According to the PN-EN ISO 527-1:2020-01 standard, the stress-strain curve obtained for PLA classifies this material as having a yield point with no increase in stress after yielding. The addition of hydroxyapatitewhether nHAp or µHAp, at both 20% and 40% concentrations -causes the material to be classified as brittle, with no yield point, according to the same standard. PCL-based materials, on the other hand, despite the additive, can be classified as materials with a yield point that show an increase in stress after yielding. By carefully examining the fracture morphology of the samples after the tensile test, a reflection of this classification can be found. The Supplementary Information in Figure provides fracture images of the PLA and PCL references. PLA, due to its high glass transition temperature (see section 3.2), is a brittle material at room temperature, although small plastic deformations occur before the specimen breaks. In contrast, pure PCL is a highly ductile material, with a strain at break of 534 %, compared to just 4.9 % for PLA.