Injection molded direct joining (IMDJ) is one of the metal-plastic direct joining processes and is based on a combination of a special surface treatment of a metal piece and an insert molding. This study employed a chemical processing as the special surface treatment to form nano-structures on the metal piece. We investigated relationship between joining strengths and molding conditions; we focused on pressure of a mold cavity and injection speed as molding conditions in this work. To evaluate the IMDJ samples processed under various molding conditions, we carried out tensile-shear tests. Then we compared the results of the tests to discuss how much each condition variation affected the joining strength. From the discussion, we found an interesting effect of the injection speed, which is unique to the IMDJ using a metal piece with nano-structures. The findings of this study will promote a better understanding of the IMDJ.

Effects of molding conditions on injection molded direct joining using a metal with nano-structured surface

Surface modification pretreatment on laser direct joining of glass fibre reinforced polyamide to steel was studied to assess its effect on the joint's mechanical performance. The steel part was structured by laser radiation to accomplish a proper mechanical interlock when joining with the polymer. In a second step, the opposite side of the micro-structured metal was irradiated by a continuous wave (cw) fibre laser system until reaching the melting temperature of the polymer in both materials interface. The metal micro-structuring was produced by two different laser sources (nanosecond pulses (ns) and cw) in order to study the effect of different groove geometries on the joint's failure force under tensile-shear tests. The impact of structure density and clamping pressure was also assessed. A tight dependence of aspect ratio and recast material height of patterns on joint’s failure force was found for the micro-patterns that were produced by nanosecond pulses. The greatest strength was achieved in the case of patterns produced by ns-pulses. The trend concerning the effect of structure density was validated for the patterns that were produced by ns-pulses and cw-radiation. The changes in clamping pressure did not evidence a significant influence on the joint quality. The morphological features of the detached surfaces showed that the micro-geometric structure aspect ratio has a meaningful effect on the failure mode in the case of structures that were generated by nanosecond pulses.

Experimental investigation into metal micro-patterning by laser on polymer-metal hybrid joining

Interfacial interaction and joining property of direct injection-molded polymer-metal hybrid structures: A molecular dynamics simulation study

Joining strength dependence on molding conditions and surface textures in blast-assisted metal-polymer direct joining

Large-area mechanical interlocking via nanopores: Ultra-high-strength direct bonding of polymer and metal materials

The joining of metal and polymer surfaces is a promising technology to reduce the total weight of parts and to improve interface reliability. In this study, a micro square grid (200 μm × 200 μm) was fabricated on an aluminum surface using laser ablation. Molten glass-reinforced poly(butylene terephthalate), poly(styrene) and acrylonitrile---butadiene---styrene were introduced to the micro square grids by a precise injection molding machine. The maximum load tensile test was used as a measure of the joining strength between aluminum and the polymer. The tensile strength tests assisted in the differentiation of three modes of separation: interface-peeling, cohesive failure and matrix fracture. The maximum load increased with the effective joined area where interface-peeling was observed. The maximum load ceased at a certain effective joined area, and matrix fracture occurred. Cohesive failure was observed where the effective joined area was smaller than the area for which matrix fracture was observed, and the joined strength was larger than that observed for interface-peeling. The maximum stress, which was calculated by dividing cross-sectional area by the maximum load, at the matrix fracture was proportional to the polymer tensile strength.

Shuhei Nakamura

Papers

Direct joining of a laser-ablated metal surface and polymers by precise injection molding