A study on fiber sedimentation velocity in epoxy/steel fiber composites used for hybrid injection molds

Abstract

Composites based on metallic fibers and thermosetting polymers are being increasingly used for molding blocks of hybrid injection molds, thereby improving the mechanical and thermal properties. However, an adequate study on the behavior of steel fibers in a reactive epoxy resin is necessary to understand how to maintain suitable mold properties. In this paper, the sedimentation velocity of short steel fiber suspensions in reactive epoxy resin was estimated using a model emerging from the Stokes equation and considering the resin rheology and correction factors for the fiber shape and concentration. DMP (2,4,6-tris (dimethylamino-methyl) phenol) was the accelerator more suitable for this type of composites because it increases the rate of cure and reduces the gel time more pronouncedly than any of the other common accelerators. Samples were manufactured with epoxy resin, short steel fiber and DMP as accelerator, and using anti-sedimentation equipment. The distribution of the fibers was observed in all composites. The viscosity data were used to predict the time in the anti-sedimentation equipment necessary to reach a minimum sedimentation velocity using the mathematical model. Results showed that this velocity is recommended to be below 3.28 × 10−8 m/s to avoid sedimentation of the steel fibers.