Strength and Fracture Characteristics of Silica Sol Shell Reinforced with Abaca Fibers Impregnated with Aluminum Dihydrogen Phosphate

Abaca fibers were alkaline boiling treated with sodium hydroxide aqueous solution combined with impregnating in aluminum dihydrogen phosphate solution to improve the thermal shock resistance and reinforce shells for investment casting. The microstructure and thermal shock resistance of the treated fibers were analyzed, and their influence on the properties of reinforced shells was investigated. It is found that the hemicellulose and lignin at the surfaces of the fibers undergoing alkaline boiling were removed. A dense protective film was formed on the boiled fibers surfaces through impregnating in a solution of 15.0 wt.% aluminum dihydrogen phosphate. Moreover, the results demonstrated that the weight loss of the boiled-impregnated fibers reduces by 44.61%, compared to the raw fibers, indicating significantly improving the thermal shock resistance. Furthermore, the high-temperature strength of specimens reinforced with boiled-impregnated fibers of 1.29 wt.% reached a peak of 20.11 MPa, increasing by 68.12% compared to the unreinforced. And the alkaline boiled-immersed fibers reinforced shell occurred at elevated temperature a low deformation underweight of only 0.49%. Especially, the impregnated fibers with thermal shock resistance not only ensured good permeability of reinforced shells, but also enhanced the high-temperature cracking resistance capacity. This fully demonstrates the effectiveness of impregnating treatment in improving thermal shock resistance of fibers, and it is very promising to be applied in practical shell-making.