Atmospheric Plasma Preparation of Stainless Steel Nutplates for Improved Adhesive Bonding
Atmospheric pressure plasma has been demonstrated as a viable method of preparing commercially-available, bonded nutplates for installation. Nutplates are often installed on aircraft after storage in nitrogen purged packages with no additional surface preparation. This method has an accepted shelf-life of only one year and the nutplates are subject variations in performance which results in occasional disbonds. These disbonds necessitate expensive and time consuming re-work. Surfx has developed a nutplate plasma treater and a plasma process for activating the nutplate surface prior to installation. Plasma preparation of the nutplate generated a hydrophilic surface with a water contact angle of <5 °. Surface analysis by X-ray photoelectron spectroscopy revealed that surface contamination was removed by plasma treatment. Initial trials were conducted on packaged nutplates that had exceeded their maximum allowable shelf-life. Preparing nutplate surfaces with plasma yielded excellent adhesion. Plasma activation of the nutplate resulted in a drastic increase in torque-out strength from 9 ± 2 Nm to 18 ± 3 Nm and reduced undesired adhesive failure modes. Plasma process time is less than 10 seconds. This technology offers the potential for significant cost savings over the production cycle of an aircraft.
Author: Thomas Williams
Conference: SAMPE Seattle 2017