Experimental and Simulation Analysis of Fused Deposition Modeling 3D-Printed Polylactic Acid Joints Developed Using Susceptor-Free Microwave Heating Approach

Microwave joining of additively manufactured polymer parts typically employs a carbon-rich susceptor to form the joints, resulting in carbon contamination and joint distortion due to non-uniform heating. This work presents a susceptor-free approach for microwave joining of fused deposition modeling (FDM) fabricated polylactic acid (PLA) plates using a microwave-absorbing epoxy resin as the interlayer material. Experimental and FEM approaches were used to study microwave joining of additively manufactured PLA specimens. PLA plates were lap joined using two different approaches (specimens named S1 and S2) based on the stepped heating and cooling cycles, considering their glass transition temperature (63.2 °C) and melting point (156 °C). A FEM model was simulated to analyze the microwave heating behavior of PLA and epoxy by examining the electric field distribution, temperature and conductive heat. Simulated and experimental time-temperature profiles showed strong agreement. TGA analysis revealed that joined PLA specimens possess almost similar thermal properties to 3D-printed PLA plates. Further, the XRD and FTIR results confirmed the absence of epoxy in the joined PLA specimens. SEM micrographs of the S2 specimen revealed small interwoven structures, highlighting a smooth transition between plates. The joint shear test revealed a 174% higher ultimate tensile stress for the S2 specimen than for the S1 specimen.