achieved. Residual debris was removed with clean, dry air. Grit blasted parts were finally wiped with lint-free towels soaked in DS-108 prior to bonding. The surface was solvent cleaned until no residue came off the surface, and finally dry wiped with a clean cloth. Plasma Surface Activation A Surfx Technologies® Atomflo™ plasma controller was used for the preparation of both the substrate and the nutplate surfaces. The Atomflo actively controls and monitors all plasma process conditions and logs this information for future reference. Plasma activation of the nutplates was achieved using the Nutplate Plasma Cleaner™, or NPC. The NPC, also developed by Surfx, is a surface preparation tool specifically designed for nutplates and other bonded fasteners. An image of this tool is provided in Figure 2. Industrial grade helium and oxygen were fed into the NPC at 30 liters per minute (LPM) and 0.2 LPM, respectively. The plasma was ignited using 80 W of RF power at 27.12 MHz. Unless stated otherwise, the nutplate was inserted into the NPC for 5 seconds and then removed. Figure 3 shows an image of the NPC in use. The nutplate is seated into the NPC and a plasma discharge is generated beneath the bonding surface. Reactive species from the plasma rapidly remove surface contaminants leaving behind a clean and active surface. The high surface energy imparted by the plasma cleaning process is ideal for adhesive bonding applications. The NPC can be configured to treat any size and style of fastener. Plasma activation of the substrate coupons was achieved with the Surfx Aircraft Plasma Cleaner™, or APC. The APC features a hexagonal, showerhead plasma source affixed to a flexible handle. An image w w w. s a m p e . o r g Figure 2. Surfx® Nutplate Plasma Cleaner™ with nutplate inserted. Figure 3. Nutplate Plasma Cleaner cleaning a nutplate and exhibiting blue light from the plasma glow. S E P T E M B E R /O C TO B E R 2 0 2 0 | SAMPE JOURNAL | 19http://pccomposites.com http://www.sampe.org