Influence of Sisal Fiber-Reinforced Shells for Investment Casting Using Air Fluidization Spread Technology

A novel process for manufacturing fiber-reinforced silica sol shells for investment casting is proposed. The influence of different fiber lengths and additions on the bending strength of the shell is investigated. Specifically, sisal fibers were suspended in a self-made fiber placement device under the influence of air fluidization and adhered to the surface of the backup slurry of shell. Both silica sol-immersed and untreated sisal fibers were employed as reinforcing agents for the investment shell. The results illustrate that fibers could be evenly placed on the surface of the shell with slurry by means of the air fluidization spread, thereby improving the strength of the fiber-reinforced shell. When the fiber length remained constant, the shell strength exhibited an initial increase followed by a decrease with an increase in fiber addition. At a fiber addition of 1.0%, the green strength of the shell reinforced with both treated and untreated fibers of length 4 mm reached its maximum values, which were 3.35 MPa and 3.14 MPa, respectively. When the fiber addition was 0.25%, the fired strength of the shell reinforced with the aforementioned two types of fibers reached their respective maximum values of 6.12 MPa and 5.86 MPa.