<p>Micro-voids within the bead microstructure of additively manufactured short carbon fiber- reinforced polymer composites are known to compromise the material performance. Unfortunately, a comprehensive understanding of the formation mechanisms of micro-voids during polymer processing is currently lacking. The present study considers micro-void formation at fiber interfaces, particularly those occurring at the end of suspended fibers. Micro-computed tomography (µCT) image acquisition techniques are used to characterize microstructural features of a 13wt% carbon fiber reinforced acrylonitrile-butadiene-styrene (CF/ABS) composite bead manufactured via Large Area Additive Manufacturing (LAAM). The results reveal a significant collection of micro-voids at the tips of fibers approaching 80% of the total micro-void volume fraction. In addition, fiber tip micro-voids are relatively larger and less spherical than micro-voids isolated within the ABS matrix. Theoretical formulations of several known mechanisms for micro-void formation during LAAM material processing indicate that localized fluid pressure likely plays a pivotal role in micro-void formation. To better expose this mechanism, we simulate the hydrostatic flow-field pressure distribution surrounding a single rigid fiber suspended in simple shear flow using finite element analysis (FEA). Computed results demonstrate that the polymer matrix pressure decreases significantly at the fiber ends where significant micro-void formation is experimentally observed to occur. Our approach provides the fiber surface pressure distribution in simple shear flow that typifies nozzle regions with extreme flow conditions, enhancing our understanding of micro-void development mechanisms as the polymer melt flows through the nozzle.</p>