Study on the Strength of Short Carbon Fiber-Reinforced Silicon Sol Shells for the Investment Casting Process

Abstract

Short carbon fibers are used to improve the performance of investment casting shells by mixing short-cut carbon fibers with the silica sol slurries. The influence of fiber length and content on the flexural strength and deformation under weight of fiber-reinforced shells at elevated and normal temperatures and after firing was investigated. The fractures of the shells were observed by SEM. When the carbon fiber content increased from 0.2 to 1%, the bending strength of the shell at room temperature increased significantly compared to the specimens without fibers. The Green strength of the shell reached up to 3.180 MPa, for a carbon fiber content of 0.6% and a length of 4 mm, which was 38.5% higher than that of the specimen without fibers. When the fiber content was 1%, the flexural strength of the specimen at normal temperature was 22.45% higher than that of the unreinforced specimens, and the deformation underweight at elevated temperature was reduced about 14.32%. The strength of the composite shell was increased by 24.22% after roasting after the carbon fiber reinforcing. The SEM observation and analysis revealed that the failure of the fiber-reinforced silica sol shell has a strong influence on the tensile fracture and debonding of the carbon fibers.