Bismaleimides (BMIs) are commercially available resins often used in structural parts for military vehicles because they process similarly to epoxy resins, while providing higher glass transition temperatures important for high-performance structural composites. However, cured BMI matrix materials are hydrophilic and when used in humid environments, such as in naval environments, result in galvanic corrosion to adjacent metal parts – especially when BMI composites are reinforced with electrically conductive carbon-based fibers and/or graphite fibers. Despite these issues, BMIs are widely utilized as a prepreg matrix in manufacturing electrical circuit boards and structural composites. They are also used as a coating material and as the matrix in glass-reinforced pipes, particularly for use in high-temperature and chemical environments.
Navy researchers have laminated BMI-carbon fiber composites with an outermost layer made of a self-extinguishing cyanate-ester (CE) matrix material and electrically/non-electrically conductive fibers (specifically excluding graphite and carbon fibers), to alleviate galvanic corrosion at the interface with adjacent metal parts. At the same time, the self-extinguishing CE layer reduces the composite’s vulnerability to fire. The self-extinguishing property of the CE matrix material is due to the crosslinked network and the high-char yield obtained at high-temperatures. The resistance to galvanic corrosion is attributable to the electrically non-conductive, non-carbon-based fibers used to reinforce this polycyanurate layer.
- Method uses existing BMI-composite fabrication processes that are already qualified by the DoD
- Multi-ply composite structures using other thermoset and thermoplastic resins can achieve improved resistance to fire and galvanic corrosion by using self-extinguishing cyanate esters as the outermost layer
- At least two orders of magnitude of improvement in fire burn-through resistance
- US patent 9,669,599 available for license
- Potential for collaboration with Navy researchers