SBIR-STTR Award

An automated surface preparation process will be developed for improving the adhesive bonding of organic matrix composites. The process will utilize high-speed atmospheric pressure plasma to yield the strongest bonds possible, i.e., 100% cohesive failure within the epoxy adhesive. The automated process will replace the unreliable, manual abrasion techniques that have been used for surface preparation in the past. Atmospheric plasma treatment is safe, reliable, low-cost and has no environmental, health and safety concerns. When implemented across the DoD complex, this process will save the government millions in manufacturing costs, and will yield lighter, stronger and faster warefighter systems.

Benefit:
Joining technology is a major concern in aircraft manufacturing and repair. Current abrasion techniques used to prepare organic matrix composites for bonding are unreliable and yield joints of low strength. A new surface preparation process is proposed that uses atmospheric pressure plasma to clean and activate the composite surface for bonding. This process is automated, completely reliable and generates joints of maximum strength. The anticipated benefits are a highly reliable and cost effective joining technology that can be used in the manufacture and repair of jet aircraft, helicopters, satellites, and many other aerospace systems. A direct benefit will be the production of lighter weight and higher performance aircraft for commercial and military applications

Keywords:
Organic Matrix Composites, Surface Preparation For Bond, Atmospheric Plasma

Peel ply, sanding and atmospheric plasma treatment have been examined as alternative methods for the surface preparation of bismaleimide carbon-fiber composites prior to bonding. It was found that atmospheric plasma treatment of the composite surface decreases the water contact angle from 82±2° to 20±2°. X-ray photoemission spectroscopy of the treated composites revealed a 91% increase in surface oxygen fraction with plasma exposure. This surface oxygen increase correlated to the plasma?s ability to recover the knock-down in double lap shear strength observed on peel plied and lightly sanded non-peel plied samples, from 1390±210 psi to 2090±20 psi and from 2000±100 to 2250±50 psi, respectively. Wedge crack extension testing after a seven-day hot-wet environmental exposure revealed that adding atmospheric plasma treatment after light sanding decreases the wedge crack length from 0.197 to 0.085 inches. In addition, oxygen plasma exposure on the peel ply composites increased the percent cohesive failure from an unacceptable value of 86±3% to an acceptable value of 98±1%. These results indicate that automated atmospheric pressure plasma treatment of organic matrix composites is a viable technology for surface preparation prior to structural adhesive bonding.

Benefit:
An exciting new technology is being developed for the automated surface preparation of organic matrix composites. This method will eliminate many of the problems encountered during joining of structural composites on jet aircraft, satellites, helicopters and other aerospace systems. The new preparation method greatly reduces manufacturing time and cost, and delivers systems with much stronger and tougher joints. In addition to aerospace, this process technology can be adapted to other industries, including renewable energy, automotive, and consumer electronics. The phase II project proposed herein aligns well with the government's Open Manufacturing initiative, since it will dramatically reduce the expense of acquiring future warfighter systems.

Keywords:
Surface Preparation, Adhesive Bonding, Organic Matrix Composites, Joining Technology, Atmospheric Pressure Plasmas