new Concept For Composite Compression Springs · possible variations in fiber orientation,...

Institute for Design and Precision Engineering

Machine Elements Group

Research Group „Wire and Springs“

Univ.-Prof. Dr.-Ing. Ulf Kletzin

9th INTERNATIONAL CONGRESS

of Spring IndustryTaormina, Italy - 29.09.2017

NEW CONCEPT FOR COMPOSITE

COMPRESSION SPRINGSby

Martin Petrich, Jorge Llimpe, Stefan Titze, Ulf Kletzin

Institute for Design and Precision Engineering, Machine Elements Group

Department of Mechanical Engineering, Technische Universität Ilmenau, Germany

[email protected]

03677/69-1865

WB 428029.09.2017

Martin Petrich

[email protected]

+49 (0) 3677/69-1865

TU Ilmenau - Germany

Campus of TU Ilmenau© Stephan Pöhler – www.helibild.de





Page 1

1. Introduction to composite springs

2. Theoretical description

3. Development of a manufacturing method

4. Comparison of theoretical and practical results

5. Conclusion and Outlook

NEW CONCEPT FOR COMPOSITE COMPRESSION SPRINGS

AGENDA

Martin Petrich

[email protected]

+49 (0) 3677/69-1865

TU Ilmenau - Germany 29.09.2017





Page 2







AGENDA

Martin Petrich

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+49 (0) 3677/69-1865






Page 3

Composite production

(in general) [1]

Leaf spring [2] Meander spring

Bellow spring [4] Disc spring [4]

Power spring [5] Spiral spring [6]


[2]

Martin Petrich

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Layering / Shaping /

Fibers Matrix Laminate (ply) Pressing / Curing → Composite

[3]





Page 4

C-spring [7] [8]

Helical compression spring

[9] [10]


Martin Petrich

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Summary – composite springs

+ investigated and used for over 50 years

+ excellent spring characteristics

+ corrosion resistance, internal damping,

fatigue behaviour

+ lightweight design

+ functional integration

- expensive moulds

- slow manufacturing (handwork, curing time)

- often high safety factors





Page 5

➢ Fiber composites represent excellent spring materials:

• very good mechanical and chemical properties at low density

• various types of fibers (textiles) and matrix materials available

• redundant fatigue behaviour (detectable)

• local layup adaptions for precise adjustment of characteristics

• …

➢ Why should a new composite compression spring be developed?

• compression springs are frequently used

• simple shape for easier and cost efficient production

• usage of common (flat) textile fabrics

• various possibilities (parameters) for adjusting the spring curve

➢ The composite volute spring with rectangular cross section

is a suitable solution for the demands!


Motivation

Martin Petrich

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Calculation?

Manufacturing?





Page 6







AGENDA

Martin Petrich

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Page 7

According to [11], the force-displacement-curve is

linear for s ≤ 0,6 sc:

𝐹 = 𝑞3 ⋅2⋅𝐺⋅𝑏⋅𝑡3

𝜋⋅𝑛𝑓⋅ 𝑟𝐾1+𝑟𝐾𝑛 ⋅ 𝑟𝐾12 +𝑟𝐾𝑛

2 ⋅ 𝑠

with 𝑞3 =𝛽𝑡−0,63

3⋅𝛽𝑡and 𝛽𝑡 = 𝑏/𝑡

G – shear modulus

b – strip width

t – strip thickness

nf – number of active coils

2. Theoretical description of the volute spring

Spring curve – linear part

29.09.2017

Martin Petrich

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[11]





Page 8

For s > 0,6 sc the number of active coils nf

reduces, the characteristic becomes

non-linear (progressive):

𝐹 = 𝑞3 ⋅𝐺⋅𝑏⋅𝑡3

𝜋⋅𝑟𝐾𝑥2 ⋅𝑛𝑓 𝑟𝐾1+𝑟𝐾𝑛

⋅ 𝑠

with 𝑟𝐾𝑥 = 𝑟𝐾𝑛 +𝑚 ⋅ (𝑟𝐾1 − 𝑟𝐾𝑛)

and 1 ≥ 𝑚 ≥ 0 for segmentation into intervals.

