Improvement and Evaluation of the Interlaminar Bonding Strength of FDM Parts by Atmospheric-Pressure Plasma

Abstract

Additive Manufacturing has the feature that the on-demand manufacture of the arbitrary shape can be performed. However, as one of weak points, interlaminar bonding strength is low. It is because the building principle is based on lamination. This research aims at improvement in the adhesive strength between laminations by performing hydrophilization treatment to the lamination plane of a FDM parts using atmospheric pressure plasma. Atmospheric-pressure plasma is characterized by generating glow-discharge condition under an atmospheric pressure. It can use for surface treatment etc. using active species (radical ion, an electron, etc.). For example, they are cleaning effects, such as soil removal of an organic substance, an effect to the roughened surface for forming unevenness in the surface, etc. Although a tensile test is usually performed on evaluation of adhesive strength, a lot of hours are needed for experimental preparation. The surface free energy of an object surface is effective as one of the evaluation indices for evaluating the adhesive strength of a lamination plane. However, in order to find an experimental condition in research initial stages, such as material search and manufacturing conditions, it can become effective in respect of an hour and cost to use surface free energy as an evaluation index. In this paper, the effect to the surface free energy by atmospheric pressure plasma is investigated first. And the influence on the rupture strength improvement by atmospheric pressure plasma is investigated. Next, it is searched for the effective irradiation conditions of atmospheric pressure plasma. The influence of the atmospheric pressure plasma to the building parts of FDM was experimented based on surface free energy. The rupture test was done and improvement in rupture stress was confirmed by plasma irradiation. The result that the irradiation range and irradiation distance of an atmospheric-pressure-plasma head had large influence on the increase in surface free energy was obtained. It was observed that surface free energy increases about 75% to an initial sample by irradiation of atmospheric pressure plasma.