fibre composite electromagnetic interference shielding materials for use in airborne vehicles...

Fibre Composite Electromagnetic Interference Shielding Materials

for use in Airborne Vehicles

Presented by Adrian BerghorstSchool of Mechanical Engineering

University of KwaZulu-Natal

Work completed by Denver Maharaj and Adrian Berghorst.Supervisor: Dr. Chris Von Klemperer

Slide 2 © CSIR 2006 www.csir.co.za

• Primary goal: Produce an electromagnetic shielding solution a for fibre reinforced polymer (FRP) airframe.

• Secondary goal: Produce a lightning protection solution for a fibre reinforced polymer (FRP) airframe.

Goals of the Research.

SeekerII graphic from: http://www.denel.co.za/Aerospace/UAV.asp

Graphic from: http://chamorrobible.org/gpw/gpw-20061026.htm

Slide 3 © CSIR 2006 www.csir.co.za

• Design a suitable FRP with adequate electromagnetic shielding efficiency (EMSE) and electrical conductivity.

• Design a suitable secondary bonding solution with adequate EMSE and electrical conductivity.

Areas of Research.

Slide 4 © CSIR 2006 www.csir.co.za

• Electromagnetic interference (EMI) is a disturbance or disruption in the performance of an electronic device due to the transmission of radiation from a source.

• EMI is prevented by placing a shield between the source and the device.

Electromagnetic Interference Information.

Slide 5 © CSIR 2006 www.csir.co.za

Lightning Strike Information.

• On average a commercial airliner is struck by lightning once a year.

• Lightning strikes the aircraft, the current travels along the skin, and exits at an extreme point.

• Eg: nose to vertical stabiliser.

Graphics from: http://www.cst.com

Slide 6 © CSIR 2006 www.csir.co.za

EMI Research

• EMI in aircraft may be classified into three sub-classes: 1. on-board systems 2.passenger carry-on devices3.externally generated EMI

• The frequency range of interest in this work is 800 MHz to 5 GHz.• Interference can range from slight static to interference with

avionics.• EMI interacts with a shielding material by reflection, absorption, or

transmission.

Slide 7 © CSIR 2006 www.csir.co.za

EMI Research – FRP Laminates

• Adding discontinuous filler materials to the resin.

• Including continuous aluminium mesh layer in the reinforcing.

• Using material with better electrical conductivity (carbon fibre as opposed to glass fibre).

Aluminium powder under a microscope.

Alumesh 401 when viewed at 100x magnification

Slide 8 © CSIR 2006 www.csir.co.za

• Materials used:• Carbon Fibre

• Stitched, woven, & Unidirectional.• Discontinuous Filler

• Aluminium, & Copper.• Resin

• LR20 (LH281 Hardener), & Prime 27 (Prime 20 slow Hardener)

• Continuous Mesh Layer• Alumesh 401

EMI Research – FRP Laminates

The Scientific Atlanta 5754 compact antenna range test set-up at the

University of Pretoria

Slide 9 © CSIR 2006 www.csir.co.za

• The best shielding solution was unidirectional carbon fibre laminates with filler and alumesh.

EMI Research – FRP Laminates

0

5

10

15

20

25

30

35

40

45

0 1000 2000 3000 4000 5000 6000

Frequency (MHz)

EM

SE

(d

B) Aluminium Plate

No Filler

7.5% Filler

15% Filler

0

5

10

15

20

25

30

35

40

45

0 1000 2000 3000 4000 5000 6000

Frequency (MHz)

EM

SE

(d

B) Aluminium Plate

No Filler

1 Ply

2 Ply

Hybrid powder doped unidirectional Metal mesh unidirectional

Slide 10 © CSIR 2006 www.csir.co.za

EMI Research – FRP Laminates

% Difference in Average Shielding Effectivness Relative to Aluminium Plate

-6

-4

-2

0

2

4

6

8

10

12A

l bas

e

0%al

7.5%

al

15%

al

7.5%

cu

15%

cu

7.5%

alcu

15%

alcu

1 la

yer

2 la

yers

Laminate

[%]

Unidirectional

Woven

Stitched

Slide 11 © CSIR 2006 www.csir.co.za

• Adding discontinuous fillers to the adhesive.

• Several different adhesives.

• Varying filler fractions.

EMI Research – Secondary Bonding

Adhesive samples prepared for inspection.

Slide 12 © CSIR 2006 www.csir.co.za

• Materials used• Adhesives

• Adekit H9940, Araldite 420, Cy221.

• Discontinuous Fillers• Aluminium, Copper, & Silver.

