Session: 03-13-02: Testing and Characterization

Paper Number: 159569

159569 - Role of Infill Patterns on Interlayer Shear Strain and Fracture in Creep of 3d-Printed Polymer 

The creep behavior of 3D-printed polymers differs significantly from cast polymers due to the influence of interlayer bonding, where shear stress plays a pivotal role. This study investigates the role of shear stress in the bonding and fracture mechanisms of individual layers in 3D-printed Tough PLA by analyzing various infill patterns (Honeycomb, Grid, and Line) and densities (40% and 90%). Tensile and creep tests were conducted, with strain fields measured using Digital Image Correlation.Results showed that the Line pattern exhibited the highest normalized Ultimate Tensile Strength but poor creep resistance due to concentrated shear strain between layers, leading to premature failure. In contrast, the Honeycomb pattern demonstrated superior creep resistance and more uniform shear strain distribution, particularly at higher densities, indicating enhanced interlayer bonding. Failure mechanisms varied: the Line pattern experienced localized shear strain along filaments, weakening bonds, while the Grid and Honeycomb patterns displayed evenly distributed shear strains, with failure initiating at stress-concentrated intersections. Higher densities generally improved creep resistance by increasing internal support and reducing strain concentrations, thereby strengthening layer-to-layer adhesion. However, unexpected strain concentrations in high-density (90%) Honeycomb samples were attributed to slicing algorithm flaws, potentially compromising interlayer integrity. ANOVA analysis confirmed that infill patterns and stress levels significantly influenced creep behavior, with notable interactions between these factors.

Presenting Author: Mohamad Alagheband Florida State University

Presenting Author Biography: Mohamad Alagheband is a Ph.D. candidate in Civil Engineering at Florida State University, specializing in crashworthiness analysis, and advanced engineering design. With over seven years of industry experience in mechanical design and product development, he applies cutting-edge techniques such as non-linear analysis, machine learning, and optimization to solve complex engineering challenges.
As a Research Assistant on a Florida Department of Transportation (FDOT)-funded project, Mohamad has conducted structural integrity and injury assessments for transit buses, contributing to improved safety standards. His research has led to multiple peer-reviewed publications in esteemed journals like International Journal of Fatigue, the Journal of Materials Engineering and Performance. He also serves as a reviewer for leading journals, including Journal of Hazardous Materials Advances.
Recognized for his academic contributions, Mohamad received the 2024 Graduate Research Excellence Award from Florida State University.