While in some previous posts we focused on talking about different automated processes for dry material deposition (ADMP, Pick-and-place and DAFP), this post deals with information about dry reinforcements aimed at aerospace infusion process and automation.
- Why dry reinforcements?
Dry reinforcements offer significant advantages versus prepreg materials that have been traditionally used in the aerospace sector. They present several benefits, thanks to their low prices, their long shelf life, reduction in inventory costs, potential to increase parts integration and potential to avoid the costly autoclave curing process.
The growth of the resin infusion process in the aerospace industry (as can bee seen in the image above and our -Aerospace Looking to Dry Fiber/Infused Composites post) is increasing the need to adapt dry materials to the aerospace and new technologies requirements.
What is driving innovation in dry reinforcements?
Although there is still much to do in the area, material suppliers offer more and more products oriented to automated dry material deposition processes. Focusing our attention on dry reinforcements, the main research and developments in the area are aimed at:
Binders which are compatible with the resin to be infused and ease the manageability of the fiber during the material deposition.
Thin layers of thermoplastic veils to facilitate the flow of resin infusion and provide the final part with a greater toughness.
Dry carbon fibers that provide the strength and stiffness in a unique or multiple directions (unidirectional or multiaxial reinforcements). Different forms of dry carbon fabrics can be used to this end. NCF (Non crimp fabrics) are the most used fabrics nowadays, whereas the woven fabrics have also improved their properties in order to ensure the achievement of the required qualities.
The combination of the dry reinforcements with the proper resin is essential in order to manufacture a good quality part. Great developments are being carried out in this area.
Unidirectional tapes or Non Crimp Fabrics: Different choices for automation.
Unidirectional tapes up to 1″ offer high flexibility in terms of the geometries they can achieve. Automated process, such as the Dry Automated Fiber Placement (DAFP), use these tapes to produce preforms that will be infused during further stages. The productivity they can reach is low so far.
Wider Non Crimp Fabrics (NCF) can be used with the automated process such as ADMP and Pick-and-Place. The improvements in these materials and related automated deposition technologies could revolutionize the composites sector because of the great production rates they can accomplish.
You can have an overview of these different automated process in our post Making a Preform – How Can I Count the Ways?
What are the most common dry material forms used by the latest aerospace programmes?
It is known that the Saertex group supplies high-performance multiaxial and unidirectional NCFs for the manufacturing of the Bombardier´s C-Series and Learjet 85´s major primary structures.
Meanwhile, AeroComposit has qualified Hexcel´s OoA Hi-Tape material to produce Irkut Ms-21´s wings and wingboxes, whereas Spirit AeroSystems has also used the same material to form a skin of an engine nacelle outer fan cowl. Aircraft structures made with HiTape are reported to demonstrate mechanical properties as high as those found in parts made with the latest generation primary structure prepregs.
Finally, it is worth mentioning that Cytec offers a material with equivalent properties, being applied also in the Irkut MS-21. Both tapes (Hexcel´s and Cytec´s) will be used to manufacture the aircraft structures automatically within a DAFP machine.