High cycle fatigue behavior and thermal properties of PLA/PCL blends produced by fused deposition modeling

In this paper, high cycle fatigue behavior and thermal properties of blend specimens made of polylactic acid (PLA) and polycaprolactone (PCL) were studied and the influence of crystallization was investigated on the fatigue behavior. In this regard, fused deposition modeling method was employed to manufacture neat-PLA, neat-PCL, PLA/10wt.% PCL (90/10), and PLA/20wt.% PCL (80/20) specimens. The results show that the addition of 10wt.% and 20wt.% of PCL to the neat-PLA increases the elongation of the specimens by 32% and 284%, respectively, compared to that of the neat-PLA. However, Young’s modulus respectively decreases by 22% and 34%. According to the differential scanning calorimetry (DSC) test results, the 90/10 blend has the highest X c, PLA (10.5%) in comparison to the neat-PLA and 80/20 blend. The implementation of high cycle fatigue (HCF) tests on the 3D printed specimens indicated that the 90/10 blend offer the best HCF behavior. In addition, the neat-PLA, 90/10, and 80/20 exhibit a fatigue limit of 9.39 MPa, 15.47 MPa, and 13.62 MPa, respectively. These results reveal the direct effect of crystallinity (X c, PLA ) on the fatigue behavior of the specimens. The fractography evaluation exhibited that adding PCL to PLA may cause the formation of numerous voids in the 80/20 blend, resulting in degradation in fatigue strength especially under higher stress amplitudes.