Effects of coating on the fatigue endurance of FDM lattice structures

Additive Manufacturing techniques, such as Fused Deposition Modeling (FDM), are widely used to produce lattice structures with complex unit cell geometries. These structures can be designed to meet specific requirements in a wide range of application fields, ranging from biomedical to mechanical sectors. The mechanical behavior of these structures is often impaired by a low surface quality. However, the mechanical strength of polymer lattice structures can be significantly improved with the use of post-processing treatments. Coating post-processing is one of the treatments that showed the best results. Nevertheless, research interests are often targeted at studying the static mechanical properties rather than the fatigue behavior of polymer components. In this work, the effect of a polymeric coating on the fatigue life of Polylactic acid (PLA) lattice structures, produced by FDM, was investigated. Specimens have been designed to enable the application of both tensile and compressive loads. Preliminary tensile tests were carried out to assess the static strength of the specimen before the fatigue tests. Experimental fatigue tests were performed with varying testing frequencies and displacements. The results evidenced differences in the behavior of coated and non-coated components when subjected to different testing frequencies and loading conditions. The polymeric coating produced an increase in fatigue endurance across different testing frequencies over a particular displacement range.