Evaluation of the geometrical discontinuity effect on mixed-mode I/II fracture load of FDM 3D-printed parts

Abstract

The main objective of this manuscript is to evaluate the capability of the fracture criteria and numerical methods to predict fracture properties of the specimens fabricated using the Fused Deposition Modelling (FDM) 3D-Printing method. Different thermoplastic materials are 3D printed in Semi-Circular Bending (SCB) specimens configuration and subjected to three-point bending loading to investigate their failure behaviour, including final load-bearing and crack path trajectory. The Acrylonitrile Butadiene Styrene (ABS) due to its brittle behavior, was selected for the mixed mode fracture study. The SCB samples with various pre-crack angles indicating different modes of loading conditions are manufactured. Cracked SCB specimens are produced with and without geometrical discontinuities as holes to verify the effect of stress concentration on their fracture behavior. The results of the three-point bending tests demonstrated that the Extended Finite Element-Cohesive Zone Model (XFEM-CZM) and Average Strain Energy Density (ASED) criterion are capable of predicting the fracture behavior of the 3D-Printed ABS material under mixed-mode I/II loading. The appropriate XFEM-CZM damage criterion was used to estimate the crack growth path. The final failure load was obtained using the ASED and XFEM criteria. The maximum error rate between the experimental results and the presented theories was 10%, which confirms the employed criteria' accuracy. The results showed that a stress raiser like a hole in the 3D-Printed specimens might reduce the loading capacity of the material by 17%.