Innovations in Designing Damage Tolerant Rotorcraft Components by Interface Tailoring

The performance of a composite material is heavily influenced by the strength and toughness of the interlaminar region, which is the resin rich area between the plies of a fiber reinforced composite.  The interlaminar region generally provides a direct path for crack propagation since no continuous reinforcement is present and is often the cause of failure in materials subjected to cyclic loading such as the composites used in rotorcraft.  Four principle methods exist for the enhancement of the interlaminar strength, namely; interleaves, fiber whiskerization, Z-pinning or stitching and nanocomposite matrices.  However, all existing technologies have limitations that have not facilitated their widespread adoption in commercial composites.  The focus of this research will be to create nanoscale Z-pins located only in the interlaminar region to yield lightweight composites with increased strength and toughness, and ultimately more durable materials.  Unlike existing treatments, the technology proposed here is low cost, environmentally benign, compatible with prepreg processing, can be extended to a production-scale and does not require advanced tooling or resin transfer processes.  In addition to the increased strength offered by the interlaminar treatment, our proposed reinforcement materials could enable multifunctionality by providing embedded strain sensitivity for SHM.