Comparison of the accuracy of analytical models for basalt fiber–reinforced poly(lactic acid) composites prepared by injection molding and fused filament fabrication

We compared the accuracy of analytical models for short fiber–reinforced composites prepared by injection molding and fused filament fabrication (FFF). The microstructural features define the strength of the composites, and they are greatly dependent on the processing conditions. We collected data on fiber length, orientation, and porosity via X-ray micro-computed tomography (µ-CT) and determined the critical fiber length experimentally. We used this data as input for the modified rule of mixtures and the modeling framework based on the Halpin–Tsai method, and found that the cumulative error for FFF is more than twice that for injection-molded composites. We also showed that experimentally determined matrix strength for FFF gives a lower strength limit which is applicable for engineering parts. We presented a new approach for the modeling of the tensile strength of neat FFF products, in which the printed structure is divided into contact zones and bulk material zones. The matrix strength calculated this way was found to approximate the experimental results with an error of 5%.