Characterization of Unidirectional Aligned Discontinuous Fiber Reinforced Composites Containing a Toughened Epoxy Resin Produced Using the HiPerDiF Process

Aligned discontinuous fiber reinforced composites (ADFRC) offer promising applications due to their manufacturability and tailorable mechanical properties. In this study, the high performance discontinuous fiber (HiPerDiF) technology is used to produce ADFRC consisting of 3 and 6 mm long virgin carbon fibers and a highly toughened commercial epoxy resin (CYCOM 977–2). The HiPerDiF machine settings were optimized and the resultant physical and mechanical attributes systematically analyzed to show improvements in tensile performance and microstructure quality. There was an increase in stiffness by 3%, strength by 28% and failure strain by 26% compared to samples produced with initial machine settings. 73% of fibers were spatially aligned within 10° and 62% of fibers aligned in-plane within ±10°. ADFRC specimens with 6 mm fibers at 23% fiber volume fraction were optimally prepared to retain 32% of the stiffness, 30% of the strength and 57% of the failure strain in comparison with tested unidirectional continuous composite specimens containing similar constituent materials. This work has demonstrated the viability of producing aligned discontinuous fiber preform in high volume resulting in composites with improved tensile performance. With the upscaled HiPerDiF machine, improved mechanical performance can be achieved when the machine settings and fiber properties are optimized to maintain a high alignment and consistent areal weight.