Study of a Single Joint Between Two FDM-Printed PLA Filaments

Area of Science:

• Materials Science
• Additive Manufacturing
• Mechanical Engineering

Background:

• Isolating and testing the mechanical properties of individual fused deposition modeling (FDM) joints has been a significant challenge.
• Understanding FDM joint strength is crucial for improving simulations and predicting material performance.

Purpose of the Study:

• To develop a novel methodology for evaluating the apparent tensile strength (ATS) and fracture mechanisms of single FDM joints.
• To investigate the influence of nozzle and bed temperatures on FDM joint interlayer bonding.

Main Methods:

• Introduction of a cruciform single-joint test (CSJT) using a cross-shaped specimen and a rapid mechanical clamping protocol.
• Systematic variation of nozzle (180-215 °C) and bed (30-120 °C) temperatures, with a minimum of 12 samples per condition.
• Classification of failure mechanisms (joint vs. filament failure) and computation of ATS from tensile tests and optical micrographs.

Main Results:

• Detachment probability of joints decreased sharply above 210 °C nozzle temperature, while ATS increased towards a plateau of ~50 MPa.
• Bed temperature showed a smoother influence, with decreasing detachment ratio and increasing ATS.
• Nozzle temperature was identified as the primary factor influencing joint strength, mapping a transition from joint-controlled to filament-controlled failure.

Conclusions:

• The developed CSJT method provides a reliable, high-throughput, and material-efficient approach to quantify FDM interlayer bonding.
• The findings offer critical data for informing process simulations and optimizing FDM printing parameters for enhanced material strength.