Laser Processing of Henkel LOCTITE® EA 7000 AERO Film
Laser Processing of Henkel LOCTITE® EA 7000 AERO Film
Introduction
Henkel LOCTITE® EA 7000 AERO, an epoxy film adhesive for composite bonding applications, is formulated to provide resistance to high temperatures, fracture toughness, and peel resistance. It offers excellent hot-wet properties, low temperature tolerance (-67°F/55°C), dual temperature cure capabilities (250°F/121°C or 350°F/171°C) and superior adhesion. Comprised of a 200µm thick epoxy adhesive, a 100µm thick polymer cover film, and a 140µm thick paper carrier, Henkel LOCTITE EA AERO 7000 is illustrated in Figure 1.
Figure 1. LOCTITE EA 7000 AERO diagram illustrating the top polymer cover film layer (100µm), the bottom paper carrier layer (140µm), and the epoxy adhesive layer (200µm) sandwiched in between.
Henkel LOCTITE EA 7000 AERO bonds well to both prepreg and cured composites and is used for initial composite assembly, parts, and repairs in both structural adhesives and surface treatments for the Aircraft OEM and MRO industries. LOCTITE EA 7000 AERO is suitable for laser cutting, in which the non-contact nature of laser processing enables applications with small features and fine geometry to be processed with virtually no material deformation or discoloration. Other laser processes are not suggested, as they are not conducive to the intended use of this material. Universal Laser Systems® (ULS) makes it possible to produce a high degree of dimensional accuracy, with virtually no material deformation during processing.
Laser Processing Notes
Henkel LOCTITE EA 7000 AERO was tested to assess laser processing compatibility and the best configuration of laser peak power and wavelength. The epoxy adhesive layer in LOCTITE EA 7000 AERO absorbs 9.3µm wavelength CO2 laser energy more efficiently than other wavelengths, meaning that laser cutting this material can be performed at higher speeds and with minimal discoloration using a single 75 watt 9.3µm CO2 laser source. A microscopy image of the 9.3µm processed edge of LOCTITE EA 7000 AERO taken at 300x magnification is shown in Figure 2. The 3D image in Figure 3 depicts how the epoxy adhesive responds to laser cutting when using the 9.3µm laser wavelength.
Figure 2. Microscopy image (300x) of the edge of LOCTITE EA 7000 AERO after laser cutting with the cover film and paper carrier in place. The heat-affected zone measures 250µm.
Figure 3. 3D-rendered microscopy image (300x) of the edge of LOCTITE EA 7000 AERO.
Henkel LOCTITE EA 7000 AERO was also tested with the alternate system configuration of a 10.6µm CO2 laser wavelength. The results of these tests were compared by analyzing the heat affects, processed edge quality, and post-processing requirements. The results of the comparison of these system configurations are listed in tabular form in Table 1 and shown photographically in Figure 4. The 9.3µm wavelength produces a noticeably better edge with this material and is the recommended configuration.
Table 1 System Configuration Comparison
System Configuration
Heat-Affected Zone
Process Characteristics
Post-Processing Requirements
9.3µm (Recommended)
Minimal heat-affected zone of approximately 250µm
This configuration results in a smooth edge with no discoloration and minimal heat effects
No post-processing required
10.6µm
Increased heat-affected zone of approximately 300µm
This configuration shows similar results as the 9.3µm configuration but with increased heat effects
Figure 4. Comparison microscopy images (300x) of the edge resulting from laser cutting with the 9.3µm (left) and 10.6µm (right) wavelengths.
Processing Example
Henkel LOCTITE EA 7000 AERO applications requiring fine geometry and intricate detail with no degradation of the material’s physical properties can be achieved with ULS technology. An example demonstrating the results of laser cutting LOCTITE EA 7000 AERO using the recommended system configuration is shown in Figure 5.
Figure 5. Example of the geometry possible when laser cutting LOCTITE EA 7000 AERO.
Conclusion
Henkel LOCTITE EA 7000 AERO applications requiring fine geometry and intricate detail without degrading the physical properties of the material can be achieved with ULS technology. Through this testing it was determined that laser cutting is viable and that a 75 watt 9.3µm CO2 laser source is the best system configuration. An example demonstrating the results of laser cutting Henkel LOCTITE EA 7000 AERO using the recommended system configuration with the 9.3µm wavelength is shown in Figure 5.
