*Article* **Fracture Resistance Analysis of 3D-Printed Polymers**

### **Ali Zolfagharian 1,\*, Mohammad Reza Khosravani 2 and Akif Kaynak 1**


Received: 4 January 2020; Accepted: 23 January 2020; Published: 2 February 2020

**Abstract:** Three-dimensional (3D)-printed parts are an essential subcategory of additive manufacturing with the recent proliferation of research in this area. However, 3D-printed parts fabricated by di fferent techniques di ffer in terms of microstructure and material properties. Catastrophic failures often occur due to unstable crack propagations and therefore a study of fracture behavior of 3D-printed components is a vital component of engineering design. In this paper, experimental tests and numerical studies of fracture modes are presented. A series of experiments were performed on 3D-printed nylon samples made by fused deposition modeling (FDM) and multi-jet fusion (MJF) to determine the load-carrying capacity of U-notched plates fabricated by two di fferent 3D printing techniques. The equivalent material concept (EMC) was used in conjunction with the J-integral failure criterion to investigate the failure of the notched samples. Numerical simulations indicated that when EMC was combined with the J-integral criterion the experimental results could be predicted successfully for the 3D-printed polymer samples.

**Keywords:** mechanical fracture; 3D printing; mixed mode fracture; load-carrying capacity
