| About this Abstract |
| Meeting |
2024 ASC Technical Conference, US-Japan Joint Symposium, D30 Meeting
|
| Symposium
|
2024 ASC Technical Conference, US-Japan Joint Symposium, D30 Meeting
|
| Presentation Title |
Assessing Micro-Void Formation at the Tips of Fibers within the Microstructure of Additively Manufactured Polymer Composite Bead |
| Author(s) |
Aigbe Awenlimobor, Neshat Sayah, Douglas E. Smith |
| On-Site Speaker (Planned) |
Douglas E. Smith |
| Abstract Scope |
Micro-voids within the bead microstructure of additively manufactured short carbon fiber-reinforced polymer composites is 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 nucleation 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 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 90% 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 nucleation during LAAM material processing indicate that localized fluid pressure likely plays a pivotal role in micro-void formation. To better expose this mechanism, an optimization technique is developed that incorporates exact gradients and Hessians of Jeffery’s hydrostatic flow-field pressure distribution equations for flow surrounding a single rigid ellipsoidal fiber. Computed results demonstrate that the polymer matrix pressure decreases signficantly at the fiber ends where micro-void nucleation is experimentally observed to occur. The simulations in this study include homogeneous flows typical of conditions found within a LAAM extrusion-deposition nozzle. Our approach provides the fiber surface pressure distribution in various flow regimes, enhancing our understanding of micro-void development mechanisms as the polymer melt flows through the nozzle. |
| Proceedings Inclusion? |
Definite: Post-meeting proceedings |