Abrasion processes form the core of the most common surface preparation procedures used for adhesive bonding of both metals and composites. This is a good thing: many surfaces presented to the bonding technician are heavily oxidized and contaminated, and a well-designed abrasion and solvent wiping process can convert these surfaces to a chemically clean, active state that is excellent for bonding. However, although a particular abrasion and wiping process may produce a visually clean surface, this is no guarantee that the surface is chemically clean and will result in good adhesion to adhesives, paints, or other coatings. In particular, abrasives of similar grit size and backing material differ greatly in the chemical cleanliness of the abraded surface that they produce. This presentation discusses the effect of different abrasion and solvent wiping processes on the chemical composition of the resulting surface, and the effect of this composition on adhesion of structural epoxies. Case studies of field failures due to lack of control of these processes are presented, along with techniques and strategies for easily qualifying abrasion processes for adhesive bonding while quantifying the quality of the surface.
- Appreciate the sensitivity of abrasion processes to seemingly minor differences in materials and procedure
- Develop new or improve existing abrasion processes which have measurable (i.e. quantifiable) quality
- Qualify materials and supplies for surface treatment processes based on performance characteristics
Why Is It Important?
Abrasion processes are very common in manufacturing and repair of metallic and composite aircraft, however, the processes are not well understood and poorly controlled. This presentation puts abrasion processes on a firm scientific footing and provides the industry with techniques for control and troubleshooting.