Scalability, Production, and Application of Stretch Broken Carbon Fiber for Primary Aircraft Structure

The work done in developing stretch broken carbon fiber technology is described. The objectives of the program include the scale up of the process to demonstrate production feasibility, as well as reducing the maximum filament stretch break length to ~50mm/2” or below, less than half of what was achieved on previous programs. The shorter break length is considered to be critical in order to achieve formability into complex geometries. The new stretch break line at Montana State University, BC3, has been commissioned to achieve the required material characteristics and throughput. To date, 6 tows have been successfully stretch broken simultaneously, representing a significant improvement compared with what was achieved on previous programs. Possible geometries and forming evaluation methods are described. Mechanical testing is to be conducted, including both equivalency testing of continuous vs stretch broken carbon fiber and a later minimal level allowables program. It is expected that there will be no strength reduction when using SBCF in a cured laminate as was the case on the prior programs; this will be verified under the current program with material from the new BC3 stretch break line. Single tow SBCF spools will shortly be available for evaluation by potential prepreg manufacturers and other end users.