ATMOSPHERIC PRESSURE PLASMA TREATMENT OF ORGANIC MATRIX COMPOSITES FOR STRUCTURAL ADHESIVE BONDING

摘要

Bonding of organic matrix composites with adhesives is a key process in the manufacture ofrnaircraft, helicopter, and other warfighter systems. Current surface preparation methods are basedrnon manual mechanical roughening of the composite surface through sanding or peel ply removal.rnAn alternative to manual roughening is atmospheric pressure plasma treatment, which can bernautomated. The effects of plasma treatment on bismaleimide-carbon fiber composite have beenrnstudied with both argon and helium based plasma. Plasma treatment decreased the water contactrnangle from 82 ° on the untreated composite surface to <25 ° after exposure. A set of mechanicalrntests was performed on the composites to compare the effects of plasma surface preparationrnversus mechanical abrasion. It was found that double lap shear strength increases up to 50 %,rnfrom 9.6 MPa on a peel ply surface to 14.4 MPa after plasma exposure on the same surface usingrn3M AF 191K film adhesive. Wedge crack extension tests showed a decrease in extension lengthrnfrom 5.0 to 2.2 mm on lightly sanded non-peel ply panels and an increase in cohesive failurernfrom 86 to 98 % on peel ply panels after plasma. These results show that integrating plasmarntreatment as a surface preparation step prior to bonding can improve structural bondrnperformance.