Study of the interlaminar fracture under mode I loading on FFF printed parts

The present study aims the development of a methodology for the analysis and evaluation of the fracture toughness under mode I loading of 3D printed parts, produced by the fused filament fabrication (FFF) additive technology. This work is motivated by the urgent need of improvement in this area, in order to extend the reliability of this process to applications which require high mechanical performance. For this purpose, a specific geometry was developed, taking into account the inherent characteristics of both, the applied material and process used for the production of double cantilever beam (DCB) tests. A set of experimental tests was performed with pure and short fibre reinforced Polyamide 12 (PA 12), and, in parallel, a numerical analysis was also followed for each series. Posteriorly, an inspection on the fracture surfaces was made, by microscopy, in order to refine the conclusions obtained and furtherly comprehend the variables in play. The obtained results provided a consistent value for the fracture toughness for only one of the cases studied, being this the unreinforced material. However, for the reinforced material, a set of conclusions which justify its behaviour was also able to be attained. The followed approach for the numerical analysis also revealed to be as suitable for this specific combination of material and additive process.