Three Advanced Surface Treatment Techniques for Carbon Fiber Composites
Carbon fiber composites are renowned for their superior workability, which has propelled their extensive use in a multitude of sectors and industries. When it comes to joining carbon fiber composite parts to replace mechanical components, adhesive bonding is a common approach. However, before adhesive bonding can be effectively applied, the surface of the carbon fiber composite must be properly prepared.
1. Abrasive Surface Texturing
This technique is designed to eliminate surface contaminants and create a highly textured surface, which increases the bonding area for adhesives and enhances the mechanical interlock. It involves manual abrasion using steel brushes, sandpaper, or files; automated processes like belt sanding, wheel grinding, or abrasive blasting; and precision mechanical abrasion that offers high efficiency, reduced operator dependency, and excellent repeatability and cost-effectiveness.
2. Plasma Flame Treatment
Plasma flame treatment involves the use of a gas or gas/oxygen flame to partially oxidize the surface, generating polar groups that boost the surface energy of the polymer. This method is particularly effective for thicker substrates compared to corona treatment and is well-suited for uneven thermoplastic composite parts. The process offers the flexibility to adjust gas-to-oxygen ratios, flow rates, exposure times, and flame-to-substrate distances, making it a highly effective approach for polypropylene-based composite materials.
3. Solvent Cleaning
The most straightforward of the surface treatments, solvent cleaning removes wax, grease, and other low molecular weight contaminants from the bonding surface. It relies on the solubility of contaminants in the solvent, with the stipulation that the solvent should not introduce new contaminants. Commonly utilized solvents include acetone, butanone, methyl isobutyl ketone, xylene, trichloroethylene, ethanol, and isopropanol.
Despite its simplicity, solvent cleaning has its drawbacks, such as the potential to adversely affect the substrate material, leading to dissolution, stress cracking, or crazing in thermoplastic carbon fiber composites. There's also the risk of cross-contamination between samples or through the reuse of solvent-soaked wipes. Additionally, the fumes produced can pose health hazards to workers and the method may not be feasible for large-scale production due to these concerns.
