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Short carbon fiber-reinforced polymer composites are widely employed in additive manufacturing (AM) techniques, including Large Area Additive Manufacturing (LAAM) polymer extrusion-deposition, due to their superior mechanical properties compared to neat polymers. The mechanical and thermal properties of these composites are significantly influenced by factors such as fiber volume fraction, orientation, length, and distribution, and void distribution and volume fraction within the microstructure of the printed beads. This paper presents an experimental study that aims to quantitatively assess the relationship between void volume fraction and fiber orientation within the microstructure of both single freely extruded strands and single deposited beads of Short Carbon Fiber reinforced Acrylonitrile Butadiene Styrene (SCF/ABS) manufactured via a LAAM system. The study employs high-resolution 3D microcomputed tomography (ฮผCT) to evaluate the fiber orientation, fiber volume fraction, and void volume fraction within the microstructure of the SCF/ABS composite parts. The findings demonstrate that the print direction ๐ดzz component of the fiber orientation tensor in the regions near the edges of the single freely extruded strand is higher than those near the center, likely due to increased nozzle shear rate near the wall. Furthermore, within a single deposited bead on the print bed, the ๐ดzz component varies throughout the microstructure. Measurements also show that regions with relatively higher void volume fraction have a corresponding lower fiber ๐ดzz and fiber volume fraction for both the single freely extruded strand and the single deposited bead.
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This content will become publicly available on June 1, 2026
Intrabead and interbead fracture analysis of large area additive manufactured polymer and polymer composites
Large-Area Additive Manufacturing (LAAM) has seen increased application in manufacturing meter-scale, polymeric composite structural parts, especially for tooling and fixturing. Unfortunately, LAAM introduces manufacturing-induced defects in printed composites, e.g., intrabead microvoids and poor interbead adhesion that are not otherwise seen when traditional manufacturing methods are used, causing degradation of mechanical and fracture properties. In this paper, the fracture behavior of neat acrylonitrile butadiene styrene (ABS) and short carbon fiber-reinforced ABS (CF/ABS) fabricated by LAAM is compared and analyzed by evaluating their energy release rate ๐บ๐ผ๐ and fracture mechanisms. A double cantilever beam with doublers (DCB-D) test for single-bead, double-bead, and multiple-bead configurations is developed by incorporating rigid doublers to reduce the compressive failure at the crack tip, allowing for the measurement of crack propagation. A new data reduction method for these configurations is derived to remove the doubler effect from the ๐บ๐ผ๐ calculation, producing โpureโ intrabead and interbead ๐บ๐ผ๐ values. We show that CF/ABS is more damage tolerant than ABS at the intrabead level, but less damage tolerant than ABS at the interbead level. The development of plastic ligaments in ABS helps dissipate additional strain energy, improving the overall energy release rate. The experimental fracture test approach developed here is expected to provide mechanistic insight into their damage tolerance capability, accelerating the qualification process of LAAM-produced polymer and polymer composites.
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- Award ID(s):
- 2055628
- PAR ID:
- 10608167
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Composites Science and Technology
- Volume:
- 266
- Issue:
- C
- ISSN:
- 0266-3538
- Page Range / eLocation ID:
- 111173
- Subject(s) / Keyword(s):
- Large area additive manufacturing Mode I fracture Short fiber polymer composites Energy release rate
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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