Session: 17-15-01: Society-Wide Micro/Nano Poster Forum

Paper Number: 99944

99944 - Experimental and Numerical Investigation of the Influence of Crack Front Orientation in Mode 1 Plane Strain Fracture Toughness of a Vero Material System via Polyjet Additive Manufacturing 

Polyjet printing, a subclass of the Additive Manufacturing method, has been used to fabricate three-dimensional structures out of a broad variety of photopolymers, including Digital ABS, Polypropylene, and Vero material system. By using a layer-by-layer deposition procedure, this method allows for the fabrication of parts with a wide range of material compositions and thermo-mechanical properties that may be matched to the application's requirements. An investigation on the impact of process-induced variation on the Mode I fracture toughness value of a Vero material system is presented in this work. An extensive set of experiments on compact tension C-T specimens were carried out, followed by finite element analysis. To accomplish this goal, the compact tension specimens with crack fronts parallel to the print direction and with crack fronts perpendicular to the print direction were fabricated. It was observed that the orientation of the crack front with respect to the print and build directions had a significant impact on the values of Mode I fracture toughness. For example, when the crack front was parallel to the print direction, the K_1C value decreased by 49.54 percent, critical strain energy density G_1C values decreased by 41.56 percent, and peak load intensity decreased by 52.76 percent. The presence of numerous micro voids in the weak zone between two successive layers can be linked to the significant decrease in fracture parameter values along the build direction.  To reproduce the experimental findings, C-T samples were modeled in a CAD modeler and then subjected to Finite element analysis in the Ansys workbench. A pre meshed crack tool splitting the top and bottom faces of the crack surface is used. Nodes were positioned at the crack front. The mesh was generated with a resolution of 4 utilizing the patch confirming method, a sphere of influence defined the edge sizing. The element type used was Tetrahedron. The loading pins are modeled as rigid bodies and boundary conditions are applied at the top and bottom pin to emulate the plane strain conditions. The Representative Volume Element method is used to acquire homogenized property values for a composite that contains the Vero material system as the matrix and carbon nanofibers as reinforcement. The integration of carbon nanofibers is accomplished using a customized material configuration, and the influence of the nanofibers on fracture is studied. By comparative analysis, it was observed that a tailored arrangement perpendicular to the fracture front in a 3D printed C-T specimen has a stiffening effect on the specimen and a relaxing impact was recorded for the 3D printed specimen that had been generated with a tailored network parallel to the crack front, indicating that an additively created part may be prone to hyperplastic failure under certain conditions.

Presenting Author: VISHWANATH KHAPPER North Carolina Agricultural and Technical State University

Presenting Author Biography: Vishwanath Khapper is a graduate student at the Joint School of Nanoscience and Nanoengineering in Greensboro, pursuing his PhD <br/><br/>Since he earned his master&#39;s degree, he has been working on composites and attempting to gain an understanding of the thermomechanical properties of composite material systems. In continuation of this, he is currently engaged in research on nanocomposites and is attempting to understand the fracture behavior of additively manufactured nanocomposites.

Authors:

VISHWANATH KHAPPER North Carolina Agricultural and Technical State University
Ram Mohan North Carolina Agricultural and Technical State University