Nanomodifications and Experimental Investigations of Process-Induced Effects on Mode 1 Fracture Behavior of Vero Pure White Material System in Polyjet Additive Manufacturing Setup
Authors: Khapper Vishwanath , Mohan Ram V. 
Published: January 2025

Abstract
This study investigates the Mode I fracture behavior of a Vero Pure White material system integrated with Carbon Nanofibers (CNF) within a PolyJet additive manufacturing setup. PolyJet printing, known for its ability to fabricate complex structures with high precision, is utilized to enhance the mechanical properties of the printed components by introducing a tailored nanocomposite system. Integrating CNF into the VeroPureWhite resin aims to improve the material’s fracture toughness and overall mechanical performance. Specifically, the focus is on understanding the influence of process parameters and the distribution of CNF on the fracture behavior of the printed specimens. The study employed a novel two-step method to integrate Carbon Nanofibers into the Vero Pure White resin. The CNF was uniformly dispersed within the resin using bath sonication, ensuring consistent distribution throughout the material. Specimens were designed with voids specifically for nanocomposite infusion, using the Air injection feature of PolyJet printing that created these voids without introducing support material, thereby maintaining the purity of the nanocomposite blend. Cylindrical voids and CNF resin blends were printed for samples with crack fronts parallel to the material deposition direction and cubical voids for samples with crack fronts perpendicular to the material deposition direction. The Vero Pure White-CNF blend was then precisely introduced into these voids during printing. The printed specimens were tested using ASTM D5045 standards to evaluate their mechanical performance, particularly the fracture behavior. Fracture toughness tests revealed significant improvements in mechanical properties when a crack encountered the CNF-resin blend inclusions. For specimens with crack fronts parallel to the material deposition direction, peak loads ranged from 822 N to 888 N, with Mode I fracture toughness (K1C) values averaging 1.453 MPa0.5. These samples’ critical strain energy release rates (G1C) ranged from 1294 J/m2 to 1571 J/m2, indicating a high energy absorption capacity. Specimens with crack fronts perpendicular to the material deposition direction exhibited even greater mechanical strength, with peak loads ranging from 1431 N to 1531 N and an average K1C value of 2.50 MPa0.5.
The G1C values for these samples varied from 1730 J/m2 to 2036 J/m2, reflecting differences in energy absorption at the fracture point. The data variations could be attributed to variations in the nanocomposite distribution or the architecture of the voids. The study highlights the effectiveness of integrating Carbon Nanofibers into the VeroPureWhite material system to enhance the structural properties of 3D-printed components. The introduction of CNF significantly improved the specimens’ fracture toughness and energy absorption capacity, particularly in samples with crack fronts perpendicular to the material deposition direction. These findings demonstrate the potential of nanocomposite material inclusions in additive manufacturing, allowing the production of structural components with customized and tailored mechanical properties, thereby expanding the applications of 3D printing in industries that demand high-performance materials.