Polymer matrix composites (PMCs) are susceptible to impacts that often result in microcracks and delaminations that can greatly reduce their mechanical integrity. Current injection repair techniques are limited to low glass transition temperature (T_g) composites due to the temperature and viscosity limitations of current repair resins. Bisphenol E cyanate ester (BECy) has both a high T_g and low prepolymer viscosity that makes it an ideal resin for the injection repair of high temperature PMCs. In addition, alumina nanoparticles have been shown to increase the strengths of some adhesives as well as impart shear thinning properties in suspension; both of which are desirable effects for injection repair.

Lap shear tests were performed to evaluate adhesive properties of BECy and BECy-alumina nanocomposites. Effects of substrate, temperature, nanoparticle loading, and moisture were investigated. A resin-injection process was developed and the efficiency of BECy in repairing bismaleimide-carbon fiber composite plates was studied through ultrasonic evaluation and compression-after-impact tests.