Abstract: In order to develop novel hollow composite materials, a new type of skin-core structure of water-soluble core mold was prepared by using sand with different particle size, and the surface roughness of the core mold was studied by its formability, mechanical properties, water-soluble collapsibility and particle size. The results show that the skin-core structure of water-soluble core mold has good formability, high strength, and good water-soluble collapsibility while ensuring surface precision. It combines the advantages of small particle size, light weight and large particle size, and high temperature resistance. The Teflon film successfully prevented the resin from immersing in the core mold in the composite. The gradient particle size water-soluble core mold process can well meet the requirements of the core mold with large aspect ratio, and provides a new idea for the preparation of shaped parts with small opening and large aspect ratio.

Key words: water-solubles, kin-core structure, hollow-composite