Hydraulic bulge forming comparison of continuous and stretch broken carbon fiber prepreg laminates

The demand for carbon fiber reinforced polymer composites is motivated by the increased need for high-strength, low-density materials, particularly in the automotive and aerospace industries. Continuous carbon fibers have limited formability due to their inherent brittleness which does not allow for plastic deformation. To address this limitation, stretch broken carbon fiber (SBCF) is being developed. SBCF is a form of carbon fiber created by statistically distributed breakage of aligned fibers at inherent flaw points. The final material is constituted of collimated shorter fibers with an average length larger than chopped fibers. In this work a hydraulic bulge test was used to evaluate the out-of-autoclave elevated temperature formability of quasi-isotropic prepreg laminates prepared with Hexcel IM-7 12K continuous fibers and Montana State University SBCF newly generated materials impregnated with Cycom 977-3 resin. The enhanced formability of SBCF composites, when compared to the continuous ones, was demonstrated by a symmetrical stress response and a pseudo-plastic deformation mechanism until failure.