• Filler Fractions Tested• 0% → 15% by weight• 0% → 25% by volume

EMI Research – Secondary Bonding

The Scientific Atlanta 5754 compact antenna range test set-up at the

University of Pretoria

Slide 13 © CSIR 2006 www.csir.co.za

EMI Research – Secondary Bonding

Shielding Properties of Adhesives

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00

750.

0000

1015

.625

0

1281

.250

0

1546

.875

0

1812

.500

0

2078

.125

0

2343

.750

0

2609

.375

0

2875

.000

0

3140

.625

0

3406

.250

0

3671

.875

0

3937

.500

0

4203

.125

0

4468

.750

0

4734

.375

0

5000

.000

0

Frequency (MHz)

EM

SE

(d

B) Solid Metal

Adekit (V)

Adekit (H)

Araldite (V)

Araldite (H)

Slide 14 © CSIR 2006 www.csir.co.za

• EMSE Ratio (Solid/Bonded) = 0.97 (3% difference)• Average Difference (Solid – Bonded) = 1.13 Db

Shielding Properties of Adhesives

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

Frequency (MHz)

EM

SE

(d

B)

Adekit (V)

Adekit (H)

Araldite (V)

Araldite (H)

EMI Research – Secondary Bonding

Slide 15 © CSIR 2006 www.csir.co.za

• Tested in accordance with ASTM B193-02, Standard test method for Resistivity of electrical conductor materials.

Electrical Conductivity – FRP Laminates

The RCL universal bridge circuit used to measure electrical resistance

Slide 16 © CSIR 2006 www.csir.co.za

• Average conductivity: 0.31 • Maximum Conductivity: 0.81• Minimum conductivity: 0.06

Electrical Conductivity – FRP Laminates

Conductivity

0.0000

0.1000

0.2000

0.3000

0.4000

0.5000

0.6000

0.7000

0.8000

0.9000

-1 1 3 5 7 9 11 13 15

Filler [%] or Mesh Layers (5 = 1 layer & 15 = 2 layers)

Co

nd

uct

ivit

y [O

hm

/cm

]stitched al

stitched cu

stitched al+cu

stitched mesh

woven al

woven cu

woven al+cu

woven mesh

unidirectional al

unidirectional cu

unidirectional al+cu

unidirectional mesh

Slide 17 © CSIR 2006 www.csir.co.za

Electrical Conductivity – Secondary Bonding

• Tested in accordance with ASTM D 2739-72, Standard test method for volume resistivity of conductive adhesives.

Electrical conductivity sample according to ASTM D2739.

Slide 18 © CSIR 2006 www.csir.co.za

• Electrical conductivity in excess of 8.62

• Samples tested up to 25% filler by volume.

Electrical Conductivity – Secondary Bonding

24.97% (by volume), 72.37% (by weight) Cu in Araldite 420.

24.78% (by volume), 40.63% (by weight) Al in Adekit H9940.

Slide 19 © CSIR 2006 www.csir.co.za

• Tensile testing according to ASTM 638-02a, Standard test method for Tensile properties of plastics.

• Flexural testing according to ASTM 6272-02, Standard test methods for Flexural properties of unreinforced and reinforced plastics and electrical insulating materials by four-point bending.

Mechanical Strength – FRP Laminates

Tensile test

Flexural test

Slide 20 © CSIR 2006 www.csir.co.za

Mechanical Strength – FRP Laminates

Slide 21 © CSIR 2006 www.csir.co.za

Mechanical Strength – FRP Laminates

Slide 22 © CSIR 2006 www.csir.co.za

• Lap Shear Testing According to ASTM D 1002– 01, Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal)

Mechanical Strength – Secondary Bonding

Sample in lap shear testing.

Slide 23 © CSIR 2006 www.csir.co.za

• Initial drop in strength• 66.3% Aluminium• 56.4% Copper• 41.4% Silver

Mechanical Strength – Secondary Bonding

• Lap shear testing to be done on volume basis

Slide 24 © CSIR 2006 www.csir.co.za

Conclusion• Better strength properties compared to orthodox

materials.• Better fatigue and corrosive properties.• Weight saving due to increased strength properties.• Long term cost saving.

• Higher initial cost compared with orthodox materials.• Difficulty in shielding from EMI.• Difficulty in conducting lightning strike.

Slide 25 © CSIR 2006 www.csir.co.za

Boeing 787 Dreamliner graphic from www.boeing.com

Denel SeekerII graphic from: http://www.denel.co.za/Aerospace/UAV.asp