Predictive Modelling of the Elastic Properties of 3D Printed Short Fibre Reinforced Polymers

  • Canegrati, Andrea (Politecnico di Milano)
  • Martulli, Luca (Politecnico di Milano)
  • Mancassola, Zeno (Politecnico di Milano)
  • Kostovic, Milutin (Consiglio Nazionale delle Ricerche)
  • Rollo, Gennaro (Consiglio Nazionale delle Ricerche)
  • Sorrentino, Andrea (Consiglio Nazionale delle Ricerche)
  • Carboni, Michele (Politecnico di Milano)
  • Bernasconi, Andrea (Politecnico di Milano)

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Fused Filament Fabrication (FFF) is a 3D printing technology which recently enabled polymer-base composite to be processed. An FFF printer deposits semi-molten material beads layer-wise on a printing platform to create a nearly free-form object. What currently hinders the outbreak of this technology in industry is, among other issues, the limited ability to predict the mechanical properties of the printed part since the design stage. There is a general lack of physical-oriented models for the stiffness prediction of 3D printed part. In the present work, a newly developed analytical model, called Equivalent Spring Model (ESM) is proposed for the stiffness prediction of short fibre composite specimens printed via FFF. Each printed bead is divided into different portions according to its overlap with other beads and the fibre orientation. Each portion is then modeled as an equivalent spring, whose stiffness is defined based on the local elastic properties of the bead. ESM requires in input few quantities: the elastic properties of the material and the nominal printing parameters. ESM was validated against experimental datasets and its accuracy was assessed in comparison to the Classical Laminate Theory (CLT). ESM proved to be effective and quite accurate despite the few input parameters required. Therefore, it could be considered as a powerful tool to support the design phase of a 3D printed part.