Low viscosity cyanate ester resin for the injection repair of hole-edge delaminations in bismaleimide/carbon fiber composites

The repair efficiency of bisphenol E cyanate ester (BECy) resin was investigated for the injection repair of high temperature polymer-matrix composites by ultrasonic C-scan mapping, fluorescent dye penetration, optical microscopy, hole plate shear (HPS), and post delamination compression tests. Bismaleimide/carbon fiber (BMI-cf) composites were chosen as a model substrate. A vacuum-based resin injection repair method was used for repairing the pre-damaged composite specimens. The effect of surface wettability on the repair efficiency of BECy on BMI-cf composite substrate was studied by temperature dependent contact angle measurements. C-scan, fluorescent dye penetration, and optical microscopy images of pristine, delaminated, and repaired specimens reveal efficient infiltration of resin in specimens repaired at elevated temperatures. The repair efficiency calculated from HPS and post delamination compression tests was observed to be 155% and 100%, respectively, illustrating the capability of BECy for repairing high temperature structural composites.