is increased



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Adoption of integral constructions




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Selective local reinforcement in main load directions


Corrugations increase panel

stability

Orient fibres in load direction



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Example: Wing structure

Source: M.C. Niu, Airframe Structural Design, Conmilit Press, 1991 23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 38

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§ Formleichtbau



Leitfaden


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§ Positive§ Combination of different materials is possible§ „Simple“ Recycling and Repair

§ Negative§ Weight§ Prone to corrosion

Structural components can be realized by assembling together single structural elements

Source: Eurocopter23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 40

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Integral construction: Single structural elements are co-bonded or co-cured together

Integral skin tear straps

Viable Repair Plans

Co-cured hat section stringers

Bolted frames

Fabric surface plies

Source: Boeing


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Composites in der A380


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§ Metallic Structures:§ Glare Technologies§ Extrusion Profiles in

conjunction with advanced welding Techniques

§ Composite Structures§ Tape-laying processes§ Preforming technologies in

conjunction with LCM-Processes (RTM, RFI)

§ Pultrusion technologies for Stringers and Beams

Technological Trends at Airbus (cont.)

[4] Neil Harris, The A380, Leader on Manufacturing technology, Farnborough 20th/21st July 2004


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l Large parts and complex shapesl Optimum ply distribution l First application on A380

(A380 rear section)

Solutions for complex fibre elements

[4] Neil Harris, The A380, Leader on Manufacturing technology, Farnborough 20th/21st July 2004


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Boeing 787: Airframe Material Selection:

Carbon laminate

Carbon sandwich

Fiberglass

Aluminum

Aluminum/steel/titanium pylons

53%

Source: Boeing


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Sandwich constructions are a good example for lightweightstructural elements

Laminate

Adhesive layer

Honeycomb

Adhesive layer

Laminate


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Sandwich: Typical core materials

Stegkern Wellblechkern Wabenkern

Massiv- oder Schaumstoffkern

gelochter Massiv- oder Schaumstoffkern !

Source: Dr. Habil. Alois Starlinger, Handouts of the lecture “Bemessen von Sandwichbauteilen”

HoneycombCorrugated core

Cellular materials (foams) or balsa

Web


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Load-carrying behavior of sandwich structures

zN

QMb

xσσN σσb ττ xz

h

zN

QMb

xσσN σσb ττ xz

STRESS-DISTRIBUTION IN NON-CONNECTED LAYERS

Source: Dr. Habil. Alois Starlinger, Handouts of the lecture “Bemessen von Sandwichbauteilen”

STRESS-DISTRIBUTION IN CONNECTED LAYERS


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Learning from nature§ Lightweight structures § Lightweight structures made of fiber

reinforced polymers allow high performance race cars with an extraordinary safety level

lightweightmaterials

integration of functions

material orientation

material arrangement



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Learning from nature§ Technical structures § tree-trunks carry the high loads of the tree

tops and can reach an age of several 100 years



material orientation




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materialorientation


nature

Learning from nature


§ Compared to natural structures, technical structures are (often) made of materials, with superior mechanical performance.

§ The excellent lightweight performance of natural structures is reached by:§ the designed anisotropy in the

material performance§ the optimal placement of the material

in structures with high geometrical complexity

§ integration of many functions into the structure


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Integration of functionsExample: Lightweight structure in transportation

acoustic treatment

interior surfacesupport for ... venting

hosehousing for ...

structure damping treatment

pipes for fluids

exterior surface

wires


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support for ...

venting hose

housing for ...

interior surface

acoustic treatment

structurewires damping treatment

pipes for fluids

exterior surface

1 multifunctional component



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transportation structure with add-on functionstransportation structure with add-on functions

multiple suppliers

multiple designs

multiple sets of tools

multiple part references

transportation structure with integrated functions

one supplier

one design

one set of tools

one part references


opportunity to save weight and costs23.09.15PAOLO ERMANNI - 151-3207-HS2015-K2-LEICHBAUKONSTRUKTIONEN 54

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§ BASIS: Lotus Evora§ CHALLENGE: The wheelbase has to be

extended by 30 cm in order to accommodate all the components

§ SOLUTION: rear end (everything behind the passenger compartment) made out of RFP § new rear structure made out of CFRP

sandwich§ new rear bodywork, partly as a sandwich

§ Training for 30 students on the example of a four-seat electric-powered sport car

Functions Integration – Example SunCar2011


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§ Built-in "Fail-Safe behavior" in the bodywork§ In the event of a crash, the bodywork can not break and no sharp-edged fragments

Functions Integration: Example SunCar2011


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§ Solar cells integrated in the vehicle roof and the hatchback§ Solar cells are integrated directly into the body



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§ Built-in thermal insulation of the batteries in the sandwich structure of the chassis§ The foam core has structural functions and

also serves to isolate the batteries§ Electrical conductors have been partially

integrated into the composite structure § Instead of additional cables in channels



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§ Integrated heating/cooling circuits in the composite structures have been object of a bachelor thesis


Leichtbaukonstruktionen - ETH Z€¦ · Courtesy of Dr. Markus Zogg, Inspire ICS PAOLO ERMANNI...

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