Bonded repairs for carbon/BMI composite at high operating temperatures

The increased use of carbon reinforced polymer composite structures in civilian and military aircraft has produced new challenges for on-aircraft bonded repairs. Carbon/bismaleimide (BMI) composite structure provides an added complexity associated with the application of adhesively bonded repairs. Commercially available carbon/BMI composite usually requires a post-cure temperature in excess of 220 °C to achieve the high strength properties at elevated operating temperatures. Application of bonded repairs in situ often places an upper limit on the temperatures that can be employed for curing the adhesive at 177 °C. Consequently, the adhesive bond needs to achieve similar mechanical properties to the parent matrix material without the benefit of the high post-cure temperature. The current work examines a range of repair options that can be used to recover strength and the selection of adhesives and processes to successfully apply the repairs using vacuum assisted pressure.