In recent years, the additive manufacturing market has grown rapidly. There are a number of different kinds of 3D printing techniques. One of the more commonly used processes is stereolithography. There is a significant literature gap between the knowledge of the properties of stereolithographic resins. Compared to the tensile properties, the compressive properties do not seem to be as commonly available. The paper presents the results of mechanical testing of four types of resins from Formlabs® to determine the mechanical properties they hold under compression. The test specimens for compression were designed according to ASTM D695-15 for the Compressive Properties of Rigid Plastics standard.&nbsp;Testing was performed on Clear, Tough, Durable and High-Temperature resins with and without post-processing. Post-processing was carried out using a customized curing oven that was constructed in order to follow the process specification provided by the resin manufacturer.&nbsp;It was found that the Tough and Durable resins performed similarly when green (TG, DG), but the post-processing treatment made the&nbsp; Tough Resin (TC) behave like glass while the Durable resin (DC) kept behaving like an elastomer. The ultimate strength for TG is 292.5 MPa, and the ultimate strain is 0.72 mm/mm. For TC, the ultimate strength was 301.2, and the ultimate strength was 0.674 mm/mm. The post-processing treatment did not increase the strength of the material in compression, but increased it stiffness. The Secant elastic modulus changed from 179.89 MPa to 978.18 MPa.The value of the secant elastic modulus for TG is lower than 73.9 MPa reported in previous literature, where the test were conducted at 0.024 inches per minute. They are also lower than the elastic modulus measured in tensile reported by the manufacturer of 1.7 and 2.7GPa,&nbsp; for TG and TC, respectively.For the High Temperature (HT) resin we saw a change in the nature of the material due to the post-treatment similar to what was observed between TG and TC. However, the HT resin seemed to be fragile even at its green state (HTG) when handled, behaving mechanically similarly to the clear resins. The high-temperature resins were extremely brittle and shattered upon failure. The ultimate strength for the green samples is 232.4971 MPa, and the ultimate strain is 0.6118 mm/mm. For the high temperature cured samples, the ultimate strength is 192.0730 MPa, and the ultimate strain is 0.3872 mm/mm. The secant elastic modulus was 391.22 MPa for HTG and 1162.65 MPa for HTC, in line with the 0.45 GPa and 1.26 GPa reported by the manufacturer in tensile.We estimated the tangent modulus of the stress-strain curve according to the standard. We also used&nbsp; a Polynomial fitting and were able to separate the elastic modulus from the viscous modulus. We found that the viscous modulus is non-linear and depends upon the velocity of the test.The tests presented here are the first comparison of different types of Formlab resins under compression and can shed some light on the anisotropic behavior of many of these resins.&nbsp;&nbsp;

Elastoplastic Behavior of Sla Resins in Compression

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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