Torsional Performance of Vat-Photopolymerized Tough Resin: Influence of Gauge Length and UV Post-Curing

Abstract Background A myriad of materials, ranging from soft sensors to bone substitutes, undergo torsional loading throughout their operational lifespan. Many of these materials are produced using additive manufacturing (AM) technology due to its broad applicability. Understanding the torsional behavior of these AM components is crucial prior to their utilization. However, research on the torsional behavior of solid additively-manufactured resin polymers remains very limited. Objective To address the gap in understanding the torsional behavior of additively-manufactured resin polymers, this study aimed to investigate the effect of varying gage lengths and UV post-curing durations on the torsional capacity, shear modulus, and energy absorption characteristics of these materials. Methods Torsion specimens were fabricated using vat photopolymerization (VPP) with AnyCubic UV Tough Resin. The specimens were prepared with different gage lengths (20, 40, 60, and 80 mm) and were subjected to five UV post-curing durations (0, 15, 30, 60, 90, and 120 min). Monotonic torsion was applied to the specimens until failure at a rate of 0.1 revolutions per minute. Results The tests revealed ductile failure patterns across all specimens. Longer post-curing times were found to correlate with increased torsional capacities and shear moduli. However, conclusions regarding energy absorption per unit volume remained inconclusive. The results showed that UV exposure had a significantly greater impact on the mechanical properties of the specimens compared to the gage length. Additionally, a normalized trilinear model was proposed to characterize the behavior of additively-manufactured resin polymers under monotonic torsion, which facilitates numerical simulation of material responses in finite element software.