This approach can be used to analyze a spring

that is known in its dimensions.

A dimensioning (design) on this basis is not

possible due to the numerous parameters

to be determined.

Evaluation of test designs


Spring curve – non-linear part

29.09.2017

Martin Petrich

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[11]





Page 9

Composite strips consist of several layers with

possible variations in fiber orientation,

thickness, fiber material, etc.

For complex layups, a common procedure is the

calculation of the engineering constants, based

on the Classical Laminate Theory (CLT).

Otherwise, test specimen can be produced for

more accurate input values.


Martin Petrich

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Mechanical properties of the composite

Mt

F

Mt

The strip material of the spring is basically

loaded by a torsion moment Mt, which results

from the force. Therefore, the shear modulus

G has to be considered.

Simplification





Page 10


Martin Petrich

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Spring examples - Mechanical properties of the composite

In this example, the engineering constants are calculated with

the Excel-sheet AlfaLAM [12]

Input values:

• 8 layers of E-glass fibers with epoxy matrix

• Fiber orientation 45°and - 45°(symmetrical)

• Fiber volume content 𝜑 = 0,4 (medium value)

Output values:

• Stiffness matrix and flexibility matrix of composite

• Strain and stress (layer wise)

• Coefficients for engineering





Page 11


Martin Petrich

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Spring examples – glass fibers

Spring 1

b = 40 mm

t = 1,52 mm

nf = 3

rK1 = 28,5 mm

rK3 = 21 mm

L0 = 100 mm

G = 8674 N/mm²

Spring 2

b = 32 mm

t = 0,75 mm

nf = 3,5

rK1 = 17,8 mm

rK3,5= 13,5 mm

L0 = 105 mm

G = 8674 N/mm²

[11]

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60

Fo

rce

[N

]

Displacement [mm]

Calculation of glass fiber volute springs

Spring1_Calc_linear

Spring1_Calc_nonlinear

Spring2_Calc_linear






Page 12







AGENDA

Martin Petrich

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+49 (0) 3677/69-1865






Page 13


Winding technology

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Preparation

• Manufacturing a winding core

• Preparation of a carrier film

• Pre-cutting fibers/textiles

Lamination• Fiber layering

• Wetting with resin

Winding• Winding from inner

to outer diameter

• Curing (tempering)

Post-processing

• Releasing from core

• Removing carrier film

• Grinding / cleaning





Page 14


Martin Petrich

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Testing the manufacturing method

Carrier filmGlass fibers

Winding

Demoulding

Finishing





Page 15







AGENDA

Martin Petrich

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Page 16

Spring 1

b = 40 mm

t = 1,52 mm

nf = 3

rK1 = 28,5 mm

rK3 = 21 mm

L0 = 100 mm

G = 8674 N/mm²

Spring 2

b = 32 mm

t = 0,75 mm

nf = 3,5

rK1 = 17,8 mm

rK3,5= 13,5 mm

L0 = 105 mm

G = 8674 N/mm² 0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60

Fo

rce

[N

]

Displacement [mm]

Measurements - Glass fiber springs

Spring1_#1

Spring1_#2

Spring1_#3

Spring2

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60

Fo

rce

[N

]

Displacement [mm]

Comparison of calculated and measured forces- Glass fiber springs -

Spring1_Calc_linear


Spring1_#1

Spring1_#2

Spring1_#3

Spring2_Calc_linear


Spring2


Martin Petrich

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Measurements of spring characteristics – glass fibers





Page 17

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60

Fo

rce

[N

]

Displacement [mm]

Measurements - Carbon fiber springs

Spring1_#1

Spring1_#2

Spring1_#3

Spring3

Spring 1

b = 40 mm

t = 1,32 mm

nf = 3

rK1 = 28,5 mm

rK3 = 21 mm

L0 = 100 mm

G = 24316 N/mm²

Spring 3

b = 11 mm

t = 1,32 mm

nf = 3,25

rK1 = 19 mm

rK3,5= 15,5 mm

L0 = 100 mm

G = 11906 N/mm²

(+20°/-20°layup)


