Enhancement of FDM ULTEM® 9085 bond strength via atmospheric plasma treatment

Abstract

Abstract The present study investigates a process to improve the bond strength of ULTEM® 9085 manufactured via fused deposition modeling and presents an application of this technique as a repair method for damaged 3D-printed structures. The initial surface characteristics, roughness, and wettability of AM parts are shown to vary with the print orientation. Atmospheric plasma treatment (APT) was utilized to improve the wetting characteristics and bond behavior of ULTEM® 9085 as verified by contact angle measurements, XPS analysis, and flatwise tensile testing. The plasma treated samples displayed improved wettability of the polymer surface with a decrease in the contact angle from 115° to 22°. Furthermore, flatwise tensile testing of treated samples that were initially hydrophobic showed a 35 % increase in interfacial strength. The surface modifications were characterized by XPS. Increases in the concentration of oxygen on the surface contributed to the improved wettability of the samples, while increases in the concentration of carboxyl groups led to enhanced interfacial bond strength with an epoxy paste adhesive. However, with overexposure to plasma treatment weakly bound ash forms on the surface and leads to a degradation of strength. An optimized plasma treatment is proposed for ULTEM® 9085, and an application for a repair doubler was tested. Utilizing a damaged tensile dogbone specimen, this plasma treatment and bonding technique are shown to produce a 100 % recovery of strength, demonstrating the applicability and potential for repairing 3D-printed structures.