Laser hole drilling and texturing (for joining) of composites

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AILU Workshop: Laser processing of polymer, metal and cerramic

composites

Laser hole drilling and texturing (for joining)

of composites

Dr Paul French

Photonics in Engineering Research Group General Engineering Research Institute (GERI)

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Composite Laser Processing

Introduction

 Acoustic Liners

 Macro Laser Processing Acoustic Liner Application

 Aerospace Surface Engineering

 Micromachining Aerospace Application

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Composite Laser Processing

Acoustic Liner Technology

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Composite Laser Processing

Acoustic Liner Technology

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Composite Laser Processing

Acoustic Liner Technology

Close up of a acoustic liner with honeycomb structure

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Composite Laser Processing

LLEC Drilling Station

Raycon 5 axis CNC drilling system with a JK704 Nd-YAG laser.

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Percussion Drilling of Carbon Composite

 Selection of laser parameters are important for percussion drilling

 Parameters to consider are:

⇒ Assist Gas Type

⇒ Gas Pressure

⇒ Focal Position

⇒ Peak Power

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Percussion Drilling of Carbon Composite

Gas Type

 Inert assist gas are usually used when processing carbon composite

material, Argon, Nitrogen.

 Carbon dioxide produces a superior result with respect to surface finish.

 Possibly due to its thermodynamic properties.

 Carbon dioxide has a higher enthalpy than argon or nitrogen, processes

at a lower temperature.

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Percussion Drilling of Carbon Composite

Gas Pressure

 Low gas pressure give better result compared to high gas pressure delivery.

 Gas pressure operating in the one bar region measured at the nozzle.

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Percussion Drilling of Carbon Composite

Focal Position

 Better hole quality occurs when the focus is above the surface of the sample

 Similar result are found when percussion drilling metals such as nickel alloys

found in components of aerospace engines.

 The reason for this result may be due the partition of energy with in the

laser pulse.

 The diverging beam interacts with the walls of the hole

 Partition of the pulse energy means more energy goes into ejected material

momentum than creating melt within the matrix

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Percussion Drilling of Carbon Composite

Pulse Energy / Peak Power

 For single shot penetration for drilling on the fly applications:

 Relativity low pulse energies gave better results combined with short

pulse widths.

 Example for 1 and 2 ply carbon fibre 5J 0.6 ms pulses.

 Hole formed by a single shot,

drilling on the fly applications.

 Best results with simple square pulse

shapes, ie ramping-up pulses gave poor holes quality.

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Percussion Drilling of Carbon Composite

SEM Analysis

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Micro-engineering of Carbon Composite

Surface Texturing

 The strength of the adhesive bond requires that the adhesive completely

spreads over the surface of the substrates joined.

 This is called wetting the surface

 Bonding is also improved when some mechanical interlocking exists between

The adhesive and small irregularities on the surface of the material to be joined

 Usually produced by mechanical braiding

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Micro-engineering of Carbon Composite

Surface Tension

 If the surface tension value of the liquid is greater than the surface free energy of the substrate the liquid molecules stay bound together

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Micro-engineering of Carbon Composite

Surface Tension

 When the surface free energy value of the substrate is higher than that of

the liquid it allows the liquid to uniformly wet the surface

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Micro-engineering of Carbon Composite

Mechanical Braiding

 A need to raise the surface free energy of the composite. A number of

possible treatments:

 Plasma treatment –high voltage electrodes in low pressure inert gas

atmosphere.

 Corona discharge treatment.

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Micro-engineering of Carbon Composite

Mechanical Braiding

 Mechanical Abrading Results

Signs of fibre damage

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Micro-engineering of Carbon Composite

Micro / Nano Laser Systems

 Fianium Laser Systems.

 FemtoPower 1060-8-pp

 Pulse Length 20ps.

 Wavelength 1064 nm.

 Rep Rate 200kHz or 500kHz

 Maximum Pulse Energy 6 µJ

 Laser Power 2.1W

 Experimental Spot Size 26µJ

 Pulse Length 10ps.

 Wavelength 1064 nm.

 Rep Rate 1,2,3,4…20 MHz

 Maximum Pulse Energy 3 µJ

 Laser Power 8 W

 Experimental Spot Size 30µJ

Master Source

High-Power Amplifier

Shutter Control

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Micro-engineering of Carbon Composite

Laser Braiding

 Investigating the Fianium picosecond laser system ability to surface

structure carbon composite and increase its surface energy,(Laser Abrading)

20mm/sec

30mm/sec 30 Passes

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Micro-engineering of Carbon Composite

Contact Angle

Unprocessed carbon composite Contact Angle: 117 Deg

Laser processed surface Contact Angle: 57 Deg

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Micro-engineering of Carbon Composite

Contact Angle

Measurement of Contact Angle for Carbon Composite Pitch 0.1 mm

Velocity mm/sec C o n t a c t A n g l e Mechanical Braided Unprocessed Surface

 Laser abraiding produced superior results compared with mechanical

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Composite Laser Processing

Summary

 Carbon composite material is becoming an increasingly

important material in the aerospace sector in the 21st _century

 The laser industry / academia must develop the technique

that will allow laser material processing to have a future in the aerospace sector

 Laser cutting and drilling are two obvious techniques with

macro applications in drilling of acoustic liners, component trimming.

 Micromachining laser systems can be used in surface engineering

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AILU Workshop: Laser processing of polymer, metal and cerramic

composites

Laser hole drilling and texturing (for joining)

of composites

Dr Paul French

Photonics in Engineering Research Group General Engineering Research Institute (GERI)

Liverpool John Moores University

Thank You for Listening

Any Questions