Stochastic fracture of additively manufactured porous composites

Abstract

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.

The Effect of Porosity on Mechanical Properties of Fused Deposition Manufactured Polymers and Composites

“…The 80 % infill showed an m = 14 for and m = 13 for TS, whereas the other infills ranged from m=24-39 for and m = 24-40 for TS. These low m values mean a large scatter in and TS values.Like past results[29,37,38], the strain values show lower m values compared to strength values. The showed an increasing trend with increasing density.…”

“…The reliability of the 80 % infill seems to be correlated to the large distribution of density, as shown in Figure 2b. In our previous study, we reported similar and values for short carbon-fiber composite samples at the same infill parameter settings [18,37,38]. The strain at fracture m value was much lower than previous carbon-fiber composite results.…”

“…This topic is broken down into three experiments: stochastic fracture of additively manufactured porous ABS (chapter five), stochastic fracture of additively manufactured porous composites (chapter six) [37], and mechanical reliability of short carbon-fiber reinforced ABS produced via vibrationassisted fused deposition modeling (chapter seven) [38]. Chapters six and seven are summaries of published papers [37,38], of which the author is not the first author. This paper will focus specifically on what the author has contributed to the work while still discussing the findings in meaningful ways.…”

“…This paper covers three topics on which the author has worked extensively: stochastic fracture of additively manufactured porous ABS (chapter five); stochastic fracture of additively manufactured porous composites (chapter six) [37]; and mechanical reliability of short carbon-fiber reinforced ABS produced via vibration-assisted fused deposition modeling (chapter seven) [38]. The broad goal of these three papers is to understand the variability of FDMed materials.…”

Comparative Screening of the Structural and Thermomechanical Properties of FDM Filaments Comprising Thermoplastics Loaded with Cellulose, Carbon and Glass Fibers

“…Advances in new and low-cost additive manufacturing (AM) combined with developments in polymer materials technologies related to AM play a critical role in the life cycle of today's consumer and high-technology products [1][2][3][4][5]. Enjoying the high level of flexibility from the prototyping to the mass production phases, recent advances have been effective to replace conventional product development strategies.…”