Abstract
Stretch breaking of carbon fibers is a process to break single to multiple tows to produce discontinuous, aligned fibers within a tow. The process stretches the carbon fibers causing breakage according to intrinsic flaws leading to a distribution of fiber lengths within the tow. These breaks allow the stretch broken fiber tows to exhibit increased formability during composites manufacturing that is useful to produce parts with complex geometries. This work aims to establish a repeatable method to characterize the carbon fibers flaw types, and their distributions, that lead to fiber breakage to better understand the stretch breaking process.
To assess the flaws exploited by the stretch breaking process, single continuous carbon fibers were extracted from a Hexcel IM7-12K tow and tensile tested both in water and in air at a gauge length of 25 mm. The Weibull distribution was used to describe the strength behavior of brittle carbon fibers. Higher strength values were overall recorded for fibers tested in water when compared to the ones tested in air. Scanning electron microscopy was used for flaw characterization.
