Figure 2. Cross-section of CFRP cut at 30.5 kW laser power, at a single laser pass (left), at 12 laser passes (middle) and at 16 laser passes (right)
manufactured and turned at high number of revolutions instead. An overview of the setup is given in Figure 1.
Results Using 30.5 kW of laser power focused down to a spot of 244 µm in diameter, it was possible to cut a 1.4 mm thick CFRP laminate in a one pass strategy at 1.2 m/s and with a mean HAZ of 139 µm (Figure 2, left). With a multi-pass strategy finding its optimum in a range between 12 to 16 passes, the HAZ was further reduced down to 78 µm at 12 passes (Figure 2, middle), and the energy input needed was reduced by approximately 26 percent.
The effective feed rate can be increased up to 1.63 m/s in the multi-pass strategy — 26 m/s per pass — at an optimum 16 passes (Figure 2, above), with the ultra-high power laser system.
This makes it an attractive option for industrial
applications with high production volumes and medium quality requirements. However, fissures and chipping behavior were
Figure 4. Laser-based CFRP cutting process (left) and cut specimens (right)
the current state, the process can be used to cut several mm of 2D CFRP specimens, Figure 4. By using a programmable focusing optic as well as modified exposure strategies such as parallel lines, laminates thicker than 10 mm can be cut with a maximum HAZ of 230 µm as well.
The authors work for the Institute of Laser and System Technologies, Hamburg University of Technology, Hamburg, Germany. Part of this work was supported by the German Federal Ministry for Economic Affairs and Energy (BMWi) within the frame of the project 01 MX 12049. The authors would like to thank BMWi as well as PT-DLR project management agency for their support. Furthermore, the authors express their gratitude to Precitec Optronik GmbH for providing the optical system, and Rhein Composite GmbH for providing the carbon fiber fabrics.
Figure 3. Cross-section of CFRP with laser wavelength-absorbing additives, cut at 5 kW laser power
www.lia.org 1.800.34.LASER 11
observed especially close to the surface of the specimens, probably resulting from high process pressures. It is assumed that this behavior results from an insufficient absorption of the laser wavelength by the matrix, leading to fast energy deposition within the material, and finally to partial evaporation below the surface. Further investigations, e.g., cutting experiments with a laminate including absorbing particles such as carbon-black in the matrix, are needed to prove or disprove this theory. This approach has already proved to be very efficient at comparatively lower laser powers of up to 5 kW, as shown in Figure 3. At
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