Laser hole drilling and texturing (for joining) of composites

Transcription

1 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

2 Composite Laser Processing Introduction Acoustic Liners Macro Laser Processing Acoustic Liner Application Aerospace Surface Engineering Micromachining Aerospace Application Summary

3 Composite Laser Processing Acoustic Liner Technology Ref: Airport Noise Symposium, San Diego, Boeing

4 Composite Laser Processing Acoustic Liner Technology Why drill holes in composites? Ref: AST Duct Liner Workshop April Goodrich Aerospace

5 Composite Laser Processing Acoustic Liner Technology Ref: Interdisciplinary Microsystems Group University of Florida Close up of a acoustic liner with honeycomb structure

6 Composite Laser Processing LLEC Drilling Station Raycon 5 axis CNC drilling system with a JK704 Nd-YAG laser.

7 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 Pulse Shape

8 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. ARGON NITROGEN CO2

9 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. At high pressure surface delamination occurs

10 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

11 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.

12 Percussion Drilling of Carbon Composite SEM Analysis Single Ply General condition of single ply hole 2-Ply Surface condition of the hole

13 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 Investigated use of laser micromachining

14 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 Poor wetting means a poor bond

15 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 This is important to achieving a good bond

16 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. Simple mechanical abrading. See fibre tools below

17 Micro-engineering of Carbon Composite Mechanical Braiding Mechanical Abrading Results Signs of fibre damage

18 Micro-engineering of Carbon Composite Micro / Nano Laser Systems Fianium Laser Systems. Pulse Length 20ps. Wavelength 1064 nm. Rep Rate 200kHz or 500kHz Maximum Pulse Energy 6 µj Laser Power 2.1W Experimental Spot Size 26µJ Master Source High-Power Amplifier Shutter Control Stages FemtoPower pp 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 FemtoPower µJ-pp

19 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) 30 Passes 20mm/sec 30mm/sec.7 W, 3.4 µj 500 khz. 10 mm/sec

20 Micro-engineering of Carbon Composite Contact Angle Unprocessed carbon composite Contact Angle: 117 Deg Laser processed surface Contact Angle: 57 Deg

21 Micro-engineering of Carbon Composite Contact Angle e l g n A t c a t n o C Measurement of Contact Angle for Carbon Composite Pitch 0.1 mm Unprocessed Surface Mechanical Braided Velocity mm/sec Laser abraiding produced superior results compared with mechanical braiding.

22 Composite Laser Processing Summary Carbon composite material is becoming an increasingly important material in the aerospace sector in the 21 st 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 i.e. surface texturing prior to bonding.

23 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