Page 1 PLASMA SURFACE ENGINEERING OF FIBER REINFORCED COMPOSITES FOR THE REMOVAL OF CONTAMINANTS AND IMPROVEMENT OF ADHESIVE JOINT STRENGTH Nathaniel Eternal, Raul Gonzalez and Daphne Pappas Plasmatreat USA, 30695 Huntwood Ave, Hayward, CA 94544 Abstract Over the past few decades, the automotive and aerospace industries have shown increased interest in carbon fiber reinforced plastic composite (CFRP) materials due to their light weight and low production cost. However, these composite materials exhibit poor performance in structural applications due to the weak interface when bonded to other dissimilar materials, such as adhesives, metals and polymers. As carbon-based materials, CFRPs have low surface energy that presents bonding challenges. Surface residual contaminants originating in mold release materials or handling also contribute to poor adhesive joint strength. Treatment under atmospheric pressure plasmas (APPs) has emerged as an alternative solution to engineer composite surfaces without affecting the bulk properties of the materials. The technology utilizes a dry gaseous medium and does not involve any harsh liquid solvent chemistries. APPs contain gaseous species that can react and remove organic surface contaminants very rapidly. Furthermore, they can be instrumental in the chemical functionalization and activation of the surface through the grafting of oxygen-based polar groups. Literature references report the increase of surface energy, improved fracture toughness and increase of adhesive strength due to the APP treatment. In this paper, the details of the application of atmospheric-pressure plasma processes on fiber reinforced composites and results from the improved mold release and adhesive strength due to the application of Openair® plasmas are presented. Background The materials used in the automotive industry can be very complex and involve the synergy of several types of dissimilar materials. In the past, some of these materials were mechanically bonded but recent requirements for light-weighting have led to the adoption of adhesive materials. Besides the reduced structural weight, adhesively bonded materials offer many advantages, such as increased joint stiffness and improved resistance to fatigue. Specifically, adhesively bonded joints in polymeric composite structures are capable of bonding thick layers to thin layers without distortion, reduce the levels of localized stress forces that are present in mechanical joints and allow the bonding of different types of materials [1]. Overall, the cost advantage is significant due to lower material cost and reduced manual labor. Factors Affecting Surface Adhesion in Polymer Composites Surface Energy The selection of the optimum adhesive for a particular set of materials that need to be joined together, as well as the interfacial properties are critical for its performance. The ability to form a bond between two materials is mainly dependent on the chemical composition of the two components as well as their surface topography. The chemical bonds that are formed can be either primary (covalent, ionic, metallic) or secondary (van der Waals, London dispersion, or hydrogen).