Martin Petrich

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Measurements of spring characteristics – carbon fibers

0

20

40

60

80

100

120

140

160

0 10 20 30 40 50 60

Fo

rce

[N

]

Displacement [mm]

Comparison of calculated and measured forces- Carbon fiber springs

Spring1_Calc_linear


Spring1_#1

Spring1_#2

Spring1_#3

Spring3

Spring3_Calc_linear






Page 18


Martin Petrich

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+49 (0) 3677/69-1865


Comparison of calculated spring rates

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

0 10 20 30 40 50 60

Sp

rin

g r

ate

[N

/m

m]

Displacement [mm]

Comparison of spring characteristics GF_Spring1_linearGF_Spring1_nonlinearGF_Spring2_linearGF_Spring2_nonlinearCF_Spring1_linearCF_Spring1_nonlinearCF_Spring3_linearCF_Spring3_nonlinear





Page 19


Martin Petrich

[email protected]

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Simplified comparison to helical compression springs (steel wire)

• Composite springs

are not competitive in

case of these properties

• The composite springs

are not optimized

• Other advantages have

to be considered for the

choice of composite

materials

→ functional integration of

damping characteristics

(replacement of spring-

damper-units for example)

“Productivity”:

- composite: about 1 per mould in 4-12 hours, with tempering, depending on matrix

- steel springs: several per second* According to DIN 2098

Spring 1 Helical spring* Spring 1 Helical spring*

Glass fiber Spring Steel Wire Carbon fiber Spring Steel Wire

d mm - 1,25 - 2,00

b mm 40 - 40 -

t mm 1,52 - 1,32 -

nf 3 18,5 3 8,5

rmin mm 21 - 21 -

rmax mm 28,5 - 28,5 -

Dm mm - 10 - 20

L0 mm 100 93,5 100 94

Ln mm 40 30 40 27,6

R linear N/mm 1,35 1,37 2,50 2,44

Fn N 80 87,1 120 162

G N/mm² 8674 81500 24316 81500

Weight g 70,5 6,2 49,3 16,4

Material costs € < 5 € << 1 € < 10 € << 1 €





Page 20

Spring1 dimensions

b = 40 mm t = variable

nf = 3 nt = 5

rK3 = 21 mm rK1 = variable

a = 0,1 mm

Comparison by spring rate R

→ significant advantages for fiber materials

→ good accordance to the weight of the test springs

Steel CFRP GFRP

ρ [g/cm³] 7,90 1,42 1,74

G [GPa] 70,0 24,3 8,7

R [N/mm] 2,33 2,23 2,24

t [mm] 0,85 1,25 1,90

m [g] 197 54 108

Rtest [N/mm] - 2,5 1,35

ttest [mm] - 1,32 1,52

mtest [g] - 49,3 70,5


Martin Petrich

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Simplified comparison to volute springs (steel strip) linear calculation

0

5

10

15

20

25

30

35

40

45

50

0,0 0,5 1,0 1,5 2,0 2,5 3,0

Spri

ng

rate

R [

N/m

m]

Strip thickness t [mm]

Material comparison

R steel R CFRP R GFRP

0

5

10

15

20

25

30

35

40

45

50

0,0 0,5 1,0 1,5 2,0 2,5 3,0

Spri

ng

rate

R [

N/m

m]


Material comparison


0

50

100

150

200

250

300

0

5

10

15

20

25

30

35

40

45

50

0,0 0,5 1,0 1,5 2,0 2,5 3,0

Wei

ght

m [

g]

Spri

ng

rate

R [

N/m

m]


Material comparison


m steel m CFRP m GFRP

0

50

100

150

200

250

300

0

5

10

15

20

25

30

35

40

45

50

0,0 0,5 1,0 1,5 2,0 2,5 3,0

Wei

ght

m [

g]

Spri

ng

rate

R [

N/m

m]


Material comparison



0

50

100

150

200

250

300

0,0 0,5 1,0 1,5 2,0 2,5 3,0

Wei

ght

m [

g]


Material comparison






Page 21







AGENDA

Martin Petrich

[email protected]

