Dependence of the nano structure size on joining strength and polymer infiltration in injection molded direct joining

Abstract

Metal-polymer hybrids are widely used because of the large demands of lightweight materials. The hybrid joint can be generated by the polymer infiltration into metal surface textures through injection molded direct joining (IMDJ). Generally, nanostructures are suitable for small metal parts. We aimed to study the effect of nanostructure size on the polymer infiltration and joining strength. Nano-porous structures with different sizes (diameter in 70, 400, 600 nm) and similar porosity of 40 % were fabricated on metal surface by anodizing and etching process. These metal pieces were utilized for IMDJ at injection speeds of 10, 100, 200 300 mm/s. The negative dependence of polymer infiltration on the injection speed was confirmed when the structure size is in 70 nm while the positive dependence when larger than 400 nm. However, the negative dependence of joining strength on the injection speed was confirmed in all nanostructures. It is considered that although polymer can infiltrate deeper into the large structure at high injection speed, the reduction of well infiltration area leads to the negative strength dependence on speed.