Multiscale characterization of an in-situ foamed 3D printed lightweight structure for the design of a complex digital twin

Additive manufacturing coupled with in-situ foamed low density polymers allows the creation of high-performance lightweight structures. In this study, an approach considering material properties as isotropic is proposed to describe the elastic behavior of a large-scale structure made of in-situ foamed Polylactic acid (PLA). The aim of this work is to elaborate a digital twin of the flexural behavior of a complex 3D printed in-situ foamed structure (a part of a surfboard manufactured by WYVE, Anglet, France) with a multiscale approach. Firstly, a characterization of the material in its filament and foamed forms is carried out to apprehend the impact of the in-situ foaming on the chemical structure and composition, the thermal behavior and the morphology. Secondly, the tensile and flexural properties of the foamed PLA are studied to obtain a behavior law useful to correlate the real behavior in flexion of a part of the surfboard with its digital twin. Finally, an experimental and numerical correlation is conducted through digital image correlation to assess the viability of the digital twin. The printing settings used resulted in an expansion ratio of 2.8. The specific moduli of elasticity and bending (printed flat and on-edge) are respectively 1442 MPa, 1320 MPa and 923 MPa. The experiment confirms that the numerical model proposed correlates with a mean error lower than 5 %. Given the fact that the low PLA density obtained depends greatly on the printing settings, it offers great versatility in printing with a targeted rigidity for broad industrial applications.