On the use of laser-scanning vibrometry for mechanical performance evaluation of 3D printed specimens

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In this study, we explored the suitability of laser-scanning vibrometry (LSV) for evaluation of the mechanical behavior of rectangular prisms produced by Fused Filament Fabrication (FFF). Our hypothesis was that LSV would be able to discriminate the mechanical behavior of specimens fabricated with different process parameters combinations. Build orientation, raster angle, nozzle temperature, printing speed and layer thickness were the process parameters of interest. Based on a factorial design of experiment approach, 48 different process parameter combinations were taken into account and 96 polylactic acid (PLA) rectangular prisms were fabricated. The characterization of their dynamical behavior provided frequency data, making possible the computation of an equivalent elastic modulus metric. Statistical analysis of the equivalent elastic modulus dataset confirmed the significant influences of raster angle, build orientation and nozzle temperature. Moreover, multivariate regression models served to rank, not only the significant influences of individual process parameters, but also the significant quadratic and cubic interactions between them. The previous knowledge was then applied to generate an ad hoc model selecting the most important factors (linear and interactions). The predicted equivalent elastic moduli provided by our ad hoc model were used in modal analysis simulations of both 3D printed rectangular prisms and a complex part. The simulated frequencies thus obtained were generally closer to the experimental ones (≤11%), as compared to modal analysis simulations based on internal geometry modelling (≤33%). The use of LSV appears very promising in the characterization of the mechanical behavior and integrity of 3D printed parts. Other additive manufacturing technologies may benefit from the use of this technique and from the adoption of the presented methodology to test, simulate and optimize the properties of 3D printed products.