Chemical and Materials Engineering Department, San Jose State University, San Jose, CA, 95192, USA.
Sigray, Inc., Concord, CA, USA.
Sci Rep. 2018 Oct 18;8(1):15437. doi: 10.1038/s41598-018-33863-4.
Extrusion-based fused deposition modeling (FDM) introduces inter-bead pores into dense materials, which results in part-to-part mechanical property variations, i.e., low mechanical reliability. In addition, the internal structure of FDMed materials can be made porous intentionally to tailor mechanical properties, introduce functionality, reduce material consumption, or decrease production time. Despite these potential benefits, the effects of porosity on the mechanical reliability of FDMed composites are still unclear. Accordingly, we investigated the stochastic fracture of 241 FDMed short-carbon-fiber-reinforced-ABS with porosity ranging from 13 to 53 vol.% under tensile load. Weibull analysis was performed to quantify the variations in mechanical properties. We observed an increase in Weibull modulus of fracture/tensile strength for porosity higher than ~40 vol.% and a decrease in Weibull modulus of fracture strain for an increase in porosity from 25 to 53 vol.%. Micromechanics-based 2D simulations indicated that the mechanical reliability of FDMed composites depends on variations in bead strength and elastic modulus of beads. The change in raster orientation from 45°/-45° to 0° more than doubled the Weibull modulus. We identified five different types of pores via high-resolution X-ray computed tomography. A 22% and 48% decrease in carbon fiber length due to extrusion was revealed for two different regions of the filament.
挤出式熔融沉积制造（FDM）在致密材料中引入了珠间孔隙，从而导致了零件间力学性能的变化，即力学可靠性低。此外，FDMed 材料的内部结构也可以有意制成多孔状，以调整力学性能、引入功能、减少材料消耗或缩短生产时间。尽管有这些潜在的好处，但孔隙率对 FDMed 复合材料力学可靠性的影响仍不清楚。因此，我们研究了在拉伸载荷下，241 个孔隙率范围为 13%至 53%的短碳纤维增强 ABS 的 241 个 FDMed 随机断裂。我们进行了威布尔分析来量化力学性能的变化。我们观察到，当孔隙率高于约 40%时，断裂/拉伸强度的威布尔模数增加，而当孔隙率从 25%增加到 53%时，断裂应变的威布尔模数降低。基于细观力学的 2D 模拟表明，FDMed 复合材料的力学可靠性取决于珠强度和珠弹性模量的变化。将拉丝方向从 45°/-45°变为 0°，威布尔模数增加了一倍多。我们通过高分辨率 X 射线计算机断层扫描识别了五种不同类型的孔隙。在灯丝的两个不同区域，碳纤维长度由于挤出而分别减少了 22%和 48%。