+49 (0) 3677/69-1865






Page 22

- Composite springs have various advantages

- Composite volute spring was not tested and used so far

- Existing theoretical description can be used in first proximity

- Mechanical properties can be calculated by common theories

- Manufacturing method was developed and successfully approved

- Measurements of force-displacement-curves have shown a good comparability to

calculated curves for both glass and carbon fiber composites

- Almost linear spring characteristics, no fatigue up to the block length, no setting

- Simplified comparison to helical steel wire springs shows disadvantages in weight

but significant advantages by comparing volute springs


Conclusion

29.09.2017

Martin Petrich

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+49 (0) 3677/69-1865






Page 23

- Adjustment of spring characteristics by several

parameters (layup, fiber orientation, coil distance)

- Testing different load cycles and fatigue properties

- Investigations on frictional behaviour and damping

- Improved production / automation

- FEM-simulations for layer wise stress/strain/fatigue analysis

- …


Outlook

29.09.2017

Martin Petrich

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+49 (0) 3677/69-1865






Page 24

Thank you for your kind attention!

M. Sc. Martin Petrich

E-Mail: [email protected]

Phone: +49 (0) 3677 69 1865

Research Group Wire and Springs


Max-Planck-Ring 12

Werner-Bischoff-Bau WBB 4260

98693 Ilmenau

Germany

Martin Petrich

[email protected]

+49 (0) 3677/69-1865


mailto:[email protected]





Page 25

Ressources[1] R&G Faserverbundwerkstoffe GmbH: „Composite materials handbook“;

URL: http://www.r-g.de/w/images/6/69/R%26G_Handbuch.pdf; Waldenbuch, 2009

[2] Stimpfl, J.: “Leichtbau in faserverstärktem Kunststoff für Fahrwerksfedern im Automobil“;

VDFI Lecture event „Federn aus faserverstärkten Kunststoffen“, Siegen, 20.04.2016

[3] DANTO-Invention GmbH & Co. KG: „DANTO Feder“; URL: http://www.hannovermesse.de/

produkt/feder-aus-faser-kunststoff-verbunden/2310289/L161872; last visit: 26.07.2017

[4] Hufenbach, W.; Werner, J.; Körner, I.; Köhler, C.: „Neuartige Leichtbaufedern in Faserverbundbauweise –

Bauweisen / Auslegung / Fertigung“; Ilmenauer Federntag; 2010

[5] Scharr, G.: „Faserverstärkte Kunststoffe – Federwerkstoffe für den Leichtbau“; VDI-Berichte Nr. 1972; 2006

[6] Zemann, R.: „Federleicht“; URL: https://www.tuwien.ac.at/aktuelles/news_detail/article/8511/;

last visit: 26.07.2017

[7] Otto Bock Healthcare Deutschland GmbH: „C-Walk Prothesenfuß 1C40“;

URL: http://www.ottobock.de/prothetik/produkte-a-bis-z/prothesenfuesse/c-walk/; last visit: 26.07.2017

[8] Michel, S.: „Schneckenblattfeder“; URL: http://schneckenblattfeder.de/brochure/sbf-produktinfo.pdf;


[9] Sardou SA: „Helical coil springs“; URL: http://www.sardou.net/images/ressort/DSC01555_petit.JPG;


[10] Leichtbauzentrum Sachsen GmbH: „Schraubendruckfeder aus Faserverbundkunststoff“;

URL: http://industrieanzeiger.industrie.de/wp-content/uploads/2/9/2997285.jpg; last visit: 26.07.2017

[11] Meissner, M.; Schorcht, H.-J.; Kletzin, U.: „Metallfedern“; 3. Auflage, Springer Vieweg, 2015

[12] Weber, T.: „AlfaLam“; Excel-sheet Version 1.3.1; URL: http://www.klub.tu-

darmstadt.de/forschung_klub/downloads_3/downloads_klub.de.jsp; last visit: 30.07.2017

Martin Petrich

[email protected]

+49 (0) 3677/69-1865


new Concept For Composite Compression Springs · possible variations in fiber orientation,...

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Transcript of new Concept For Composite Compression Springs · possible variations in fiber orientation,...