3D printed elastomeric polyurethane: Viscoelastic experimental characterizations and constitutive modelling with nonlinear viscosity functions

Abstract

Digital Light Synthesis (DLS) technology creates ample opportunities for making 3D printed soft polymers for a wide range of grades and properties. In DLS, a 3D printer uses a continuous building technique in which the curing process is activated by an ultraviolet (UV) light. In this contribution, EUP40, a recently invented commercially available elastomeric polyurethane (EPU) printed by the DLS technology, is experimentally characterised. For characterizing the mechanical properties, an extensive viscoelastic experimental study on the digitally printed EPU taking the strain rate-dependence are conducted. The study reveals a significant time-dependency on its mechanical responses. Moreover, the material demonstrates noticeable nonlinear viscosities that depend on strain and strain rates. Based on the experimental findings for the printed elastomer, a large strain viscoelastic model is devised where evolution laws are enhanced by strain and strain rate-dependent nonlinear viscosities. Following identifications of relevant material parameters, we validate the model with the experimental data that show its good predictability. Such an extensive experimental study along with a constitutive model will help in designing and simulating more complex cellular and structured metamaterials using 3D printed elastomeric polyurethanes.

Additive manufacturing and the COVID-19 challenges: An in-depth study

“…The built part is supported by a structure, which holds pattern in the liquid resin bath, and prevents the newly formed layer from moving out of the position from the already built portion. Once a layer is scanned and cured, the platform or the support structure moves downward or upward by several micrometers (μm, based on the resolution of a printer) to make another layer of liquid resin available to be cured [22] , [23] , [7] , [8] , [21] .…”

“…Parts can be fabricated in a single step removing the need for assembly in some cases, thus reducing post-processing and lead times. Thanks to these attractive manufacturing advantages, AM is extensively utilised in medical, aerospace, and automotive industries [5] , [6] , [7] , [8] , to mention a few. The advantage of part customisation is utilised highly in medical applications, in which parts can be customised to the individual patient's data [9] , [10] .…”

Experimental Characterization Framework for SLA Additive Manufacturing Materials

“…Knowing how the printed material behaves in those situations is of great importance for designing purposes, therefore uni-axial tests of loading and unloading were performed imposing a series of cycles with increasing strain as can be seen in Figure 7 . If the unloading curve changes with the maximum strain reached, the Mullins effect is presented in the printed material [ 18 , 29 , 31 ] and further investigation is needed. The material proposed for the present framework does not show significant Mullins effect since the unloading curves of Figure 7 at different strains ( = 0.15 and 0.3) present similar slopes.…”

“…Finally, they take advantage of this behavior to produce optimized printing orientations for final parts. Hossain et al [ 18 ] studied the behavior of a printed material obtained by digital light projector DLP process, focusing on the viscoelastic constitutive behaviour at low strain rates. However, the author does not focus on the influence of the printing parameters in the behaviour of the material.…”

Optimization of Manufacturing Parameters and Tensile Specimen Geometry for Fused Deposition Modeling (FDM) 3D-Printed PETG

“…Build orientation, layer thickness, and feed rate are discussed on 3D-printed PLA samples in [48], and layer thickness and raster angle parameters for PLA and ABS in [49]. In order to model the mechanical response of additive manufactured polymers [50][51][52], well-known homogenization techniques are used in composite materials [53], for example by using a variation of carbon-fiber content in thermoplastic matrix-based composites built by the FDM [54] and also for identifying substructure-related anisotropic properties [55] to be used in computations [56,57].…”