The fracture assessment of additively manufactured PLA and graphene reinforced PLA (PLA-GR) has been performed in this paper. Tensile and fracture specimens were fabricated with three different raster orientations (0/90, 30/−60 and 45/−45) in order to analyse the effect of the printing strategy on the resulting mechanical properties. A total of 30 tensile tests and 120 fracture tests were performed, covering fracture samples with defects of different notch radii (0 mm, 0.25 mm, 0.5 mm, 1 mm and 2 mm). The Theory of Critical Distances was applied over the fracture results, obtaining estimations of the corresponding critical distances and the subsequent predictions of the apparent fracture toughness. Graphene addition has a different effect depending on the raster orientation. Graphene causes a significant improvement of tensile and fracture properties for specimens fabricated at 30/−60 and 45/−45. However, this phenomenon is not observed in raster orientation 0/90. SEM analysis shows a clear change in the fracture micromechanisms between PLA and PLA-GR. It can be also observed how graphene samples of 30/−60 and 45/−45 present a similar aspect of the fracture surfaces, which are different from those observed in raster orientation 0/90.

本文对增材制造的 PLA 和石墨烯增强 PLA (PLA-GR) 进行了断裂评估。以三种不同的光栅方向（0/90、30/-60 和 45/-45）制造拉伸和断裂试样，以分析打印策略对所得机械性能的影响。共进行了 30 次拉伸试验和 120 次断裂试验，覆盖了具有不同缺口半径（0 毫米、0.25 毫米、0.5 毫米、1 毫米和 2 毫米）缺陷的断裂样品。临界距离理论应用于断裂结果，获得相应临界距离的估计和随后的表观断裂韧度预测。石墨烯添加具有不同的效果，具体取决于光栅方向。石墨烯显着改善了以 30/-60 和 45/-45 制造的试样的拉伸和断裂性能。但是，在光栅方向 0/90 中没有观察到这种现象。SEM 分析表明 PLA 和 PLA-GR 之间的断裂微观机制发生了明显的变化。还可以观察到 30/-60 和 45/-45 的石墨烯样品如何呈现断裂表面的相似方面，这与在光栅取向 0/90 中观察到的不同。