Session: 02-01-04: 7th Annual Conference-Wide Symposium on Additive Manufacturing: Polymers II

Paper Number: 99462

99462 - Induced Anisotropy in the Fracturing Behavior of 3d Printed Parts Analyzed by the Size Effect Method 

In the recent past, additive manufacturing, colloquially referred to as 3D printing, has revolutionized the field of materials design and manufacturing in a wide variety of engineering applications. This paper analyzes via the size effect method, the induced anisotropy in the fracturing behavior of 3D printed parts made using Acrylonitrile Butadiene Styrene (commonly abbreviated as ABS). The aspects of fracturing behavior considered include the strength, fracture toughness, the nonlinear fracture process zone (FPZ) size, and the degree of quasibrittleness. 3D printed ABS specimens of various sizes and various relative orientations of the pre-crack and the 3D printed layers are considered. The fracture properties are measured via fracture tests on single edge notch bending specimens. The measurements are seen to conform to the well-known size effect laws for strength and fracture toughness.

It is demonstrated that the 3D printed parts exhibit considerable anisotropy in their fracturing behavior, which would not occur in the monolithic counterparts. This occurs not only for the strength and fracture toughness, but also the FPZ size and therefore the degree of quasibrittleness. For the ABS polymer considered here it appears that if the crack path involves breaking through the microlayers, it can result in low strength but high toughness i.e. greater degree of quasibrittleness. On the other hand if the crack path involves breaking through the macro layers, it can result in high strength and low toughness, i.e. greater degree of brittleness.

It is demonstrated that the size effect method provides a rigorous way of evaluating the fracturing behavior since it enables the determination of the true fracture toughness, the fracture process zone size and the degree of quasibrittleness. It aids in determining the size range for which LEFM can and cannot be applied, depending on the orientation. This is important, since if unaccounted for, one might end up testing only the apparent fracture toughness which cannot be applied to specimens of larger or smaller size. Thus in conclusion, the results obtained in this study show that strong anisotropy can result in the fracturing behavior of 3D printed parts. Due to micro layering and macro layering, considerable quasibrittleness is also induced in the fracturing behavior, and the degree of quasibrittleness is also anisotropic. Neither of these anisotropies would exist in the same part if it was manufactured as a monolith. Therefore, these effects must be accounted for in order to develop reliable designs for 3D printed parts.

Presenting Author: Kedar Kirane Stony Brook University

Presenting Author Biography: Prof. Kedar Kirane is an assistant professor of mechanical engineering at Stony Brook University (SUNY) in New York, USA. His research focuses on understanding and predicting the failure of various conventional and advanced composite materials. These include fiber reinforced composites, nanocomposites, geological materials, concrete, and polycrystalline alloys. Prof. Kirane obtained his Ph.D. in 2014 from Northwestern University and joined the Mechanical Engineering faculty at Stony Brook University in Sept 2017. He also holds an M.S. degree from the Ohio State University (2007) and a B.S from the University of Pune, India (2004), both in mechanical engineering. Prior to joining Stony Brook, Prof. Kirane worked as a senior researcher at the ExxonMobil Upstream Research Company and has also held a development engineer position at Goodyear Tire & Rubber company in the Engineering Mechanics group. He is the recipient of ASME Material Division's Orr Early Career award, DOD Army Research Office’s Young Investigator award and ASME Applied Mechanics Division’s Haythornthwaite Research Initiation Grant for his work in the field of fracture and scaling of advanced composite materials. At Stony Brook University, Prof Kirane teaches undergraduate as well as graduate courses on solid mechanics, composite materials and fracture mechanics.

Authors:

Kedar Kirane Stony Brook University
Anar Nurizada Stony Brook University