Distribution and reinforcement effect of carbon fiber at the interface in injection welding of polyamide 6 composites

Abstract

To meet the lightweight production requirements of automobiles and achieve high strength, reinforced thermoplastic composite materials are gradually replacing metal materials. Injection molding is the preferred manufacturing method to enable the production of complex‐shaped parts, facilitate production, and reduce costs. In this study, carbon fiber (CF) was added to the commonly used resin‐reinforcing material, polyamide (nylon) PA6, to create a CF‐reinforced thermoplastic composite (polyamide 6 [PA6]/CF) that was welded using injection molding. This study not only investigates the impact of different welding conditions on shear strength but also discusses the sequence of welding. Achieving 85% of the shear strength of the PA6 base material under ideal circumstances. The CF distribution and reinforcement mechanism were analyzed by observing the connection interface and cross section using a polarizing microscope and a scanning electron microscope. When PA6/CF was used as the secondary molded body, the welding results were better. The addition of CF had a significant strengthening effect on the strength of the PA6 injection welding.Highlights Carbon fiber‐reinforced thermoplastic composite materials were prepared, and welding with PA6 was achieved using the injection molding method. The optimal welding parameters were determined by varying the mold, injection speed, injection temperature, and order of injection. The maximum welding shear strength reached 85% of the base material shear strength. The positive effect of specific fiber distribution on welding strength was analyzed by observing the interface using a scanning electron microscope and a polarizing microscope. This study provides valuable insights into the optimization of welding processes for carbon fiber thermoplastic composite materials, offering possibilities for connecting dissimilar materials with poor compatibility.

Interface enhancement and distribution of carbon fibers in injection welding

“…Table 2 shows the test conditions for the secondary molded body connection. Due to findings in our previous research, it was observed that mold temperature has a significant impact on the strength of PA6 and CFRTP injection welding, with the optimal welding effect observed at 120°C 40,41 . Based on the previous research findings, the optimal welding strength for PA6 was determined to be 44 MPa 35 .…”

“…Table 2 shows the test conditions for the secondary molded body connection. Due to findings in our previous research, it was observed that mold temperature has a significant impact on the strength of PA6 and CFRTP injection welding, with the optimal welding effect observed at 120 C. 40,41 Based on the previous research findings, the optimal welding strength for PA6 was determined to be 44 MPa. 35 Therefore, in this study, the discussion on injection molding parameters is limited to variations in injection temperature and injection speed, with the mold temperature set at 120 C. The test was conducted at a tensile speed of 2 mm/min and temperature of 23 C. The average values were calculated for every five samples.…”