Fibre Composite Electromagnetic Interference Shielding Materials for use in Airborne Vehicles Presented by Adrian Berghorst School of Mechanical Engineering University of KwaZulu-Natal Work completed by Denver Maharaj and Adrian Berghorst. Supervisor: Dr. Chris Von Klemperer

Slide 2 © CSIR 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: Graphic from:

Slide 3 © CSIR 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 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 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:

Slide 6 © CSIR EMI Research EMI in aircraft may be classified into three sub-classes: 1. on-board systems 2.passenger carry-on devices 3.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 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 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 The best shielding solution was unidirectional carbon fibre laminates with filler and alumesh. EMI Research – FRP Laminates Hybrid powder doped unidirectional Metal mesh unidirectional

Slide 10 © CSIR EMI Research – FRP Laminates

Slide 11 © CSIR Adding discontinuous fillers to the adhesive. Several different adhesives. Varying filler fractions. EMI Research – Secondary Bonding Adhesive samples prepared for inspection.

Slide 12 © CSIR 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 EMI Research – Secondary Bonding

Slide 14 © CSIR EMSE Ratio (Solid/Bonded) = 0.97 (3% difference) Average Difference (Solid – Bonded) = 1.13 Db EMI Research – Secondary Bonding

Slide 15 © CSIR 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 Average conductivity: 0.31 Maximum Conductivity: 0.81 Minimum conductivity: 0.06 Electrical Conductivity – FRP Laminates

Slide 17 © CSIR Electrical Conductivity – Secondary Bonding Tested in accordance with ASTM D , Standard test method for volume resistivity of conductive adhesives. Electrical conductivity sample according to ASTM D2739.

Slide 18 © CSIR 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 % (by volume), 40.63% (by weight) Al in Adekit H9940.

Slide 19 © CSIR Tensile testing according to ASTM a, Standard test method for Tensile properties of plastics. Flexural testing according to ASTM , 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 Mechanical Strength – FRP Laminates

Slide 21 © CSIR Mechanical Strength – FRP Laminates

Slide 22 © CSIR 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 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 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 Boeing 787 Dreamliner graphic from Denel SeekerII graphic from: