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.
Benefit: The proposed interlaminar treatment has great potential for commercialization because the techniques proposed are applied as a secondary treatment to existing prepregs. The use of existing prepreg materials will not only allow HARP Engineering to effectively market the technology quickly by purchasing and modifying available prepreg, but will also present a highly desirable solution to customers by offering an enhanced version of the resin and fiber system they currently use. Many OEMs that use composites are reluctant to change their fiber and resin system due to the expensive qualification testing requirements and established maintenance schedules. We will be able to provide an enhanced version of the same prepreg and therefore can ensure that performance is very similar but with improved interlaminar strength and delamination resistance. Furthermore, the use of the same prepreg materials will ensure that the OEMs can use the same material design and layup processes thus minimizing the cost to adopt our materials. These aspects of our technology are expected to greatly facilitate our commercialization efforts. The market for prepreg composites is growing rapidly and the interlaminar region possesses the biggest concerns for durability, safety and lifetime this class of materials. If successful, the proposed technology would represent a major advance in the development and acceptance of composite materials.
Keywords: Fiber Reinforced Composite, Fiber Reinforced Composite, prepreg, Delamination, toughness, interlaminar, carbon fiber
