Title: Effect of Process Variables on the Uncured Handleability and Formability of Stretch Broken Carbon Fiber
Authors: Riad Morshed Rezaul, Cecily Ryan, Roberta Amendola, Dilpreet Bajwa, Douglas Cairns
Abstract: Carbon fiber reinforced polymer composites find extensive application in the aerospace industry due to their outstanding strength and stiffness. When manufacturing components with complex geometries, discontinuous carbon fibers offer superior formability compared to continuous carbon fibers. Stretch broken carbon fiber (SBCF) is a type of discontinuous carbon fiber generated by stretch breaking the fibers at their natural flaws. The resulting fibers are shorter in length compared to the continuous fibers. Uncured SBCF tows can be challenging to handle due to lack of fiber continuity. As with continuous fiber tows, a thin polymeric coating known as sizing can be applied to the SBCF. In SBCF, this coating serves to increase handleability as measured via tensile strength. The objective of this work is to investigate how the process variables during the stretch breaking process (sizing bath concentration, stretch ratio, nip force, and line speed) can be tuned to generate SBCF reliably and with consistent properties. The preliminary evaluation of the generated SBCF tows with a sizing bath concentration of 10 wt.% resulted in 1.75 wt.% sizing deposition on the tow, which meets the target sizing deposition of 1.5 wt.% to 2 wt.% in our present work. The room temperature tow tenacity of 290.86 N suggests the potential of the SBCF tows to provide desired tow handleability and back-tension ability during the prepreg production. The elevated temperature tow tenacity of 10.11 N indicates the potential formability of the SBCF tows. Replication of these results over multiple batches in SBCF generation also supports the reproducibility of these values under consistent processing conditions. From the fiber length distribution of the SBCF, it was observed that the fiber length ranges from 22 mm to 43 mm (mean fiber length is ~32 mm).
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Conference: CAMX 2022
Publication Date: 2022/10/17
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